Obtaining of carbon nanoparticles in pulsed modulated RF discharge plasma

Abstract

Carbon nanoparticles were synthesized using a 13.56 MHz RF discharge plasma in pulsed mode to control the size of the nanoparticles. An Ar/CH4 gas mixture was injected into the chamber to create capacitive coupled plasma medium, the main part of which is an electrode connected to the RF generator and a grounded electrode arranged in parallel. The synthesis experiments were carried out at room temperature and under the following conditions: pressure in the working chamber 0.99 Torr; concentration of Ar(96%)+CH4(4%) gas mixture; synthesis time 5 seconds; at discharge power 10 W. The frequency of the RF discharge plasma pulse during modulation was varied from 10 Hz to 10 kHz, also the duty-cycle was 50% for each performed experiment. Experimental observations have revealed that the size of carbon nanoparticles increases with the frequency of the pulse signal. It has also been determined that by using a frequency of the modulated pulsed RF signal it is possible to control the size of carbon nanoparticles in the range of 40-70 nm. The synthesized nanoparticles were collected directly on a copper mesh for TEM microscopy, which was placed on the surface of the bottom electrode. TEM image analysis showed two types of nanoparticles, some of which are an agglomerate of nanoparticles with an amorphous structure, while the others are nanometer-sized with crystalline structures.