On epitaxial growth of diamond films on (100) silicon substrates

We have investigated characteristics of polycrystalline diamond thin films formed by plasma-enhanced chemical vapor deposition method on silicon substrates using Raman spectroscopy, analytical and high-resolution transmission electron microscopy techniques. Grains with average size 1 μm in diameter were observed in these films. The Raman spectra from these films contain the strongest peak at 1335 cm−1, providing the characteristic signature for sp3 (diamond) bonding. The broad peak centered around 1550 cm−1 is believed to be due to some graphitic bonding. From detailed high-resolution images and microdiffraction, films were characterized to be cubic diamond with a lattice parameter of 3.56 Å. Diamond crystallites with fivefold external morphologies were also observed. The large crystallites in the films exhibited preferential texture in 〈011〉 type orientations. These crystallites were found to be twinned in {111} planes. The large 〈011〉 crystallites exhibited matching in {111} or {200} lattice planes of diamond with {022} planes of silicon. This is in agreement with our previous work on the growth of Ni on MgO, which showed that textured growth can occur by matching a set of lattice planes in the absence of matching of lattice constants.