Papers by Keyword: HF-CVD

Abstract: In the present report, a two dimensional (2D) model was developed to describe the fluid dynamics, heat and mass transfer of a Chemical Vapor Deposition activated by a Hot Filament (HFCVD) reactor, as well as the chemical generation of the precursor species which are present in the growth of non-stoichiometric silicon rich oxide (SRO) films. The SRO is known for have excellent photo luminescent properties which are useful in optoelectronic applications. This material can be obtained by the HFCVD technique which offers important advantages such as the easily to obtain thin films with diverse structural, compositional and optical characteristics. During deposition is a priority to control key parameters as inlet flow, substrate temperature and pressure so it compels to know previous theoretical information about these parameters which can be obtained by computational simulation. Therefore, by means of commercial Computational Fluid Dynamics (CFD) were solved the continuity, momentum and energy equations in steady state. Also, a thermodynamic equilibrium study of the SiO₂(s) + H₂ (g) reaction was carried out with the Factsage software. The thermodynamic equilibrium results provide the main chemical species which are present during the deposit process of the SRO films. The 2D model was used to simulate the temperature and velocity distribution of the hydrogen in the deposit process. The theoretical calculated temperatures were compared with those obtained experimentally by thermocouple measurements. From the simulation results, the temperature and gas velocity profiles were obtained at different hydrogen flow levels (50, 75, 100 sccm) and temperature source-substrate distances (5, 6 and 7mm) for a 50 sccm level. SEM micrographs and profilometry measurements disclose that the outlet configuration affects substantially both the thickness and surface uniformity of the SRO films. This parameter was modified to obtain a better quality (thickness and uniformity) and a large deposit area.

Abstract: Friction and wear behavior of fine-grained diamond (FGD) films were investigated in the ambient air, deionized water and paraffin oil lubricating environment. The FGD films were deposited on WC substrates using HFCVD method and the tribologcial tests were conducted in a ball-on-plate type reciprocating friction tester where the mating balls were made of ball-bearing steel. Scanning electron microscopy (SEM), surface profilometer and Raman spectrascropy were used to study the characterizations of the deposited FGD films, and after sliding tests, the worn areas on both mating balls and FGD films were investigated and the wear debris layer adhered to the friction area of FGD films were analyzed with EDX. The experiment results suggested that FGD films exhibited steady friction coefficient as about 0.25 in water, lower than that in open air, which is up to 0.40; but the mating ball in water suffered much severer wear lost and its specific wear rate was more than two times higher than that in air, up to 3.6E-4 mm3N-1m-1. As while, a thick and compact layer of wear debris was observed on the worn area of FGD films sliding with water lubrication while only little debris existed in the diamond grain boundaries, which might dominate the friction process and attribute to the lower friction coefficient and higher specific wear rate in water environment. In oil environment, furthermore, both the friction coefficient and specific wear rate reached minimum value as low as 0.1 and 1.1E-4 mm3N-1m-1, no observable wear scar could be measured on the sliding surface of the FGD film.