CHEMICAL-VAPOR-DEPOSITION OF GALLIUM SULFIDE - PHASE-CONTROL BY MOLECULAR DESIGN

Gallium sulfide (GaS) thin films have been grown at 380-420-degrees-C by atmospheric pressure metal-organic chemical vapor deposition (MOCVD) using the single-source precursors [(tBu)2-Ga(StBu)]2, [(tBu)GaS]4, and [(tBu)GaS]7. 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(1:1). 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)]2 deposition results in the formation of the thermodynamic hexagonal phase of GaS. Deposition using [(tBu)GaS]4 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.