Synthesis and characterisation of DLC and diamond films for gas sensing applications

Over the last decade diamond like carbon (DLC) and diamond films have been extensively studied. These studies were only focused on the synthesis and characterization of this material. DLC films have some unique properties as a semiconductor such as a high elastic modulus, high mechanical hardness, very low surface roughness, and chemical inertness that qualifies it to be a valuable material for several applications. Its band gap varies approximately between 1eV to 4 eV. This material has been extensively used in electronic, optical, mechanical and biomedical applications. In this research work diamond and DLC thin films are deposited on a silicon substrate (Si <100 >/<111>), alumina strips by using direct current (DC) magnetron sputtering system under varying conditions such as temperature, pressure, power, voltage, deposition rate, argon, nitrogen as well as oxygen gas flow rate. The as-deposited thin films were characterized using several characterization techniques. The roughness of the sample was studied using atomic force microscopy (AFM) and it was estimated to be 0.292- 3.2 nm. Scanning Electron Microscopy (SEM) equipped with Energy Dispersed X-ray (EDX) was used to investigate the morphology and the composition or stoichiometry of the sample. SEM confirmed that the samples are uniform and fairly smooth which is in agreement with the AFM results. X-ray diffraction (XRD) was used to study the crystallinity of the sample and the films were found to be polycrystalline with the pronounce peak of DLC. Raman analysis was used to determine the quality of the DLC films using the ratio of the areas under the sp3 to sp2 curves. The ratio of sp3 to sp2 areas under the curve was found to vary between 0.7 to 0.9 for samples prepared under different conditions. RBS was used to as a rough measure of continuity of the films or coverage of the substrates by carbon. This research was aimed at attempting to determine the gas sensing properties of DLC and diamond films at different concentrations of various gasses and at different sensor temperatures. It was found that DLC films are corrosive resistant to poisonous gasses such as H2S. DLC films were found to respond more favourably to NO2 and NH3 at room temperature than to other gasses like CO, H2 and H2S which indicates that DLC sensors are very selective – a desirable property in a gas sensor.

Grantor dc:publisher.institution

University of Zululand

Year dc:date.issued

2014

Author dc:creator

• Chonco, N.P

Advisors dc:contributor.advisor

• Ndwandwe, O.M
• Mwakikunga, B

Licence

• https://devspace.unizulu.ac.za/bitstreams/db0503a5-6b2f-4ffb-8616-b60dd1e18a2f/download