Title

Characterization of a novel methyl radical source and related thin film growth studies

Semester

Fall

Date of Graduation

2000

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

Charter Stinespring.

Abstract

An ultrahigh vacuum compatible methyl (CH3) radical source has been developed. The methyl radicals were generated by dc- and microwave-discharge processes in either of two ways. In the first, argon (Ar) or an Ar/Xe mixture was passed through the discharge to produce inert gas metastables that react with methane to produce the desired species. This was referred to as the indirect mode of operation. In the second or direct mode, an inert gas/methane mixture was passed directly through the discharge. The discharge/reaction products were sampled using a skimmer, and the resulting molecular beam was either characterized using a mass spectrometer or used in nucleation and growth experiments.;The characterization studies showed that a "clean" flux of CH3 radicals was produced for a 7.5% CH4 mixture, a source pressure of 200 mT and a residence time of ∼60 ms. The flux of CH3 radicals in this case was 3.3 x 1014 cm -2 s-1. Higher CH3 fluxes and yields could be achieved under different conditions, however undesired species also became significant.;Several thin films were grown using the CH3 radical source. These were characterized using Auger electron spectroscopy (AES), atomic force microscopy (AFM), and secondary electron microscopy (SEM). At a sample temperature of 652°C, silicon carbide (SiC-C) and diamond (sp3-C) were immediately detected by curve fitting of the carbon Auger KLL (C-KLL) peak. At increased sample temperature, there was an induction period in the growth of sp3-C. Graphitic (sp2-C) carbon was only detected in a film grown at an increased flux of all species. Samples grown at 652°C were remarkably smooth, while films grown at elevated temperatures contained numerous surface features. In general, the growth results support the model of surfactant mediated growth of carbon films on silicon. In addition, the results demonstrate a marked dependence on the growth species.

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