Effect of Crystallographic Orientation on the Thermal Properties of Free-Standing CVD Diamond Films

The purpose of this study is to prepare CVD diamond films with varying degrees of (110) crystallographic orientation via hot filament chemical vapor deposition (HFCVD), investigate their thermal properties, and explore the influence of crystallographic orientation on thermal performance. Scanning electron microscopy (SEM), X-ray diffraction (XRD), laser Raman spectroscopy, and laser thermal conductivity analysis were employed to characterize the surface morphology, grain size, structural features, and thermal properties of the CVD diamond films. The results revealed a general negative correlation between the (110) crystallographic orientation and thermal conductivity in the CVD diamond films. Specifically, stronger (110) orientation resulted in lower thermal conductivity, which fundamentally depends on grain size and crystallinity. Enhanced (110) orientation promoted secondary nucleation, leading to reduced grain size and degraded thermal conductivity. Additionally, the thermal conductivity was inversely related to the full width at half maximum (FWHM) of the diamond Raman peak. Upon reducing the methane concentration from 3.1% to 2.4%, the negative correlation between (110) orientation and thermal conductivity persisted, while samples with similar crystallographic orientations exhibited a significant improvement in thermal conductivity, ranging from 25.17% to 29.80%.