Formation of Nanographite Flakes on SiO2 Substrate by Plasma Deposition of Carbon and Subsequent Annealing

The effect of plasma treatment in methane and the subsequent heat treatment of silicon dioxide substrates is studied. At the first stage, carbon film was deposited in an inductively coupled plasma on the surface of a SiO2 substrate. The Raman spectra of the deposited film contained a broad photoluminescence band in the range from 1000 to 3500 cm(-1), corresponding to amorphous carbon. The deposited films contained hydrogen and oxygen. In the second stage of the process, the obtained films were heat treated at 650 degrees C in an argon atmosphere during at a 30 min. As a result, a film several nanometers thick remains on the surface of the substrate. Raman spectra show the peaks characteristic of nanocrystalline graphite. Measurements of the carrier mobility in a film using the Hall effect method showed a value of similar to 250 cm(2)V(-1)s(-1). It was established from the temperature dependences of resistances that the mechanism of electrical conductivity corresponds to the model of a Efros-Shklovskii variable range hopping mechanism. The sizes of graphite nanocrystals determined from the temperature dependences of resistances are approximately equal to 3 nm.