Sputtering deposition and characterization of ultrathin amorphous carbon films

This dissertation focuses on experimental investigations of ultrathin, ultrasmooth amorphous carbon (a-C) films deposited on Si(100) substrates by radio frequency (RF) sputtering and characterization of the nanomechanical and nanotribological properties and thermal stability of the films. Ultrathin a-C films of thickness 5–100 nm and typical root-mean-square roughness of 0.15–1 nm were deposited on ultrasmooth Si(100) substrates using pure argon as the sputtering gas. A low-pressure RF argon discharge model was used to analyze the plasma parameters in the film growth environment. These plasma parameters correlate the deposition conditions with the film growth processes.; Atomic force microscopy (AFM) and surface force microscopy (SFM) were used to characterize the nanomechanical and nanotribological properties of the a-C films. X-ray photoelectron spectroscopy (XPS) was used to investigate the compositions and microstructures of the films. Sputter-etching measurements of the a-C films by energetic argon ion bombardment were used to study the surface binding energy of carbon atoms in a-C films deposited under different conditions. The dependence of film properties on deposition conditions was studied, and relations between nanomechanical and nanotribological properties were discussed in terms of a modified deformation index. The deformation and nanotribology mechanisms of the a-C films were compared with those of other films, such as TiC and Cr films (both 100 nm thick), and bulk Si(100).; Reactive RF sputtering of nitrogenated amorphous carbon (a-CN_x) films was investigated by introducing nitrogen into the a-C films during film growth by using an argon-nitrogen gas mixture as the sputtering gas. The alloying effect of nitrogen on the film growth and properties, such as hardness and surface energy, was studied and interpreted in terms of the changes in the plasma environment induced due to differences in the composition of the sputtering gas mixture.; The thermal stability of the a-C films and the role of residual stresses in the a-C films were studied in high-vacuum annealing experiments performed in the XPS vacuum chamber. The changes in the film composition and microstructure during sequential annealing cycles at 495°C were analyzed in light of XPS spectra. A new method was proposed to quantify the compressive stresses in ultrathin films (less than 10 nm) using implanted argon atoms as stress-sensing probes in conjunction with XPS analysis.