Preparation And Properties Of ZnMgO Thin Films

Zn_1-xMg_xO is a solid solution formed by ZnO and MgO according to a certain proportion.As a wide direct band gap semiconductor material,it is six square wurtzite structure,the band gap is 3.3 eV,the band gap of MgO is 7.8 eV.The radius of Mg²⁺?0.57??is very close to Zn²⁺?0.60??,Zn²⁺can easily replaced by Mg²⁺,which can improve in the UV region?200 nm⁴00 nm?transmittance of ZnO,increase the band gap value,and applied to short wavelength devices.However,the crystal structure difference and large lattice mismatch between MgO?rock salt,4.22??and ZnO?wurtzite,3.25??,Mg²⁺can not be unlimited solid solution in ZnO.Low Mg content Zn_1-xMg_x O?x?0.3?thin films,high Mg content Zn_1-xMg_xO?x>0.3?thin films and high Mg content Zn_1-xMg_xO?x>0.3?films with buffer layer were prepared by sol-gel method on quartz glass substrates in this paper.The phase composition,optical,surface morphology and electrical properties of Zn1-xMgxO thin films were analyzed by XRD,thermal analyzer,UV-VIS spectrophotometer,AFM and semiconductor characteristic analysis system?2430?.The main content is as following:1.Low Mg content oriented Zn_1-xMg_x O?x?0.3?thin films prepared by sol-gel method.Effect of growth orientation of the films by stabilizer type?MEA?DEA?had studied,which proved DEA had the advantages of prepared orientation low Mg content Zn_1-xMg_xO?x?0.3?thin film.At the same time,the effect of annealing temperature and Mg content of prepared single-phase six square Zn_1-xMg_xO?x?0.3?is also studied,The Zn_0.7Mg_0.3O thin films prepared by annealing at 450?have a single phase ZnO structure and the optical band gap can be adjusted to 3.79 eV.2.The high Mg content Zn1-xMgxO?x>0.3?thin films were successfully prepared by sol-gel method.It was found that Mg content and annealing temperature could affect the solubility limit of Mg²⁺in ZnO.The effects of annealing temperature on the phase segregation and optical absorption edge shift of Zn_0.5Mg_0.5O films were investigated.It is found that the optical absorption edge of the Zn_0.5Mg_0.5O thin films annealed at 400?is the largest and the phase segregation is avoided.At the same time,the optical band gap of Zn_1-xMg_xO?x=0⁰.8?thin films annealed at 400?was studied.The results showed that,with the increase of Mg content,the absorption edge in the UV-visible transmittance spectrum blue shifted regularlity,the optical band gap tuning from 3.3 eV to 4.2 eV.3.The effects of buffer layer type,annealing mode,annealing temperature and Mg content on the phase composition and the band gap adjustment of high Mg content Zn1-xMgx O?x>0.3?thin films with buffer layer were studied.Based on the pure ZnO buffer layer,the phase composition of Zn_0.5Mg_0.5O films is not single phase ZnO structure,phase segregation is occured,and the UV-visible transmittance spectrum also has a notable double absorption edge phenomenon;The Zn0.5Mg0.5O thin films based on Zn_0.8Mg_0.2O buffer layer also has the phase segregation,but the transmittance spectrum has only a single absorption edge,the optical band gap is adjusted to 3.61 eV.The Zn0.5Mg0.5O thin films with the concentration gradient buffer layer annealed at 450?rapidly have a single phase wurtzite structure,and no phase segregation occured.The blue shift of the optical absorption edge is largest,and the band gap value is adjusted to 3.76 eV.