Investigation Of Preparation And Luminescent Properties Of Wide Bandgap Semiconducting Materials-ZnO,TiO₂ And Diamond

The development of wide bandgap semiconductor materials brings a new technological and industrial revolution and promotes the development of information technology. Relative to SiC and GaN, ZnO,TiO₂ and diamond were new wide bandgap semiconductor materials. With excellent optical, electrical properties, they reveal potential application in various fields. Up to now, there are many unknown domains for them. In this paper, several characterization ways were adopted to study their optical properties. The main results are listed as follows:1,Polycrystalline wurtzite ZnO nanorods were prepared by hydrothermal method. In addition to 390nm emission peak related to near band edge emission, we also observe a wide peak at 570nm from fluorescence spectrum resulted from the surface Zn (OH)₂ or OH^-. The temperature-resolved spectra are also regarded as confirmation. Mn and Cr-doped ZnO thin films were grown by sol - gel process and magnetron sputtering. Lattice constant changes are considered to be inconsistent with Zinc ions'radius. Besides, doping of transition metals into makes the conduction band moving down and valence band up due to sp-d orbital hybridization coupling and then narrows bandgap. In addition, Mn-doped ZnO films reveal emission peak at 415nm corresponding to Mn²⁺ of the ⁴A₁(G)â†'⁶A₁(S) transitions.2,Hydrothermal and sol - gel methods were employed to prepare different sized TiO₂ nanoparticles and Fe doped TiO₂ films. XRD patterns of TiO₂ nanoparticles show anatase structure by annealed below 650℃and anatase structure accompanying rutile at higher temperatures. Fluorescence spectra display a broad peak ranged from 350nm to 550nm, which include near band-edge emission peak at 400nm and 480nm defect peak linked to O vacancies or surface defect states. We observe red shift of the broad peak with increasing annealing temperatures, which may be related to both quantum size effect and rutile TiO₂. Fe-doped TiO₂ films remain anatase structure with smaller lattice constant. After Fe doped, the intensity of TiO₂ emission peak is weakened.3,The luminescent properties of free-standing diamond films prepared by DC plasma jet chemical vapor deposition technology are investigated. Fluorescence spectroscopy reveals two main emission peaks centered at 440nm and 530nm associated with dislocation defects and nitrogen-vacancy complexes, respectively. In addition, we also investigate boron-doped diamond films by hot filament chemical vapor deposition. Multi-peak fitting fluorescence spectra show that the intensity of 440nm enhances with increasing boron concentrations.4,Summarize the luminescent properties of these three materials and the modification of band gap after doping.