Electrical Switching in Semiconductor-Metal Self-Assembled VO2 Disordered Metamaterial Coatings.

Sunil Kumar,Francis Maury,Naoufal Bahlawane

doi:10.1038/srep37699

Abstract

As a strongly correlated metal oxide, VO2 inspires several highly technological applications. The challenging reliable wafer-scale synthesis of high quality polycrystalline VO2 coatings is demonstrated on 4” Si taking advantage of the oxidative sintering of chemically vapor deposited VO2 films. This approach results in films with a semiconductor-metal transition (SMT) quality approaching that of the epitaxial counterpart. SMT occurs with an abrupt electrical resistivity change exceeding three orders of magnitude with a narrow hysteresis width. Spatially resolved infrared and Raman analyses evidence the self-assembly of VO2 disordered metamaterial, compresing monoclinic (M1 and M2) and rutile (R) domains, at the transition temperature region. The M2 mediation of the M1-R transition is spatially confined and related to the localized strain-stabilization of the M2 phase. The presence of the M2 phase is supposed to play a role as a minor semiconducting phase far above the SMT temperature. In terms of application, we show that the VO2 disordered self-assembly of M and R phases is highly stable and can be thermally triggered with high precision using short heating or cooling pulses with adjusted strengths. Such a control enables an accurate and tunable thermal control of the electrical switching.

Highlights

The property of exhibiting phase transitions in strongly correlated metal oxides has opened up new application possibilities
The as-grown films using cyclohexane as a liquid carrier are X-ray diffraction (XRD)-amorphous (Fig. 1a), which contrasts with the crystalline VO2 films obtained with ethanol at this temperature range[23]
Indigenous oxidative sintering approach was implemented in this study to induce an efficient densification of the grown VO2 film

Summary

Introduction

The property of exhibiting phase transitions in strongly correlated metal oxides has opened up new application possibilities. VO2 undergoes a first order phase transition from a highly resistive semiconducting monoclinic (M1) phase to a metallic rutile (R) phase with an effective change of electrical resistivity of 3–4 orders of magnitude within a narrow range of temperature[2,3,4]. VO2 effectively reflects the IR radiation in the high temperature rutile phase while being IR transparent at the low temperature monoclinic phase[5,6,7,8] Such unique combination of properties marks it as a crucial material of study for developing intelligent thermal, resistive and optical switches[9,10,11,12,13,14,15], and from the fundamental point of view. The investigation of the electrical and optical properties across the SMT reveals the self-assembly of a VO2–disordered metamaterial in which the coalescence and confinement of metallic domains are highly controllable

Methods

Results

Conclusion