Material synthesis by the transformation of organometallic compounds (precursors) by vapor deposition techniques such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) has been in the forefront of modern day research and development of new materials. There exists a need for new routes for designing and synthesizing new precursors as well as the application of established molecular precursors to derive tuneable materials for technological demands. With regard to the precursor chemistry, a most detailed understanding of the mechanistic complexity of materials formation from molecular precursors is very important for further development of new processes and advanced materials. To emphasize and stimulate research in these areas, this volume comprises a selection of case studies covering various key-aspects of the interplay of precursor chemistry with the process conditions of materials formation, particularly looking at the similarities and differences of CVD, ALD and nanoparticle synthesis, e.g. colloid chemistry, involving tailored molecular precursors.

Cyclic molecular systems of the type, A(XX')B(YY')n (where A, B = Al, N or Si, C; X, X', Y, Y'= 11, CH3, etc. and n 2 and 3), were studied as potential single-source precursors for the CVD of AlN and SiC films. These compounds provide the required elements for die product film already covalently bound to one another in a single, volatile molecular source and, in the case of the SiC precursors (where n = 2), they contain built-in ring-strain energy to lower the decomposition onset temperature. Efforts have included the study of the (CH3)2AlNH23 --> AIN CVD system by mass-spectrometric/time-of-flight measurements and the investigation of substituted disilacyclobutanes as single- source SiC precursors. The mass-spec/-TOF studies have indicated that a slow decomposition of the (CH3)2AlNH23 (I) precursor to produce methane and a series of higher oligomeric products occurs during its vaporization at 75-100 deg C. These oligomeric species are believed to be intermediates formed in the gas- phase thermal decomposition of I to AlN. This precursor was used to deposit high quality AlN films up to 2 micrometers thick on Si and sapphire substrates in a LPCVD apparatus and is being tested for use in the deposition of AlN interface layers in A1203-reinforced metal matrix composites. Disilacyclobutane, SiH2CH22, was found to yield stoichiometric, crack-free, adherent, polycrystalline SiC films on Si (100) and Si (111) surfaces by LPCVD at temperatures as low as 690 OC. Chemical vapor deposition (CVD), AIN, SiC, Organometallic precursor.

Various routes towards novel chlorogallium bis(alkoxides) and heteroleptic gallium alkoxides have been investigated. Compounds of the type, [GaCl(OR2)2] and [Ga(OR2)2(OR')] (R = CH2CH2NMe2, CH2CH2NEt2, CH2CH2CH2NMe2; R' = Me, Et, iPr, tBu), were synthesised using air sensitive methods and analysed by a variety of techniques. The chlorogallium bis(alkoxides) showed diastereotopic NMR splitting and in depth 1H NMR studies and DFT calculations were carried out on [GaCl(OCH2CH2CH2NMe2)2] to investigate the in situ ring conversion mechanism. Thermogravimetric analysis was employed to study the decomposition characteristics of the compounds, which were then used as single-source precursors towards gallium oxide thin films using aerosol-assisted chemical vapour deposition (AACVD). Amorphous, transparent films of Ga2O3 were deposited at 450 °C onto glass and quartz substrates. Subsequent annealing at 1000 °C gave crystalline films. Nitrogen-doped indium oxide films were deposited by AACVD via the in situ reaction of [In{NtBu(SiMe3)}3] and three equivalents of HOCH2CH2NMe2. The resultant films had a range of morphologies depending on solvent and temperature employed during the deposition. The cubic phase In2O3 films deposited had band gaps of ~2.9 eV suggesting nitrogen incorporation. These films were tested on steel and titanium substrates for their visible light water-splitting properties. Films were tested for their hydrogen production but limited activity as a photocatalyst was observed in the visible region. However, In2O3 nanoparticles produced using a solvothermal method and Ti- and Ta-doped In2O3 thin films grown via AACVD were tested for their gas sensing properties. Sensors were tested against reducing oxidising gases. The In2O3 nanoparticles showed the highest response to all gases, in particular ethanol. In2O3:Ta also showed a significant response to ethanol and smaller responses to other gases. Overall, novel precursors have been used as single-source precursors to main group oxide thin films, which were deposited via AACVD. Photocatalytic and gas sensing applications of these films have been explored.

Molecular engineering of ternary single source precursors based on the [{PBu3}2Cu(SR')2In(SR')2] architecture have afforded the first liquid CIS ternary single source precursors (when R = Et, n-Pr), which are suitable for low temperature deposition (