Preparation and Characterization of Chromium Containing amorphous Hydrogenated Carbon Films (A-C:H/Cr)
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Mat. Res. Soc. Symp. Proc. Vol. 388 @1995 Materials Research Society
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Fig. 1: Experimental set up for the dc biased rf sputtering deposition. A pure a-C:H film has been deposited for comparison by replacing the Cr target by a copper electrode. This electrode was completely coated with hydrocarbons in a pure methane plasma at a pressure of about 8.0 x 10-3 hPa and a rf power of 250 W. Therefore, no copper was sputtere r- eand ta pure a-C:H film was deposited on the substrate. The temperature and bias voltage of the substrate were also kept at 200.C and 200 V, respectively. In all cases above, the chamber was pumped down to a pressure of about I x 10-6 hPa before the deposition. The samples for the photoelectron spectroscopic measurements were in situ transferred to the spectrometer (Leybold EA10/100) after the deposition. X-ray photoelectron spectra were recorded with Mg Ka radiation (hv = 1253.6 eV) and an energy resolution of about 0.9 eV. The binding energy scale was calibrated by setting the binding energy of the Au 4F/2 core line of a gold moerence sample at EB = 84.0 eV. The thickness of the samples was in the range of 5 to 20 nm. No surface charging effects were observed. XPS spectra of a polycrystalline chromium reference sample were also recorded. The sample was sputter-cleaned with Ar were ion bombardment measurement. at.%, respectively.The residual contaminaand I the below 3 at.% before tions of oxygen and carbon hPa. pressure of the measuring chamber during the data acquisition was about 10-9 base I x The RESULTS AND DISCUSSION Determination of Cr Concentration and Deposition Rate The Cr, C, a and Ar concentration of the films were determined by XPS. The oxygen contamination was found to be below 0.3 at.% and the Ar content between about 0.2 and 0.5 at.% in all films. The Cr concentration as a function of the methane flow is shown in Fig. 2. As expected, more and more hydrocarbons are incorporated into the films by increasing the flow of methane and therefore, the relative Cr concentration decreases. In Fig. 3 the deposition rate is drawn as a function of the methane flow. The rate increases with increasing methane flow again due to the higher hydrocarbon incorporation. The deposition rate was determined from the optical analysis of a-C:H/Cr films which will be discussed in detail elsewhere15.
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CH 4 FLOW (sccm) Fig. 2: Chromium concentration as a function of methane flow.
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Fig. 3: Deposition rate versus methane flow.
Compared to a-C:H/Cr films deposited under similar conditions but unheated substrates 9 the concentrations of carbon and argon are significantly lower. Obviously, the higher desorption and higher mobil
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