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Gallium sulfide (Gas) thin films have been grown at 380-420 "C by atmospheric pressure metal-organic chemical vapor deposition (MOCVD) using the single-source precursors [ (tB~)2-Ga(StBu)]2, [ (tBu)GaS]4, and [(tBu)GaS17. Characterization of the films by X-ray photoelectron spectroscopy (XPS), Rutherford backscattering (RBS), and energy-dispersive X-ray (EDX) analysis shows all the films to be of chemical composition Ga:S (1:l). However, from transmission electron microscopy (TEM) and X-ray diffraction (XRD) the film structure was found to be dependent on the molecular precursor. In the case of films grown from [(tBu)2Ga(StBu)12 deposition results in the formation of the thermodynamic hexagonal phase of Gas. Deposition using [(tBu)GaS14 as the precursor gives a novel metastable face-centered cubic phase of Gas. Use of [(tBu)GaS]7 as the precursor results in amorphous films. The relationship between the molecular precursor and the deposited films is discussed in terms of the possibility of molecular control over solid-state phase synthesis.

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The low-temperature deposition of thin-film materials from molecular precursors has been an area of increasing interest since the first studies by Manasevit over 20 years ago.1,2In principle, metal-organic chemical vapor deposition (MOCVD) offers significant advantages over physical vapor deposition (PVD) methods, for example, simple apparatus, mild process conditions, control over composition, high deposition rates, and possible large scale processing. However, one drawback with the more traditional molecular precursors is that many are toxic and/or pyrophoric. Thus, much effort has been aimed at the development of new stable precursors,3 in particular those containing all the desired elements in a single molecule.

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