Development of YDC thin films by spray pyrolysis for the fabrication of p-Si/n-YDC photodiode

Nebulizer spray pyrolysis (NSP) technique has been successfully employed for the deposition of well-dispersed highly homogeneous spindle-shaped yttrium-doped cerium oxide (YDC) films. Optical studies revealed a decreasing trend of transmittance with the increasing Y doping percentage up to 20% and then increase in transmittance at 25% either due to the increased crystal defect induced photon scattering or the increased metal-to-oxygen ratio at higher Y doping. PL spectra showed four distinct broad peaks at 3.34 eV (near-band-edge emission (NBE) at UV), and 3.14, 2.91 and 2.65 eV (deep-level emission (DLE) in the visible spectra at violet, blue and green, respectively) corresponding to the wavelengths 365, 394, 425 and 465 nm, respectively. XRD studies confirmed the polycrystalline cubic fluorite single-phase structures preferentially orientated along (200) and (111) reflections without any impurity peaks. SEM images showed that YDC films are grown with small granules containing spherical-shaped particles having many cracks and patches. The average width of tiny granules inside the well-aligned taper-like structures is found within the order of 138 nm. The observed changes in the rectification ratio of p-Si/n-YDC diode with voltage are allied to the corresponding changes in both series (Rs) and shunt resistances (Rsh) of the heterojunction. The transient photocurrent characteristics indicate that the prepared heterostructure is highly stable and has quick response, which advocates the use of prepared heterojunction device in UV detector and white light photodetector applications.