Real Time Spectroellipsometry Study of the Evolution of Bonding in Diamond Thin Films during Nucleation and Growth

Real time spectroellipsometry (RTSE) has been performed during the nucleation and growth of nanocrystalline thins films prepared by plasma-enhanced chemical vapor deposition onto Si substrates. RTSE shows that a significant volume fraction of nondiamond (or ${\mathrm{sp}}^2$-bonded) carbon forms during thin film coalescence and is trapped near the substrate interface between $\sim 300Å$ diamond nuclei. Although this behavior is observed over a range of C${\mathrm{H}}_4$/${\mathrm{H}}_2$/${\mathrm{O}}_2$ gas compositions, the interfacial ${\mathrm{sp}}^2$-bonded carbon volume can be minimized by operating just within the growth-etch boundary of the diamond growth phase diagram.