Carbon Nitride Films Using a Filtered Cathodic ARC
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In an attempt to synthesize O-C3 N4 , a metastable phase structure, we utilized the concept of energetic condensation. Previously, a filtered cathodic arc system had been used by Lossy et al. [10] to deposit amorphous diamond. They found that quenching of the energetic ions was necessary to synthesize this metastable phase of carbon. 0.7. q
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Investigator Figure 1. Plot of the Cl-xNx composition versus various investigators. EXPERIMENTAL
A series of experiments was carried out using the filtered cathodic arc with a nitrogen background gas. The run pressures were varied to obtain different nitrogen contents in the films. The highest concentration of nitrogen was obtained with a run pressure of 1 x 10-3 Toff. However, these films contained only 5 at.% nitrogen. Next, a Kaufman ion source was used in conjunction with the filtered cathodic arc to increase the activated nitrogen species at the substrate. These films had a nitrogen content of 17 at.%. Since both of these processing techniques produced low concentrations of nitrogen, it was inferred that a higher concentration of activated nitrogen species was required in the vicinity of the substrate. This was accomplished by using a radio frequency inductively coupled nitrogen plasma. The filtered cathodic arc was slightly modified in order to obtain a high nitrogen plasma density in front of the substrates. RF copper coils were placed in front of the substrate (see Figure 2) and were powered by a RF 1 kW power generator at a frequency of 13.56 MHz. A series of films were grown under different substrate bias conditions and Table I summarizes the process parameters. The target for the cathodic arc was made of 99.9995% pure graphite and nitrogen (99.9995% purity) was introduced as the processing gas. The substrate was water
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cooled to quench the energetic ions. During the process, the water temperature ranged from 10 to 30* C. A thermal compound, part number 120-8 manufactured by Wakefield Engineering, was applied to the back of the substrates in order to increase thermal contact with the water cooled substrate holder. The experiments were run for 10 minutes with a duty cycle of 1 minute on and one minute off. Films were grown on single crystal sapphire, silicon (100), molybdenum and quartz. The silicon and molybdenum substrates were cleaned in an unbuffered HF bath and the sapphire and quartz substrates were cleaned in an alcohol bath. The composition of these films was obtained by Auger Electron Spectroscopy (AES) and Electron Energy Loss Spectroscopy (EELS). Bonding information was obtained by EELS and IR spectroscopy.
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Figure 2. Schematic diagram of the filtered cathodic arc system modified by the addition of rf coils. Table I. Process parameters used for deposition of CNx films. Sample ID Base Pressure (T
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