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Fine Machining of Large-Diameter 6H-SiC Wafers

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Journal of materials Science & Technology 2006年第5期22卷 681-684页

作者： Xiufang CHEN Juan LI Deying MA Xiaobo HU Xiangang XU Minhua JIANG State key laboratory of crystal materials Shandong UniversityJinan 250100China

Three main machining processes of large-diameter 6H-SiC wafers were introduced in this paper. These processes include cutting, lapping and polishing. Lapping causes great residual stresses and deep damage layer which can be reduced gradually with subsequent polishing processes. Surfaces prepared by mechanical polishing （MP） appeared a large number of scratches with depth of 5-8 nm. These scratches can be effectively removed by chemo-mechanical polishing （CMP）. After CMP. extremely smooth and low damage layer surface with roughness Ra=0.3 nm was obtained. Atomic force microscopy （AFM） and optical microscopy were used to observe the surface morphology of samples and a high resolution X-ray diffractometer （HRXRD） was used for the crystal lattice perfection of the subsurface region. Changes of surface residual stresses during machining processes were investigated by HRXRD.

关键词： 6H-SiC Chemo-mechanical polishing (CMP) Roughness

Surface Polishing of 6H-SiC Substrates

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Journal of materials Science & Technology 2007年第3期23卷 430-432页

作者： Xiufang CHEN Xiangang XU Juan LI Shouzhen JIANG Lina NING Yingmin WANG Deying MA Xiaobo HU Minhua JIANG State key laboratory of crystal materials Shandong University Jinan 250100 China

The surface polishing for silicon carbide （SIC） substrates was investigated and results were presented for mechanical polishing （MP） and chemo-mechanical polishing （CMP）. High quality surfaces were obtained after CMP with colloidal silica. The removal mechanism of scratches in MP and detailed physical and chemical process during CMP were analyzed. The effects of MP and CMP on the surface roughness were assessed by optical microscopy （OM）, atomic force microscopy （AFM） and step profilometry. KOH etching and high resolution X-ray diffractometry （H RXRD） were applied to evaluate the subsurface damage of 6H-SiC substrates.

关键词： SiC Chemo-mechanical polishing (CMP) Roughness Subsurface damage

Two-Photon Absorption-Induced Emission Properties of Dye HMASPS Doped Polymer

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Chinese Physics Letters 2002年第2期19卷 208-210页

作者： Wang Dong Zhou Guang-Yong Ren Yan Yang Sheng-Jun Xu Xin-Guang Shao Zong-Shu Jiang Min-Hua State key laboratory of crystal materials Shandong University Ji'nan 250100

The 0.01M two-photon absorption dye trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methyl-pyridinium p-toluene sulfonate (HMASPS) doped polymer has been prepared. When pumped by the picosecond pulse from the pulsed mode-locked Nd:YAG laser, the polymer emits more intense upconverted fluorescence and superradiance compared to the solution sample of the dye. The two-photon pumped lasing with oscillating pulses has also been obtained. Compared to the dye in its solution state, the emission spectra of the polymer are all blueshifted. The polymer has a long upconverted fluorescent lifetime of about 4.041±0.04ns.

关键词： Photons

Effect of interchain coupling on a biexciton in organic polymers

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Chinese Physics B 2009年第7期18卷 2961-2966页

作者：高琨解士杰李元尹笋刘德胜赵显 School of Physics Shandong University State key laboratory of crystal materials Shandong University

The effect of interchain coupling on the formation and the stability of a biexciton is studied in poly （p-phenylene vinylene） chains in the framework of the tight-binding approach. We obtain an intrachain exciton and biexciton as well as an interchain exciton and biexciton through a double-photon *** is found that a biexciton is energetically favourable to two single excitons even when there exists an interchain *** is a turnover value t⊥c of the interchain coupling for the formation of a biexciton,beyond which two excitons are combined into one *** binding energy of a biexciton is calculated to decrease with the increase of interchain coupling,which indicates that a biexciton is relatively stable in polymers with a weak interchain *** conclusion is consistent with the experimental *** addition,a suggestion about how to improve the yielding efficiency or the formation of biexcitons in actual applications is given.

关键词： biexciton polymers binding energy

Thermal Oxidation of Silicon Carbide Substrates

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Journal of materials Science & Technology 2009年第1期25卷 115-118页

作者： Xiufang Chen Liana Ning Yingmin Wang Juan Li Xiangang Xu Xiaobo Hu Minhua Jiang State key laboratory of crystal materials Shandong University Jinan 250100 China

Thermal oxidation was used to remove the subsurface damage of silicon carbide （SIC） surfaces. The anisotropy of oxidation and the composition of oxide layers on Si and C faces were analyzed. Regular pits were observed on the surface after the removal of the oxide layers, which were detrimental to the growth of high quality epitaxial layers. The thickness and composition of the oxide layers were characterized by Rutherford backscattering spectrometry （RBS） and X-ray photoelectron spectroscopy （XPS）, respectively. Epitaxial growth was performed in a metal organic chemical vapor deposition （MOCVD） system. The substrate surface morphology after removing the oxide layer and gallium nitride （GaN） epilayer surface were observed by atomic force microscopy （AFM）. The results showed that the GaN epilayer grown on the oxidized substrates was superior to that on the unoxidized substrates.

关键词： SiC Thermal oxidation GaN epitaxy

Growth,Optical Properties and Defects of High-Doped Yb∶YAl_(3)(BO_(3))_(4) crystal

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Journal of Rare Earths 2006年第Z1期24卷 152-155页

作者： Zhao Hongyang Li Jing Wang Jiyang Zhang Huaijin Wang Xuping Liang Ximin State key laboratory of crystal materials Shandong UniversityJinan 250100China

High-doped Yb∶YAl_(3)(BO_(3))_(4)(Yb∶YAB)crystals were grown by the flux method using K_(2)Mo_(3)O_(10)as the *** efficient segregation coefficient was measured by using *** absorption and fluorescence spectra was measured at room temperature and compared the spectral parameters with Yb∶YAB of other Yb^(3+)*** the increase of the Yb^(3+)concentration,the main absorption and fluorescence peaks almost do not change,but the absorption coefficient and FWHM *** defects were investigated by using chemical etching *** main defects are cracks,inclusions,dislocations and twins,which of them are more than low-doped crystals.

关键词： crystal growth laser material defects

Effect of Strontium Ion on the Growth and Second-Harmonic Generation Properties of GdCa_(4)O(BO_(3))_(3) crystal

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Chinese Physics Letters 2001年第1期18卷 63-64页

作者： ZHANG Shu-Jun CHENG Zhen-Xiang LIU Jun-Hai HAN Jian-Ru WANG Ji-Yang SHAO Zong-Shu CHEN Huan-Chu State key laboratory of crystal materials Shandong UniversityJi'nan 250100

Large sized and optical quality GdCa_(4)O(BO_(3))_(3)(GdCOB)crystal with calcium partially substituted by strontium(Sr)ions was grown for the first *** x-ray powder diffraction shows that the Sr ion has an effect on the cell parameters of the GdCOB crystal Second-harmonic generation(SHG)experiments were performed on the Sr:GdCOB and GdCOB crystals along the spatial phase-matching *** results show that the cw green laser output power is 1.04 W when the laser diode pump power is 10 W in the Nd:YVO_(4)/Sr:GdCOB intracavity *** the slope efficiency of Nd:YVO_(4) and the fundamental laser in cavity,the intracavity SHG conversion efficiency of the GdCOB crystal is 21%while it is 24%for the Sr:GdCOB crystal,the SHG conversion efficiency is improved by 14%.The effect of the Sr ions on the nonlinearity of the GdCOB crystal is also discussed by using the anion group theory.

关键词： intracavity pump crystal

Spectral properties of Nd-doped BiB_3O_6 crystal

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Science China Chemistry 2001年第5期44卷 510-515页

作者：江怀东滕冰王继扬胡小波刘宏张承乾 State key laboratory of crystal materials Shandong University Jinan China

Transparent Nd: BiB3O6 crystal has been grown by top-seeded method. The refraction indices of the crystal were measured and the parameters of chromatic dispersion were fitted. The room temperature absorption spectra of the crystal have been measured and compared with that of 0.2 mol/L NdCl3 solution. According to Judd-Ofelt (JO) theory, the spectral strength parameters Ω2 = 0.1776×10?20 cm2, Ω4 = 0.1282?10?201 cm2 and Ω6 = 0.1357X10-20 cm2 of Nd3+ ion were fitted. The radiative transition probabilities AJ,J’, oscillator strengths fJ,J’, radiative lifetime rand the branching ratio βJ’ have all been calculated. Based on these parameters, the properties and application perspective are discussed.

关键词： Nd: BiB3O6 crystal Judd-Ofelt theory spectrum parameters

2H-SiC Dendritic Nanocrystals In Situ Formation from Amorphous Silicon Carbide under Electron Beam Irradiation

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Journal of Rare Earths 2006年第Z1期24卷 54-55页

作者： Li Xianxiang Hu Xiaobo Jiang Shouzheng Dong Jie Xu Xiangang Jiang Minhua State key laboratory of crystal materials Shandong UniversityJinan 250100China

Under electron beam irradiation,the in-situ formation of 2H-SiC dentritic nanocrystals from amorphous silicon carbide at room temperature was *** homogenous transition mainly occurs at the thin edge and on the surface of specimen where the energy obtained from electron beam irradiation is high enough to cause the amorphous crystallizing into 2H-SiC.

关键词： electron beam irradiation 2H-SiC dendritic nanocrystal amorphous silicon carbide