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Author	van den Broek, B.; Houssa, M.; Scalise, E.; Pourtois, G.; Afanas'ev, V.V.; Stesmans, A.
Title	First-principles electronic functionalization of silicene and germanene by adatom chemisorption			Type	A1 Journal article
Year	2014	Publication	Applied surface science	Abbreviated Journal	Appl Surf Sci
Volume	291	Issue		Pages	104-108
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	This study presents first-principles results on the electronic functionalization of silicene and germanene monolayers by means of chemisorption of adatom species H, Li, F, Sc, Ti, V. Three general adatom-monolayer configurations are considered, each having its distinct effect on the electronic structure, yielding metallic or semiconducting dispersions depending on the adatom species and configuration. The induced bandgap is a (in)direct F gap ranging from 0.2 to 2.3 eV for both silicene and germanene. In general the alternating configuration was found to be the most energetically stable. The boatlike and chairlike conformers are degenerate with the former having anisotropic effective carrier masses. The top configuration leads to the planar monolayer and predominately to a gapped dispersion. The hollow configuration with V adatoms retains the Dirac cone, but with strong orbital planar hybridization at the Fermi level. We also observe a planar surface state the Fermi level for the latter systems. (C) 2013 Elsevier B.V. All rights reserved.
Address
Corporate Author				Thesis
Publisher		Place of Publication	Amsterdam	Editor
Language		Wos	000329327700023	Publication Date	2013-09-17
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0169-4332;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.387	Times cited	32	Open Access
Notes				Approved	Most recent IF: 3.387; 2014 IF: 2.711
Call Number	UA @ lucian @ c:irua:113766			Serial	1208
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Author	Scalise, E.; Houssa, M.; Pourtois, G.; Afanas'ev, V.V.; Stesmans, A.
Title	First-principles study of strained 2D MoS₂			Type	A1 Journal article
Year	2014	Publication	Physica. E: Low-dimensional systems and nanostructures	Abbreviated Journal	Physica E
Volume	56	Issue		Pages	416-421
Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	The electronic and vibrational properties of 2D honeycomb structures of molybdenum disulfide (MoS2) subjected to strain have been investigated using first-principles calculations based on density functional theory. We have studied the evolution of the electronic properties of bulk and layered MoS2, going down from a few layers up to a mono-layer, and next investigated the effect of bi-axial strain on their electronic structure and vibrational frequencies. Both for tensile and compressive biaxial strains, the shrinking of the energy band-gap of MoS2 with increasing level of applied strain is observed and a transition limit of the system from semiconducting to metallic is predicted to occur for strains in the range of 8-10%. We also found a progressive downshift (upshift) of both the E-2g(1) and A(1g) Raman active modes with increasing level of applied tensile (compressive) strain. Interestingly, significant changes in the curvature of the conduction and valence band near their extrema upon the application of strain are also predicted, with correlated variations of the electron and hole effective masses. These changes present interesting possibilities for engineering the electronic properties of 2D structures of MoS2. (C) 2012 Elsevier B.V. All rights reserved.
Address
Corporate Author				Thesis
Publisher	North-Holland	Place of Publication	Amsterdam	Editor
Language		Wos	000330815800070	Publication Date	2012-08-08
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1386-9477;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	2.221	Times cited	72	Open Access
Notes				Approved	Most recent IF: 2.221; 2014 IF: 2.000
Call Number	UA @ lucian @ c:irua:115761			Serial	1220
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Author	Clima, S.; Govoreanu, B.; Jurczak, M.; Pourtois, G.
Title	HfO_x as RRAM material : first principles insights on the working principles			Type	A1 Journal article
Year	2014	Publication	Microelectronic engineering	Abbreviated Journal	Microelectron Eng
Volume	120	Issue		Pages	13-18
Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	First-principles simulations were employed to gain atomistic insights on the working principles of amorphous HfO2 based Resistive Random Access Memory stack: the nature of the defect responsible for the switching between the High and Low Resistive States has been unambiguously identified to be the substoichiometric Hf sites (commonly called oxygen vacancy-V-O) and the kinetics of the process have been investigated through the study of O diffusion. Also the role of each material layer in the TiN/HfO2/Hf/TiN RRAM stack and the impact of the deposition techniques have been examined: metallic Hf sputtering is needed to provide an oxygen exchange layer that plays the role of defect buffer. TiN shall be a good defect barrier for O but a bad defect buffer layer. A possible scenario to explain the device degradation (switching failure) mechanism has been proposed – the relaxation of the metastable amorphous phase towards crystalline structure leads to denser, more structured cluster that can increase the defect migration barriers. (C) 2013 Elsevier B.V. All rights reserved.
Address
Corporate Author				Thesis
Publisher		Place of Publication	Amsterdam	Editor
Language		Wos	000336697300004	Publication Date	2013-08-19
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0167-9317;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	1.806	Times cited	22	Open Access
Notes				Approved	Most recent IF: 1.806; 2014 IF: 1.197
Call Number	UA @ lucian @ c:irua:117767			Serial	3535
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Author	Houssa, M.; van den Broek, B.; Scalise, E.; Ealet, B.; Pourtois, G.; Chiappe, D.; Cinquanta, E.; Grazianetti, C.; Fanciulli, M.; Molle, A.; Afanas’ev, V.V.; Stesmans, A.;
Title	Theoretical aspects of graphene-like group IV semiconductors			Type	A1 Journal article
Year	2014	Publication	Applied surface science	Abbreviated Journal	Appl Surf Sci
Volume	291	Issue		Pages	98-103
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Silicene and germanene are the silicon and germanium counterparts of graphene, respectively. Recent experimental works have reported the growth of silicene on (1 1 1)Ag surfaces with different atomic configurations, depending on the growth temperature and surface coverage. We first theoretically study the structural and electronic properties of silicene on (1 1 1) Ag surfaces, focusing on the (4 x 4) silicene/Ag structure. Due to symmetry breaking in the silicene layer (nonequivalent number of top and bottom Si atoms), the corrugated silicene layer, with the Ag substrate removed, is predicted to be semiconducting, with a computed energy bandgap of about 0.3 eV. However, the hybridization between the Si 3p orbitals and the Ag 5s orbital in the silicene/(1 1 1)Ag slab model leads to an overall metallic system, with a distribution of local electronic density of states, which is related to the slightly disordered structure of the silicene layer on the (1 1 1)Ag surface. We next study the interaction of silicene and germanene with different hexagonal non-metallic substrates, namely ZnS and ZnSe. On reconstructed (0 0 0 1)ZnS or ZnSe surfaces, which should be more energetically stable for very thin layers, silicene and germanene are found to be semiconducting. Remarkably, the nature and magnitude of their energy bandgap can be controlled by an out-of-plane electric field, an important finding for the potential use of these materials in nanoelectronic devices. (C) 2013 Elsevier B. V. All rights reserved.
Address
Corporate Author				Thesis
Publisher		Place of Publication	Amsterdam	Editor
Language		Wos	000329327700022	Publication Date	2013-09-18
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0169-4332;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.387	Times cited	20	Open Access
Notes				Approved	Most recent IF: 3.387; 2014 IF: 2.711
Call Number	UA @ lucian @ c:irua:113765			Serial	3603
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Author	Scalise, E.; Cinquanta, E.; Houssa, M.; van den Broek, B.; Chiappe, D.; Grazianetti, C.; Pourtois, G.; Ealet, B.; Molle, A.; Fanciulli, M.; Afanas’ev, V.V.; Stesmans, A.;
Title	Vibrational properties of epitaxial silicene layers on (111) Ag			Type	A1 Journal article
Year	2014	Publication	Applied surface science	Abbreviated Journal	Appl Surf Sci
Volume	291	Issue		Pages	113-117
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	The electronic and vibrational properties of three different reconstructions of silicene on Ag(1 1 1) are calculated and compared to experimental results. The 2D epitaxial silicon layers, namely the (4 x 4), (root 13 x root 13) and (2 root 3 x 2 root 3) phases, exhibit different electronic and vibrational properties. Few peaks in the experimental Raman spectrum are identified and attributed to the vibrational modes of the silicene layers. The position and behavior of the Raman peaks with respect to the excitation energy are shown to be a fundamental tool to investigate and discern different phases of silicene on Ag( 1 1 1). (C) 2013 Elsevier B.V. All rights reserved.
Address
Corporate Author				Thesis
Publisher		Place of Publication	Amsterdam	Editor
Language		Wos	000329327700025	Publication Date	2013-09-01
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0169-4332;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.387	Times cited	36	Open Access
Notes				Approved	Most recent IF: 3.387; 2014 IF: 2.711
Call Number	UA @ lucian @ c:irua:113767			Serial	3843
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Author	Schoeters, B.; Leenaerts, O.; Pourtois, G.; Partoens, B.
Title	Ab-initio study of the segregation and electronic properties of neutral and charged B and P dopants in Si and Si/SiO2 nanowires			Type	A1 Journal article
Year	2015	Publication	Journal of applied physics	Abbreviated Journal	J Appl Phys
Volume	118	Issue	118	Pages	104306
Keywords	A1 Journal article; Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	We perform first-principles calculations to investigate the preferred positions of B and P dopants, both neutral and in their preferred charge state, in Si and Si/SiO2 core-shell nanowires (NWs). In order to understand the observed trends in the formation energy, we isolate the different effects that determine these formation energies. By making the distinction between the unrelaxed and the relaxed formation energy, we separate the impact of the relaxation from that of the chemical environment. The unrelaxed formation energies are determined by three effects: (i) the effect of strain caused by size mismatch between the dopant and the host atoms, (ii) the local position of the band edges, and (iii) a screening effect. In the case of the SiNW (Si/SiO2 NW), these effects result in an increase of the formation energy away from the center (interface). The effect of relaxation depends on the relative size mismatch between the dopant and host atoms. A large size mismatch causes substantial relaxation that reduces the formation energy considerably, with the relaxation being more pronounced towards the edge of the wires. These effects explain the surface segregation of the B dopants in a SiNW, since the atomic relaxation induces a continuous drop of the formation energy towards the edge. However, for the P dopants, the formation energy starts to rise when moving from the center but drops to a minimum just next to the surface, indicating a different type of behavior. It also explains that the preferential location for B dopants in Si/SiO2 core-shell NWs is inside the oxide shell just next to the interface, whereas the P dopants prefer the positions next to the interface inside the Si core, which is in agreement with recent experiments. These preferred locations have an important impact on the electronic properties of these core-shell NWs. Our simulations indicate the possibility of hole gas formation when B segregates into the oxide shell.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000361636900031	Publication Date	2015-09-09
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0021-8979	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	2.068	Times cited	3	Open Access
Notes	This work was carried out using the Turing HPC infrastructure at the CalcUA core facility of the Universiteit Antwerpen, a division of the Flemish Supercomputer Center VSC, funded by the Hercules Foundation, the Flemish government and the Universiteit Antwerpen.			Approved	Most recent IF: 2.068; 2015 IF: 2.183
Call Number	c:irua:128729			Serial	4056
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Author	Xu, X.; Vereecke, G.; Chen, C.; Pourtois, G.; Armini, S.; Verellen, N.; Tsai, W.K.; Kim, D.W.; Lee, E.; Lin, C.Y.; Van Dorpe, P.; Struyf, H.; Holsteyns, F.; Moshchalkov, V.; Indekeu, J.; De Gendt, S.;
Title	Capturing wetting states in nanopatterned silicon			Type	A1 Journal article
Year	2014	Publication	ACS nano	Abbreviated Journal	Acs Nano
Volume	8	Issue	1	Pages	885-893
Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Spectacular progress in developing advanced Si circuits with reduced size, along the track of Moore's law, has been relying on necessary developments in wet cleaning of nanopatterned Si wafers to provide contaminant free surfaces. The most efficient cleaning is achieved when complete wetting can be realized. In this work, ordered arrays of silicon nanopillars on a hitherto unexplored small scale have been used to study the wetting behavior on nanomodulated surfaces in a substantial range of surface treatments and geometrical parameters. With the use of optical reflectance measurements, the nanoscale water imbibition depths have been measured and the transition to the superhydrophobic Cassie-Baxter state has been accurately determined. For pillars of high aspect ratio (about 15), the transition occurs even when the surface is grafted with a hydrophilic functional group. We have found a striking consistent deviation between the contact angle measurements and the straightforward application of the classical wetting models. Molecular dynamics simulations show that these deviations can be attributed to the long overlooked atomic-scale surface perturbations that are introduced during the nanofabrication process. When the transition condition is approached, transient states of partial imbibition that characterize intermediate states between the Wenzel and Cassie-Baxter states are revealed in our experiments.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000330542900092	Publication Date	2013-12-31
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1936-0851;1936-086X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	13.942	Times cited	39	Open Access
Notes				Approved	Most recent IF: 13.942; 2014 IF: 12.881
Call Number	UA @ lucian @ c:irua:114871			Serial	276
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Author	Clima, S.; Kaczer, B.; Govoreanu, B.; Popovici, M.; Swerts, J.; Verhulst, A.S.; Jurczak, M.; De Gendt, S.; Pourtois, G.
Title	Determination of ultimate leakage through rutile TiO₂ and tetragonal ZrO₂ from ab initio complex band calculations			Type	A1 Journal article
Year	2013	Publication	IEEE electron device letters	Abbreviated Journal	Ieee Electr Device L
Volume	34	Issue	3	Pages	402-404
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	First-principle complex band structures have been computed for rutile TiO2 and tetragonal ZrO2 insulating materials that are of current technological relevance to dynamic random accessmemorymetal-insulator-metal (MIM) capacitors. From the magnitude of the complex wave vectors in different orientations, the most penetrating orientations have been identified. Tunneling effective masses m(tunnel) have been extracted, are shown to be a crucial parameter for the intrinsic leakage, and are identified to be an important parameter in further scaling of MIM capacitors.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000315723000024	Publication Date	2013-01-31
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0741-3106;1558-0563;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.048	Times cited	3	Open Access
Notes				Approved	Most recent IF: 3.048; 2013 IF: 3.023
Call Number	UA @ lucian @ c:irua:108295			Serial	680
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Author	Neyts, E.C.; Thijsse, B.J.; Mees, M.J.; Bal, K.M.; Pourtois, G.
Title	Establishing uniform acceptance in force biased Monte Carlo simulations			Type	A1 Journal article
Year	2012	Publication	Journal of chemical theory and computation	Abbreviated Journal	J Chem Theory Comput
Volume	8	Issue	6	Pages	1865-1869
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Uniform acceptance force biased Monte Carlo (UFMC) simulations have previously been shown to be a powerful tool to simulate atomic scale processes, enabling one to follow the dynamical path during the simulation. In this contribution, we present a simple proof to demonstrate that this uniform acceptance still complies with the condition of detailed balance, on the condition that the characteristic parameter lambda = 1/2 and that the maximum allowed step size is chosen to be sufficiently small. Furthermore, the relation to Metropolis Monte Carlo (MMC) is also established, and it is shown that UFMC reduces to MMC by choosing the characteristic parameter lambda = 0 [Rao, M. et al. Mol. Phys. 1979, 37, 1773]. Finally, a simple example compares the UFMC and MMC methods.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000305092400002	Publication Date	2012-05-16
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1549-9618;1549-9626;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	5.245	Times cited	20	Open Access
Notes				Approved	Most recent IF: 5.245; 2012 IF: 5.389
Call Number	UA @ lucian @ c:irua:99090			Serial	1082
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Author	Nishio, K.; Lu, A.K.A.; Pourtois, G.
Title	Low-strain Si/O superlattices with tunable electronic properties : ab initio calculations			Type	A1 Journal article
Year	2015	Publication	Physical review : B : condensed matter and materials physics	Abbreviated Journal	Phys Rev B
Volume	91	Issue	91	Pages	165303
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	We propose that low-strain Si/O superlattices can be constructed by connecting reconstructed Si{001} surfaces by Si-O-Si bridges. Ab initio calculations show that our models are energetically more favorable than all the models proposed so far. The part of our Si/O superlattice model is experimentally accessible just by oxidizing a Si( 001) substrate. To complete our Si/O superlattice model, we propose a three-step method. We also explore the potential of our Si/O superlattice models for new materials used in future Si electronics. We find that the location of the channel where the carriers travel can be controlled between the interfaces and the Si layers by the insertion of O atoms into the Si-Si dimers. By revealing the origins of the interface electron and hole states, we find that similar interface states should be easily achieved for Si slabs and Si substrates. Interestingly, the interface electrons and holes have small effective masses in the direction parallel to the channel and large effective masses in the direction normal to the channel, which makes the Si/O superlattices attractive to be used for channel materials. We also find that the valley splitting of Si is enhanced by the formation of the Si/O/Si interfaces, which is ideal for developing Si-based qubits. Our findings open new perspectives to design and control the electronic properties of Si.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000352986700002	Publication Date	2015-04-16
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1098-0121;1550-235X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.836	Times cited	6	Open Access
Notes				Approved	Most recent IF: 3.836; 2015 IF: 3.736
Call Number	c:irua:125998			Serial	1852
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Author	Sorée, B.; Magnus, W.; Szepieniec, M.; Vandenbreghe, W.; Verhulst, A.; Pourtois, G.; Groeseneken, G.; de Gendt, S.; Heyns, M.
Title	Novel device concepts for nanotechnology : the nanowire pinch-off FET and graphene tunnelFET			Type	A2 Journal article
Year	2010	Publication	ECS transactions	Abbreviated Journal
Volume	28	Issue		Pages	15-26
Keywords	A2 Journal article; Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	We explain the basic operation of a nanowire pinch-off FET and graphene nanoribbon tunnelFET. For the nanowire pinch-off FET we construct an analytical model to obtain the threshold voltage as a function of radius and doping density. We use the gradual channel approximation to calculate the current-voltage characteristics of this device and we show that the nanowire pinch-off FET has a subthreshold slope of 60 mV/dec and good ION and ION/IOFF ratios. For the graphene nanoribbon tunnelFET we show that an improved analytical model yields more realistic results for the transmission probability and hence the tunneling current. The first simulation results for the graphene nanoribbon tunnelFET show promising subthreshold slopes.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos		Publication Date	0000-00-00
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1938-5862	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor		Times cited		Open Access
Notes				Approved	Most recent IF: NA
Call Number	UA @ lucian @ c:irua:89510			Serial	2375
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Author	Scarrozza, M.; Pourtois, G.; Houssa, M.; Heyns, M.; Stesmans, A.
Title	Oxidation of the GaAs(001) surface : insights from first-principles calculations			Type	A1 Journal article
Year	2012	Publication	Physical review : B : condensed matter and materials physics	Abbreviated Journal	Phys Rev B
Volume	85	Issue	19	Pages	195307-195307,8
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	We performed a detailed investigation of the oxidation of the technologically relevant GaAs(001)-beta 2(2x4) surface via density functional calculations. The purpose is to gain insights on the atomistic mechanisms and local bondings that underlie the degradation of the surface properties once exposed to oxygen. The study comprises the adsorption of single O atoms, through the sampling of several adsorption sites, and the subsequent formation of the O adsorbate at increasing coverage by taking into account multiple-atom adsorption. Based on the evaluation of the energetics and the structural properties of the atomistic models generated, the results here reported delineate a consistent picture of the initial stage of the surface oxidation: (i) at low coverage, in the limit of single O insertions, oxygen is incorporated on the surface forming a twofold-bridging Ga-O-As bond; (ii) at increasing coverage, as multiple O atoms are involved, this is accompanied by the formation of a threefold-coordinated bond (with two Ga and one As atoms); (iii) the latter has important implications regarding the electronic properties of the adsorbate since this O bonding may result in the formation of As dangling bonds. Moreover, a clear trend of increased energy gain for the incorporation of neighboring O atoms compared to single O insertions indicates that the formation of oxide clusters is favored over a regime of uniform oxidation. Our findings provide a detailed description of the O bonding and stress the importance of modeling the adsorption of multiple O atoms for an accurate description of the surface oxidation.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000303755700006	Publication Date	2012-05-08
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1098-0121;1550-235X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.836	Times cited	15	Open Access
Notes				Approved	Most recent IF: 3.836; 2012 IF: 3.767
Call Number	UA @ lucian @ c:irua:99122			Serial	2538
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Author	Phung, Q.M.; Vancoillie, S.; Delabie, A.; Pourtois, G.; Pierloot, K.
Title	Ruthenocene and cyclopentadienyl pyrrolyl ruthenium as precursors for ruthenium atomic layer deposition : a comparative study of dissociation enthalpies			Type	A1 Journal article
Year	2012	Publication	Theoretical chemistry accounts : theory, computation, and modeling	Abbreviated Journal	Theor Chem Acc
Volume	131	Issue	7	Pages	1238
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	RuCp2 (ruthenocene) and RuCpPy (cyclopentadienyl pyrrolyl ruthenium) complexes are used in ruthenium (Ru) atomic layer deposition (ALD) but exhibit a markedly different reactivity with respect to the substrate and co-reactant. In search of an explanation, we report here the results of a comparative study of the heterolytic and homolytic dissociation enthalpy of these two ruthenium complexes, making use of either density functional theory (DFT) or multiconfigurational perturbation theory (CASPT2). While both methods predict distinctly different absolute dissociation enthalpies, they agree on the relative values between both molecules. A reduced heterolytic dissociation enthalpy is obtained for RuCpPy compared to RuCp2, although the difference obtained from CASPT2 (19.9 kcal/mol) is slightly larger than the one obtained with any of the DFT functionals (around 17 kcal/mol). Both methods also agree on the more pronounced stability of the Cp- ligand in RuCpPy than in RuCp2 (by around 9 kcal/mol with DFT and by 6 kcal/mol with CASPT2).
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000307274300003	Publication Date	2012-07-07
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1432-881X;1432-2234;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	1.89	Times cited	5	Open Access
Notes				Approved	Most recent IF: 1.89; 2012 IF: 2.233
Call Number	UA @ lucian @ c:irua:101139			Serial	2935
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Author	Scalise, E.; Houssa, M.; Pourtois, G.; Afanas'ev, V.; Stesmans, A.
Title	Strain-induced semiconductor to metal transition in the two-dimensional honeycomb structure of MoS₂			Type	A1 Journal article
Year	2012	Publication	Nano Research	Abbreviated Journal	Nano Res
Volume	5	Issue	1	Pages	43-48
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	The electronic properties of two-dimensional honeycomb structures of molybdenum disulfide (MoS(2)) subjected to biaxial strain have been investigated using first-principles calculations based on density functional theory. On applying compressive or tensile bi-axial strain on bi-layer and mono-layer MoS(2), the electronic properties are predicted to change from semiconducting to metallic. These changes present very interesting possibilities for engineering the electronic properties of two-dimensional structures of MoS(2).
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000299085200006	Publication Date	2011-11-10
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1998-0124;1998-0000;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	7.354	Times cited	407	Open Access
Notes				Approved	Most recent IF: 7.354; 2012 IF: 7.392
Call Number	UA @ lucian @ c:irua:96262			Serial	3169
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Author	Mees, M.J.; Pourtois, G.; Neyts, E.C.; Thijsse, B.J.; Stesmans, A.
Title	Uniform-acceptance force-bias Monte Carlo method with time scale to study solid-state diffusion			Type	A1 Journal article
Year	2012	Publication	Physical review : B : condensed matter and materials physics	Abbreviated Journal	Phys Rev B
Volume	85	Issue	13	Pages	134301-134301,9
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Monte Carlo (MC) methods have a long-standing history as partners of molecular dynamics (MD) to simulate the evolution of materials at the atomic scale. Among these techniques, the uniform-acceptance force-bias Monte Carlo (UFMC) method [ G. Dereli Mol. Simul. 8 351 (1992)] has recently attracted attention [ M. Timonova et al. Phys. Rev. B 81 144107 (2010)] thanks to its apparent capacity of being able to simulate physical processes in a reduced number of iterations compared to classical MD methods. The origin of this efficiency remains, however, unclear. In this work we derive a UFMC method starting from basic thermodynamic principles, which leads to an intuitive and unambiguous formalism. The approach includes a statistically relevant time step per Monte Carlo iteration, showing a significant speed-up compared to MD simulations. This time-stamped force-bias Monte Carlo (tfMC) formalism is tested on both simple one-dimensional and three-dimensional systems. Both test-cases give excellent results in agreement with analytical solutions and literature reports. The inclusion of a time scale, the simplicity of the method, and the enhancement of the time step compared to classical MD methods make this method very appealing for studying the dynamics of many-particle systems.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000302290500001	Publication Date	2012-04-03
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1098-0121;1550-235X;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.836	Times cited	31	Open Access
Notes				Approved	Most recent IF: 3.836; 2012 IF: 3.767
Call Number	UA @ lucian @ c:irua:97160			Serial	3809
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Author	Scalise, E.; Houssa, M.; Pourtois, G.; van den Broek, B.; Afanas'ev, V.; Stesmans, A.
Title	Vibrational properties of silicene and germanene			Type	A1 Journal article
Year	2013	Publication	Nano Research	Abbreviated Journal	Nano Res
Volume	6	Issue	1	Pages	19-28
Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	The structural and vibrational properties of two-dimensional hexagonal silicon (silicene) and germanium (germanene) are investigated by means of first-principles calculations. It is predict that the silicene (germanene) structure with a small buckling of 0.44 (0.7 ) and bond lengths of 2.28 (2.44 ) is energetically the most favorable, and it does not exhibit imaginary phonon mode. The calculated non-resonance Raman spectra of silicene is characterized by a main peak at about 575 cm(-1), namely the G-like peak. For germanene, the highest peak is at about 290 cm(-1). Extensive calculations on armchair silicene nanoribbons and armchair germanene nanoribbons are also performed, with and without hydrogenation of the edges. The studies reveal other Raman peaks mainly distributed at lower frequencies than the G-like peak which could be attributed to the defects at the edges of the ribbons, thus not present in the Raman spectra of non-defective silicene and germanene. Particularly the Raman peak corresponding to the D mode is found to be located at around 515 cm(-1) for silicene and 270 cm(-1) for germanene. The calculated G-like and the D peaks are likely the fingerprints of the Raman spectra of the low-buckled structures of silicene and germanene.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000313658800003	Publication Date	2012-12-17
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1998-0124;1998-0000;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	7.354	Times cited	105	Open Access
Notes				Approved	Most recent IF: 7.354; 2013 IF: 6.963
Call Number	UA @ lucian @ c:irua:110106			Serial	3846
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Author	Clima, S.; Chen, Y.Y.; Fantini, A.; Goux, L.; Degraeve, R.; Govoreanu, B.; Pourtois, G.; Jurczak, M.
Title	Intrinsic tailing of resistive states distributions in amorphous <tex>HfO_x </tex> and TaO_x based resistive random access memories			Type	A1 Journal article
Year	2015	Publication	IEEE electron device letters	Abbreviated Journal	Ieee Electr Device L
Volume	36	Issue	36	Pages	769-771
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	We report on the ineffectiveness of programming oxide-based resistive random access memory (OxRAM) at low current with a program and verify algorithm due to intrinsic relaxation of the verified distribution to the natural state distribution obtained by single-pulse programming without verify process. Based on oxygen defect formation thermodynamics and on their diffusion barriers in amorphous HfOx and TaOx, we describe the intrinsic nature of tailing of the verified low resistive state and high resistive state distributions. We introduce different scenarios to explain fast distribution widening phenomenon, which is a fundamental limitation for OxRAM current scaling and device reliability.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000358570300011	Publication Date	2015-06-23
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0741-3106	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.048	Times cited	33	Open Access
Notes				Approved	Most recent IF: 3.048; 2015 IF: 2.754
Call Number	UA @ lucian @ c:irua:134412			Serial	4200
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Author	Sankaran, K.; Swerts, J.; Couet, S.; Stokbro, K.; Pourtois, G.
Title	Oscillatory behavior of the tunnel magnetoresistance due to thickness variations in Ta vertical bar CoFe vertical bar MgO magnetic tunnel junctions : a first-principles study			Type	A1 Journal article
Year	2016	Publication	Physical review B	Abbreviated Journal	Phys Rev B
Volume	94	Issue	94	Pages	094424
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	To investigate the impact of both the CoFe ferromagnetic layer thickness and the capping paramagnetic layer on the tunnel magnetoresistance (TMR), we performed first-principles simulations on epitaxial magnetic tunnel junctions contacted with either CoFe or Ta paramagnetic capping layers. We observed a strong oscillation of the TMR amplitude with respect to the thickness of the ferromagnetic layer. The TMR is found to be amplified whenever the MgO spin tunnel barrier is thickened. Quantization of the electronic structure of the ferromagnetic layers is found to be at the origin of this oscillatory behavior. Metals such as Ta contacting the magnetic layer are found to enhance the amplitude of the oscillations due to the occurrence of an interface dipole. The latter drives the band alignment and tunes the nature of the spin channels that are active during the tunneling process. Subsequently, the regular transmission spin channels are modulated in the magnetic tunnel junction stack and other complex ones are being activated.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000383860700004	Publication Date	2016-09-20
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	2469-9950;2469-9969;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.836	Times cited	4	Open Access
Notes				Approved	Most recent IF: 3.836
Call Number	UA @ lucian @ c:irua:137122			Serial	4468
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Author	van den Broek, B.; Houssa, M.; Lu, A.; Pourtois, G.; Afanas'ev, V.; Stesmans, A.
Title	Silicene nanoribbons on transition metal dichalcogenide substrates : effects on electronic structure and ballistic transport			Type	A1 Journal article
Year	2016	Publication	Nano Research	Abbreviated Journal	Nano Res
Volume	9	Issue	9	Pages	3394-3406
Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	The idea of stacking multiple monolayers of different two-dimensional materials has become a global pursuit. In this work, a silicene armchair nanoribbon of width W and van der Waals-bonded to different transition-metal dichalcogenide (TMD) bilayer substrates MoX2 and WX2, where X = S, Se, Te is considered. The orbital resolved electronic structure and ballistic transport properties of these systems are simulated by employing van der Waals-corrected density functional theory and nonequilibrium Green's functions. We find that the lattice mismatch with the underlying substrate determines the electronic structure, correlated with the silicene buckling distortion and ultimately with the contact resistance of the two-terminal system. The smallest lattice mismatch, obtained with the MoTe2 substrate, results in the silicene ribbon properties coming close to those of a freestanding one. With the TMD bilayer acting as a dielectric layer, the electronic structure is tunable from a direct to an indirect semiconducting layer, and subsequently to a metallic electronic dispersion layer, with a moderate applied perpendicular electric field.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000386770300018	Publication Date	2016-08-20
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1998-0124	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	7.354	Times cited	2	Open Access
Notes				Approved	Most recent IF: 7.354
Call Number	UA @ lucian @ c:irua:138210			Serial	4469
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Author	de de Meux, A.J.; Bhoolokam, A.; Pourtois, G.; Genoe, J.; Heremans, P.
Title	Oxygen vacancies effects in a-IGZO : formation mechanisms, hysteresis, and negative bias stress effects			Type	A1 Journal article
Year	2017	Publication	Physica status solidi : A : applications and materials science	Abbreviated Journal	Phys Status Solidi A
Volume	214	Issue	6	Pages	1600889
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	The amorphous oxide semiconductor Indium-Gallium-Zinc-Oxide (a-IGZO) has gained a large technological relevance as a semiconductor for thin-film transistors in active-matrix displays. Yet, major questions remain unanswered regarding the atomic origin of threshold voltage control, doping level, hysteresis, negative bias stress (NBS), and negative bias illumination stress (NBIS). We undertake a systematic study of the effects of oxygen vacancies on the properties of a-IGZO by relating experimental observations to microscopic insights gained from first-principle simulations. It is found that the amorphous nature of the semiconductor allows unusually large atomic relaxations. In some cases, oxygen vacancies are found to behave as perfect shallow donors without the formation of structural defects. Once structural defects are formed, their transition states can vary upon charge and discharge cycles. We associate this phenomenon to a possible presence of hysteresis in the transfer curve of the devices. Under NBS, the creation of oxygen vacancies becomes energetically very stable, hence thermodynamically very likely. This generation process is correlated with the occurrence of the negative bias stress instabilities observed in a-IGZO transistors. While oxygen vacancies can therefore be related to NBS and hysteresis, it appears unlikely from our results that they are direct causes of NBIS, contrary to common belief.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000403339900012	Publication Date	2017-03-02
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1862-6300	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	1.775	Times cited	8	Open Access	Not_Open_Access
Notes				Approved	Most recent IF: 1.775
Call Number	UA @ lucian @ c:irua:144219			Serial	4678
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Author	Lu, A.K.A.; Houssa, M.; Radu, I.P.; Pourtois, G.
Title	Toward an understanding of the electric field-induced electrostatic doping in van der Waals heterostructures : a first-principles study			Type	A1 Journal article
Year	2017	Publication	ACS applied materials and interfaces	Abbreviated Journal	Acs Appl Mater Inter
Volume	9	Issue	8	Pages	7725-7734
Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Since the discovery of graphene, a broad range of two-dimensional (2D) materials has captured the attention of the scientific communities. Materials, such as hexagonal boron nitride (hBN) and the transition metal dichalcogenides (TMDs) family, have shown promising semiconducting and insulating properties that are very appealing for the semiconductor industry. Recently, the possibility of taking advantage of the properties of 2D-based heterostructures has been investigated for low-power nanoelectronic applications. In this work, we aim at evaluating the relation between the nature of the materials used in such heterostructures and the amplitude of the layer-to-layer charge transfer induced by an external electric field, as is typically present in nanoelectronic gated devices. A broad range of combinations of TMDs, graphene, and hBN has been investigated using density functional theory. Our results show that the electric field induced charge transfer strongly depends on the nature of the 2D materials used in the van der Waals heterostructures and to a lesser extent on the relative orientation of the materials in the structure. Our findings contribute to the building of the fundamental understanding required to engineer electrostatically the doping of 2D materials and to establish the factors that drive the charge transfer mechanisms in electron tunneling-based devices. These are key ingredients for the development of 2D -based nanoelectronic devices.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000395494200119	Publication Date	2017-02-13
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1944-8244	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	7.504	Times cited	10	Open Access	Not_Open_Access
Notes				Approved	Most recent IF: 7.504
Call Number	UA @ lucian @ c:irua:142483			Serial	4696
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Author	Dabral, A.; Lu, A.K.A.; Chiappe, D.; Houssa, M.; Pourtois, G.
Title	A systematic study of various 2D materials in the light of defect formation and oxidation			Type	A1 Journal article
Year	2019	Publication	Physical chemistry, chemical physics	Abbreviated Journal	Phys Chem Chem Phys
Volume	21	Issue	3	Pages	1089-1099
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	The thermodynamic aspects of various 2D materials are explored using Density Functional Theory (DFT). Various metal chalcogenides (MX2, M = metal, chalcogen X = S, Se, Te) are investigated with respect to their interaction and stability under different ambient conditions met in the integration process of a transistor device. Their interaction with high- dielectrics is also addressed, in order to assess their possible integration in Complementary Metal Oxide Semiconductor (CMOS) field effect transistors. 2D materials show promise for high performance nanoelectronic devices, but the presence of defects (vacancies, grain boundaries,...) can significantly impact their electronic properties. To assess the impact of defects, their enthalpies of formation and their signature levels in the density of states have been studied. We find, consistently with literature reports, that chalcogen vacancies are the most likely source of defects. It is shown that while pristine 2D materials are in general stable whenever set in contact with different ambient atmospheres, the presence of defective sites affects the electronic properties of the 2D materials to varying degrees. We observe that all the 2D materials studied in the present work show strong reactivity towards radical oxygen plasma treatments while reactivity towards other common gas phase chemical such as O-2 and H2O and groups present at the high- surface varies significantly between species. While energy band-gaps, effective masses and contact resistivities are key criteria in selection of 2D materials for scaled CMOS and tunneling based devices, the phase and ambient stabilities might also play a very important role in the development of reliable nanoelectronic applications.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000456147000009	Publication Date	2018-12-19
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1463-9076; 1463-9084	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	4.123	Times cited	1	Open Access	Not_Open_Access
Notes				Approved	Most recent IF: 4.123
Call Number	UA @ admin @ c:irua:156715			Serial	5267
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Author	Vohra, A.; Khanam, A.; Slotte, J.; Makkonen, I.; Pourtois, G.; Loo, R.; Vandervorst, W.
Title	Evolution of phosphorus-vacancy clusters in epitaxial germanium			Type	A1 Journal article
Year	2019	Publication	Journal of applied physics	Abbreviated Journal	J Appl Phys
Volume	125	Issue	2	Pages	025701
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	The E centers (dopant-vacancy pairs) play a significant role in dopant deactivation in semiconductors. In order to gain insight into dopant-defect interactions during epitaxial growth of in situ phosphorus doped Ge, positron annihilation spectroscopy, which is sensitive to open-volume defects, was performed on Ge layers grown by chemical vapor deposition with different concentrations of phosphorus (similar to 1 x 10(18)-1 x 10(20) cm(-3)). Experimental results supported by first-principles calculations based on the two component density-functional theory gave evidence for the existence of mono-vacancies decorated by several phosphorus atoms as the dominant defect type in the epitaxial Ge. The concentration of vacancies increases with the amount of P-doping. The number of P atoms around the vacancy also increases, depending on the P concentration. The evolution of P-n-V clusters in Ge contributes significantly to the dopant deactivation. Published under license by AIP Publishing.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000455922100057	Publication Date	2019-01-08
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0021-8979; 1089-7550	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	2.068	Times cited	5	Open Access	Not_Open_Access
Notes				Approved	Most recent IF: 2.068
Call Number	UA @ admin @ c:irua:156722			Serial	5274
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Author	Dhayalan, S.K.; Nuytten, T.; Pourtois, G.; Simoen, E.; Pezzoli, F.; Cinquanta, E.; Bonera, E.; Loo, R.; Rosseel, E.; Hikavyy, A.; Shimura, Y.; Vandervorst, W.
Title	Insights into the C Distribution in Si:C/Si:C:P and the Annealing Behavior of Si:C Layers			Type	A1 Journal article
Year	2019	Publication	ECS journal of solid state science and technology	Abbreviated Journal	Ecs J Solid State Sc
Volume	8	Issue	4	Pages	P209-P216
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Si:C and Si:C:P alloys are potential candidates for source-drain stressor applications in n-type Fin Field Effect Transistors (FinFETs). Increasing the C content to achieve high strain results in the arrangement of C atoms as third nearest neighbors (3nn) in the Si: C lattice. During thermal annealing, the presence of C atoms as 3nn may promote clustering at the interstitial sites, causing loss of stress. The concentration of C atoms as 3nn is reduced by the incorporation of a small amount of Ge atoms during the growth, whereas in-situ P doping does not influence this 3nn distribution [J Solid State Sci. Technol vol 6, p 755, 2017]. Small amounts of Ge are provided during low temperature selective epitaxial growth scheme, which are based on cyclic deposition and etching (CDE). In this work, we aim to provide physical insights into the aforementioned phenomena, to understand the behavior of 3nn C atoms and the types of defects that are formed in the annealed Si: C films. Using ab-initio simulations, the Ge-C interaction in the Si matrix is investigated and this insight is used to explain how the Ge incorporation leads to a reduced 3nn distribution of the C atoms. The interaction between C and P in the Si: C: P films is also investigated to explain why the P incorporation has not led to a reduction in the 3nn distribution. We then report on the Raman characterization of Si: C layers subjected to post epi annealing. As the penetration depth of the laser is dependent on the wavelength, Raman measurements at two different wavelengths enable us to probe the depth distribution of 3nn C atoms after applying different annealing conditions. We observed a homogeneous loss in 3nn C throughout the layer. Whereas in the kinematic modeling of high resolution X-ray diffraction spectra, a gradient in the substitutional C loss was observed close to the epitaxial layer/substrate interface. This gradient can be due to the out diffusion of C atoms into the Si substrate or to the formation of interstitial C clusters, which cannot be distinguished in HR-XRD. Deep Level Transient Spectroscopy indicated that the prominent out-diffusing species was interstitial CO complex while the interstitial C defects were also prevalent in the epi layer. (c) 2019 The Electrochemical Society.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000465069200001	Publication Date	2019-04-18
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	2162-8769; 2162-8777	ISBN		Additional Links	UA library record; WoS full record
Impact Factor	1.787	Times cited		Open Access	Not_Open_Access
Notes				Approved	Most recent IF: 1.787
Call Number	UA @ admin @ c:irua:160399			Serial	5275
Permanent link to this record



Author	Vohra, A.; Khanam, A.; Slotte, J.; Makkonen, I.; Pourtois, G.; Porret, C.; Loo, R.; Vandervorst, W.
Title	Heavily phosphorus doped germanium : strong interaction of phosphorus with vacancies and impact of tin alloying on doping activation			Type	A1 Journal article
Year	2019	Publication	Journal of applied physics	Abbreviated Journal	J Appl Phys
Volume	125	Issue	22	Pages	225703
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	We examined the vacancy trapping proficiency of Sn and P atoms in germanium using positron annihilation spectroscopy measurements, sensitive to the open-volume defects. Epitaxial Ge1 xSnx films were grown by chemical vapor deposition with different P concentrations in the 3: 0 1019-1: 5 1020 cm 3 range. We corroborate our findings with first principles simulations. Codoping of Ge with a Sn concentration of up to 9% is not an efficient method to suppress the free vacancy concentration and the formation of larger phosphorus-vacancy complexes. Experimental results confirm an increase in the number of P atoms around the monovacancy with P-doping, leading to dopant deactivation in epitaxial germanium-tin layers with similar Sn content. Vice versa, no impact on the improvement of maximum achieved P activation in Ge with increasing Sn-doping has been observed. Theoretical calculations also confirm that Pn-V (vacancy) complexes are energetically more stable than the corresponding SnmPn-V and Snm-V defect structures with the same number of alien atoms (Sn or P) around the monovacancy. he strong attraction of vacancies to the phosphorus atoms remains the dominant dopant deactivation mechanism in Ge as well as in Ge1 xSnx. Published under license by AIP Publishing.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000471698600044	Publication Date	2019-06-10
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0021-8979; 1089-7550	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	2.068	Times cited	1	Open Access
Notes				Approved	Most recent IF: 2.068
Call Number	UA @ admin @ c:irua:161333			Serial	6300
Permanent link to this record



Author	Clima, S.; Garbin, D.; Devulder, W.; Keukelier, J.; Opsomer, K.; Goux, L.; Kar, G.S.; Pourtois, G.
Title	Material relaxation in chalcogenide OTS SELECTOR materials			Type	A1 Journal article
Year	2019	Publication	Microelectronic engineering	Abbreviated Journal	Microelectron Eng
Volume	215	Issue	215	Pages	110996
Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Nature of the mobility-gap states in amorphous Ge-rich Ge50Se50 was found to be related to homopolar Ge bonds in the chains/clusters of Ge atoms. Threshold switching material suffers Ge-Ge bond concentration drift during material ageing, which can explain the observed reliability of the aGe(50)Se(50) selector devices. Strong Ge-N bonds were introduced to alleviate the observed instability.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000480665600008	Publication Date	2019-05-21
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0167-9317	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	1.806	Times cited	1	Open Access
Notes				Approved	Most recent IF: 1.806
Call Number	UA @ admin @ c:irua:161905			Serial	6308
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Author	Khanam, A.; Vohra, A.; Slotte, J.; Makkonen, I.; Loo, R.; Pourtois, G.; Vandervorst, W.
Title	A demonstration of donor passivation through direct formation of V-As-i complexes in As-doped Ge_1-XSn_x			Type	A1 Journal article
Year	2020	Publication	Journal Of Applied Physics	Abbreviated Journal	J Appl Phys
Volume	127	Issue	19	Pages	195703
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Positron annihilation spectroscopy in the Doppler and coincidence Doppler mode was applied on Ge1 xSnx epitaxial layers, grown by chemical vapor deposition with different total As concentrations (1019-1021 cm3), high active As concentrations (1019 cm3), and similar Sn concentrations (5.9%-6.4%). Positron traps are identified as mono-vacancy complexes. Vacancy-As complexes, V-Asi, formed during the growth were studied to deepen the understanding of the electrical passivation of the Ge1 xSnx:As epilayers. Larger monovacancy complexes, V-Asi (i 2), are formed as the As doping increases. The total As concentration shows a significant impact on the saturation of the number of As atoms (i 1/4 4) around the vacancies in the sample epilayers. The presence of V-Asi complexes decreases the dopant activation in the Ge1 xSnx:As epilayers. Furthermore, the presence of Sn failed to hinder the formation of larger V-Asi complexes and thus failed to reduce the donor-deactivation.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000536196000003	Publication Date	2020-05-15
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	0021-8979; 1089-7550	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.2	Times cited		Open Access
Notes	; ;			Approved	Most recent IF: 3.2; 2020 IF: 2.068
Call Number	UA @ admin @ c:irua:170252			Serial	6447
Permanent link to this record



Author	Mehta, A.N.; Mo, J.; Pourtois, G.; Dabral, A.; Groven, B.; Bender, H.; Favia, P.; Caymax, M.; Vandervorst, W.
Title	Grain-boundary-induced strain and distortion in epitaxial bilayer MoS₂ lattice			Type	A1 Journal article
Year	2020	Publication	Journal Of Physical Chemistry C	Abbreviated Journal	J Phys Chem C
Volume	124	Issue	11	Pages	6472-6478
Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Grain boundaries between 60 degrees rotated and twinned crystals constitute the dominant type of extended line defects in two-dimensional transition metal dichalcogenides (2D MX2) when grown on a single crystalline template through van der Waals epitaxy. The two most common 60 degrees grain boundaries in MX2 layers, i.e., beta- and gamma-boundaries, introduce distinct distortion and strain into the 2D lattice. They impart a localized tensile or compressive strain on the subsequent layer, respectively, due to van der Waals coupling in bilayer MX2 as determined by combining atomic resolution electron microscopy, geometric phase analysis, and density functional theory. Based on these observations, an alternate route to strain engineering through controlling intrinsic van der Waals forces in homobilayer MX2 is proposed. In contrast to the commonly used external means, this approach enables the localized application of strain to tune the electronic properties of the 2D semiconducting channel in ultra-scaled nanoelectronic applications.
Address
Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000526396000067	Publication Date	2020-02-21
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1932-7447; 1932-7455	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	3.7	Times cited	2	Open Access
Notes	; ;			Approved	Most recent IF: 3.7; 2020 IF: 4.536
Call Number	UA @ admin @ c:irua:168625			Serial	6528
Permanent link to this record



Author	Clima, S.; Garbin, D.; Opsomer, K.; Avasarala, N.S.; Devulder, W.; Shlyakhov, I.; Keukelier, J.; Donadio, G.L.; Witters, T.; Kundu, S.; Govoreanu, B.; Goux, L.; Detavernier, C.; Afanas'ev, V.; Kar, G.S.; Pourtois, G.
Title	Ovonic threshold-switching GexSey chalcogenide materials : stoichiometry, trap nature, and material relaxation from first principles			Type	A1 Journal article
Year	2020	Publication	Physica Status Solidi-Rapid Research Letters	Abbreviated Journal	Phys Status Solidi-R
Volume		Issue		Pages	1900672
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	Density functional theory simulations are used to identify the structural factors that define the material properties of ovonic threshold switches (OTS). They show that the nature of mobility-gap trap states in amorphous Ge-rich Ge50Se50 is related to Ge-Ge bonds, whereas in Se-rich Ge30Se70 the Ge valence-alternating-pairs and Se lone-pairs dominate. To obtain a faithful description of the electronic structure and delocalization of states, it is required to combine hybrid exchange-correlation functionals with large unit-cell models. The extent of localization of electronic states depends on the applied external electric field. Hence, OTS materials undergo structural changes during electrical cycling of the device, with a decrease in the population of less exothermic Ge-Ge bonds in favor of more exothermic Ge-Se. This reduces the amount of charge traps, which translates into coordination changes, an increase in mobility-gap, and subsequently changes in the selector-device electrical parameters. The threshold voltage drift process can be explained by natural evolution of the nonpreferred Ge-Ge bonds (or “chains”/clusters thereof) in Ge-rich GexSe1-x. The effect of extrinsic doping is shown for Si and N, which introduce strong covalent bonds into the system, increase both mobility-gap and crystallization temperature, and decrease the leakage current.
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Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000512431100001	Publication Date	2020-01-28
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	1862-6254	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	2.8	Times cited	3	Open Access
Notes	; This work was carried out in the framework of the imec Core CMOS-Emerging Memory Program. Financial support from EU H2020-NMBPTO-IND-2018 project “INTERSECT” (Grant No. 814487) is acknowledged. ;			Approved	Most recent IF: 2.8; 2020 IF: 3.032
Call Number	UA @ admin @ c:irua:166492			Serial	6575
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Author	Vohra, A.; Makkonen, I.; Pourtois, G.; Slotte, J.; Porret, C.; Rosseel, E.; Khanam, A.; Tirrito, M.; Douhard, B.; Loo, R.; Vandervorst, W.
Title	Source/drain materials for Ge nMOS devices: phosphorus activation in epitaxial Si, Ge, Ge_1-xSn_x and Si_yGe_1-x-ySn_x			Type	A1 Journal article
Year	2020	Publication	Ecs Journal Of Solid State Science And Technology	Abbreviated Journal	Ecs J Solid State Sc
Volume	9	Issue	4	Pages	044010-44012
Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Abstract	This paper benchmarks various epitaxial growth schemes based on n-type group-IV materials as viable source/drain candidates for Ge nMOS devices. Si:P grown at low temperature on Ge, gives an active carrier concentration as high as 3.5 x 10(20) cm(-3) and a contact resistivity down to 7.5 x 10(-9) Omega.cm(2). However, Si:P growth is highly defective due to large lattice mismatch between Si and Ge. Within the material stacks assessed, one option for Ge nMOS source/drain stressors would be to stack Si:P, deposited at contact level, on top of a selectively grown n-SiyGe1-x-ySnx at source/drain level, in line with the concept of Si passivation of n-Ge surfaces to achieve low contact resistivities as reported in literature (Martens et al. 2011 Appl. Phys. Lett., 98, 013 504). The saturation in active carrier concentration with increasing P (or As)-doping is the major bottleneck in achieving low contact resistivities for as-grown Ge or SiyGe1-x-ySnx. We focus on understanding various dopant deactivation mechanisms in P-doped Ge and Ge1-xSnx alloys. First principles simulation results suggest that P deactivation in Ge and Ge1-xSnx can be explained both by P-clustering and donor-vacancy complexes. Positron annihilation spectroscopy analysis, suggests that dopant deactivation in P-doped Ge and Ge1-xSnx is primarily due to the formation of P-n-V and SnmPn-V clusters. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.
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Corporate Author				Thesis
Publisher		Place of Publication		Editor
Language		Wos	000531473500002	Publication Date	2020-04-27
Series Editor		Series Title		Abbreviated Series Title
Series Volume		Series Issue		Edition
ISSN	2162-8769; 2162-8777	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
Impact Factor	2.2	Times cited		Open Access
Notes	; The imec core CMOS program members, European Commission, the TAKEMI5 ECSEL project, local authorities and the imec pilot line are acknowledged for their support. Air Liquide Advanced Materials is acknowledged for providing advanced precursor gases. A. V. acknowledges his long stay abroad grant and a grant for participation in congress abroad from the Research Foundation-Flanders (Application No. V410518N and K159219N). I. M. acknowledges financial support from Academy of Finland (Project Nos. 285 809, 293 932 and 319 178). CSC-IT Center for Science, Finland is acknowledged for providing the computational resources. ;			Approved	Most recent IF: 2.2; 2020 IF: 1.787
Call Number	UA @ admin @ c:irua:169502			Serial	6607
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