STRUCTURE AND CHEMICAL-COMPOSITION OF BN THIN-FILMS GROWN BY PULSED-LASER DEPOSITION (PLD)

BN thin films are grown on Si(100) substrates in a pulsed-laser deposi tion (PLD) process using a pulsed CO2 laser, a hexagonal-phase BN (h-B N) target, and N-2 as processing gas. The effect of RF power coupled t o the substrate during PLD is investigated. Films are analysed using o ptical microscopy and micro-Raman and X-ray photoemission spectroscopi es. They are generally composed of a fine-grained matrix in which part icles 10-100 mu m in size are embedded, with the morphology and chemic al composition dependent on the lateral position on the film surface r elative to the laser-induced plasma plume from the target. The roughne ss and contaminant concentration (B2O3, elemental B, and boron-oxynitr ide) are largest nearest the plasma-affected region. The matrix materi al over the entire film surface exhibits weak, broad spectral structur es, indicating an amorphous structure. Certain regions have in additio n h-BN Raman peaks that are shifted by up to 15 cm(-1) to lower wave n umbers relative to crystalline h-BN due to strain built in during depo sition. No peaks characteristic of cubic BN or B2O3 are found. Positio ns further from the plasma-affected region show stronger peaks, implyi ng more crystalline order. The highest degree of crystallinity is reac hed for deposition with RF power applied to the substrate mainly durin g the laser pulses, as opposed to deposition with power applied betwee n pulses or to deposition without RF power. In general, embedded parti cles have more intense Raman peaks than the surrounding matrix, compar able in strength to those of the target, suggesting that they arise fr om material ejection.