Laser photodeposition of molybdenum oxide thin films from organometallic precursors
Thin films of molybdenum oxides, MoO[subscript] X where 2 ≤ x < 3, were prepared on silicon substrates by laser induced chemical vapor deposition. An excimer laser operating at 193 nm was used to dissociate Mo(CO)[subscript]6 in an oxygen containing atmosphere. The dependence of film properties, such as stoichiometry, morphology, and crystallinity, on various deposition parameters, such as substrate temperature, oxygen concentration, laser pulse rate, pulse intensity, and beam orientation, was investigated. Deposited films were analyzed using Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, Auger electron microscopy, and X-ray diffraction. Raman spectra of solid MoO[subscript]2, [gamma]-Mo[subscript]4O[subscript]11, [eta]-Mo[subscript]4O[subscript]11, [alpha]-MoO[subscript]3, and [beta]-MoO[subscript]3 are reported;Polycrystalline thin films (approximately 600 A) of the electrically and optically anisotropic [gamma]-Mo[subscript]4O[subscript]11 compound were deposited on 100°C substrates. On 60°C substrates, powdery MoO[subscript]2 deposits, indicative of a diffusion limited deposition process, were formed. The process was determined to be photolytically initiated in the gas phase, with perpendicular incidence of the laser beam being necessary to form crystalline films. Various steps in the process leading to [gamma]-Mo[subscript]4O[subscript]11 are discussed;Novel apparatus, designed for performing laser photodeposition and thin film Raman spectroscopy, is presented. Alternative organometallic molybdenum compounds, such as Mo( C[subscript]3H[subscript]5)[subscript]4 and Mo[subscript]2( CF[subscript]3CO[subscript]2)[subscript]4, were prepared and evaluated as precursors for laser photodeposition processes.