Fabrication of amorphous carbon thin films deposited from oyster mushroom waste extract using chemical vapor deposition (CVD) technique

Amorphous carbon (a-C) gained the researchers’ attention due to its unique properties that give a lot of benefits in various fields, especially in electronic devices. Nowadays, the production of a-C thin films has evolved from using the traditionally toxic and explosive carbon precursor to renewable and environmentally friendly precursors, such as palm oil, camphor oil, palmyra sugar, and coconut sap. The fabrication of a-C thin films from a novel oyster mushroom waste extract was performed using the Chemical Vapor Deposition (CVD) technique. The extract of the waste-derived base component of oyster mushrooms was used as the carbon precursor to synthesize a-C, while n-type and p-type silicon served as the substrate. In the initial phase, Soxhlet extraction was performed with n-hexane and ethanol as solvents, followed by characterization of the mushroom waste extract through Thermogravimetric (TGA) and CHNS analysis was carried out. Findings indicate that n-hexane is a more advantageous solvent due to its higher carbon percentage, 70.387%. The ideal decomposition temperature, determined by TGA, is established at 350°C. The next phase involved the deposition of undoped a-C and nitrogen-doped a-C (a-CN) thin films using CVD with different parameters, including the amount of precursor, the deposition temperatures, and the gas flow rate, which affect the properties of a-C thin films. The main objective of this research is to determine the structural and electrical characteristics of the undoped a-C and a-CN. Characterization was done using the UV-Vis Spectroscopy for the optical properties, Raman Spectroscopy, Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray Spectroscopy (EDX) for the structural properties, and Current-Voltage (I-V) Measurement for the electrical properties. The optimum parameters for undoped a-C and a-CN thin films have been identified. Throughout this research, undoped a-C thin films deposited with 2 ml oyster mushroom waste extract at 850°C and 40 sccm, while maintaining a precursor temperature of 350°C and a deposition time of 30 minutes, were found to offer the best electrical properties, achieving a conductivity value of 1.66 × 102 S.cm−1. In contrast, the a-CN thin films that were synthesized at 850°C and 35 sccm are considered the best parameters to obtain an optimum result in electrical properties, with the value of 1.73 × 102 S.cm−1. The findings indicate an enhancement in the electrical conductivity with the introduction of nitrogen dopant into the films. This research presents an excellent opportunity to showcase a new ‘green’ alternative precursor to produce a-C, along with potential as a material for electronic devices.