Enhancement in UV emission and band gap by Fe doping in ZnO thin films

Abstract

Enhancement of the optical band gap of ZnO from 3.14 to 3.29 eV has been obtained using Fe dopant. Undoped and doped ZnO films are deposited by sol-gel spin coating. XRD patterns indicate polycrystalline nature and hexagonal wurtzite structure of Zn1−xFexO films. EDX analysis confirms the presence of iron dopant. The photoluminescence spectra show an ultraviolet emission peak at 398 nm (NBE emission) and defect emission peak at 485 nm. Intensity of the NBE emission is much higher for the doped samples with its ratio to defect emission intensity highest for 2 at. %doping. The NBE emission shifts to higher energy with increasing dopant concentration in a manner similar to that exhibited by the band gap. Surface morphology has been studied using FESEM.

Optical and sensing properties of Fe doped ZnO nanocrystalline thin films

“…2. All the films have a hexagonal wurtzite structure with major diffraction peaks along (1 0 0), (0 0 2) and (1 0 1) planes [1,3,16,21]. No impurity peak relating to iron is found.…”

“…In [12], the films were deposited by spray pyrolysis and the decrease in optical band gap was attributed to s-d and p-d hybridization. Previously, Srivastava et al [1] reported an increment in optical band gap in Fe doped ZnO films of a thickness 500 nm obtained by sol-gel spin coating using precursor solutions of the molarity of 0.1 M. It was concluded that sp hybridization is responsible for this behavior. Other reports in the literature regarding the increase in the band gap of Fe doped ZnO with an increase in dopant concentration, explained it by Burstein Moss effect [13] and quantum confinement [14].…”

“…Zinc oxide has large direct band gap (3.37 eV) and exciton binding energies (60 meV) at room temperature. It is cost effective and environmentally safe also [1][2][3][4][5]. Possible applications of ZnO films are in UV lasers and blue luminescent devices, photo detectors, photoelectronic devices, etc.…”

“…chemical vapor deposition, thermal evaporation, successive ionic layer absorption and reaction, magnetron sputtering, pulsed laser deposition, laser chemical vapor deposition, sol-gel, spray pyrolysis, screen printing, etc. [1,3,[16][17][18][19][20][21][22]. Spray pyrolysis is Optical and sensing properties of Fe doped ZnO nanocrystalline thin films 355 a non-vacuum process that produces good quality films.…”

Temperature dependence of the optical band gap of sol-gel derived Fe-doped ZnO films

“…Fe doped ZnO films have been prepared by variety of preparation methods such as DC thermal plasma [7], RF magnetron sputtering [8,9], spray pyrolysis [10], chemical co-precipitation [11] and sol-gel [12,13]. Compared with other methods, the sol-gel offers the greatest possibility for depositing a film with large area at low cost for applications.…”