| Wurtzite structure of zinc oxide has a wide band gap(3.37 eV)which has been widely used in semiconductor photoelectric catalysis and microelectronic devices.Fully understanding the ZnO surface and interface characteristics and understanding the surface electronic structure and geometrical structure will be necessary for studying surface reaction.Moreover,it also plays a decisive role in preparation for high quality of heterogeneous and homogeneous epitaxial film.In our work,we use ultra high vacuum surface analysis techniques(including LEED-low energy electron diffraction,XPS-X-ray photoelectron spectroscopy and STM-scanning tunneling microscopy)to study the physical and chemical properties of metal oxide surface.We select two ZnO representative two surfaces:the polar ZnO(0001)surface and nonpolar ZnO(10-10)surface.We use STM as the main technique to study the geometric and electronic structure.The main research contents and results are as followed:(1)We use ultra high vacuum surface analysis techniques to study the geometric and electronic structure of ZnO(0001)surface in ultra high vacuum condition.On the basis of previous work,we determine the ZnO(0001)surface morphology characteristics:the surface has a large number of triangular islands.Its step height is about 3 A and there are a lot of different sizes of triangular islands and holes on the terrace.Moreover,the triangle holes on the island are the same or opposite directions.This phenomenon is determined by the mechanism of ZnO(0001)surface.In addition,we get the higher resolution STM images.It is worth mentioning that we find the step edge of triangle island is not a straight line but a wavy line.We also find the sawtooth morphology.Moreover,we summarize and analyze the ZnO(0001)surface morphology characteristics,trying to explain the reasons of the formation of triangular island structure.The research for the ZnO(0001)clean surface lay the foundation for the molecule adsorption and catalysis reaction.(2)We have a research about the different amount of oxygen adsorbed on ZnO(0001)surface at room temperature and high temperature.Because of the oxygen vacancy,we get a peak on higher binding energy compared to the standard O1s peak after adsorption,which shows a certain amount of oxygen have been adsorbed on ZnO(0001)surface at room temperature.But due to quantity of the lack oxygen is limited,so increasing the exposure of oxygen,the XPS results do not changed.For the adsorption of oxygen at higher temperature,there was no oxygen adsorbed on the surface due to the high energy.So even increase the exposure of oxygen,the XPS and STM results do not have any changes.(3)We use ultra high vacuum surface analysis techniques to study the electronic structure and geometric structure of ZnO(10-10)surface.After several cycles of preparation,we can use STM to get atomic resolution ZnO(10-10)surface topography:along the[0001]and[1-210]direction presents nearly rectangular flat steps with a single atomic layer height(3 A).The light chain is the zinc which along the direction[1-210].The atomic resolution of STM image of ZnO(10-10)is necessary for the later research. |
