Preparation And Optical Properties Of Mg_xZn_1-xO Alloy Materials

ZnO is an important semiconductor and it has very important application in our real life and scientific research. Since it has large exciton binding energy (60meV) at room temperature and a wide direct band gap (3.3eV), it is a perfect material for optoelectronic devices such as light emitting diodes, laser diode. Because the ionic radius of Mg2+(0.57A) is quite similar to that of Zn2+(0.60A), Mg2+can be readily incorporated into the ZnO lattices by substituting the cation sites without causing significant changes in lattice structure. Besides the band gap of MgO is7.7eV, so we can tune the band gap of ZnO by changing the concentration of Mg. In this dissertation, systematic explorations have been carried out on new synthetic stratergies of MgxZn1-xO alloy materials based on chemical solution method. And we gained MgxZn1-xO alloy materials whose band gap can be tuned by using these methods.A novel cation exchange method was used to prepare the MgxZn1-xO alloy materials. The band gap of samples can be tuned from3.16to3.37eV. We investigated the effect of Mg2+:Zn2+and reaction time on the properties of MgxZn1-xO alloys and observed that there exsit an optimal reaction time to gain the MgxZn1-xO alloy which owns a larger band gap.MgxZn1-xO alloy powders were prepared by sol-gel method. From the UV-vis spectrum, we could see that the absorption edge of the MgxZn1-xO powders gradually shifts to higher energy side obviously with increasing the Mg content. The band gap of MgxZn1-xO powders can be tuned from3.01eV to3.41eV. We investigate the effects of annealing temperature and two kinds of sol stabilizers (S)(diethanolamine and triethanolamine) on the optical properties of the Mg0.5Zn0.5O alloy powders. The results show that there exsit an optimal point (S:M2+=1:1,550℃) to gain samples with a larger band gap.We prepared MgxZn1-xO (x=0.1-0.4) films by sol-gel spin coating method and investigated the effects of RTA (Rapid Thermal Annealing) and CTA (Conventional Thermal Annealing) on structural and optical properties of the samples. The Eg of RTA-treated sample is approximately0.2eV larger than that of CTA-treated sample for the same Mg content. We contrasted the UV-vis spectrum of MgxZn1-xO alloy powders and MgxZn1-xO films and found that MgxZn1-xO alloy films own a larger band gap for the same Mg content.