Diamond nucleation and growth on horizontally and vertically aligned Si substrates at low pressure in a linear antenna microwave plasma system

In this work, the spontaneous nucleation and early stages of diamond growth in a linear antenna microwave plasma reactor on horizontally (HorS) and vertically (VerS) aligned non-treated and seeded silicon substrates are studied for different deposition durations (5 and 10 h) and gas mixtures. Diamond growth is initiated using a CH4/H-2/CO2 gas mixture with varying hydrogen content at low pressure (10 Pa). The scanning electron microscope and atomic force microscope images reveal variation in the topographical properties of samples depending on the sample alignment and z-position on VerS. Independently of the deposition conditions, the grain size and density (for non-treated samples) and film thickness (for seeded samples) decreases in the downward direction as the measured position is farther from the plasma source. The grain population exhibits polymodal size (width and height) distribution for both vertical and horizontal alignments. Moreover, for both non-treated and seeded samples the density and size of diamond grains as well as the diamond film thickness grown on HorS are similar to the size/density/thickness on VerS at a specific z-position (1 cm higher in the z-axis).