High resolution Hall measurements across the VO2 metal-insulator transition reveal impact of spatial phase separation

Yamin, Tony; Strelniker, Yakov M.; Sharoni, Amos

doi:10.1038/srep19496

Cited by 18 publications

(5 citation statements)

References 53 publications

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“…With thinning, the sheet resistance of the metallic phase increases faster than that in the insulating phase, resulting in the decrease in transition magnitude (Figure b). We extract the beginning and the end of the transition using the Effective-Medium approximation, , taking the transition beginning at 95% of the sample semiconducting and end when 95% is metallic. The transition width and the hysteresis width both increase with thinning, as evidenced in Figure c,d, respectively.…”

Section: Resultsmentioning

confidence: 99%

Ultrathin Films of VO₂ on r-Cut Sapphire Achieved by Postdeposition Etching

Yamin¹,

Wissberg²,

Cohen

et al. 2016

ACS Appl. Mater. Interfaces

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The metal-insulator transition (MIT) properties of correlated oxides thin films, such as VO2, are dramatically affected by strain induced at the interface with the substrate, which usually changes with deposition thickness. For VO2 grown on r-cut sapphire, there is a minimum deposition thickness required for a significant MIT to appear, around 60 nm. We show that in these thicker films an interface layer develops, which accompanies the relaxation of film strain and enhanced electronic transition. If these interface dislocations are stable at room temperature, we conjectured, a new route opens to control thickness of VO2 films by postdeposition thinning of relaxed films, overcoming the need for thickness-dependent strain-engineered substrates. This is possible only if thinning does not alter the films' electronic properties. We find that wet etching in a dilute NaOH solution can effectively thin the VO2 films, which continue to show a significant MIT, even when etched to 10 nm, for which directly deposited films show nearly no transition. The structural and chemical composition were not modified by the etching, but the grain size and film roughness were, which modified the hysteresis width and magnitude of the MIT resistance change.

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Section: Resultsmentioning

confidence: 99%

Ultrathin Films of VO₂ on r-Cut Sapphire Achieved by Postdeposition Etching

Yamin¹,

Wissberg²,

Cohen

et al. 2016

ACS Appl. Mater. Interfaces

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mentioning

confidence: 77%

“…While TL < 335 K, ΔR/Rmax is nearly constant, after which it decreases linearly to zero. Using the effective medium approximation [34] we find that the slope-change point at 335 K roughly coincides with the percolation threshold of the phase separated system.[10]We stress there are fundamental differences between the RRM properties and other memory effects in TMOs. First, it is not of magnetic origin, as opposed to the memory reported in manganite systems or other magnetic-particle systems, as is clear from the fact that VO2 is non-magnetic.…”

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confidence: 99%

Ramp‐Reversal Memory and Phase‐Boundary Scarring in Transition Metal Oxides

et al. 2017

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Transition metal oxides (TMOs) are complex electronic systems which exhibit a multitude of collective phenomena. Two archetypal examples are VO2 and NdNiO3, which undergo a metal-insulator phase-transition (MIT), the origin of which is still under debate. Here we report the discovery of a memory effect in both systems, manifest through an increase of resistance at a specific temperature, which is set by reversing the temperature-ramp from heating to cooling during the MIT. The characteristics of this ramp-reversal memory effect do not coincide with any previously reported history or memory effects in manganites, electronglass or magnetic systems. From a broad range of experimental features, supported by theoretical modelling, we find that the main ingredients for the effect to arise are the spatial Submitted to 22222222224222 phase-separation of metallic and insulating regions during the MIT and the coupling of lattice strain to the local critical temperature of the phase transition. We conclude that the emergent memory effect originates from phase boundaries at the reversal-temperature leaving "scars" in the underlying lattice structure, giving rise to a local increase in the transition temperature.The universality and robustness of the effect shed new light on the MIT in complex oxides.TMOs are a hallmark example of complex electron systems; the competition between charge, spin, strain, lattice, oxidation and other degrees of freedom, having similar energy scales, give rise to numerous collective phenomena [1][2][3] including superconductivity, [4] colossal magnetoresistance [5] and metal-insulator transitions (MIT). [6] In many thin film TMOs which exhibit a temperature (T)-driven phase transition, complexity is manifest through the coexistence of multiple phases where a single phase is expected, [7][8][9][10][11] providing the setting required for emergent phenomena to develop.[1]An intriguing feature found in many of the systems that exhibit the aforementioned phenomena, is the appearance of internal memory, where the system's properties (e.g. resistance or magnetization) depend on the measurement history. Such memory effects appear in various forms and measurement settings, having very different microscopic origins, many of which are still poorly understood. Examples include dynamical memory and slow relaxation in electron-glass systems such as amorphous oxides, [12,13] spatially phase-separated memory in colossal-magnetoresistance manganites, [14] shape-memory in martensitic alloys, [15] and more. [16,17] Here we report the appearance of an unexpected memory effect within the MIT in two prototypical examples of complex TMOs, namely VO2 and NdNiO3 (NNO). The characteristics of the observed effect differ substantially from those of previously reported memory effects, indicating a different microscopic origin.VO2 and NNO both exhibit an MIT, however its features and microscopic origin are quite different. In VO2 the MIT occurs above room temperature, ~340 K, and is accompanied by a structural transition from...

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“…Thus, the Schottky barrier height Φ B can be determined experimentally as E A that begins to deviate from the linearity. This approach can also be used to determine the conduction band edge difference between insulating VO 2 and MoS 2 (Δ E c ) because the band of insulating VO 2 is expected to rarely bend even in contact with MoS 2 and under gating because of the high carrier density of > 10 18 cm –3 and the strongly correlated nature of the carriers in the insulating state. − …”

Section: Resultsmentioning

confidence: 99%

Barrier Formation at the Contacts of Vanadium Dioxide and Transition-Metal Dichalcogenides

Yamamoto

Nouchi

Kanki

et al. 2019

ACS Appl. Mater. Interfaces

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Phase-transition field-effect transistors (FETs) are a class of steep-slope devices that show abrupt on/off switching owing to the metal−insulator transition (MIT) induced in the contacting materials. An important avenue to develop phase-transition FETs is to understand the charge injection mechanism at the junction of the contacting MIT materials and semiconductor channels. Here, toward the realization of high-performance phase-transition FETs, we investigate the contact properties of heterojunctions between semiconducting transition-metal dichalcogenides (TMDCs) and vanadium dioxide (VO 2 ) that undergoes a MIT at a critical temperature (T c ) of approximately 340 K. We fabricated transistors based on molybdenum disulfide (MoS 2 ) and tungsten diselenide (WSe 2 ) in contact with the VO 2 source/drain electrodes. The VO 2 -contacted MoS 2 transistor exhibited n-type transport both below and above T c . Across the MIT, the on-current was observed to increase only by a factor of 5, in contrast to the order-of-magnitude change in the resistance of the VO 2 electrodes, suggesting the existence of high contact resistance. The Arrhenius analyses of the gatedependent drain current confirmed the formation of the interfacial barrier at the VO 2 /MoS 2 contacts, irrespective of the phase state of VO 2 . The VO 2 -contacted WSe 2 transistor showed ambipolar transport, indicating that the Fermi level lies near the mid gap of WSe 2 . These observations provide insights into the contact properties of phase-transition FETs based on VO 2 and TMDCs and suggest the need for contact engineering for high-performance operations.

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High resolution Hall measurements across the VO2 metal-insulator transition reveal impact of spatial phase separation

Cited by 18 publications

References 53 publications

Ultrathin Films of VO₂ on r-Cut Sapphire Achieved by Postdeposition Etching

Ultrathin Films of VO₂ on r-Cut Sapphire Achieved by Postdeposition Etching

Ramp‐Reversal Memory and Phase‐Boundary Scarring in Transition Metal Oxides

Barrier Formation at the Contacts of Vanadium Dioxide and Transition-Metal Dichalcogenides

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High resolution Hall measurements across the VO2 metal-insulator transition reveal impact of spatial phase separation

Cited by 18 publications

References 53 publications

Ultrathin Films of VO2 on r-Cut Sapphire Achieved by Postdeposition Etching

Ultrathin Films of VO2 on r-Cut Sapphire Achieved by Postdeposition Etching

Ramp‐Reversal Memory and Phase‐Boundary Scarring in Transition Metal Oxides

Barrier Formation at the Contacts of Vanadium Dioxide and Transition-Metal Dichalcogenides

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Product

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Ultrathin Films of VO₂ on r-Cut Sapphire Achieved by Postdeposition Etching

Ultrathin Films of VO₂ on r-Cut Sapphire Achieved by Postdeposition Etching