Characterizations of electron beam evaporated silicon thin films on plastic substrates for solar cells applications

Samples of thin film silicon (Si) on low cost polyethylene terephthalate (PET) plastic substrates were prepared by electron beam (e-beam) evaporation technique. Five samples of different thicknesses were deposited. Structural, optical, surface morphology and electrical characterizations were then carried out on these samples by energy dispersion X-ray (EDX) spectroscopy, high resolution X-ray diffraction (HR-XRD), UV spectrophotometer, atomic force microscopy (AFM) and four-probe meter. EDX spectra for these as-evaporated Si thin films on PET showed that the peak at 1.7398 eV belongs to Si atom which confirms the existence of the Si thin film layer. HR-XRD result showed that the chosen sample was highly amorphous. The transmission and reflection were carried out from wavelength 200 nm to 2000 nm and the optical band gap of the samples was calculated by Tauc's relations. The root mean square (RMS) of surface roughness was low (smooth morphology) and found to be independent to the thickness of the film. The films were found to be highly resistive due to their intrinsic nature (no doping applied during the deposition). The effects of the properties towards thin film solar cells fabrication were subsequently discussed.