Transparent conductive ZnO thin films grown by chemical spray pyrolysis: the effect of Mg S. Kurtaran 1 • S. Aldag 1 • G. Ofofoglu 1 • I. Akyuz 1 • F. Atay 1 Received: 8 March 2016 / Accepted: 18 April 2016 Ó Springer Science+Business Media New York 2016 Abstract Mg doped ZnO films have been prepared via Ultrasonic Spray Pyrolysis technique. Effect of Mg con- centration on the structural, optical, surface and electrical properties of ZnO films have been investigated. X-ray diffraction studies showed that all of the samples are polycrystalline with hexagonal wurtzite structure. Thick- nesses and optical constants (refractive index and extinc- tion coefficient) have been determined using spectroscopic ellipsometry technique and Cauchy–Urbach model. UV– VIS spectroscopy has been used to take transmittance measurements and optical band gap values have been cal- culated using optical method. Surface morphologies and roughness values of the films have been investigated by atomic force microscopy. A four-probe setup has been used to determine the electrical resistivity values. Photolumi- nescence spectra showed an ultraviolet emission band around 365–400 nm and the visible emission peaks between 469 and 590 nm. It has been concluded that Mg doped ZnO films have value to work on and may be promising materials for optoelectronic applications. 1 Introduction As we know, ZnO is a promising candidate for future high quantum efficiency light emitting/detecting device operat- ing in the blue and ultra-violet regions, owing to its wide and direct band gap of 3.37 eV at room temperature and a large exciton binding energy of 60 meV [1–6]. Previous works on ZnO thin films focused on the variations of optical, electrical and structural properties with different additive elements [7–20]. However, there are studies about the effect of dopants such as Al or Mg on the orientation of crystalline domains and electrical properties of the films. While some elements, such as Cd, decrease the band gap, when ZnO thin film is doped with Mg, the band gap became larger with increase of Mg content [5, 6, 21–25]. One of the most important approaches involved in designing optical and electrical confinement structures is band gap engineering. ZnO has ability to make alloys with Magnesium, Cadmium and Aluminium oxides. In particu- lar, alloys made from ZnO and MgO give wide band gap semiconducting material with a highly tunable band gap, which can be controlled by Mg concentration in a wide range. Therefore, Mg atom is an important element for the realization of ZnO-based optoelectronic devices and solar cells. A number of different techniques have been used to elaborate Mg doped ZnO films, such as radio frequency (rf) magnetron sputtering [26–28], spray pyrolysis [9, 29–32], pulsed laser deposition [24, 33, 34], chemical vapor deposition [35–38] and sol–gel method [22, 39–42]. Among them, the spray pyrolysis is an attractive method, because large-area films with good uniformity can be grown at low cost. Recently, Mg doped ZnO films have found great interest, because of their wider band gap compared to pure ZnO and possibility of band gap modu- lation through adjusting Mg content. The aim of this study is to produce Mg doped ZnO thin films with an economic manner using ultrasonic spray pyrolysis (USP) technique and investigate the effects of Mg doping rate on the structural, optical, surface and electrical properties of ZnO films. & S. Kurtaran skurtaran@ogu.edu.tr 1 Department of Physics, Eskisehir Osmangazi University, 26480 Eskisehir, Turkey 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-016-4862-1