MOCVD of Vanadium Oxide Films with a Novel Vanadium(III) Precursor

Abstract

Vanadium forms several oxides with a wide variety of properties and technological applications in the fields of catalysis, solid-state batteries, electrochromic devices, and infrared modulators. [1][2][3][4] The ability of vanadium atoms to possess multiple oxidation states, and the facile conversion between oxides of different stoichiometry, makes the synthesis of pure vanadium oxide phases complicated. [5,6] Divanadium pentaoxide (V 2 O 5 ) and vanadium dioxide (VO 2 ) are the two main oxide phases, and several chemical and physical methods have been used to obtain such oxides. [6][7][8][9][10][11] Among vapor phase techniques CVD offers the opportunity of preparing metal oxide films with good quality and uniformity. [6,9,12] In the CVD of vanadium oxide, VO [16] The best synthetic way consisted in reacting VCl 3 Ã 3THF with Na(OCMe 2-CH 2 OMe) in THF, prepared in-situ from the corresponding alcohol MeOCH 2 CMe 2 OH and Na, at a temperature below À78 8C. After the work-up, a 20% yield of pure [V(OCMe 2-CH 2 OMe) 3 ], as a violet oil, was recovered by sublimation. The complex was characterized by elemental analysis and electron impact mass spectrometry (EIMS).The EI spectrum (see Table 1) is characterized by the presence of the molecular peak M þ (m/z ¼ 360) in 12% relative abundance.The structure of the alcohol, which allows both chelation with the metal and transfers of part of the molecule to the metal, and the presence of the electron-donating methoxy groups, help in stabilizing different ions; the most abundant ions corresponding to species orginated by the loss of at least one alkoxide group.The peaks at 315 m/z (rel. abun. 33%) and at 257 m/z (rel. abun. 97%) can be easily ascribed to the species The other quite abundant peaks at 140 m/z (rel. abun. 88%) and 125 m/z (rel. abun. 95%) are from fragments which contain only part of an alkoxide group; it is reasonable to suppose that, like most of the fragments, they keep a VO 2 core, which is promising for the deposistion of VO x of the desired stoichiometry. We tentatively suggest that the ion at 140 m/z is a radical cationic hydroxy species with the formula [V(OH)OC 4 H 7 ] þ , and the ion at 125 m/z is a vanadyl species with the formula [V(O)OC 3 H 6 ] þ . The second part of the work consisted of using the complex as the precursor for the MOCVD of vanadium oxide films by means of a horizontal, hot-wall reactor set at 550 8C, and using N 2 as the carrier gas and a mixture of O 2 and H 2 O as the reactant gas.First, by setting the flow rate of the reactant gas at 400 sccm we were able to grow vanadium dioxide on Si(100) (sample A) and on fused silica glass substrates (sample A 0 ) in the same run; sample A, which was closer to the entrance

Vanadium Oxide Compounds: Structure, Properties, and Growth from the Gas Phase

“…[173,174] This crystalline phase was also observed as a dominant structure using PECVD at 207-72°C starting from VO(O i Pr) 3 under oxygen-rich conditions. [175] Crociani et al [176] have investigated V(O-C-(CH 3 ) 2 CH 2 OCH 3 ) 3 and reported the possibility of growing either VO 2 or V 2 O 5 at 550°C via a fine adjustment of the oxygen/water ratio as the reactant gas. The CVD of V 2 O 5 was reported starting from VO(OC 2 H 5 ) 3 , [177,178] and VO(OC 3 H 7 ) 3 resulting in the growth of V 2 O 5 and V 6 O 13 thin films at 350-00°C.…”

“…Crociani et al have investigated V(O‐C(CH 3 ) 2 CH 2 OCH 3 ) 3 and reported the possibility of growing either VO 2 or V 2 O 5 at 550°C via a fine adjustment of the oxygen/water ratio as the reactant gas. The CVD of V 2 O 5 was reported starting from VO(OC 2 H 5 ) 3 , and VO(OC 3 H 7 ) 3 resulting in the growth of V 2 O 5 and V 6 O 13 thin films at 350–00°C …”

Synthesis of vanadium oxide films with controlled morphologies: Impact on the metal-insulator transition behaviour

“…The growth of single phase VO 2 remains a challenge due to the fact that a number of stable phases of vanadium oxides could form in a narrow range of composition, thus, requiring a strict control on growth conditions for obtaining a single pure phase of VO 2 . Various types of thin film deposition techniques have been employed for VO 2 film synthesis like pulsed laser deposition (PLD) , molecular beam epitaxy (MBE) , magnetron sputtering , chemical vapour deposition (CVD) , sol–gel processing and atomic layer deposition . In this study, we use direct liquid injection–metal organic chemical vapour deposition (DLI–MOCVD) and a single source precursor to grow VO 2 films of varying thickness and microstructure.…”

Phase identification of vanadium oxide thin films prepared by atomic layer deposition using X-ray absorption spectroscopy

“…Several thin lm growth techniques, such as molecular beam epitaxy, 16 sputtering, 17 pulsed laser deposition, 18 electrodeposition, chemical vapor deposition, 19 and atomic layer deposition (ALD) 4 have been used to deposit VO x thin lms with different stoichiometries. ALD is a proven, extraordinarily controllable thin lm deposition technique with great features, including atomically precise lm thicknesses due to self-limiting reactions, uniform and conformal growth over large areas as well as over three-dimensional structures, pinhole free morphologies, and high reproducibility.…”