Influence of krypton atoms on the structure of hydrogenated amorphous carbon deposited by plasma enhanced chemical vapor deposition

Abstract

Hydrogenated amorphous carbon ͑a-C:H͒ films were prepared by plasma enhanced chemical vapor deposition using methane ͑CH 4 ͒ plus krypton ͑Kr͒ mixed atmosphere. The depositions were performed as function of the bias voltage and krypton partial pressure. The goal of this work was to study the influence of krypton gas on the physical properties of a-C:H films deposited on the cathode electrode. Krypton concentration up to 1.6 at. %, determined by Rutherford Back-Scattering, was obtained at high Kr partial pressure and bias of Ϫ120 V. The structure of the films was analyzed by means of optical transmission spectroscopy, multi-wavelength Raman scattering and Fourier Transform Infrared spectroscopy. It was verified that the structure of the films remains unchanged up to a concentration of Kr of about 1.0 at. %. A slight graphitization of the films occurs for higher concentration. The observed variation in the film structure, optical band gap, stress, and hydrogen concentration were associated mainly with the subplantation process of hydrocarbons radicals, rather than the krypton ion energy.

Complete characterization by Raman spectroscopy of the structural properties of thin hydrogenated diamond-like carbon films exposed to rapid thermal annealing

“…1, [54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][87][88][89][90] The D band is a breathing mode of A 1g symmetry, and its intensity is strictly related to the occurrence of six-fold aromatic rings in the scattering medium. Table I) which reduces aromatic ring formation.…”

“…By correct interpretation of the different parameters derived from the spectral analysis from curve fitting of MW Raman 35,[54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] and PL 38-40,69-73 spectra, we report that it is possible to distinguish between DLC:H films with minute differences in bonding configuration, microstructure, and hydrogen content and to follow their thermally induced structural evolution. Most importantly, we introduce a new analysis method of Raman spectra that permits distinguishing between films prepared with different density, thickness, and RTA treatment.…”

“…The objective of the present paper is to demonstrate that it is possible to completely characterize the structural properties of as-deposited and post-annealed DLC:H films and to resolve the structural differences between different types of films by using multi-wavelength (MW) Raman spectroscopy 35,[54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] and photoluminescence (PL) spectroscopy. [38][39][40][69][70][71][72][73] During data analysis, the key to achieve a complete and comprehensive structural characterization is (a) to take account of both the structural and topological disorder of the amorphous network, (b) be aware that the evolution of the sp 2 and sp 3 phases can in principle be independent, (c) that this evolution depends on the treatment of the film post-deposition, and finally (d) that sp 2 clusters possess locally different band gaps that are more or less resonant with different Raman laser wavelengths.…”