In-situ measurement of nanoscale thin film thickness for next-generation photovoltaics

This project addresses two key objectives in thin film research: improving thickness control during deposition and investigating CuAlFeS₂ as a potential intermediate band semiconductor for photovoltaic applications. Real-time thickness monitoring was implemented using a Quartz Crystal Microbalance (QCM) integrated into a Nano-PVD magnetron sputtering system. To calibrate the QCM, the tooling factor was experimentally determined by comparing QCM-reported values to actual film thicknesses measured via optical profilometry across three titanium films. A tooling factor of 66.7% was obtained for one magnetron gun, consistent with expected geometric disparities between the sensor and substrate. In the second phase, CuAlFeS₂ thin films with varying aluminium content were fabricated via co-sputtering from CuFeS₂ and Al targets. Energy-Dispersive X-ray Spectroscopy (EDS) confirmed partial incorporation of Cu, Al, and S; however, Fe was not detected, likely due to low sputtering efficiency and preferential ejection of other species. These findings highlight the limitations of RF sputtering for complex quaternary compounds under non-reactive conditions. This work provides a foundation for future optimisation of real-time thickness control and compositionally tuned synthesis of CuAlFeS₂ for photovoltaic applications.