Spectroscopic studies of refractory and dielectric thin films

Abstract

This work demonstrated the application of the techniques and methodology of surface science to investigate the mechanisms of thin film deposition processes on solid surfaces. The synthesis of boron nitride (BN) thin films was studied using X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). In this model system, diborane (B2H6) , ammonia (NH3) and hydrazine (N2H4) were used as precursors to deposit BN thin films on a clean Ru(0001) surface. The results showed that ammonia reaction with diborane yielded only boron-rich boron nitride overlayers. However, stoichiometric BN films in excess of one monolayer could be produced when hydrazine was substituted for ammonia. The effects of oxygen on boron-rich and stoichiometric boron-nitrogen films were also examined. In the second part of this work, high resolution electron energy loss spectroscopy (HREELS) was used to characterize defect centers in MgO and in lithium-doped MgO thin films. The HREELS results showed that MgO thin films grown on Mo(100) were nearly defect-free at temperatures up to 1100 K. HREELS measurements indicated that annealings to higher temperatures induced F-type defect centers in the MgO films. The formation of [Li+O-] defect centers was also observed when the MgO films were doped with lithium and annealed to temperatures above 1100 K. Finally in the last part of this effort, TDS and HREELS w ere combined to examine the adsorptions of formaldehyde (H2CO) and ammonia on NiO thin film surfaces. These adsorption studies demonstrated the use of surface-sensitive techniques to characterize the chemical properties of oxide film surfaces.