Optical and Electrical Properties of ZnMgO with High Mg Content Elaborated by Ultrasonic Spray Pyrolysis Using Water‐Based Solutions

Abstract

ZnMgO thin films are elaborated by ultrasonic spray pyrolysis using water‐based solutions only, for an Mg composition as high as 70 mol%. The elaboration conditions are optimized and the structural, optical, and electrical properties of the ZnMgO films are investigated with respect to the Mg concentration using X‐Ray fluorescence, X‐Ray diffraction, atomic force microscopy, Raman and transmission spectroscopies, and van der Pauw/Hall effect electrical measurements. The obtained properties are correlated to analyze the miscibility and, for single‐phase material, the optoelectronic, optical, and transport properties with respect to the composition. The elaborated thin films exhibit a monotonous increase in the bandgap, a high transparency above 90% in the visible region, and a dramatic decrease in the n‐type carrier concentration, for Mg compositions lower than 30 mol% where wurtzite single‐phase structure is evidenced. A compensation mechanism of the n‐type dopants in ZnO, attributed to interstitial Zn which acts as a shallow donor, is given as an explanation of this variation of the carrier concentration. These optoelectronic properties show that ZnMgO can be efficiently used in applications such as UV detectors and solar cells.

ZnMgO Thin Films by Ultrasonic Spray Pyrolysis: Modulation of Optical and Electrical Properties by Post‐annealing and Magnesium Composition

“…These parameters are the precursors' solution pH and concentration, the shaping air pressure, and the flow rate. The other deposition parameters, namely the growth temperature, the nozzle-to-substrate distance, the number of spray cycles, the nozzle speed, and dwell time, were fixed to their optimized values as obtained in previous studies using the Accumist nozzle [6,14] since they are not noticeably affected by the Impact nozzle. Table 1 summarizes the deposition parameters range and the obtained optimal values; and 2) The postannealing temperature, varied from 200 to 400 °C and its duration, varied from 0.5 to 2 h under nitrogen atmosphere.…”

“…A schematic view of this system is shown in Figure 1. This nozzle offers the advantage, compared to that used in previous studies (Accumist), [6,14] of producing homogeneous films on larger surfaces. Deposition was carried out in ambient atmosphere.…”