ABSTRACT
Aerosol-assisted chemical vapour deposition of substituted polyoxometalates H4 [PMo11 VO40 ], H7 [PMo8 V4 O40 ], [nBu4 N]4 [PVW11 O40 ] and [nBu4 N]5 [PV2 W10 O40 ] resulted in the formation of vanadium-doped metal oxide thin films. Depositions were carried out at 550 °C in methanol or acetonitrile for the POMs that contained molybdenum or tungsten, respectively. The as-deposited films were X-ray amorphous and relatively non-adherent. However, on annealing in air at 600 °C, decolourised translucent films that were more mechanically robust were obtained. Films deposited from H4 [PMo11 VO40 ] and H7 [PMo8 V4 O40 ] consisted of V-doped MoO3 in the orthorhombic phase and films from [nBu4 N]4 [PVW11 O40 ] and [nBu4 N]5 [PV2 W10 O40 ] comprised of monoclinic V-doped WO3 . All films were fully characterised by using X-ray photoelectron spectroscopy, energy-dispersive X-ray diffraction, scanning electron microscopy and UV/Vis spectroscopy.
ABSTRACT
Thin films of ceria (CeO(2)) have many applications, and their synthesis by liquid-injection MOCVD (metal-organic chemical vapor deposition) or ALD (atomic layer deposition) requires volatile precursor compounds. Here we report the synthesis of a series of homoleptic and heteroleptic Ce(IV) complexes with donor-functionalized alkoxide ligands mmp (1-methoxy-2-methylpropan-2-olate), dmap (1-(dimethylamino)propan-2-olate), and dmop (2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)propan-2-olate) and their potential as precursors for MOCVD and ALD of CeO(2). New complexes were synthesized by alcohol exchange reactions with [Ce(OBu(t))(4)]. [Ce(mmp)(4)] and [Ce(dmap)(4)] were both found to be excellent precursors for liquid-injection MOCVD of CeO(2), depositing high purity thin films with very low carbon contamination, and both have a large temperature window for diffusion controlled growth (350-600 °C for [Ce(mmp)(4)]; 300-600 °C for [Ce(dmap)(4)]). [Ce(mmp)(4)] is also an excellent precursor for liquid-injection ALD of CeO(2) using H(2)O as oxygen source and demonstrates self-limiting growth from 150 to 350 °C. [Ce(dmap)(4)] has lower thermal stability than [Ce(mmp)(4)] and does not show self-limiting growth in ALD. Heteroleptic complexes show a tendency to undergo ligand redistribution reactions to form mixtures in solution and are unsuitable as precursors for liquid-injection CVD.
ABSTRACT
Thin films of tungsten carbonitride have been formed on glass by low-pressure chemical vapour deposition (LP)CVD at 550 degrees C from four closely related precursors: [W(mu-N(t)Bu)(N(t)Bu)Cl(2)(H(2)N(t)Bu)](2), [W(N(t)Bu)(2)Cl(2)(TMEDA)] (TMEDA = N,N,N',N'-tetramethylethylenediamine), [W(N(t)Bu)(2)Cl(2)(py)(2)] (py = pyridine) and [W(N(t)Bu)(2)Cl(N{SiMe(3)}(2))]. The grey mirror-like films were grown with a nitrogen or ammonia bleed gas. In all cases the chlorine content of the deposited films was less than 1 at% and the oxygen content of the films was lower for those grown using ammonia. Surprisingly, the use of ammonia did not significantly change the carbon content of the resulting films. Despite the coordination environment around the metal being essentially the same and the materials having a comparable volatility, some differences in film quality were observed. The films were uniform, adhesive, abrasion resistant, conformal and hard, being resistant to scratching with a steel scalpel. X-Ray powder diffraction patterns of all the films showed the formation of beta-WN(x)C(y). As a comparison the aerosol-assisted chemical vapour deposition (AA)CVD of [W(mu-N(t)Bu)(N(t)Bu)Cl(2)(H(2)N(t)Bu)](2) was investigated and amorphous tungsten carbonitride films were deposited.
ABSTRACT
The reaction of Me3In and ROH (R = CH2CH2NMe2, CH(CH3)CH2NMe2, C(CH3)2CH2OMe, CH2CH2OMe) in toluene under aerosol assisted chemical vapor deposition (AACVD) conditions leads to the production of indium oxide thin films on glass. The indium oxide films were deposited at 550 degrees C and analyzed by scanning electron microscopy (SEM), X-ray powder diffraction, wavelength dispersive analysis of X-rays (WDX), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. This CVD technique offers a rapid, convenient route to In2O3, which presumably involves the in situ formation of dimethylindium alkoxides, of the type [Me2InOR]2. In order to identify compounds present in the aerosol mist, the solution-phase reaction between Me3In and ROH (R = CH2CH2NMe2, C(CH3)2CH2OMe, CH(CH3)CH2NMe2, CH(CH2NMe2)2) at room temperature in toluene was carried out. Dimeric indium alkoxides, of the type [Me2In(OR)]2, were isolated, and their structures were determined by X-ray crystallography.
