Preparation And Characterization Of MgZnO Thin Film And Its Devices

MgZnO film has a lot of advance, such as high transmittance, wide band gap and the band gap can be continuously adjusted. MgZnO film is widely used in CIGS thin film solar cells, UV detector and other photo-electronic devices. The current research on MgZnO film is still in the laboratory stage and not been put into commercial applications, so the growth of high quality MgZnO film is particularly important. The Mg elemental composition in MgZnO film, growth methods, growth conditions and post-processing will influence the properties of the MgZnO film, also the properties of the MgZnO film will determines the device performance.The MgZnO thin film is been grown by RF magnetron sputtering method. We focused our attention on the effects of different growth conditions and post-processing of MgZnO thin film properties. By changing the sputtering time, sputtering power, substrate, annealing temperature and annealing time we analysis the structure and optical properties of MgZnO film. Also we compared the difference of the properties of MgZnO film grown in different conditions, aimed at finding the best conditions to sputtering MgZnO film.The main contents and results of this paper are as follows:1. We studied the effects of sputtering time on the MgZnO film properties. The sputtering time was15min,25min,35min and45min, respectively. The properties of MgZnO films were analyzed by XRD, AFM and transmittance test. We investigated how the sputtering time influence the structure, grain size, film thickness and band gap. With the sputtering time increasing, we found that the grain size, the thickness of thin films and the band gap also increased, and the diffraction peak location shifted to a large angle. These phenomena indicate that the Mg/Zn ratio in MgZnO thin film becomes large with the increasing sputtering time.2. We studied the effects of sputtering power on the MgZnO film properties. The sputtering power was100W,150W and200W, respectively. The properties of MgZnO films were analyzed by XRD, SEM and transmittance test. We investigated how the sputtering power influence the structure, grain size, film thickness and band gap. As the sputtering power increased, the half width of the diffraction peak decreased, this indicated that the crystal quality becomes better, also the thickness are increasing. The increased band gap and the right shift of diffraction peak position indicated the Mg/Zn increased with the increasing sputtering power. This because during the sputtering process, Mg2+is easier binding with O2-than Zn2+. However the grain will melting when the sputtering power is too large, so the sputtering of150W is best for the growth of high quality MgZnO thin films.3. We studied the effects of substrate on the MgZnO film properties. The thin films were fabricated on soda-lime glass, quartz, Si and sapphire. The properties of MgZnO films were analyzed by XRD and transmittance test. We investigated how the substrates influence the structure, grain size, film thickness and band gap of MgZnO films. We found that the quality of thin films grown on sapphire and quartz are better than those grown on soda-lime glass and Si. But the transmittance of the films grown on sapphire is lower than that grown on quartz. Also the price of sapphire is much higher than other substrate, so we think quartz is the most suitable substrate for the growth of MgZnO thin films.4. We studied the effects of Mg content in MgZnO thin film on the film properties. The properties of MgZnO thin films were analyzed by XRD and transmittance test. We investigated how the Mg contents influence the structure and optical properties of MgZnO films and calculated the grain size, film thickness and band gap. We found that the crystalline quality of Mg0.16Zn0.84O and Mg0.23Zn0.77O are better than others. The grown rate of Mg0.16Zn0.84O is faster than the other three samples. The band gap of MgZnO thin films increasing with the Mg contents increased.5. We studied the effects of thermal annealing on the MgZnO film properties. Firstly, we studied the effect of annealing temperature on MgZnO film properties. The annealing temperature is200℃and400℃, the annealing time is60min. Also we studied the effect of annealing time on MgZnO film propertiea. The annealing time is30min,60min and90min, the annealing temperature is300℃. The properties of MgZnO films were analyzed by XRD and transmittance test. As the annealing temperature increased, the FWHM of the diffraction peak decreases, this indicated that the crystalline quality is getting better. This indicated that the annealing process can eliminate the stress of grain and contribute to the recrystallization process. The higher the annealing temperature, the grain growth faster and the the grain size get larger. The thickness of MgZnO thin films get thinner after annealing process, and the thickness decreased with the increasing annealing temperature. This indicated the annealing process can release the stress in the films.