In this study, we have synthesized boron, carbon, and nitrogen containing films through rf magnetron sputtering. We investigated the effects of deposition parameters on the chemical environment of B, C, and N atoms inside the films deposited. Techniques used for this purpose were GIR-FTIR, XPS, TEM and EELS. A hydrogen terminated surface was generated on the substrates before deposition. A 20nm Ti buffer-layer was deposited on the hydrogen terminated Si substrate just before the B-C-N films were deposited on the substrate. As for the boron and carbon source a 2 inch diameter B₄C target was used. During the deposition the pressure of the chamber was kept at 2.5 x 10^-3 torrs during the deposition while the magnetron power on the B₄C target was adjusted to be 200 watts during period of deposition (~ 90 mins). A separate r.f. power supply attached to the substrate holder was used to apply and independently adjust the d.c. bias on the substrate between gr ound and -500 V. Meanwhile, gas flow into the reaction chamber was controlled by two mass flow controllers which helped manage the Ar to N₂ gas ratio for the deposition.

GIR-FTIR experiments on the B-C-N films deposited indicated presence of multiple features between 600 cm^-1 to 1700 cm^-1 range in the infrared spectra. Analysis of the IR spectra and the corresponding XPS data from the films has been done in a collective manner. The results from this study suggested under nitrogen rich synthesis conditions (higher N₂ ratio in Ar/N₂ mixture) carbon in the B-C-N films prefers to be surrounded by other carbon atoms rather than boron and/or nitrogen. Furthermore, we have observed a similar behavior in the chemistry of B-C-N films deposited with increasing substrate bias using again IR and XPS data together. In order to better understand these results, we have compared and evaluated the energetic for various nearest-neighbor and structur al configurations of carbon atoms on a single BN sheet environment using DFT calculations. These theoretical calculations also indicated that structures and configurations that increase the relative amount of C-C bonding with respect to C-B and/or C-N were energetically favorable than otherwise. As a conclusion, carbon tends to phase-segregate in to carbon clusters rather than displaying a homogeneous distribution in the films deposited in this study.

The InAlGaN materials system is employed in several important technologies including light emitting diodes, blue/green lasers, and electronic devices. Realization of the technological promise of the nitride materials system has required growth of high quality epitaxial material. This requirement has motivated many experimental and theoretical studies of GaN surfaces, with attempts to understand epitaxial growth in terms of the surface structure. Nitride surfaces exhibit considerable complexity in their atomic structure, the nature of which is dependent on the relative abundance of the group-III and group-V species and the crystallographic orientation of the surface. In addition surface states are the source of electrons in the two-dimensional electron gas at the AlGaN/GaN interface in high-electron mobility transistors, and this has motivated studies of surface electronic structure.

In this talk I will present the results of first-principles calculations employing pseudopotential density functional theory. The calculations provide insight into the atomic and electronic structure of nitride surfaces. Some emphasis will be placed on the group-III metallic adlayers which are stabilized under group-III rich conditions, and how these structures impact surface diffusion and impurity incorporation.

This work was supported in part by the US-DARPA-VIGIL program (Dr. H. Temkin).