X-ray photoelectron spectroscopy of initial stages of nucleation and growth of diamond thin films during plasma assisted chemical vapor deposition

Abstract

We have carried out x-ray photoelectron spectroscopy on diamond thin films deposited by microwave assisted chemical vapor deposition technique using a H2-CH4 plasma. Films grown for different lengths of time, from 1 min to several hours, were analyzed for the surface composition in the C 1s and Si 2p regions. The results indicate the presence of SiC in the initial stage of nucleation due to the carbon interaction with the Si substrate. Graphite starts to form in early stages of nucleation as the substrate becomes supersaturated with carbon. A diamond peak starts to appear after the incubation period and a simultaneous decrease in the carbide and graphite peak intensities was observed. Graphite is preferentially etched during the growth but SiC remains as an impurity even after several hours of deposition.

Studies on nucleation process in diamond CVD: an overview of recent developments

“…The deposit subsequently disappeared, and the final deposit contained only polycrystalline diamond. Several other experiments on Ni and Pt in HFCVD [17], on Si [19] and Cu [32,34,62] in MW PACVD have also provided direct evidence for the formation of graphite on the substrates prior to diamond nucleation. It was found that the graphite film formed initially on the substrate surface greatly enhanced diamond nucleation [32,34].…”

“…Volmer-Weber 3-D island growth [58] is the mode of nucleation and growth of polycrystalline diamond films directly on non-diamond substrates due to the highest surface energies of diamond among any known materials (see Tables 3 and 4 Diamond nucleation on non-diamond substrates is generally proposed to occur mostly on an intermediate layer of diamond-like amorphous carbon [9][10][11]30,35,61], metal carbides [12,14,16,22,23,25,28,29,40,[62][63][64][65][66][67][68][69][70], or graphite [13,17,19,32,34,62,71] formed at the substrate surface due to chemical interactions between activated gas species and the surface during the incubation period. Such intermediate layers provide nucleation sites for diamond crystallite growth [9,17,70], and hence enhance diamond nucleation densities on non-diamond substrates [21,37,70,71] and offer an opportunity for controlling the morphology [21,37], orientation and texture [28,<...>…”

“…These studies have led to a reasonable understanding of growth mechanisms and processing parameters. Recently, extensive work [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] on the nucleation and early growth stages has been performed in an effort to enhance diamond nucleation and to control film morphology. As a result, technology problems associated with the nucleation of polycrystalline diamond films have been adequately addressed.…”

Stoichiometry of the diamond/silicon interface and its influence on the silicon content of diamond films

“…Two transitions corresponding to Si and SiC were observed at 99.3 and 100.3 eV, respectively. 8,9 Table I summarizes the peak positions and full width at half maximum values of the carbide peaks in the C͑1s͒ and Si͑2p͒ regions. The high intensity of the Si peak at 99.3 eV may be arising from the bare Si covered by the oxide layer.…”

“…8 Alternatively, a thin nondiamond carbon layer on top of the SiC may also be responsible for the nucleation of diamond. 9 Clearly, the diamond/Si interface plays a dominant role in the growth and nucleation of the diamond. In the present work, we report the influence of the microwave power density ͑MPD͒ on the crystalline quality and impurity content in the diamond films.…”