The Preparation And Charaterization Of Noval Structural Semiconductor Materials

The advanced semiconductor material have been widely used in the areas of micro-electronics, environment protection and aeronautics/astronautics and are becoming the hot area of material research, owning to their unique physical and chemistry properties. The development of nano-science and nano-technology promotes the development of advanced semiconductor materials, resulting not only in the improvement of the properties, but also in the enlargement of their structure and morphologies.In this dissertation, with TiO₂ and ZnO as the main research objects, the preparation process for novel structures was studied, the properties and structures were characterized and the growth mechanisms were proposed. Meanwhile, the application research of III-V compound semiconductor GaN in lighting indystry was also introduced.1. The TiO₂ nanotubes have been prepared successfully by hydrothermal process, for which the diameter is about 10nm-20nm. The products are in anatase phase, and with multiple walls. The growth mechanism of TiO₂ nanotubes was discussed. Blue shift can be observe din the UV-VIS and PL spectrum of the TiO₂ nanotubes, compared with that of raw power TiO₂. Meanwhile, it was also found that the TiO₂ nanotubes are efficient in decomposing methyl orange, which suggests that the samples have excellent photocatalyst property.2. The K₂Ti₆O₁₃ nanowires have been synthesized by hydrothermal process from TiO₂ and KOH. The structure of nanowires has been investigated using both the Rietveld powder diffraction profile fitting technique and high resolution transmissionelectron microscopy (HRTEM) image simulations. From the Rietveld analysis it was shown that the nanowires had a monoclinic structure of the space group C2/M. The good agreement between the experimental and simulated images confirms that the nanowires is composed of K^TiaOuwith layered structure. The HRTEM conclusions agree with refinement results obtained from experimental XRD data. The nanowires growth direction of the nanowires is along the [010] direction.3. ZnO tetrapod whiskers(T-ZnO) with four hollow arms have been synthesized successfully by directly heating the mixture of zinc oxide and graphite at 1100°C in air for the first time. The as-synthesized product was characterized by means of XRD, FESEM, TEM, SAED and EDS. The effects of experiment parameters on the morphology of products were studied, a possible growth mechanism was proposed. The results showed that the tetrapod whiskers with four hollow arms were composed of pure ZnO, PL spectra at room temperature revealed that an intensive green emission is raised from the recombination of the oxygen vacancy, which can enlarge the application in the visible band.4. Hierarchical growth of zinc oxide nanowires/nanosheets arrays was achieved at 1000°C-1100°C by the carbothermal reduction method using zinc oxide and carbon powder as raw materials, no O2 /Ar and catalyst were used. The characterization of the samples showed that the as-grown crystal is pure hexagonal Wurtzite structure. This new structured ZnO will be widely used in micro-sensors and micro-reactors, which provide new ideas and methods for the further research on self-assembly technology.5. By the carbonthermal reduction process, ZnO nanosheets were synthesized successfully by directly heating the mixture of zinc oxide and carbon powder in N2/H2O atmosphere. The nanosheet is about lOOnm in diameter and 50nm in thickness. The results showed that the product is composed of pure Wurtzite ZnO. It was also found that at higher reaction temperatures the nanosheets would change into hexagonal tower-shaped crystal, indicating that the morphography of the nanosheet is in hexagonal shape. The new structured ZnO will find applications in micro-sensors and composite nanodevices.At the reaction temperatureof 1120°C, the perfecttower-like ZnO crystal was formed, thus a new member of the ZnO family was created.6. In the application of III-V compound semiconductor GaN, the white LED with uniqe properties was prepared, the results can promote the development of semiconductor illumination project.