高温超导薄膜衬底材料LaAlO3单晶的超光滑表面抛光研究

本文以化学机械抛光为手段,以原子力显微镜(AFM)为工具,对高温超导薄膜衬底材料LaAlO3单晶的超光滑表面抛光进行研究.既观察到了由传统光学表面向超光滑表面过渡的过程,又观察到了超光滑表面加工的结果-表面的本征化.显示了超光滑表面抛光对外延衬底表面的重要性.     

LBO晶体超光滑表面抛光机理

胶体SiO2抛光LBO晶体获得无损伤的超光滑表面,结合前人对抛光机理的认识,探讨了超光滑表面抛光的材料去除机理,分析了化学机械抛光中的原子级材料去除机理.在此基础上,对胶体SiO2抛光LBO晶体表面材料去除机理和超光滑表面的形成进行了详细的描述,研究抛光液的pH值与材料去除率和表面粗糙度的关系.LBO晶体超光滑表面抛光的材料去除机理是抛光液与晶体表面的活泼原子层发生化学反应形成过渡的软质层,软质层在磨料和抛光盘的作用下很容易被无损伤的去除.酸性条件下,随抛光液pH值的减小抛光材料的去除率增大;抛光液pH值为4时,获得最好的表面粗糙度.     

酸碱性对雾化施液CMP氧化锆陶瓷的影响

采用精细雾化施液CMP这一抛光工艺对氧化锆陶瓷进行抛光,实验研究了抛光液中具有代表性的酸碱调节剂对抛光氧化锆陶瓷材料去除率、表面形貌和表面粗糙度的影响及酸碱性对精细雾化施液分散稳定性的影响.结果表明:针对精细雾化液抛光工艺配制的二氧化硅抛光液在碱性环境中分散稳定性更好,虽然酸性抛光液对材料去除率更高,但酸对氧化锆陶瓷表面腐蚀性过大,不宜抛光氧化锆陶瓷;有机碱作为调节剂抛光后的表面质量明显优于无机碱及无机酸、有机酸;乙二胺配置的碱性抛光液精细雾化后抛光氧化锆陶瓷可获得优质超光滑低损伤表面及较高加工效率,表面粗糙度Rq为1.67 nm,材料去除率达182.23 nm/min.     

低亚表面损伤的YCOB晶体超精密抛光

通过选择合适的研磨剂、抛光垫以及抛光材料,采用机械抛光与CMP抛光相结合的方法对应用于高激光损伤阈值的薄膜基体材料YCOB晶体进行表面加工.通过优化研磨抛光工艺后得到超光滑晶体表面,样品表面在125μm×94μm的范围内粗糙度RMS值达到0.6 nm,同时具有非常低的亚表面损伤层,经过超声清洗和有机溶剂刻蚀后,在高倍显微镜下无明显划痕.     

基于离子束抛光的KDP晶体表面嵌入铁粉清洗研究

磁流变抛光技术是实现KDP晶体超精密加工的新方法,但磁流变液中的铁粉容易嵌入质软的KDP晶体表面.本文提出了利用基于低能离子溅射原理的离子束抛光技术去除KDP表面嵌入的铁粉.利用红外拉曼光谱和白光干涉仪分别分析了低能离子束抛光前后KDP晶体表面物质结构变化和表面粗糙度的变化;结果显示,低能离子束溅射不改变KDP晶体表面的组成结构,并改善了KDP晶体表面质量,因此离子束抛光可用于KDP晶体的加工;利用飞行时间二次离子质谱分析技术分别对单点金刚石车削、磁流变抛光和低能离子束抛光后的KDP晶体表面进行元素分析,结果显示低能离子束抛光可有效去除磁流变抛光在KDP晶体表面嵌入的铁粉.     

化学机械抛光作用与单晶基片超光滑表面的获取

单晶基片的表面光洁度指标是影响后续薄膜生长质量的重要因素.本文通过对比实验的方法,就采用CMP(chemical mechanical polish)工艺获取超光滑单晶基片做了深入的观察研究,并通过AFM(atomicforce microscope)的最终检测结果给出具有说服力的结论.     

化学机械磨削(CMG)加工单晶硅片

单晶硅是半导体行业重要的功能材料,加工时首先被切割成晶片,然后通过研磨和抛光获得光滑表面.本文介绍了一种新的化学机械磨削(CMG)工艺,用于硅片的终端加工.CMG是把化学反应和机械磨削融为一体的固结磨料加工工艺,在加工效率、磨粒可控性、废料处理等方面优于化学机械抛光(CMP).利用CMG加工单晶硅片,能有效减小亚表面损伤和消除残余应力,对碳化硅、氮化硅、蓝宝石等其它功能材料的超精密加工具有一定的借鉴意义.     

化学抛光和退火对钛酸锶基片表面改性研究

本文运用原子力显微镜检测传统机械抛光和化学机械抛光以及退火前后的钛酸锶(STO)衬底表面,研究了化学机械抛光和退火对钛酸锶(STO)基片表面形貌的影响,结果表明化学抛光可以使表面粗糙度达到0.214 nm,明显优于机械抛光.对比测量退火前后钛酸锶(STO)基片的双晶摇摆曲线,表明退火可以明显改善晶体质量,有利于实现超光滑STO基片的加工.     

CVD金刚石化学机械抛光工艺研究

本文提出采用化学机械抛光的新工艺实现传统方法无法达到的超光滑、低损伤的表面抛光.本文在对金刚石氧化的化学热动力学研究基础上,配制了以高铁酸钾为主要氧化剂的化学机械抛光液,指出加快化学机械抛光过程金刚石氧化的工艺措施.研制了用于CVD金刚石化学机械抛光的可加热抛光头和摩擦力测量装置,着重研究了CVD金刚石的化学机械抛光工艺.试验得到最佳的抛光工艺参数:抛光压力为266.7 kPa,抛光盘转速为70 r/min,抛光头转速为23 r/min,抛光温度为50℃.化学机械抛光的摩擦系数在0.060 ～0.065范围内变化,为混合润滑状态.     

HgInTe晶片表面化学抛光研究

对HgInTe(MIT)晶片表面化学抛光工艺进行了研究,采用不同浓度的Br2-C3H7ON以及Br2-MeOH作为抛光液对MIT晶片进行化学抛光后发现,5;Br2-C3H7ON抛光液的抛光速度平稳且易于控制,抛光3min后可以有效去除表面划痕,获得光亮表面,表面形貌达到最佳效果.AFM分析结果表明,5;Br2-C3H7ON抛光后的晶片表面粗糙度降低67;,平整度显著增加.相比之下,5;Br2-MeOH抛光液抛光速度过快,抛光后的表面形貌较差.     

Effects of Inelastic Electron Scattering on Supersmooth Sapphire Surface with Au and Pt Nanolayers

Crystallography Reports - A comparative study of the inelastic electron scattering on supersmooth surfaces of sapphire single crystals, including those with gold and platinum nanolayers, was...     

Structural contribution to the roughness of supersmooth crystal surface

Technological advances in processing crystals (Si, sapphire α-Al₂O₃, SiC, GaN, LiNbO₃, SrTiO₃, etc.) of substrate materials and X-ray optics elements make it possible to obtain supersmooth surfaces with a periodicity characteristic of the crystal structure. These periodic structures are formed by atomically smooth terraces and steps of nano- and subnanometer sizes, respectively. A model surface with such nanostructures is proposed, and the relations between its roughness parameters and the height of atomic steps are determined. The roughness parameters calculated from these relations almost coincide with the experimental atomic force microscopy (AFM) data obtained from 1 × 1 and 10 × 10 μm areas on the surface of sapphire plates with steps. The minimum roughness parameters for vicinal crystal surfaces, which are due to the structural contribution, are calculated based on the approach proposed. A comparative analysis of the relief and roughness parameters of sapphire plate surfaces with different degrees of polishing is performed. A size effect is established: the relief height distribution changes from stochastic to regular with a decrease in the surface roughness.     

Supersmooth and modified surface of sapphire crystals: Formation,characterization, and applications in nanotechnologies

The results of studying the state of the surface of sapphire crystals by a complex of methods in different stages of crystal treatment are considered by an example of preparing sapphire substrates with a supersmooth surface. The possibility of purposefully forming regular micro- and nanoreliefs and thin transition layers using thermal and thermochemical impacts are considered. The advantages of sapphire substrates with a modified surface for forming heteroepitaxial CdTe and ZnO semiconductor films and ordered ensembles of gold nanoparticles are described. The results of the experiments on the application of crystalline sapphire as a material for X-ray optical elements are reported. These elements include total external reflection mirrors and substrates for multilayer mirrors, output windows for synchrotron radiation, and monochromators working in the reflection geometry in X-ray spectrometers. In the latter case, the problems of the defect structure of bulk crystals sapphire and the choice of a method for growing sapphire crystals of the highest structural quality are considered.     

Possible differences between the surface and bulk structure of glasses

Changes in cation co-ordination at glass surfaces (indicating an increase of the oxygen-to-cation ratio within the topmost superficial layers) are evidenced by comparing data acquired by spectroscopic techniques of different excitation depth. Based on these experimental results, a theoretical model is developed that predicts structural discrepancies between surface and bulk structure. Such reconstructed surfaces are of great importance for all kind of surface-related crystallization phenomena.     

Electron-paramagnetic resonance and photoluminescence study of Si nanocrystals-photosensitizers of singlet oxygen molecules

Si nanocrystals formed by electrochemical porosifying of c-Si wafers are investigated by means of the electron-paramagnetic resonance (EPR) and photoluminescence (PL) techniques. The PL spectra and transients give evidence of the photosensitization of singlet oxygen molecules by the energy transfer from excitons confined in Si nanocrystals to oxygen molecules adsorbed on the nanocrystal surfaces. The EPR experiments show that the singlet oxygen generation is accompanied by a slowing down of the spin-spin relaxation time of Si dangling bonds on the nanocrystal surfaces. This effect is explained by the transition of a large part of the adsorbed O₂ molecules in their ground (triplet) states to the excited (singlet) ones. The EPR data allow us to estimate the concentration of the photosensitized singlet oxygen molecules to be on the order of 10¹⁸ cm⁻³.     

Analysis of the applicability of the modified kinematic approximation to describe the off-specular neutron scattering from the surface of micro- and nanostructured objects

The applicability of the modified kinematic approximation to describe the off-specular neutron scattering from interfaces between media is analyzed. It is demonstrated that in some cases one can expect not only a qualitative but also a quantitative agreement between the data and the results of experiments and calculations based on more accurate techniques. Diffuse scattering from rough surfaces and thin films with correlated and noncorrelated roughness of the upper and lower interfaces and the neutron diffraction by stripe magnetic domains and magnetic domains with a random size distribution (magnetic roughness) are considered as examples.     

Glass surface analysis by Auger Electron Spectroscopy

This paper reviews the application of Auger Electron Spectroscopy (AES) to the analysis of glass surfaces. Attention is drawn to experimental perturbations which may occur when analyzing glasses with absorbed and/or mobile species at the surface. Previous workers [1–4] have shown, for example, that mobile ions (e.g. Na) are very difficult to measure in glasses due to their migration under the electron beam. Special techniques developed to permit the measurement of mobile ions are discussed, and some recent applications of AES in current research at the University of Florida are presented.     

High‐performance gas‐sensing properties of octahedral NiO crystals prepared via one‐step controllable synthesis route

Octahedrally shaped NiO powders have been synthesized via a one‐step composite‐hydroxide‐mediated method without any surfactant. The synthesized materials are characterized by XRD, EDS, TEM and FESEM techniques. Each particle exhibited a nearly perfect octahedron shape with sharp edges and corners as well as smooth surfaces. The octahedral NiO particles performed better gas‐sensitivity toward ethanol than that of NiO nanopowders, which was attributed to the exposed ｛111｝ facets of octahedron. The result was confirmed by the first‐principle calculation which indicated that the (111) facet was more active than (100) and (110) facet.     

Anisotropy of the electro-optic effect in magnesium-doped LiNbO3 crystals

Specific features of constructing indicatory surfaces of the electro-optic effect (EOE) are described. The generalized case for the symmetry class 3m and all three possible indicatory surfaces under orthogonal experimental conditions, when the directions of light propagation and electric field are orthogonal, is considered. The EOE surfaces are constructed for magnesium-doped lithium niobate crystals. The specific features of anisotropy of these surfaces are discussed and their extreme values and corresponding angular coordinates are found. To construct the indicatory surfaces, all absolute coefficients of the linear electro-optic effect are determined by the interferometric method. The difference in the electro-optic coefficients of pure and magnesiumdoped crystals does not exceed 10%. An advantage of doped crystals is their high durability to high-power laser radiation.

     

Characterization of organic adsorbates on model glass surfaces

Model silicate glasses in planar thin film structures are prepared using sol/gel techniques. A typical structure consists of 3.0–12.0 nm of glass on vapor deposited Ag. In this study, a pure silica and a 50/50 binary alumina-silica films are examined. Poly(methyl methacrylate) (PMMA) is adsorbed from chlorobenzene solution onto the surfaces. Infrared reflection (IR) spectroscopy, ellipsometry and quartz oscillator microgravimetry (QOM) are applied to characterize the PMMA/silicate glass interfaces formed. The QOM and IR data show that PMMA adsorption on the pure silica surface is irreversible with respect to removal by pure solvent rinse while on the binary glass surface and on a pure alumina surface, solvent rinses remove the initially adsorbed polymer. These results are interpreted in terms of Bronsted acid-base interactions involving the basic properties of the PMMA C=O group, the acidic nature of the silica and the more basic nature of the alumina containing surfaces. Further evidence for this interpretation is given by the IR spectral data which show broadening of the C=O stretching mode to lower frequencies for the irreversible adsorbed polymer on silica as compared with simulated spectra of non-surface bonding PMMA thin films. This spectral perturbation is interpreted as evidence for a hydrogen bonding interaction between OH groups on the silica surface and the C=O groups. The overall conclusion is that the surface of a 50/50 binary alumina-silica composition is dominated by the basic nature of alumina.