Thermochromic, threshold switching, and optical properties of Cr-doped VO2 thin films

Zou, Zhaorui; Zhang, Zhenhua; Xu, Jing; Yu, Ziyang; Cheng, Ming; Xiong, Rui; Lu, Zhihong; Liu, Yong; Shi, Jing

doi:10.1016/j.jallcom.2019.07.264

Cited by 28 publications

(19 citation statements)

References 42 publications

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“…1(d). This is consistent with the previous studies of V 1−x Cr x O in which the T c was shifted towards a higher temperature 38,39 . The T c increase of 2 degrees of Cr-VO 2 roughly corresponds to the Cr concentration of ~ 3%, compared to a previous study of…”

Section: Resultssupporting

confidence: 93%

“…Implanted Cr and Co ions can act as dopants and induce structural defects in VO 2 . Previous studies showed that the lattice constants of Crdoped VO 2 increased 37,39 while the T c shifted towards a higher temperature 38,39 . Figure 1 shows the temperaturedependent resistance from the Cr-VO 2 films before and after Cr-ions implantation.…”

Section: Resultsmentioning

confidence: 88%

“…Previous studies reported that the T c values of Cr-added and Co-added VO 2 shifted towards higher and lower temperatures, respectively [37][38][39][40]42 . The T c values of both Cr-and Co-VO 2 films with a flux ≥ 5 × 10 13 ions/ cm 2 shift towards a higher temperature.…”

Section: Discussionmentioning

confidence: 91%

“…Zou and coworkers reported that the width of the hysteresis loop of temperature-dependent resistance for VO 2 was reduced by Cr doping and that the MIT features of VO 2 disappeared at a Cr concentration ratio of 14% 39 . The resistance measurements of the Cr-and Co-VO 2 films show that the MIT characteristics of VO 2 mostly disappear when the flux of Cr and Co ions exceeds 10 15 ions/cm 2 , which corresponds to ~ 50% of the VO 2 cells being hit by implanted ions.…”

Section: Resultsmentioning

confidence: 99%

“…Impurities in VO 2 can modify the band structure, contribute the charge carrier density of the conduction band, disturb the SPT, and interrupt the propagation of electrons. When Cr concentration increased in VO 2 , both lattice constants and structural disorder of V 1−x Cr x O 2 increased, while the T c value moved towards a higher temperature during both heating and cooling 38,39 . This is comparable to the T c behavior of Cr-VO 2 with the ion flux of 5 × 10 13 ions/cm 2 .…”

Section: Discussionmentioning

confidence: 99%

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Decoupling the metal insulator transition and crystal field effects of VO2

Hwang

Park

Yeo

et al. 2021

Sci Rep

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VO2 is a highly correlated electron system which has a metal-to-insulator transition (MIT) with a dramatic change of conductivity accompanied by a first-order structural phase transition (SPT) near room temperature. The origin of the MIT is still controversial and there is ongoing debate over whether an SPT induces the MIT and whether the Tc can be engineered using artificial parameters. We examined the electrical and local structural properties of Cr- and Co-ion implanted VO2 (Cr-VO2 and Co-VO2) films using temperature-dependent resistance and X-ray absorption fine structure (XAFS) measurements at the V K edge. The temperature-dependent electrical resistance measurements of both Cr-VO2 and Co-VO2 films showed sharp MIT features. The Tc values of the Cr-VO2 and Co-VO2 films first decreased and then increased relative to that of pristine VO2 as the ion flux was increased. The pre-edge peak of the V K edge from the Cr-VO2 films with a Cr ion flux ≥ 1013 ions/cm2 showed no temperature-dependent behavior, implying no changes in the local density of states of V 3d t2g and eg orbitals during MIT. Extended XAFS (EXAFS) revealed that implanted Cr and Co ions and their tracks caused a substantial amount of structural disorder and distortion at both vanadium and oxygen sites. The resistance and XAFS measurements revealed that VO2 experiences a sharp MIT when the distance of V–V pairs undergoes an SPT without any transitions in either the VO6 octahedrons or the V 3d t2g and eg states. This indicates that the MIT of VO2 occurs with no changes of the crystal fields.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Decoupling the metal insulator transition and crystal field effects of VO2

Hwang

Park

Yeo

et al. 2021

Sci Rep

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Harnessing the Metal–Insulator Transition of VO₂ in Neuromorphic Computing

et al. 2022

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Future‐generation neuromorphic computing seeks to overcome the limitations of von Neumann architectures by colocating logic and memory functions, thereby emulating the function of neurons and synapses in the human brain. Despite remarkable demonstrations of high‐fidelity neuronal emulation, the predictive design of neuromorphic circuits starting from knowledge of material transformations remains challenging. VO2 is an attractive candidate since it manifests a near‐room‐temperature, discontinuous, and hysteretic metal–insulator transition. The transition provides a nonlinear dynamical response to input signals, as needed to construct neuronal circuit elements. Strategies for tuning the transformation characteristics of VO2 based on modification of material properties, interfacial structure, and field couplings, are discussed. Dynamical modulation of transformation characteristics through in situ processing is discussed as a means of imbuing synaptic function. Mechanistic understanding of site‐selective modification; external, epitaxial, and chemical strain; defect dynamics; and interfacial field coupling in modifying local atomistic structure, the implications therein for electronic structure, and ultimately, the tuning of transformation characteristics, is emphasized. Opportunities are highlighted for inverse design and for using design principles related to thermodynamics and kinetics of electronic transitions learned from VO2 to inform the design of new Mott materials, as well as to go beyond energy‐efficient computation to manifest intelligence.

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