Titanium arsenide thin films were deposited by the atmospheric-pressure chemical vapour deposition (APCVD) of TiCl 4 and tBuAsH 2 at substrate temperatures between 450 and 550°C. The deposited films are typically silver in appearance, demonstrate good adherence and were identified by X-ray powder diffraction as crystalline TiAs. X-ray photoelectron spectroscopy (XPS) and Raman microscopy support
Five titanium arsine compounds have been synthesised via the reaction of TiCl(4) with AsPh(3) (1 : 1 and 1 : 2 equivalents), or one equivalent of Ph(2)AsCH(2)AsPh(2), (t)BuAsH(2) and As(NMe(2))(3). In general, 1 : 1 and 1 : 2 adducts of the type [TiCl(4)(L)(n)] (n = 1, L = AsPh(3), Ph(2)AsCH(2)AsPh(2), and (t)BuAsH(2); n = 2, L = AsPh(3)), were isolated and characterised. However, the reaction of TiCl(4) with As(NMe(2))(3) resulted in a novel exchange between a Cl and an NMe(2) group, yielding the product [TiCl(3)(NMe(2))(mu-NMe(2))(2)AsCl]. The crystal structure of [TiCl(3)(NMe(2))(mu-NMe(2))(2)AsCl] has been determined and showed that the titanium and arsenic atoms are linked via two bridging NMe(2) groups. Additionally, crystal structures for the 1 : 1 and 1 : 2 adducts, [TiCl(4)(AsPh(3))] and [TiCl(4)(AsPh(3))(2)] have been obtained, with Ti-As bond lengths of 2.7465(13) and 2.7238(7) A observed respectively. The decomposition of the compounds has been investigated using thermogravimetric analysis, aerosol-assisted and low pressure chemical vapour deposition.
The compounds tert-butylarsenium(III) tri-μ-chlorido-bis[trichloridotitanium(IV)], (C(4)H(12)As)[Ti(2)Cl(9)] or [(t)BuAsH(3)][Ti(2)(μ-Cl)(3)Cl(6)], (II), and bis[bromidotriphenylarsenium(V)] di-μ-bromido-μ-oxido-bis[tribromidotitanium(IV)], (C(18)H(15)AsBr)(2)[Ti(2)Br(8)O] or [Ph(3)AsBr](2)[Ti(2)(μ-O)(μ-Br)(2)Br(6)], (III), were obtained unexpectedly from the reaction of simple arsane ligands with Ti(IV) halides, with (II) lying on a mirror plane in the unit cell of the space group Pbcm. Both compounds contain a completely novel ion, with [(t)BuAsH(3)](+) constituting the first structurally characterized example of a primary arsenium cation. The oxide-bridged titanium-containing [Ti(2)(μ-O)(μ-Br)(2)Br(6)](2-) dianion in (III) is also novel, while the bromidotriphenylarsenium(V) cation is structurally characterized for only the second time.
Thin films of titanium arsenide have been deposited from the atmospheric pressure chemical vapour deposition (APCVD) of [Ti(NMe(2))(4)] and (t)BuAsH(2) at substrate temperatures between 350-550 °C. Highly reflective, silver coloured films were obtained which showed borderline metallic-semiconductor resistivities. The titanium arsenide films were analyzed by scanning electron microscopy (SEM), Raman spectroscopy, wavelength dispersive analysis of X-rays (WDX), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The films showed variable titanium to arsenic ratios but at substrate temperatures of 500 and 550 °C films with a 1 : 1 ratio of Ti : As, consistent with the composition TiAs, were deposited. Powder XRD showed that all of the films were crystalline and consistent with the formation of TiAs. Both nitrogen and carbon contamination of the films were negligible.
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