Surface Analysis and Optical Properties of Cu-Doped ZnO Thin Films Deposited by Radio Frequency Magnetron Sputtering

Abstract

In this study, Cu-doped ZnO (CZO) thin films were grown on glass substrates by using the radio frequency magnetron sputtering technique. The effects of Cu doping on the structural, surface morphological, optical properties, and wettability behaviors of CZO thin films were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Visible spectroscopy, and contact angle measurement, respectively. The XRD results indicated that all CZO thin films were textured, having a preferential crystallographic orientation along the hexagonal wurtzite (002) axis. The average transmittance in the visible wavelength region was above 80% for all CZO thin films. The optical band gap of the CZO films decreased from 3.18 to 2.85 eV when the Cu-doping was increased from 2% to 10%. In addition, the water contact angle measurements were carried out to delineate the Cu-doping effects on the changes in the surface energy and wettability of the films.

Ab initio calculations of electronic properties and charge transfer in Zn-=SUB=-1-x-=/SUB=-Cu-=SUB=-x-=/SUB=-O with wurtzite structure

“…In our DFT calculations, for example, the assumed repulsion energy U eff = 5 eV for Zn 5d, Cu 3d and U eff = 8 eV for O 4p Zn 0.944 Cu 0.056 O (3 × 3 × 1) give E g = 3.11 eV which is close to the experimental value. The close optical band gap of 3.18 eV for ZnO thin films doped with 2 at.% Cu has been obtained experimentally [15] (Table 1). For pure ZnO, the calculated value for E g in point Ŵ is equal to 3.221 eV, which also complies with GGA + U calculation values 3.373 eV [12].…”

“…The degree of solubility of acceptor impurities, for example, (Na, Li and N) restricts the hole concentration in ZnSe and ZnTe compounds equivalent to ZnO [11]. Therefore, the investigation of patterns of copper influence on the electronic structure [12], dielectric [13], optical [14,15], magnetic [16][17][18] and other physical properties [19] of the materials based on n-and p-type ZnO is also a challenging problem. In view of possible production of minidevices, doped ZnO nanocrystalline powders and thin films are also addressed [20].…”

Gradient doping of Cu(I) and Cu(II) in ZnO nanorod photoanode by electrochemical deposition for enhanced photocurrent generation

“…We believe that the oxidation state (+1 or +2) of the Cu ions in the ZnO lattice is responsible for the discrepancy in the above findings. In order to properly understand the effect of doping by Cu + and Cu 2+ on the structure of ZnO (NRs), we have estimated the lattice parameters, a and c, from the (002) and (100) peaks of ZnO, using the equation (2) [43], where d is the inter-planer spacing (in Å), h , k and l are the miller indices:…”

Ab initio расчеты электронных свойств и перенос заряда в Zn-=SUB=-1-x-=/SUB=-Cu-=SUB=-x-=/SUB=-O со структурой вюртцита

“…На свойства нанопорошков ZnO, легированных медью, влияют эффекты отжига, температура и концентрация легирующей примеси Cu [9] Степень растворимости акцепторных примесей, например (Na, Li и N), ограничивает концентрацию дырок в аналогичных с ZnO соединениях ZnSe и ZnTe [11]. Поэтому изучение закономерностей влияния меди на электронную структуру [12], диэлектрические [13], оптические [14,15], магнитные [16][17][18] и другие физические свойства [19] материалов на основе ZnО n-и p-типа также остается проблемой. В связи с возможностью создания миниатюрных приборов, внимание уделяется также легированным нанокристаллическим порошкам и тонким пленкам ZnO [20].…”