[en] We study the electronic and optical properties of hexagonal 6H-SiC crystal, using ab initio full potential augmented plane wave method. The density of states (DOS) and band structure are presented based on local density function theory. From the electronic structure calculation, the imaginary part of the dielectric function has been obtained directly using the joint DOS and the optical matrix elements. With band gap correction, the real part of dielectric function can be derived from the imaginary part by the Kramers-Kronig relationship. The reflectivity for normal incidence is also calculated. The resulting spectrum is in good agreement with available experimental data in a wide energy range

[en] The authors calculate the atomic and electronic structure of β-SiC(001)-(2 x 1) using augmented plane wave and local orbital (APW + LO) method. The calculated results show that the atomic structure of β-SiC(001)-(2 x 1) surface can be described by symmetrical Si dimmer model, which is different from the asymmetrical Si dimmer model of Si(001)-(2 x 1) surface. The bond length of Si dimmer of β-SiC(001)-(2 x 1) surface is 0.269 nm, which is larger than that of Si(001)-(2 x 1) surface. The calculated results of electronic structure show that a prominent density of states exists at the Fermi level, so β-SiC(001)-(2 x 1) surface has the characteristics of metal. There are four surface state bands in the gap. Among them, two occupied surface state bands have been confirmed by valence band spectra of synchrotron radiation photoelectron spectroscopy. (authors)

[en] The work function changes for ammonia absorbed on Au, Ta and Yb have been measured at 80 K. With a layer of Cs deposited on the top of solid ammonia the work function became lower than that of Cs. By co-deposition of M (M = Cs, Na, Yb) with ammonia, a minimum work function of 0.9 (±0.1) eV was obtained which is independent on the feature of the metals as well as the substrate. The theoretical solution of 'large polaron' was used to calculate the frequency of the polarization field and the coupling constant

[en] The influence of two unparalleled axes of a variable included angle monochromator on wavelength tuning and resolution is discussed numerically in the text. And a method of measuring the unparallelism of two axes by using a paralleloscope and re-alignment of the axes is introduced

[en] Synchrotron radiation photoelectron spectroscopy is used to measure the valence-band offsets for Si/ZnS(111) and (100) heterojunctions. The valence band discontinuities obtained from the measurements are both (1.9 +- 0.1) eV for Si/ZnS(111) and Si/ZnS(100) interfaces, which is in excellent agreement with the theoretical predictions but considerably different from the experimental result of ZnS/Si(111) reported by Maierhofer et al. This suggests that the commutativity rule of band offset may not be valid for Si/ZnS polar interface and the reason is discussed

[en] An excellent software applied to synchrotron radiation experiment is introduced. With this software, due to operation of photoelectron spectroscopy control over beamlines changes from Rowland circle to a single DRAGON type, and photon transmission is improved 2-3 times. Not only X-ray Photoemission Spectroscopy (XPS) excited by X-ray gun source but also Energy Distribution Spectroscopy (EDC). Constant Final Spectroscopy (CFS) and constant initial spectroscopy (CIS) excited by synchrotron radiation can be done by the software. It runs with a graphic main menu in which operation is visible and stable, and thus suitable scientific experiments

[en] The resolution of monochromator becomes much higher with the development of synchrotron radiation beamline technology, it demands high performance of control software to drive the complex configuration of mechanical rotation and translation. On the other hand, with the number of the constructed beamlines increases rapidly, it imposes a large force on developing, a migrated and standard control software. A multi-layer technology introduced to variable angle spherical grating monochromator (VASGM) control in which the layers being inter-connected by Ethernet was discussed. The lower layer, a hardware abstract layer, operates the hardware directly and the top layer, a graphic user interface, processes the user's command and passes corresponding operation to the lower layer. The top layer can be flexibly connected with different control software. A numerical solution of VASGM was also given

[en] The behavior of interface formed by growing thin Sm film on the Si(100)2 x 1 substrate at room temperature has been investigated by cove level and valence band photoemission using synchrotron radiation. The experimental results show the existence of distinct stages corresponding to chemisorption and agglomeration of Sm atoms (coverage Θ<0.5 ML), reactive interdiffusion (0.5 ML≤Θ≤4-6 ML), and growth of metallic Sm. Compared to Si(111)7 x 7 the reactivity of Sm on the Si(100)2 x 1 substrate is enhanced and a greater tendency for interdiffusion of Sm and Si is observed. Also we have discussed the interface formation and the interface profile carefully

[en] The surface structure of GaAs(001) has been studied by using angle resolved photoemission fine structure (ARPEFS), which confirms the 'Ga bi-layer' model proposed by Biegelsen. The results show that two adjacent outmost Ga atoms (dimmer) move close together along [110] direction to form an 8.3% deviation from the bulk site. And the outmost Ga dimmers relax inward 2.1%. The surface structure of S-passivated GaAs(001) has also been investigated with the method of X-ray photoelectron diffraction (XPD). The results demonstrate that the passivated S atoms are located on the bridge of the first layer Ga atoms and bind them with the bond length of 3.62 Angstrom and the bond angle of 61.2 degree. The surface polarity of GaN(0001) grown on the substrate of Al₂O₃ is also studied by using energy dependence photoelectron diffraction as well as the calculation of multiple scattering cluster models, which confirms that its polarity is Ga termination. (authors)

[en] In measuring X-ray magnetic circular dichroism spectra by the sample current mode, signal currents are strongly affected by external fields. Aiming at the design of rotatable electromagnet inside the vacuum chamber, the authors have designed and installed a piece of gold mesh attached to magnetic poles to increase the sample current signals, and found that sample currents increase rapidly and tend to saturation with increasing bias in different magnetic fields. The stronger the external field is applied, the higher bias voltage is required to reach signal saturation. Comparing absorption spectra of an oxidated aluminum foil with a CoFe film in parallel and antiparallel magnetization under the same magnetic field and bias, the authors have found that the systematic error caused by adding magnetic field and bias is 2.17% of MCD intensity for cobalt, which indicates that the developed technique has some advantages to measure XMCD spectra. (authors)