Study Of Heterojunction Ultraviolet Detector Based On In-situ-growth Wide-bandgap Materials

Technology exists in every corner of the world in this age with rapid development of science,and ultraviolet detection?UV?has become a new technology with both practical prospect and sustainable development.Its wide application has involved the flame detection,astronomical detection,optical communications,imaging technology and optoelectronic integrated circuits.So it is imminent to develop a low cost UV photodetector with low noise current,high responsivity and sensitivity and fast response speed.So far,the wide bandgap semiconductor material based UV detectors have great advantages in the synthesis of low dimensional nanomaterials.But the shortcoming of single phase semiconductor material is clear,for example the responsivity of device cannot get breakthrough,dark current is high and response speed is very slow.In recent years,we have tried variety ways to improve the performance of device.Forming heterojunction is an effective way by using the energy level difference to improve the performance.In this paper,by using one dimensional titanium dioxide?TiO₂?as the foundation,we prepared strontium titanate?SrTiO₃/TiO₂?and barium titanate?BaTiO₃/TiO₂?composite materials to made UV photodetectors.Through related characterization and device performance test,we explored the photoelectric detection performance and working principle.At first,we prepared one-dimensional TiO₂ nanowires array by low temperature polarity hydrolysis method.The nanowires uniformly distributed on the FTO substrate which was obtained by SEM characterization.The cusp didn't adhere each other and forked obviously,which showed the morphology characteristics of one-dimensional semiconductor.The high surface-to-volume ratio and carrier transmission efficiency laid a foundation for the preparation of heterojunction.Next,we prepared SrTiO₃/TiO₂ heterojunction by two steps in-situ hydrothermal method.TiO₂ played the role of the resultant in first step reaction and the reactant in second synthesis,which effectively reduced the impurity doped.The growth of heterojunction was based on Ostwald ripening effect which accumulated continuously and eventually connected the void position of nanowires.The composites showed great ultraviolet spectral absorption selectivity and blue shift characteristics of spectral response,so the range of spectral response was adjustable.Contrast the device performance of SrTiO₃/TiO₂ and TiO₂,the light-dark current ratio,light response and recovery speed of the heterojunction have a great breakthrough,which owed to the energy level differences.Detailed analysis of the mechanism would be given in this paper.At last,we would broaden the study of in-situ-growth heterojunction materials.We prepared BaTiO₃/TiO₂ heterojunction by two steps in-situ hydrothermal method in the fourth chapter.The growth of heterojunction filled the space of nanowires and the morphology would be destroyed when we increased the precursor of the reactants.The composites showed great ultraviolet spectral absorption selectivity and red shift characteristics of spectral response.Compared with that of single TiO₂,the device performance of BaTiO₃/TiO₂ heterojunction improved.This would be explained in detailed mechanism in the paper.We prepared TiO₂ nanowires array and two kinds of heterojunction materials and made the devices used in UV detection field.The devices had large improvement in photoconduction performance,which provided a broader research direction for UV detection technology.