Xu Cunyi

NON-DESTRUCTIVE IN-SITU STUDY OF WHITE AND BLACK COATING ON PAINTED POTTERY SHERDS FROM BANCUN SITE (HENAN, CHINA) BY RAMAN MICROSCOPY

Abstract Pottery sherds from the archaeological site of Bancun (Henan, China) were analyzed by Raman microscopy and the pigments used in the coating of this ancient (c. 4000–5000 BC) pottery were determined. It was found that bauxite was used to make the white pigment. The black coating was identified as a magnetite and its particle size was in the nanometer range. This work also showed that the size of pigment had influence on the color of the coating. In principle, Raman spectra could be used not only to identify the mineral source of the pigment but also to estimate the particle size of the pigments.

Enhancement of fluorescence and Raman spectroscopies of undoped C60 film

The spectroscopic characteristics of C60 films deposited on different substrates have been investigated at room temperature. We find that the fluorescence of C60 film is enhanced by the presence of a rough silver surface and also by oxygen under excitation at 5145 A (2.41 eV) at room temperature. The enhancement of the fluorescence on the rough silver surface is mainly due to an appropriate work function of the silver surface and an external electromagnetic field induced by laser irradiation, which leads to a resonant coupling with the C60 molecular dipole. The fluorescence enhancement by oxygen is interpreted as resulting from the strong reduction in symmetry of C60 from Ih to C2v or lower due to photooxygenation of the C60 molecules. This also results in larger Jahn-Teller distortions. The kinetics of the photochemical reactions between oxygen and C60 have also been obtained with an observed rate constant of magnitude about 1.6 × 10−2s−1 by monitoring the changes of the fluorescence and Raman spectra with the irradiation time.

Raman Microscopy Study of the Pigments on the Ancient Wall Painting from the Large Grave in Wanzhang (Hebel, China)

Abstract Fragments of the ancient wall painting (c. 550 - 580 AD) from the archaeological site of Wanzhang (Heibei, China) were analyzed by Raman Microscopy. The pigments with different colors were identified by Raman Microscopy, which are respectively cinnabar, goethite, carbon black and calcite doped with other metal atoms.

Infrared spectra of a-Si:H, Cl films

Abstract Films of amorphous silicon (a-Si:H,Cl) containing about 10 atomic % hydrogen and 2–8 at % chlorine have been prepared using the r.f. glow-discharge technique with a mixture of H 2 and SiCl 4 . The infrared spectra showed in addition to the hydrogen induced absorption bands at 2100, 2000, 840, 890 and 860 cm −1 the following new absorption lines: 545 cm −1 due to SiCl stretching, 787 and 737 cm −1 which might be caused by the Si-HCl bending vibrations. The absolute chlorine content was measured using sulphocyanic mercury spectrophotometric and chlorine ion selective electrode methods.

A STUDY OF RAMAN SCATTERING AND INFRARED ABSORPTION SPECTRUM IN A NEW SERIES OF MERCURY-BASED HIGH-T c SUPERCONDUCTOR (Hg,Mo)Sr 2 (Y 1-x Ca x )Cu 2 O 6+δ

Lattice vibrations of the (Hg,Mo)Sr2(Y1-xCax)Cu2O6+δ – a new series of mercury-based high-Tc superconductor are analyzed with the aid of group theory. The vibrations of species are given. They are 4A1g + B1g + 5Eg + 7A2u + B2u + 8Eu. The 4A1g, B1g and 5Eg modes are Raman active, the 6A2u and 7Eu are infrared active. Phonon vibration characteristics of the samples are studied using Raman scattering and infrared absorption spectra. The experimental results show that the typical phonon vibrational modes appear mainly at 145, 320, 440, 578, 592 and 645 cm-1. The intensities of the 145, 320, 440, 578 and 645 peaks decrease with increasing Ca content x and the position of 645 peak moves to higher wavenumber slightly. In this article, the phonon modes are assigned and their variation behavior with increasing Ca content x are discussed.

Raman studies on the undoped and WO3-doped Y-Ba-Cu-O system

Undoped and WO3-doped Y-Ba-Cu-O ceramics have been studied by Raman spectroscopy. The results show that the peak positions at 499 and 338 cm-1 have been shifted for WO3-doped samples compared with those for undoped samples, which reveals that the oxygen contents are different for undoped and WO3-doped quenched samples in air. It is suggested that suitable WO3 doping can change the oxygen content and reduce the effect of thermal treatments on the superconductivity of the Y-Ba-Cu-O system.

Microstructure and luminescence properties of GaxIn1-xP/GaAs heterostructure

The GaxIn1-xP/GaAs heterostructures with different x values have been investigated by photoluminescence (PL), energy dispersive spectrum (EDS), and transmission electron microscopy (TEM). Experimental results suggested that the composition of epitaxial layers evidently affected the microstructure of the heterostructures. When x value was close to 0.5, the defects in the epitaxial layer decreased, and the lattice match between film and substrate approached optimum. Meanwhile, the heterostructure provided a high luminescence efficiency.

The crystallization of Bi in the annealed a-Ge/Bi bilayer and its effect on conductivity

In this paper, the crystallization behaviors and transport properties are investigated for a-Ge/Bi bilayers annealed at different temperatures. For 200 nm/100 nm bilayers, it is found that the orientations of Bi in the bilayers annealed at 200°C and 340°C are preferred, as well as the original one. But they are random when the bilayers are annealed at temperatures between 240°C and 300°C. For 200 nm/50 nm bilayers, the orientations of Bi are always preferred. Corresponding to the orientations mentioned above, the minimum on the R(300 K)-Ta curve appears only in the case of 200 nm/100 nm bilayers.

Excitation Intensity Dependence of Photoluminescence in a-C:H and a-C Films

We present the novel results of excitation intensity dependent photoluminescence (PL) in a-C:H and a-C thin films. Sublinear and superlinear phenomena of PL have been observed for a-C:H films. There are two PL bands in a-C films under lower excitation intensity. These results are qualitatively explained in the light of band tail state saturation and the contribution of gap states.