THE OPTICAL-PROPERTIES OF A-C-H FILMS BETWEEN 1.5 AND 10 EV AND THE EFFECT OF THERMAL ANNEALING ON THE FILM CHARACTER

The optical properties of amorphous hydrogenated carbon films prepared with various techniques are studied with conventional and synchrotron -radiation spectroscopic ellipsometry (SE) and the pseudodielectric fu nction [epsilon(omega)] of diamondlike and graphitelike films is prese nted in the energy region 1.5-10 eV. Characteristic features of the me asured [epsilon(omega)] and the calculated electron-energy-loss (EEL) function are found to serve as useful criteria for the classification of such materials. The results and information obtained by SE are comp ared to those obtained by EEL and Raman spectroscopy techniques, which are the most widely used for this purpose. Thermal annealing experime nts up to 675 degrees C with in situ monitoring of the [epsilon(omega) ] reveal the undergoing structural changes in the material character f rom diamondlike into graphitelike during the annealing. The major modi fications which turn the material into sp(2)-like are found to take pl ace around and above 550 degrees C. The fundamental gap along with oth er optical parameters of the materials are compared to those of diamon d and graphite and their shift with temperature is discussed and used to illustrate further the prevalence of the graphitic character during and after the annealing. Finally, the optimum growth parameters for t he production of diamondlike material are discussed in the case of the glow-discharge and ion-beam deposited films. (C) 1996 American Instit ute of Physics.