C/C复合材料石墨化度的喇曼光谱表征

采用显微激光喇曼光谱及XRD测量、表征了C/C复合材料中炭纤维、沥青炭及CVD热解炭经不同温度石墨化处理后的结构参数.结果表明:在3种炭材料的喇曼图谱上都有2个散射强度峰-D峰和G峰,峰位分别位于喇曼位移约1333及1584cm^-1处,随石墨化处理温度改变,2峰峰位没有变化,但2峰相对强度却发生变化.将D峰相对于G峰的强度R的倒数R^-1与XRD法得到的石墨化度g比照,发现2者存在一一对应关系,符合公式:g=1-exp[-2.11(R^-1-0.34)].     

铌酸锶钡晶体铁电相变的喇曼光谱研究

在20～350℃内研究了 Ba_xSr_(1-x)Nb_2O_(?)(x=0.25,T_c～67.5℃)晶体的喇曼光谱。没有观察到软模现象。发现在居里点上下很大温度范围内,铁电相和顺电相的喇曼光谱相似,低频扩展峰随温度升高而增强。认为 SBN铁电相变属于有序—无序型。     

VO2薄膜的结构、光学特性及其应用研究进展

VO2具有4种多晶型结构.其中,VO2(M)向VO2(R)的转变是可逆的,并伴随着光、电、磁等物理性能的急剧变化.从晶体学角度描述了具有可逆相变特性的VO2的晶体结构,介绍了VO2薄膜在可见光-红外光波段的高低温光谱研究情况及激光辐照下VO2薄膜的突变特性.在应用原理分析的基础上综述了VO2薄膜光学特性方面的最新应用情况.     

a轴取向YBa2Cu3O7-x薄膜的制备及其Raman光谱研究

采用直流磁控溅射法在SrTiO3(100)衬底上制备a轴取向的YBa2Cu3O7-x薄膜,用四引线法测量R-T曲线Tc0=86K.对于YBa2Cu3O7-x薄膜进行喇曼光谱测量,发现0(4)振动的声子峰(～500cm-1)强度远远大于0(2)-0(3)反相振动的声子峰(～340cm-1)强度,应用群论分析证明薄膜主要是沿a轴生长的.在较低的衬底温度下(<780℃),YBa2Cu3O7-x薄膜沿a轴生长,随着衬底温度的升高,薄膜中沿c轴生长的组分逐渐增加.     

α—Al2O3衬底上生长的GaN膜的光学性质

采用金属有机化学气相淀积方法生长了α－Ａｌ２Ｏ３衬底上外延的高质量的单晶ＧａＮ薄膜。Ｘ射线衍射光谱与喇曼散射光谱表征了ＧａＮ外延薄膜的单晶结构和单晶质量。透射光谱和光调制反射光谱定出了六角单晶ＧａＮ薄膜的直接带隙宽度和光学参数。     

α－Al_2O_3衬底上生长的GaN膜的光学性质

采用金属有机化学气相淀积（ＭＯＣＶＤ）方法生长了α－Ａｌ２Ｏ３衬底上外延的高质量的单晶ＧａＮ薄膜。Ｘ射线衍射光谱与喇曼散射光谱表征了ＧａＮ外延薄膜的单晶结构和单晶质量。透射光谱和光调制反射光谱定出了六角单晶ＧａＮ薄膜的直接带隙宽度和光学参数。     

溅射法制备VO2薄膜的研究现状

主要介绍了VO2薄膜的微、宏观相变机理,阐述了溅射法制备VO2薄膜的优势及影响薄膜性能的一些因素,指出了今后VO2薄膜的研究重点.     

真空还原制备的VO2热致相变薄膜Raman光谱和红外光谱研究

报道了利用真空还原制备的VO2薄膜的红外透射光谱和Raman光谱，并进行370－900nm波段的光透射测试以及900nm波长的热滞回线特性测试，表明所制备VO2薄膜具有优良的热致相变光学特性，结晶状态不同的薄膜其Raman谱位置有明显改变，室温时的红外光谱表现出较好的红外振动特性。讨论了薄膜结晶状态对Raman位移的影响以及VO2薄膜的红外光谱。     

木质陶瓷的X射线衍射和喇曼光谱研究

采用X射线衍射和激光喇曼光谱, 研究了以烟杆和酚醛树脂为原料制备木质陶瓷炭化过程中结构的变化特征. 研究结果表明, 炭化温度的升高可以使木质陶瓷XRD谱图中衍射峰增加, 强度增大, 同时木质陶瓷中石墨微晶的平均层间距d₀₀₂减小, 堆积厚度L _c增加, 微晶直径 L _a在973K出现转折点; 木质陶瓷的喇曼光谱图为典型的类石墨炭材料的喇曼谱图, 只出现了表征无序结构的D线和表征石墨结构的G线, 且表征无序化度的二者积分强度比R值随炭化温度的升高先增后减, 而根据Tuinstra-Koenig 经验式计算得到的微晶直径L a值表现出与R值相反的规律; 两种分析方法的结果较为一致, 均表明木质陶瓷结构在973K发生根本改变, 说明喇曼光谱有望成为木质陶瓷结构的快速测试方法.     

常压化学气相沉积方法制备非晶硅薄膜及其光致发光性能研究

使用改进的常压化学气相沉积(APCVD)系统制备了非晶硅薄膜,测量了样品的光致发光特性,使用Raman光谱和X射线光电子能谱(XPS)谱测量了薄膜的微结构特征.样品在523 nm出现发光峰,Raman光谱和XPS谱表明制备的薄膜结构中存在富氧相和富硅相的分相现象,分析认为相界面的存在是产生发光的原因.Raman光谱分峰结果表明薄膜中存在纳米晶粒.     

掺钨二氧化钒薄膜的制备与分析

通过凋研国内外的各种制备方法,比较它们的优缺点后,选用磁控溅射法.在硅片上得到了电阻变化2个数量级的二氧化钒(VO2)薄膜.对薄膜进行电学性能的测试,结果表明:掺钨后二氧化钒薄膜的相变温度比纯的二氧化钒薄膜相变温度有所降低,掺钨后薄膜的近红外透射率也随之减小.通过X射线衍射和X射线光电子谱对薄膜的微观结构和组分进行了分析.     

Significant control of metal-insulator transition temperature through catalytic excessive oxygen doping in high-performance vanadium dioxide nanobeam channel

The strategy of a reliable transition temperature control of vanadium dioxide(VO_2) is reported. Rectangular VO_2 nanobeams were synthesized by a thermal chemical vapor deposition(TCVD) system. The metal-insulator transition(MIT) temperature increases to above 380 K when the TiO_2 ratio of the source is 5 at.%, although the Ti source is not physically doped into VO_2 nanobeams. The XPS spectra of the V 2 p orbital reveal the excessive oxidation of V after the TCVD processes with a higher TiO_2 ratio, indicating that the TiO_2 precursor is important in the O-doping of the surface V O bonds when forming volatile Ti-O gas species. Thus, TiO_2 reactants can be used as a VO_2 surface chemical modifier to manipulate the MIT transition temperature and maintain a homogenous VO_2 phase, which is useful for a Mott device application with a record on/off switching ratio 10~4 and Mott transition temperature 380 K.     

Field emission from diamond and diamond-like carbon films

Field emission from diamond and diamond-like carbon thin films deposited on silicon substrates has been studied. The diamond films were synthesized using hot filament chemical vapor deposition technique. The diamond-like carbon films were deposited using the radio frequency chemical vapor deposition method. Field emission studies were carried out using a sphere-to-plane electrode configuration. The results of field emission were analyzed using the Fowler-Nordheim model. It was found that the diamond nucleation density affected the field emission properties. The films were characterized using standard scanning electron microscopy, Raman spectroscopy, and electron spin resonance techniques. Raman spectra of both diamond and diamond-like films exhibit spectral features characteristic of these structures. Raman spectrum for diamond films exhibit a well-defined peak at 1333cm^?1. Asymmetric broad peak formed in diamond-like carbon films consists of D-band and G-band around 1550 cm^?1 showing the existence of both diamond (sp³ phase) and graphite (sp² phase) in diamond-like carbon films.     

The effects of dopant impurities on Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> system Raman properties

Impurities in Cu₂ZnSnS₄ (CZTS) can alter the electronic and optical properties, which may reduce photovoltaic device efficiency. Phonon dispersion susceptibility can be used to investigate the effects of foreign dopants on pairing between atoms within lattice. In order to investigate the effect of free holes on the optical phonons and asymmetry in the Raman peaks due to impurities, Sb-, Fe-, and Ag-doped CZTS thin films were prepared and systematically studied. Doping with impurities causes a shift in Raman peak frequency as well as linewidth. An investigation has been made based on the reduced mass of the vibrating CZTS lattice that changes due to dopant addition. For polycrystalline Sb-doped CZTS, the predicted wavenumber shift for Raman ‘A’ mode follows a similar trend as evidenced in experiments and can be explained by the square-root relationship between frequency and the vibrating mass. Raman lineshape for Sb-doped CZTS thin films and nanocrystals becomes wider, asymmetric, and moves toward lower vibrational frequency when laser power density increases. Atomic force microscopy was also performed to examine surface properties.     

射频磁控溅射制备类金刚石薄膜的特性

采用射频磁控溅射技术,用高纯石墨靶在单晶硅片、抛光不锈钢片上制备了类金刚石薄膜(DLC)。采用Raman光谱、原子力显微镜、显微硬度分析仪,表征了类金刚石薄膜的微观结构、表面形貌、硬度。结果表明,制备的类金刚石薄膜中含sp2、sp3杂化碳键,具有典型的类金刚石结构特征。计算表明,对应sp3杂化碳原子含量的ID1IG为3.18;薄膜的表面十分平整光滑,表面粗糙度极低,平均粗糙度Ra为0.17 nm;薄膜硬度可以高达30.8 GPa。     

CeO2掺杂TiO2催化剂薄膜的制备与表征

以Ar为工作气体，O2为反应气体，利用射频磁控溅射技术成功地在载玻片上沉积了透明TiO2催化剂薄膜。同时利用共溅射技术制备了掺杂CeO2的TiO2催化剂薄膜。采用X射线衍射(XRD)、Raman光谱、UV-VIS-NIR分光光度计、原子力显微镜(AFM)对薄膜进行了结构和形貌表征。     

紫外光辐照下钛硅共掺杂类金刚石薄膜微结构的演化

采用中频磁控溅射Ti80Si20合金靶在单晶硅表面制备了钛硅共掺杂的类金刚石薄膜。利用紫外-可见光多波长Raman光谱表征薄膜微结构, 并结合FTIR光谱研究了紫外光辐照对类金刚石薄膜微结构的影响, 进一步讨论了紫外光辐照下薄膜微结构的演化机理。结果表明: 非晶结构的类金刚石薄膜出现反式聚乙炔和聚对苯乙炔类聚合物结构以及sp杂化的线型卡宾碳结构。紫外光辐照诱导薄膜微结构驰豫和重构, 薄膜Si-O和C-O键含量增加, C=C和C-H键含量减少; 同时薄膜sp²团簇尺寸减小而无序度增大。     

Characterization of MBa2Cu3O7-x thin films by Raman microspectroscopy

Thin film embodiments of MBa2Cu3O7-x (MBCO, M = yttrium or a rare-earth metal) prepared by several different deposition methods on a variety of substrates were investigated by Raman microspectroscopy. Several of the unique characterization capabilities of Raman spectroscopy in the analysis of MBCO thin films are highlighted by the results of these investigations. The Raman active phonons of the orthorhombic and tetragonal forms of MBCO that are most useful for characterization of textured MBCO films are diagrammed and discussed. A rapid procedure for qualitative texture mapping of MBCO thin films using Raman microscopy techniques is presented, and a new approach for investigating phase separation at the sub-micrometer level in MBCO thin films based on curve resolution of the MBCO Cu2 phonon is described. The assignment of a particular feature often observed in Raman spectra of MBCO films to cation disorder is reinforced by results of a cation substitution study. The depth of penetration of the laser into MBCO films and the type of information that can be obtained by varying the extent of defocusing of the laser are also discussed.     

富勒烯（C60）与类金刚石碳复合膜的Debye模型的模拟计算

由C60和类金刚石碳膜（DLC）组成的多层复合膜可在Si、玻璃和其它衬底上通过真空升华沉积和随后以CH4和H2作为反应剂用射频化学气相沉积（RFCVD）的方法制备,这种膜的若干特征可由拉曼谱（Raman)表征。复合膜电阻与介电常数由低频（LF）阻抗分析仪进行研究从而得到膜电阻、介电常数和频率间的关系。这些结果表明：在各种频率下的此类复合膜的电阻怀纯C60膜基本一致。但是纯C60膜随频率变化的电容率与复合膜明显不同,这些现象与结果可通过电介质的德拜模型和介质松弛理论进行分析与讨论。根据相应的Debye模型方程式,实验测得的介电常数和频率间的关系经计算机拟合,得到了复合膜的松弛时间,介电常数等。拟合结果基本上与实验数据一致。     

Raman spectra and structural analysis in ZrOxNy thin films

Raman spectroscopy has been used as a local probe to characterize the structural evolution of magnetron-sputtered decorative zirconium oxynitride ZrO_xN_y films which result from an increase of reactive gas flow in the deposition. The lines shapes, the frequency position and widths of the Raman bands show a systematic change as a function of the reactive gas flow (a mixture of both oxygen and nitrogen). The as-deposited zirconium nitride film presents a Raman spectrum with the typical broadened bands, due to the disorder induced by N vacancies. The recorded Raman spectrum of the zirconium oxide film is typical of the monoclinic phase of ZrO₂, which is revealed also by X-ray diffraction. Raman spectra of zirconium oxynitride thin films present changes, which are found to be closely related with the oxygen content in films and the subsequent structural changes.