Chemical synthesis of high quality epitaxial vanadium dioxide films with sharp electrical and optical switch properties

Abstract

The effective preparation method of epitaxial VO2 films on the r-Al2O3 substrates based on the MOCVD technique and postdeposition annealing is described. The composition, orientation and morphology of the films obtained were investigated by Raman spectroscopy, XRD, EBSD, XPS, SEM and AFM methods. The samples obtained demonstrate high crystal quality and excellent physical properties: sharp metal-insulator (>10 4 resistance change) and intensive optical reflectivity (IR and THz regions) transitions. The model of VO2 films recrystallization based on the peritectic decomposition of intergrain vanadium oxide phases is proposed.The new effective chemical synthesis of the epitaxial VO 2 films with record electrical and optical switch properties is presented.

Growth without Postannealing of Monoclinic VO2 Thin Film by Atomic Layer Deposition Using VCl4 as Precursor

“…The V and O concentrations of VO 2 film are about 25.7 at.% and 74.3 at.%, respectively, for the film before surface etching and are about 33.1 at.% and 66.9 at.%, respectively, for the film after surface etching. The results clearly indicate that the original surface of the VO 2 film has a higher oxygen concentration because the VO 2 film was exposed to air (oxygen-rich) environment, resulting in absorption of oxygen and a native oxide layer (overoxidation layer) forming on the surface of the VO 2 film [26,33,34,39,41,43,57,58]. After argon-ion etching, surface contamination and the native oxide layer of the VO 2 film had been removed, and the atomic proportion of V:O atom was about 1:2 in agreement with the stoichiometry of VO 2 .…”

“…Various techniques had been employed for preparing VO 2 films, including the sol-gel method [22,23], electron-beam evaporation [25,26], sputtering [5,17], pulsed laser deposition (PLD) [27,28], molecular beam epitaxy (MBE) [16,29], chemical vapor deposition (CVD) [30][31][32][33][34], and atomic layer deposition (ALD) [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. Among them, ALD is an excellent technique which has drawn much attention due to its many advantages, including preparation of the highly conformal thin films with almost 100% step coverage, accurate control of film thickness at the atomic scale, low growth temperature, and wide-area uniformity.…”

Phase‐selective Route to V‐O Film Formation: A Systematic MOCVD Study Into the Effects of Deposition Temperature on Structure and Morphology

“…Various precursors have been applied for the MOCVD approach: i) β ‐diketonates such as vanadium tri‐acetylacetonate [V(acac) 3 ], vanadyl bis‐acetylacetonate [VO(acac) 2 ], vanadyl bis‐hexafluoroacetylacetonate [VO(hfa) 2 ]; ii) alkoxides such as vanadyl tri‐isopropoxide [VO(O i Pr) 3 ], or vanadyl ethoxide [VO(OC 2 H 5 ) 3 ] . Nevertheless, all these studies have focused on a strict temperature range, while, to our knowledge, no reports are present in the literature investigating the effect of deposition temperature in stabilizing V‐O phases in a systematic MOCVD study keeping constant all the other deposition parameters.…”

Crystallization and inter-diffusional behaviors in the formation of VO2(B) thin film with layered W-doping

“…VO 2 structures could be in three polymorphic allotropic phases: M-phase (monoclinic), R-phase (rutile), and B-phase (monoclinic). The low-temperature semiconductor M-phase undergoes a phase transition to high-temperature metallic R-phase at about 68 ℃ [5],  which brings dramatic changes in electrical and optical characteristics, and hence higher TCR values [6][7][8]. However, the narrow transition range and high 1/f noise make it inconvenient in practical use [8,9].…”