Influence of growth time on crystalline structure, conductivity and optical properties of ZnO thin films

Abstract

This paper examines the growth of ZnO thin films on glass substrate at 350 ı C using an ultrasonic spray technique. We have investigated the influence of growth time ranging from 1 to 4 min on structural, optical and electrical properties of ZnO thin films. The as-grown films exhibit a hexagonal structure wurtzite and are (002) oriented. The maximum value of grain size G D 63.99 nm is attained for ZnO films grown at 2 min. The average transmittance is about 80%, thus the films are transparent in the visible region. The optical gap energy is found to increase from 3.26 to 3.37 eV with growth time increased from 1 to 2 min. The minimum value of electrical resistivity of the films is 0.13 cm obtained at 2 min. A systematic study on the influence of growth time on the properties of ZnO thin films deposited by ultrasonic spray at 350 ı C has been reported.

Substrate Temperature Effect on Optical property of ZnO Thin Films

“…As clearly seen in Fig. 3, the variations of both Eg and Eu correlate very well, the optical gap energy decreased with increasing of substrate temperature from 3.44 to 3.29 eV, the band gap is narrowing due to the decrease in the transition tail width and shift effect [15,21]. Witch explained by increasing in carrier concentration.…”

“…We are noting that the temperature effect is clearly observed in the layer quality. These results show that the produced ZnO thin films could be used in solar cells due to the low absorbance in the visible region [15,21]. In order to investigate the effect substrate temperatures on ZnO films further, the optical band gap energy g E was measured from the transmission spectra using the following relations [23]:…”

“…The deposition was performed at different substrate temperatures was 300, 350 and 400 °C with 2 min of deposition time [21].…”

“…ZnO thin films can be produced by several techniques such as reactive evaporation and thermal annealing [6], molecular beam epitaxy (MBE) [7], magnetron sputtered technique [8], pulsed laser deposition (PLD) [9], the low-temperature solution method [10], the sol-gel technique, chemical vapor deposition, electrochemical deposition [11] and spray pyrolysis [12], have been reported to prepare thin films of ZnO. Among these, we will focus more particularly in this paper on the ultrasonic spray technique that is a low cost method suitable for large-scale production, it has several advantages in producing nanocrystalline thin films, such as, relatively homogeneous composition, a simple and deposition on glass substrate because of the low substrate temperatures involved, easy control of film thickness and fine and porous microstructure [13].…”

The crystalline structure, conductivity and optical properties of Co-doped ZnO thin films

“…The film doped at 2 wt% has higher and sharper diffraction peak indicating an improvement in (0 0 2) peak intensity compared to the undoped ZnO thin film and the films doped at 1 and 3 wt%. The deposited films exhibit nanocrystalline structure with hexagonal wurtzite structure from the spectra [16,17]. This indicates that all films have preferential c-axis orientation along the (0 0 2) plane [18].…”