Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Chemistry

Supervisor

Dr. Oleg Semenikhin

Abstract

The properties of carbon nitride (CNx) films deposited onto various substrates using a radiofrequency magnetron sputtering technique were studied as a function of deposition parameters, especially magnetron power, gas pressure and nitrogen content in the plasma. Indium tin oxide (ITO) coated glass and fluorine tin oxide (FTO) coated glass as well as metal substrates (silver and tungsten) were used. Scanning electron microscopy (SEM) was used to study the surface morphology of the prepared CNx films. Energy-dispersive X-ray spectroscopy (EDX) as well as survey X-ray photoelectron spectroscopy (XPS) spectra were used to perform the elemental analysis of the CNx films.

Ultraviolet-visible (UV-Vis) spectrophotometry was conducted to study CNx films on ITO glass to characterize the absorption spectrum and thickness of the film, as well as estimate the material's band gap. Schottky cells were created using either ITO or FTO coated glass as the substrate, CNx films as the active material, and aluminum as the counter electrode. Current-voltage, current-time, and voltage-time plots were used to demonstrate the photovoltaic effect in the samples, as well as to show the benefits of ageing and annealing to the cell’s performance.

Different annealing conditions were explored to try and remove the high levels of oxygen that were found in the CNx films in an attempt to increase the open circuit voltage of the cells. It was concluded that oxygen comes from conducting metal oxides (ITO/FTO) during the film deposition process. Therefore, metal contacts (silver and tungsten) were subsequently used instead of ITO or FTO glass which resulted in low oxygen CNx films.

The bonding patterns in CNx films were determined using high-resolution XPS as a function of deposition parameters as well as annealing. It was found that the films contained a significant amount of pyridinic moieties, which increased upon annealing. On the contrary, the contribution of quaternary nitrogen, which is the main n-doping configuration in carbon nitride, was quite small and further decreased with annealing. The XPS results allowed us to shed light on the nature of photoactivity demonstrated by high nitrogen content carbon nitride films.

Available for download on Sunday, November 18, 2018


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