Opto-Electrical Properties Of Zn_xMg_1-xO Ternary Thin Films

With the development of science and technology,the field of electronic information has made a remarkable progress.As the foundation of electronic information field,the semiconductor materials have been the focus of attention to study.Among the multivariate compound semiconductor materials,the band gap of ZnxMg1-xO crystal can be adjusted in a wide range of 3.3 eV to 7.7 eV.Moreover,the ionic radius of Zn²⁺ is 0.060 nm,and the ionic radius of Mg²⁺ is 0.057 nm,the difference in size is very slight,so it has a slight lattice distortion when replacing the ionic.These features have important significance and broad prospects for the research of photoelectric device.In this paper,ZnxMg1-xO thin films of Mg content in the range of 0.4?0.6 were prepared to study the structural characteristics,surface morphologies,optical properties and electrical properties by the sol-gel method and hydrothermal method,and then ZnxMg1-xO thin films were studied via first principle calculation to predict the semiconductivity and functional properties.Main contents and conclusions are as follows:First of all,the Zn_0.5Mg_0.5O,Zn_0.4Mg_0.6O and Zn_0.6Mg_0.4O thin films were prepared to study the structural characteristics,optical properties and electrical properties by the sol-gel method.By XRD analysis,it shows that there are ZnO and MgO diffraction peak.With increasing annealing temperature,the peak strength are increased,the crystallization is enhanced,the defects are less,the grain size increases.The transmittance of thin film with different composition is good,Indicating a good light transmittance,and The transmittance decreases with the increasing annealing temperature.The band gap increased with the increase of annealing temperature.furthermore,the Zn_0.5Mg_0.5O thin films annealed at 400?600? were prepared to study the electrical properties,it was found that the thin films have obvious bipolar membrane characteristics of switch,but there are no cycle performance.In order to compare the influence of structure and optical properties by different composition,the samples annealed at 700? and 900? of Zn_0.5Mg_0.5O,Zn_0.4Mg_0.6O and Zn_0.6Mg_0.4O thin films are contrasted.XRD analysis shows that the peak strength of ZnO increases and the peak strength of MgO decreases with the increase of the content of Zn.The light transmittance increases with the increase of the content of Zn.However the band gap decreases gradually with the increase of Zn content,this is because that the band gap of MgO is bigger than that of ZnO,resulting in the bigger band gap.Secondly,the Zn_0.5Mg_0.5O thin films were prepared to study the structural characteristics,optical properties and electrical properties by the hydrothermal method.The hydrothermal temperature is set as 150?,the calcination temperature is set as 500?,and regard the value of pH as the first transformational experimental parameters.The XRD analysis shows that there are no diffraction peak of MgO,and the peak strength of ZnO decreases with increasing pH.The transmittance of samples slightly increases with increasing pH,the band gap is biggest at pH=11.All the thin films have rectification phenomenon and obvious bipolar membrane characteristics of switch,indicating the high on-off ratio The the value of pH is set as 10,the calcination temperature is set as 500?,and regard the hydrothermal temperature range from 150 ? to 250 ? as the second transformational experimental parameters.The XRD analysis show that there are no diffraction peak of MgO at 150 ? to 175 ?,the diffraction peak of MgO appears weakly until 200 ?.the transmittance of thin films is highest at 150 ?.The band gaps are bigger with increasing annealing temperature.All the thin films have rectification phenomenon and obvious bipolar membrane characteristics of switch,indicating the high on-off ratio.The the value of pH is set as 10,the hydrothermal temperature is set as 200?,and regard the calcination temperature range from 500 ? to 1000 ? as the last transformational experimental parameters.The XRD analysis shows that there are ZnO and MgO diffraction peak.With increasing annealing temperature,the peak strength of MgO are increased.It indicates that the MgO of cubic phase is prepared successfully by optimizing the experimental conditions.With increasing annealing temperature,the transmittance of thin films becomes lower,The band gaps are bigger obviously.By testing the electrical characteristics,the on-off ratio are bigger with increasing annealing temperature,indicating the high on-off ratio,and device has stability,because the error is smal.Finally,the related supercell model are calculated and analysis by the first principles.It is found that all the band gaps calculated by band structure are smaller than that of the experimental value,this is because that the energy of individual electronic state is overestimated during the first principles calculation,leading the top of valence band move upward and the band gap decreases.Although the calculated values are smaller than the experimental values,the changes of band gaps are consistent with previous experimental results.