Abstract:
In this study, the undoped, Erbium (Er) doped and Samarium (Sm) doped (1, 3, and 5 wt%) ZnO were synthesized using spray pyrolysis. X-ray diffraction patterns confirmed ZnO with strong diffraction peaks indexed in their right 2-theta angles. Raman spectroscopy observed A1, E1 and E2 vibrational phonon modes of wurtzite hexagonal ZnO. Scanning electron microscopy revealed nanoparticles that were well dispersed on the surface. There was agglomeration which was decreasing with an increase in the doping concentration from 1 to 5 wt% of Er and Sm. Energy-dispersive X-ray spectroscopy confirmed the main signals for Zn, O, Er, and Sm, with no other foreign elements observed. From the UV-Vis measurements, average transmittance of 74% at 550 nm was obtained for all the samples. The bandgap calculated for the thin films was decreasing from 3.31 eV for undoped ZnO to 2.96 eV and 3.11 eV for 5% Er and Sm doped samples, respectively. Schottky diodes were fabricated using aluminum (Al) and gold (Au) as the Schottky contact and palladium (Pd) as the Ohmic contact and electrical measurements performed. Both undoped and doped ZnO showed a rectifying behavior with an improvement in the rectification of up to almost 4 orders of magnitude for 5 wt% Er and Sm doped films compared to undoped ZnO which had a rectification of 2. In addition, the Schottky Barrier heights increased from 0.559 for undoped ZnO to 0.767 and 0.760 for 5 wt% Er and Sm doped, respectively. Undoped ZnO had an ideality factor of 2.49 which was decreased to 1.72 and 1.92 for Er and Sm doped ZnO devices. Also, a reduction in the leakage current and series resistance of devices was noted in undoped and doped ZnO. The fabricated devices can be used as an alternative for Schottky diode applications.
