Display Full Text | Download Full Text
1.73 MB PDF file

Degree

Doctor of Philosophy, Case Western Reserve University, Physics, 1990.

Abstract

Hydrogenated amorphous carbon films (a-C:H) have been deposited on glass, fused silica, Si, Mo, Al, and 304 stainless steel at room temperature by plasma enhanced chemical vapor deposition (PECVD). The rf glow discharge and plasma kinetics of the deposition process were investigated. Negative self-bias voltage V b and gas pressure P were used as two major deposition parameters. The hydrogen concentration, internal stress, mass density, hardness, and thickness of the deposited films were measured. In the low energy deposition region, 0 > V b > -100 V, soft polymerlike films with high hydrogen concentration and low density were found. Hard diamondlike films with high stress were deposited in the bias voltage range, -100 V > V b > -1000 V. Dark graphitic films with low hydrogen concentration were grown at V b < -1000 V. The optical absorption of a series of a-C:H films have been measured. Optical energy gaps deduced from optical absorption data using the Tauc relation lie between 0.8 eV and 1.4 eV. Doping of a-C:H films by boron and sulfur is accompanied by an increasing number of gap states, i.e., the absorption coefficient is increased and the optical gap is reduced. The thermal stability was studied by thermal desorption spectroscopy and heat tre atment at atmospheric pressure. A structural study of a-C:H films was performed using data taken on our films and from literature sources. The relation between cluster size and the intensity ratio of Raman peaks was studied. A comparison of the films as described by the graphitic cluster two-phase (GCT) model, the random covalent network (RCN) model and the all-sp² defect graphite (DG) model was made. The properties and structure of a-C:H films are sensitively dependent on the preparation conditions. Correlations between the deposition conditions, structure, and properties are determined.

Subject Headings

Physics, Condensed Matter

Keywords

Preparation properties structure hydrogenated amorphous carbon films

Advisor

R W Hoffman

Pages

82p.

Document number: case1054566593
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=case1054566593

This ETD has been downloaded 406 times (through March 2013)