Structural properties of polycrystalline diamond films prepared by Hot-filament Chemical Vapour Deposition technique

Abstract

Polycrystalline diamond layers were deposited on silicon substrate using the hot filament chemical vapour deposition (HF-CVD) technique with a mixture of propane-butane/hydrogen as a working gas. The morphology and structural properties were observed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy, respectively. The SEM measurements have executed on films at different process duration. The films showed a pyramid shape with a preferential (111) morphology. The XRD patterns of films exhibited the whole spectra of diamond structure. At filament temperature of 2140°C and 2200°C followed with increasing the gas flow and deposition duration, the reflection peak at (111) is sharp and has a high intensity indicating good crystalline films. The crystalline size of films increased from 50nm to 255nm as process duration is decreased from 34h to 13h and the filament temperature is increased up to 2150°C.

On the other hand, an increase of filament temperature, gas flow rate and process duration to 2200°C, eight sccm, and 42h, respectively, the film showed the smallest crystalline size value of 29 nm among the other samples. The stress values of films were estimated using the Raman spectrum. The films have comparative stress generated during cooling down to room temperature.