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Author |
Sethu, K.K.V.; Ghosh, S.; Couet, S.; Swerts, J.; Sorée, B.; De Boeck, J.; Kar, G.S.; Garello, K. |
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Title |
Optimization of tungsten beta-phase window for spin-orbit-torque magnetic random-access memory |
Type |
A1 Journal article |
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Year  |
2021 |
Publication |
Physical Review Applied |
Abbreviated Journal |
Phys Rev Appl |
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Volume |
16 |
Issue |
6 |
Pages |
064009 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Switching induced by spin-orbit torque (SOT) is being vigorously explored, as it allows the control of magnetization using an in-plane current, which enables a three-terminal magnetic-tunnel-junction geometry with isolated read and write paths. This significantly improves the device endurance and the read stability, and allows reliable subnanosecond switching. Tungsten in the beta phase, beta-W, has the largest reported antidamping SOT charge-to-spin conversion ratio (theta(AD) approximate to -60%) for heavy metals. However, beta-W has a limitation when one is aiming for reliable technology integration: the beta phase is limited to a thickness of a few nanometers and enters the alpha phase above 4 nm in our samples when industry-relevant deposition tools are used. Here, we report our approach to extending the range of beta-W, while simultaneously improving the SOT efficiency by introducing N and O doping of W. Resistivity and XRD measurements confirm the extension of the beta phase from 4 nm to more than 10 nm, and transport characterization shows an effective SOT efficiency larger than -44.4% (reaching approximately -60% for the bulk contribution). In addition, we demonstrate the possibility of controlling and enhancing the perpendicular magnetic anisotropy of a storage layer (Co-Fe-B). Further, we integrate the optimized W(O, N) into SOT magnetic random-access memory (SOT-MRAM) devices and project that, for the same thickness of SOT material, the switching current decreases by 25% in optimized W(O, N) compared with our standard W. Our results open the path to using and further optimizing W for integration of SOT-MRAM technology. |
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Wos |
000729005800002 |
Publication Date |
2021-12-03 |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2331-7019 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
4.808 |
Times cited |
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Open Access |
Not_Open_Access |
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Notes |
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Approved |
Most recent IF: 4.808 |
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Call Number |
UA @ admin @ c:irua:184832 |
Serial |
7007 |
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Author |
Sankaran, K.; Swerts, J.; Carpenter, R.; Couet, S.; Garello, K.; Evans, R.F.L.; Rao, S.; Kim, W.; Kundu, S.; Crotti, D.; Kar, G.S.; Pourtois, G. |
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Title |
Evidence of magnetostrictive effects on STT-MRAM performance by atomistic and spin modeling |
Type |
P1 Proceeding |
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Year |
2018 |
Publication |
2018 Ieee International Electron Devices Meeting (iedm) |
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Pages |
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Keywords |
P1 Proceeding; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Abstract |
For the first time, we demonstrate, using an atomistic description of a 30nm diameter spin-transfer-torque magnetic random access memories (STT-MRAM), that the difference in mechanical properties of its sub-nanometer layers induces a high compressive strain in the magnetic tunnel junction (MTJ) and leads to a detrimental magnetostrictive effect. Our model explains the issues met in engineering the electrical and magnetic performances in scaled STT-MRAM devices. The resulting high compressive strain built in the stack, particularly in the MgO tunnel barrier (t-MgO), and its associated non-uniform atomic displacements, impacts on the quality of the MTJ interface and leads to strain relieve mechanisms such as surface roughness and adhesion issues. We illustrate that the strain gradient induced by the different materials and their thicknesses in the stacks has a negative impact on the tunnel magneto-resistance (TMR), on the magnetic nucleation process and on the STT-MRAM performance. |
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Wos |
000459882300147 |
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ISSN |
978-1-72811-987-8; 978-1-72811-987-8 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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no |
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Call Number |
UA @ admin @ c:irua:158694 |
Serial |
7942 |
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Author |
Sankaran, K.; Swerts, J.; Couet, S.; Stokbro, K.; Pourtois, G. |
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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 |
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Year |
2016 |
Publication |
Physical review B |
Abbreviated Journal |
Phys Rev B |
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Volume |
94 |
Issue |
94 |
Pages |
094424 |
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Keywords |
A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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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. |
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Wos |
000383860700004 |
Publication Date |
2016-09-20 |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9950;2469-9969; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
3.836 |
Times cited |
4 |
Open Access |
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Notes |
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Approved |
Most recent IF: 3.836 |
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Call Number |
UA @ lucian @ c:irua:137122 |
Serial |
4468 |
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Author |
Quan Manh, P.; Pourtois, G.; Swerts, J.; Pierloot, K.; Delabie, A. |
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Title |
Atomic layer deposition of Ruthenium on Ruthenium surfaces : a theoretical study |
Type |
A1 Journal article |
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Year |
2015 |
Publication |
The journal of physical chemistry: C : nanomaterials and interfaces |
Abbreviated Journal |
J Phys Chem C |
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Volume |
119 |
Issue |
119 |
Pages |
6592-6603 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Abstract |
Atomic, layer deposition,(ALD of ruthenium using two ruthenium precursors, i.e., Ru(C5H5)(2) (RuCp2) and Ru(C5H5)(C4H4N) (RuCpPy), is studied using density functional theory. By investigating the reaction mechanisms On bare ruthenium surfaces, i.e., (001), (101), and (100), and H-terminated surfaces, an atomistic insight in the Ru ALD is provided. The calculated results show that on the Ru surfaces both RuCp2 and RuCpPy an undergo dehydrogenation and ligand dissociation reactions. RuCpPy is more reactive than RuCp2. By forming a, strong, bond between N of Py and Ru of the surface, RuCpPy can easily chemisorb on the surfaces. The reactions of RuCp2,On the Surfaces are less favorable the adsorption is not strong enough This could be a,factor contributing to the higher growth-per-cycle of Ru using RuCpPy, as observed experimentally. By Studying, the adsorption on H-terminated Ru surfaces, We showed that H Can prevent the adsorption of the precursors, thus inhibiting the growth of Ru. Our calculations indicate that the H content on the surface can have an impact on the growth-per-cycle. Finally, our simulations also demonstrate large impacts of the surface structure on the reaction mechanisms. Of the three surfaces, the (100) surface, which is the less stable and has a zigzag surface structure, is also the most reactive one. |
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Place of Publication |
Washington, D.C. |
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Wos |
000351970800015 |
Publication Date |
2015-03-04 |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1932-7447;1932-7455; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
4.536 |
Times cited |
10 |
Open Access |
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Notes |
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Approved |
Most recent IF: 4.536; 2015 IF: 4.772 |
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Call Number |
c:irua:125544 |
Serial |
171 |
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Author |
Phung, Q.M.; Vancoillie, S.; Pourtois, G.; Swerts, J.; Pierloot, K.; Delabie, A. |
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Title |
Atomic layer deposition of ruthenium on a titanium nitride surface : a density functional theory study |
Type |
A1 Journal article |
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Year |
2013 |
Publication |
The journal of physical chemistry: C : nanomaterials and interfaces |
Abbreviated Journal |
J Phys Chem C |
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Volume |
117 |
Issue |
38 |
Pages |
19442-19453 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Abstract |
Because of its excellent properties in nanotechnology applications, atomic layer deposition of ruthenium (Ru) has been the subject of numerous experimental studies. Recently, two different Ru precursors were compared for plasma-enhanced atomic layer deposition (PEALD) of Ru, and their reactivity was found to be different. Inhibition was observed for bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)(2)), while nearly linear growth behavior was observed for (methylcyclopentadienyl-pyrrolyl)ruthenium (Ru(MeCp)Py). To understand this difference in reactivity, we investigate the adsorption of RuCp, and RuCpPy (i.e., without substituents) on a TiN surface using calculations based on periodic boundary conditions density functional theory (DFT) combined with experiments based on Rutherford backscattering spectroscopy (RBS). The calculations demonstrate that the RuCpPy precursor chemisorbs on the TiN(100) surface while the RuCp2 precursor only physisorbs. We propose a reaction mechanism for the chemisorption of RuCpPy. The area density of the calculated RuCpPy surface species is compared with the experimental values from RBS. The impact of a H-plasma is also investigated. The DFT calculations and experimental results from RBS provide insight into the adsorption processes of the RuCpPy and RuCp2 precursors on the TiN(100) surface. |
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Place of Publication |
Washington, D.C. |
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Wos |
000330162500022 |
Publication Date |
2013-08-28 |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1932-7447;1932-7455; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
4.536 |
Times cited |
6 |
Open Access |
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Notes |
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Approved |
Most recent IF: 4.536; 2013 IF: 4.835 |
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Call Number |
UA @ lucian @ c:irua:114855 |
Serial |
170 |
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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. |
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Title |
Determination of ultimate leakage through rutile TiO2 and tetragonal ZrO2 from ab initio complex band calculations |
Type |
A1 Journal article |
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Year |
2013 |
Publication |
IEEE electron device letters |
Abbreviated Journal |
Ieee Electr Device L |
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Volume |
34 |
Issue |
3 |
Pages |
402-404 |
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Keywords |
A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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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. |
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Wos |
000315723000024 |
Publication Date |
2013-01-31 |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0741-3106;1558-0563; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
3.048 |
Times cited |
3 |
Open Access |
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Notes |
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Approved |
Most recent IF: 3.048; 2013 IF: 3.023 |
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Call Number |
UA @ lucian @ c:irua:108295 |
Serial |
680 |
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Author |
Dobrynin, A.N.; Ievlev, D.N.; Verschoren, G.; Swerts, J.; van Bael, M.J.; Temst, K.; Lievens, P.; Piscopiello, E.; Van Tendeloo, G.; Zhou, S.Q.; Vantomme, A. |
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Title |
Atomic-scale modification of hybrid FePt cluster-assembled films |
Type |
A1 Journal article |
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Year |
2006 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
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Volume |
73 |
Issue |
10 |
Pages |
104421,1-8 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Place of Publication |
Lancaster, Pa |
Editor |
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Wos |
000236467200069 |
Publication Date |
2006-06-10 |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1098-0121;1550-235X; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
3.836 |
Times cited |
13 |
Open Access |
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Notes |
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Approved |
Most recent IF: 3.836; 2006 IF: 3.107 |
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Call Number |
UA @ lucian @ c:irua:57736 |
Serial |
187 |
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