Thin films ZnO-QDs Synthesis applying simultaneously the techniques of colloidal synthesis and sol gel and phenomenon at Zn2+→Zn3+ + e- charge transfer, applied to Shottky diode.

Abstract

The Zinc Oxide and the Quantum dots of ZnO (ZnO-QD´s) in thin solid films were deposited by dropwise method on glass substrates and calcined in air atmosphere at temperatures of 60 °C, 100 °C, 140 °C, 160 °C and 210 °C, respectively. The samples are examined applying the techniques: Scanning Electron Microscopy (SEM), x-Ray Diffraction (XRD), Fourier transforms in the Infrared (FTIR), Photoluminescence (PL), Transmittance (%T), and absorbance (α). Tauc model, the band gap (Eg) energy is evaluated. The electrical measurements of Current-Voltage (I-V), the concentration of charge carriers, mobility and Resistance, are registered by Hall Effect. The morphology of the layers shows a structural configuration with stacked compact plates and flakes-like of crystalline conglomerates with a fibrous appearance. The films show a Wurtzite-type crystalline phase according to the XRD diffractograms. The grain size increased by ~3.6-26.1 nm. The dislocation density (δ) presents a gradual increase with the calcination temperature δ(lines/m2) ~1.57 x 1015-2.22 x 1015. On FT-IR spectroscopy analysis, various vibrational bands are associated with the CO32 ion and by-products generated by the hydrolysis of zinc acetate di-hydrate discussed. The Eg undergoes oscillatory and disorderly shifting towards higher photon energy, caused by faults at crystalline lattice of Eg ~3.7-3.87 eV. In optical analysis, the discontinuity located at UV-Vis region is associated in principle at Zn2+→Zn3+ + e- charge transfer. PL spectra at UV-Vis region records the emission bands with different relative intensity. The asymmetric Gaussian curve is associated with intrinsic defects in the crystal lattice. The deconvolution of the Gaussian curve generates different emission bands assigned to: red (RE) at ~770 nm, blue (BE), green (GE) at ~492-520 nm and yellow (YE) at ~570-600 nm. The study and systematic construction of the Schottky diode is done by placing the corresponding thin film on ITO, then PEDOT: PSS was placed, then the silver contact and finally the p-n junction was identified, obtaining better results than QD's ZnO in the Shottky diode plot.