Construction Of Photoelectron Spectroscopy Station, Beamline And Study Of Cu/3C-SiC Interface Fomation

Two aspects are included in this dissertation. One is the re-construction of photoelectron spectroscopy beamline and endstation at NSRL. The other is the study of Cu/3C-SiC interface formation.Photoelectron spectroscopy beamline and endstation at NSRL had played an important role in many kinds of new scientific experiments and obtained many important results since it was constructed. But because of some problems, the beamline couldn't be used efficiently, so it is necessary to be modified. The new beamline will cover the photon energy from 60 to 1000 eV with resolution power better than 650(E/â–³E). The monochromatic spot size at the sample is about 1 mm(h)×0.8 mm(v) with flux better than 4×10⁹ photons/s (200 mA 15×1 mrad² 0.1% b.w.).The new beamline was made of prefocusing system, entrance slit, monochromator, exit slit and re-focusing system. The cylindrical-toroidal mirrors system was selected as the prefocusing system. The imaging performance of this system is almost the same as that of the famous grazing KB system, but with reduced mirror dimensions. So the mirrors can be manufactured with better quality and lower cost comparing with other prefocusing systems. The good image quality at the entrance slit proves that this system works successfully. A 'Dragon' momochromator was selected. Because of its less optical element and the simple working mechanism with excellent performance, the 'Dragon' design has been used extensively in the VUV and soft X-ray regions. A toroidal mirror was used to re-focus the SR light along the vertical and horizontal direction on the sample spot.The ray tracing program-SHADOW had been used to examine the performance of the beamline, which included the dimensions and radius of all mirrors, the image on entrance slit by prefocusing system, the resolution power of the monochromator and the light spot size on the sample. The calculation result of flux is over 10¹¹ and 10¹⁰ photons/s(200 mA 15×1 mrad² 0.1% b.w.) at middle and high photon energy region respectively by taking into account of the acceptance of synchrotron radiation, the reflectance of all mirrors, the diffraction of grating and the geometrical transmission of the beamline.The beamline performance is strongly related to the alignment accuracy and carefully commissioning. We had tested all main components off-line and put the key parts in the beamline by precise equipment. Mirrors position was adjusted by simulative laser. The monochromator is the core of the beamline. It includes sin-bar drives and switchable device. Laser interferometer measurement shows the linear guide accuracy is within 6μm. The sin-bar length is calibrated to be 491.19 mm and the angle error is less than 4 seconds by fitting method. At 135/70μm slits, the resolution power of monochromator and the photon flux at the sample had been obtained. The resolution power is 1403, 986 for the 700 l/mm grating at 250 eV, 450 eV, and 1033, 1073 for the 1200 l/mm grating at 500 eV, 650 eV respectively by measuring the Au 4f photoemission with VSW HAC5000 hemispherical analisyser. The photon flux is better than 3×10⁹ photons/s (200 mA 15×1 mrad² 0.1% b.w.) in the energy range of 350-1000 eV and better than 10¹⁰ photons/s (200 mA 15×1 mrad² 0.1% b.w.) in the energy range of 200-500 eV. The results meet the designed specificationA new kind of 18 bit D/A was designed for the photoelectron spectrometer. This 18 bit D/A is transformed by three 16 bit D/A. Its stability and repeatabilty were tested and the results could achieve the goal. The new experiment software can control the beamline monochromator effectively as well as the experimental endstation. The program of the experiment endstation can not only do XPS mode for photoemission experiments but also do different experiment modes such as CIS, CFS, EDC, etc. which are needed for photoelectron spectroscopy experiment by using synchrotron radiation.Silicon carbide (SiC) is one of the most important wide-band gap semiconductor with excellent physical and chemical properties, and is a promising material for many applications in electronic and optoelectronic devices working in extreme conditions such as high temperature, high frequency, high voltage and high power density. SiC material will play an important role in modern semiconductor device technology. Cu is one of the most attractive materials for the future electronic devices, because of its low resistivity and high electromigration resistance. A thorough understanding of the Cu/SiC interfacal properties is important to make SiC-based technology viable. Presently however, most of basic studies of Cu/SiC system are investigating interactions between liquid copper and solid SiC substrates, while few studies of solid state interface property and reaction between Cu and SiC have been reported. The Cu/3C-SiC(111) interface formation at room temperature was investigated using synchrotron radiation photoelectron spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS) by stepwise evaporation of Cu in UHV up to a thickness of 2 ML .The binding energy of the XPS Cu2P_3/2 core level peak shifted from 933.1 eV at 0.08 ML coverage to 932.8 eV at 2 ML Cu deposition, The kinetic energy of SRPES Si2P core level peak shifted from 43.55 eV at 0ML coverage to 43.87 eV at 2 ML Cu deposition. The stable peaks indicate that no significant chemical reaction has taken place between Cu and SiC at RT. The growth of the film was initially via 2D-cluster formation and exhibited a 3D character above 0.1 ML. The surface states on the SiC surface were found to disappear when a little Cu was deposited. The height of the Schottky barrier for the Cu/3C-SiC (111) contact was found to be 1.2 eV at 2ML Cu deposition.