Article
Materials Science, Multidisciplinary
Benjamin D. Woods, M. A. Eriksson, Robert Joynt, Mark Friesen
Summary: We demonstrate that Ge concentration oscillations in the quantum well region of a Si/SiGe heterostructure can greatly enhance the spin-orbit coupling in the low-energy conduction-band valleys. This enhancement is attributed to Ge concentration oscillations generating wave-function satellite peaks in momentum space, which couple to the opposite valley through Dresselhaus spin-orbit coupling. The improved spin-orbit coupling enables fast spin manipulation in Si quantum dots using electric dipole spin resonance without the need for micro-magnets, with a Rabi frequency S2Rabi/B > 500 MHz/T near the optimal Ge oscillation wavelength lambda = 1.57 nm.
Article
Physics, Applied
Soumyarup Hait, Nanhe Kumar Gupta, Nikita Sharma, Lalit Pandey, Nakul Kumar, Vineet Barwal, Prabhat Kumar, Sujeet Chaudhary
Summary: In this work, the spin pumping phenomenon at the interface between thin tungsten disulphide (WS2) films and Co-2 FeAl (CFA) Heusler alloy films was investigated using ferromagnetic resonance (FMR) measurements. The number of monolayers in the WS2 films was confirmed using Raman spectroscopy, and atomic force microscopy and x-ray reflectivity measurements were used to quantify the smoothness of the grown interfaces as well as the individual layer thicknesses in the heterostructure stacks. The study found that damping enhancement reached about 41% with a monolayer of WS2, and the interfacial effective spin mixing conductance and spin transparency of the WS2/CFA interface were 7.47 +/- 0.97 nm(-2) and 73.35 +/- 9.52%, respectively.
JOURNAL OF APPLIED PHYSICS
(2022)
Review
Chemistry, Multidisciplinary
Wei Tang, Haoliang Liu, Zhe Li, Anlian Pan, Yu-Jia Zeng
Summary: Spin-orbit torque (SOT) plays a crucial role in the electrical manipulation of magnetization in spintronic devices, with van der Waals-layered materials showing promising properties for efficient SOT applications. By converting charge current into spin current, these materials can effectively control magnetization.
Article
Physics, Multidisciplinary
H. Ekmel Ercan, Mark Friesen, S. N. Coppersmith
Summary: The valley degree of freedom in silicon spin qubits presents both challenges and opportunities. It has been shown that there are two distinct triplets, composed of valley and orbital excitations, in the typical operating regime. However, only the valley-excited triplet offers intrinsic protection against charge noise. This protection naturally arises in dots with stronger confinement. These results reveal an inherent advantage for silicon-based multielectron qubits.
PHYSICAL REVIEW LETTERS
(2022)
Article
Chemistry, Physical
Taehyun Kim, Quynh Anh T. Nguyen, Gyu Won Kim, Min Hyeok Lee, Seok In Yoon, Sonny H. Rhim, Young Keun Kim
Summary: Spin-orbit torque (SOT) based magnetization switching is a current area of interest, and we propose a W-Si alloy as a potential spin current-generating layer in nonvolatile embedded memory and logic devices. Experimental results confirm the required properties of the proposed W-Si/CoFeB heterostructures.
APPLIED SURFACE SCIENCE
(2023)
Article
Nanoscience & Nanotechnology
Guoyi Shi, Enlong Liu, Qu Yang, Yakun Liu, Kaiming Cai, Hyunsoo Yang
Summary: The study investigated the spin-orbit torque in PtRh alloy and found that Pt0.9Rh0.1 exhibits high spin torque efficiency and spin Hall conductivity. The critical current density for SOT switching in PtRh alloy decreases as the Rh composition increases.
Article
Engineering, Electrical & Electronic
Taisuke Fujisawa, Atsushi Onogawa, Miki Horiuchi, Yuichi Sano, Chihiro Sakata, Junji Yamanaka, Kosuke O. Hara, Kentarou Sawano, Kiyokazu Nakagawa, Keisuke Arimoto
Summary: In this study, the impact of strain on hole mobility in a strained Si/SiGe/Si(110) heterostructure pMOSFET was investigated. It was found that there is a positive correlation between the hole mobility and the strain of the Si layer, while growth twins and strain relaxation of the SiGe layer in the [110] direction deteriorated the hole mobility. The study also discussed the influence of SiGe layer thickness on the off-state leakage current in pMOSFET operation, and revealed the existence of a current path through the substrate.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Article
Nanoscience & Nanotechnology
Tianli Jin, Gerard Joseph Lim, Han Yin Poh, Shuo Wu, Funan Tan, Wen Siang Lew
Summary: This study proposes a technique to modulate the spin reflection and spin density of states within a heavy-metal Pt through interfacing with a dielectric MgO layer. The researchers demonstrate tunability of the effective out-of-plane spin torque acting on the ferromagnetic Co layer, enabling current-induced SOT magnetization switching without the assistance of an external magnetic field. The influence of the MgO layer thickness on effective SOT efficiency shows saturation at 4 nm, while up to 80% of field-free magnetization switching ratio is achieved with the MgO between 5 and 8 nm. By substituting the dielectric with Ti or Pt, the researchers confirm that the MgO layer is indeed responsible for the observed field-free magnetization switching mechanism.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Physics, Applied
Wenxing Lv, Hongwei Xue, Jialin Cai, Qian Chen, Baoshun Zhang, Zongzhi Zhang, Zhongming Zeng
Summary: Recent studies have shown that two-dimensional transition metal dichalcogenides have the potential to generate strong spin-orbit torques for manipulating magnetic devices. In WTe2/ferromagnet structures, an enhancement of spin-orbit torque efficiency is observed with increasing WTe2 thickness, potentially due to spin absorption at the WTe2/Ta interface and the spin Hall effect.
APPLIED PHYSICS LETTERS
(2021)
Article
Multidisciplinary Sciences
Jan Busa, Michal Pudlak, Rashid Nazmitdinov
Summary: In this study, we analyze the ballistic electron transport through a corrugated graphene system with a curvature-induced spin-orbit interaction. The rippled structure unit is modeled by upward and downward curved surfaces. We consider the cooperative effect of N units connected together on the transmission of electrons incident at arbitrary angles and find the set of optimal angles and corresponding numbers of N units that yield the robust spin inverter phenomenon.
Article
Nanoscience & Nanotechnology
Steve Novakov, Bhakti Jariwala, Nguyen M. Vu, Azimkhan Kozhakhmetov, Joshua A. Robinson, John T. Heron
Summary: Enhanced spin transfer torques from Rashba spin current can be achieved by inserting WSe2 in heterostructures of ferromagnets and transition metal dichalcogenides, without altering the interface polarization.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Quantum Science & Technology
Surya Narayan Panda, Bivas Rana, YoshiChika Otani, Anjan Barman
Summary: This study investigates magnetization dynamics in different NM/Co20Fe60B20 heterostructures using femtosecond pulsed laser-induced time-resolved magneto-optical Kerr effect magnetometry. It is found that the SOC strength of the underlayer has a systematic influence on ultrafast demagnetization time, fast remagnetization time, and the Gilbert damping parameter. The spin pumping formalism estimates that higher SOC strength results in more efficient transport of spin current.
ADVANCED QUANTUM TECHNOLOGIES
(2022)
Article
Chemistry, Multidisciplinary
Sachin Krishnia, Yanis Sassi, Fernando Ajejas, Nicolas Sebe, Nicolas Reyren, Sophie Collin, Thibaud Denneulin, Andras Kovacs, Rafal E. Dunin-Borkowski, Albert Fert, Jean-Marie George, Vincent Cros, Henri Jaffres
Summary: By inserting a nanometer-thin Al metallic layer in Pt|Co|Al|Pt, we demonstrate that a light metal interface profoundly affects the nature of spin-orbit torques and its efficiency in ultrathin Co films. The unexpectedly large H(FL)/H(DL) ratios suggest the existence of a large Rashba interaction at the Co|Al interface, which is not expected from a metallic interface. The occurrence of enhanced torques from an interfacial origin is further validated by demonstrating current-induced magnetization reversal with a significant decrease in the critical current.
Article
Chemistry, Multidisciplinary
Chia-Tse Tai, Po-Yuan Chiu, Chia-You Liu, Hsiang-Shun Kao, C. Thomas Harris, Tzu-Ming Lu, Chi-Ti Hsieh, Shu-Wei Chang, Jiun-Yun Li
Summary: The demonstration of 2D hole gases in GeSn/Ge heterostructures shows a high mobility of up to 20,000 cm(2) V-1 s(-1). The study observed Shubnikov-de Haas oscillations and integer quantum Hall effect, and investigated the Rashba spin-orbit coupling through magneto-transport. Additionally, a transition from weak localization to weak anti-localization was observed, demonstrating the tunability of SOC strength by gating.
ADVANCED MATERIALS
(2021)
Article
Materials Science, Multidisciplinary
Kevin-P. Gradwohl, Chen-Hsun Lu, Yujia Liu, Carsten Richter, Torsten Boeck, Jens Martin, Martin Albrecht
Summary: The formation mechanisms of MD networks in Si/SiGe heterostructures are investigated in this study. The results show that the ratio between the threading dislocation density (TDD) and the average length of MDs remains constant, and the fractal dimension of the MD network can be determined using the box-counting method.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Peng Wu, Tarek Ameen, Huairuo Zhang, Leonid A. Bendersky, Hesameddin Ilatikhameneh, Gerhard Klimeck, Rajib Rahman, Albert V. Davydov, Joerg Appenzeller
Article
Engineering, Electrical & Electronic
Tarek A. Ameen, Hesameddin Ilatikhameneh, Patrick Fay, Alan Seabaugh, Rajib Rahman, Gerhard Klimeck
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2019)
Article
Physics, Applied
Timothy B. Boykin, Prasad Sarangapani, Gerhard Klimeck
JOURNAL OF APPLIED PHYSICS
(2019)
Article
Nanoscience & Nanotechnology
Tingting Shen, Daniel Valencia, Qingxiao Wang, Kuang-Chung Wang, Michael Povolotskyi, Moon J. Kim, Gerhard Klimeck, Zhihong Chen, Joerg Appenzeller
ACS APPLIED MATERIALS & INTERFACES
(2019)
Article
Engineering, Electrical & Electronic
Yuanchen Chu, Shang-Chun Lu, Nadim Chowdhury, Michael Povolotskyi, Gerhard Klimeck, Mohamed Mohamed, Tomas Palacios
IEEE ELECTRON DEVICE LETTERS
(2019)
Article
Physics, Applied
Jana M. Meyer, Jan Scharnetzky, Matthias Berl, Werner Wegscheider, Maik Hauser, Werner Dietsche, Kuang-Chun Wang, Gerhard Klimeck, Lars Tiemann, Robert H. Blick
JOURNAL OF APPLIED PHYSICS
(2019)
Article
Chemistry, Multidisciplinary
Chin-Sheng Pang, Chin-Yi Chen, Tarek Ameen, Shengjiao Zhang, Hesameddin Ilatikhameneh, Rajib Rahman, Gerhard Klimeck, Zhihong Chen
Article
Physics, Applied
Prasad Sarangapani, Yuanchen Chu, James Charles, Gerhard Klimeck, Tillmann Kubis
PHYSICAL REVIEW APPLIED
(2019)
Article
Physics, Applied
Yuanchen Chu, Jingjing Shi, Kai Miao, Yang Zhong, Prasad Sarangapani, Timothy S. Fisher, Gerhard Klimeck, Xiulin Ruan, Tillmann Kubis
APPLIED PHYSICS LETTERS
(2019)
Article
Engineering, Electrical & Electronic
Chin-Yi Chen, Hesameddin Ilatikhameneh, Jun Z. Huang, Gerhard Klimeck, Michael Povolotskyi
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2020)
Article
Engineering, Electrical & Electronic
Chin-Yi Chen, Hsin-Ying Tseng, Hesameddin Ilatikhameneh, Tarek A. Ameen, Gerhard Klimeck, Mark J. Rodwell, Michael Povolotskyi
Summary: The design of THJ-TFETs addresses the low ON-current challenge of TFETs, but faces limitations due to fabrication challenges with respect to device dimensions and material interfaces. The performance of the original THJ-TFET design is improved by engineering the doping profile to boost resonant tunneling efficiency, resulting in better SS and ON-current. Quantum transport simulations are employed to optimize THJ-TFET design in this study, considering the complexity of devices with multiple quantum wells and material interfaces in the tunneling junction.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Nanoscience & Nanotechnology
Wan Sik Hwang, Pei Zhao, Sung Geun Kim, Rusen Yan, Gerhard Klimeck, Alan Seabaugh, Susan K. Fullerton-Shirey, Huili Grace Xing, Debdeep Jena
NPJ 2D MATERIALS AND APPLICATIONS
(2019)
Proceedings Paper
Computer Science, Theory & Methods
Gerhard Klimeck
2019 8TH MEDITERRANEAN CONFERENCE ON EMBEDDED COMPUTING (MECO)
(2019)
Article
Materials Science, Multidisciplinary
Rifat Ferdous, Kok W. Chan, Menno Veldhorst, J. C. C. Hwang, C. H. Yang, Harshad Sahasrabudhe, Gerhard Klimeck, Andrea Morello, Andrew S. Dzurak, Rajib Rahman
Article
Materials Science, Multidisciplinary
Archana Tankasala, Joseph Salfi, Juanita Bocquel, Benoit Voisin, Muhammad Usman, Gerhard Klimeck, Michelle Y. Simmons, Lloyd C. L. Hollenberg, Sven Rogge, Rajib Rahman