利用磁控溅射方法改变衬底温度,制备了一系列NiO:Cu/ZnO异质pn结。实验结果表明,当衬底温度从室温升高到300℃时,NiO:Cu/ZnO异质pn结的整流特性明显得到改善;与此同时,NiO:Cu/ZnO异质pn结的光学透过率也从40%增大到80%。这可能是由于NiO:Cu薄膜结晶质量改善,薄膜内缺陷减少所致。继续增加衬底温度至400℃,异质结的整流特性有所削弱,这可能是由于生长在异质结下层的NiO:Cu薄膜影响了其上ZnO薄膜的生长,进而影响到异质结的整流特性。这一结论,得到X射线衍射(XRD)、原子力显微镜(AFM)和紫外(UV)谱测试结果的支持。
In the present study we have fabricated NiO:Cu/ZnO pn heterojunctions at various substrate temperatures by magnetron sputtering method.X-ray diffraction(XRD)analyses reveal the formation of wurtzite-type ZnO structure,and NiO:Cu films show polycrystalline when the substrate temperature is set at room temperature.The(111)peaks of NiO:Cu are improved obviously with increasing substrate temperature.However,(002)peaks of ZnO are depressed at higher substrate temperature of 400 ℃.Furthermore,the right-shift of(111)peaks of NiO:Cu with the substrate temperature indicates that the c axis distances shrink.It can be explained by that the strain caused by lattice mismatch between NiO:Cu films and substrates will be relaxed and the native defects will be decreased in the heterojunctions through increasing substrate temperature.The improvement of crystalline in heterojunctions contributes to the increased optical transmittances and the decreased optical gaps of NiO:Cu films when the substrate temperature increases.Typical rectifying properties are shown in the heterojunctions and the best rectifying property appears at 300℃,which can be attributed to the decreased defects,which is also evidenced by the results of XRD,atom force microscope(AFM)and UV spectra.Good rectification behavior and high optical transmittance in NiO:Cu/ZnO pn heterojunctions indicate that they have the application prospect of future transparent optoelectronic devices.