Research On Preparation And Optoelectronic Properties Of Infrared Transparent Conductive Films

The research topic of this paper comes from the project of National Natural Science Foundation of China,the project name is:The Research of Optoelectronic Properties and Preferred orientation Preparation of the Delafossite Structure Cu XO₂ infrared Transparent Conductive Films,the project number is:No.11404129.Infrared transparent conductive film has significant application value in military and civilian fields.In the civilian field,it can be applied to fields such as electronics and energy industries,sensing technologies,and optoelectronic technologies.For the military field,it can be applied to infrared imaging,spacecraft windows and other fields.At present,domestic and foreign scholars have obtained infrared TCO films with excellent photoelectric properties in the near-infrared band,but there are few studies on mid-infrared and far-infrared TCO films.In this paper,we prepared three mid-infrared TCO films by magnetron sputtering:CuCrO₂,In₂O₃ doped Hf（IHfO）and In₂O₃ doped W（IWO）films.And we studied their photoelectric properties.The main contents are:（1）We prepared CuCrO₂ film by Co-sputtering.We use CuO ceramic target and Cr target as sputtering source.The effect of CuO sputtering power and annealing temperature on the structure and optoelectronic properties of the thin film was studied.It was found that when the annealing temperature is gradually increased,the crystallinity become good,and the（012）crystal plane has a preferred orientation.Both the electrical conductivity and the transmittance of the thin film decrease as the annealing temperature increases.The lowest resistivity of the film was 13.36Ω·cm,and the average transmittance in the 2.5-4.5μm band was 66.5%.As CuO sputtering power gradually becomes larger,its crystallinity becomes better,and the transmittance and resistivity of the film both show a tendency of gradually decreasing.（2）IHfO thin films and IHfO/Cu/IHfO trilayer thin films were prepared by RF magnetron sputtering.It is found that as the annealing temperature increases,the IHfO thin film changes from an amorphous state to a crystalline state,and the grain size becomes larger.When the annealing temperature is gradually increased,the electrical conductivity and the transmittance of the thin film first increase and then decrease.When the film was annealed at 100°C,the transmittance of the film was the highest and the average transmittance in the range of 2.5 to 4.5μm was 77.8%,the resistivity of the film was 1.78×10^-1Ω·cm.When annealing at 300°C,the minimum resistivity of the film is 9.21×10^-3Ω·cm,and the average transmittance in the 2.5-4.5μm range is 70%.As the film is thickened,the film crystallinity becomes better,and the optical transmittance of the film gradually decreases.The IHfO/Cu/IHfO trilayer film has higher conductivity than the single IHfO film,but the infrared transmittance is slightly lower.The film thickness of the Cu layer is closely related to the optoelectric properties of the IHfO/Cu/IHfO three-layer film.The resistivity and IR transmittance of the IHfO/Cu/IHfO three-layer film shows a clear downward tendency with the increase of Cu film thickness.（3）We prepared IWO thin film by RF magnetron sputtering.The relationship between the sputtering power,O₂ flow rate and the photoelectric properties of the thin film was studied.By analyzing the XRD results,when the sputtering power gradually becomes larger,it changes from the amorphous state to the crystalline state.When the O₂ flow rate gradually increases,its conductivity decreases and the transmission increases continuously.A bilayer IWO film was also developed.The structure was as follows:the first layer was prepared by magnetron sputtering without O₂;the second layer was prepared by magnetron sputtering with O₂.As the flow rate of O₂ gradually increases,the transmittance of the bilayer film increases and the conductivity decreases.This bilayer film has superior optical and electrical properties in the mid-infrared band compared with single-layer IWO films.When the flow rate of O₂ is 0.2sccm,the resistivity of the thin film is 1.131×10^-3Ω·cm,and the average transmittance in the 2.5-4.5μm range is 74.65%.