A (-)-menthyl bonded silica phase for chiral separations: synthesis and solid state NMR characterization

A new (-)-menthyl bonded silica phase has been prepared by hydrosilation of a hydride silica intermediate. The hydride silica intermediate was synthesized by the reaction of a monoalkoxysilane (CH(3))(2)SiH(OEt) with silica gel, yielding a relatively high surface coverage (4.4 μmol/m(2)) of SiH groups. This intermediate was then used successfully in the preparation of a monomeric (-)-menthyl bonded silica phase. The bonded phase produced has been used for the chromatographic separation of enantiomers in a reversed phase mode (chiral separations). Solid state (13)C and (29)Si CP-MAS NMR spectroscopy and DRIFT spectroscopy provides valuable information on the structure of the different surface species formed on silica after modification. The surface coverage of the hydride silica intermediate and of the final bonded silica phase produced are also determined. It is found that this modification procedure can exclusively produce a monomeric coverage of SiH groups on the silica surface and can further produce a final monomeric bonded organic silica phase for the separation of enantiomers.     

Er2O3／Si外延薄膜表面和界面组分研究

利用X射线光电子能谱方法对Si基Er2O3外延薄膜的化学组分进行了分析。在X射线照射样品和氩离子轰击使样品减薄的过程中没有诱发其他的化学反应。研究了清洁的Si和有氧化层的Si衬底上外延生长的Er2O3薄膜的表面和界面化学组分情况,并对上述两种不同的衬底上外延生长Er2O3薄膜的生长模式进行初步探讨。     

Growth and characterization of AP-MOCVD iron doped titanium dioxide thin films

Atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD) was used to prepare iron doped titanium dioxide thin films. Thin films, between 40 and 150 nm thick, were deposited on Si, SiO₂ and Al₂O₃ substrates using titanium tetra isopropoxide and ferrocene as metal organic precursors. TiO₂ iron doping was achieved in the range of 1–4 at.%. The film morphology and thickness, polycrystalline texture and doping content were studied using respectively scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The influence of growth temperature, deposition time, substrate type and dopant partial pressure were studied. Electrical characterizations of the films were also performed.     

前驱气体CH_4、N_2的流量比对CH_x膜Raman谱的影响

沉积在Ｓｉ（１００）基片上的ＣＮｘ膜是用微波等离子体化学气相沉积法（ＭＷＰＣＶＤ）制备的。本文着重探讨了ＣＨ４、Ｎ２的流量比对ＣＮｘ膜的Ｒａｍａｎ谱的影响，并采用了Ｘ－射线光电子能谱（ＸＰＳ）方法分析了ＣＮｘ膜的化学状态。     

Temperature dependence of oriented growth of Pb[Yb(1/2)Nb(1/2)]O(3)-PbTiO(3) thin films deposited on LNO/Si substrates

(1-x)Pb[Yb(1/2)Nb(1/2)]O(3)-xPbTiO(3) (PYbN-PT, x=0.5)(001) oriented thin films were deposited onto LaNiO3 (LNO)/Si(001) substrates by sol-gel processing. The crystallographic texture of the films was controlled by the annealing temperature and heating rate. Highly (001) oriented LNO thin films were prepared by a simple metal organic decomposition technique, and the samples were annealed at 700 °C and 750 °C using a rapid thermal annealing process and furnace, respectively. X-ray diffraction analysis revealed that the films of PYbN-PT were highly (001) oriented along LNO/Si substrates. The degree of PYbN-PT orientation is dependent on the heating rate and annealing temperature. Annealing heating rate of 10 °C/s and high annealing temperature near 750 °C produce the greatest degree of (001) orientation, which gives rise to improved dielectric properties.     

A study of polyaniline deposited nanocrystalline diamond films for glucose detection

Nitrogen-doped nanocrystalline diamond (NCD) films have been deposited on Si substrates in CH4/Ar/N2 gas mixtures by the microwave plasma enhanced chemical vapor deposition (MPECVD) technique. Such films contain very small diamond grains (10 to 30 nm) with high electrical conductivity (126 ohms(-1) cm(-1)) compared to un-doped ones. The films were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Near edge X-ray fine structure studies showed that the nitrogen-doped NCD had slightly higher sp2/sp3 bonding ratio compared to the un-doped sample. A nitrogen-doped NCD electrode was functionalized by conducting polymer films (polyaniline) to work as an interface for biomedical applications. Glucose sensing has been demonstrated based on this functionalized electrode. Linear response of the sensor has been observed for glucose concentration up to 9 mM.     

无支撑、光学级MPCVD金刚石膜的研制

利用引进的6 kW微波等离子体化学气相沉积设备,进行了无支撑金刚石膜工艺的初步研究。在800~1050℃的基片温度范围内,金刚石膜都呈(111)择优取向;基片相对位置对沉积较大面积、光学级金刚石膜至关重要。制出0.25 mm厚Φ50 mm的无支撑金刚石膜。拉曼光谱和X射线衍射分析表明,合成的金刚石膜晶体结构完整,sp2含量极低;透过率测试结果说明了优良的光学性能:截止波长225 nm,光学透过率(λ≥2.5μm)≥70%。     

Epitaxial and polycrystalline CuInS2 layers: Structural metastability and its influence on the photoluminescence

Thin epitaxial and polycrystalline CuInS₂ (CIS) films were grown on single crystalline Si(111) and Mo-coated Si substrates, respectively, by means of molecular beam epitaxy from elemental sources. Photoluminescence (PL) measurements were performed to investigate the optical properties of both, epitaxial and polycrystalline CIS films. Epitaxial CIS samples show defect related transitions only and the PL spectra are dominated by broad luminescence peaks of deep levels, while excitonic transitions are completely absent. This contrasts sharply with the PL of the polycrystalline films, which is dominated by excitonic luminescence. Contributions due to shallow defects are observed with a small intensity only. However, luminescence peaks of defects with electronic levels deep in the band gap are not present at all. This includes the broad PL lines around 1.2 or 1.3 eV which are typical for polycrystalline CIS solar-cell material. X-ray diffraction and selected area electron diffraction measurements were employed in order to study the crystal structure. The epitaxial CIS films show a coexistence of the metastable CuAu-type (CA) ordering with the ground-state chalcopyrite (CH) structure, while the polycrystalline layers crystallize exclusively in the ground-state CH ordering. Hence, the coexistence of the metastable CA ordering and the ground-state CH structure in the epitaxial films is accompanied by a high density of electrically active intrinsic defects with levels deep in the band gap.     

X-ray absorption spectroscopy, simulation and modeling of Si-DLC films

Amorphous silicon-containing diamond-like carbon (Si-DLC) films were deposited on silicon wafers by Ar⁺ Ion Beam Assisted Deposition (IBAD) at various energy conditions. The films were examined with X-ray Absorption Near Edge Structure (XANES) spectroscopy and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. The Si K-edge X-ray Absorption Spectroscopy (XAS) results indicate that Si-DLC films have an amorphous structure, where each Si atom is coordinated to four carbon atoms or CH_n groups. This short-range order, where a Si atom is surrounded by four C atoms, was found in all Si-DLC films. The XANES spectra do not indicate Si coordination to oxygen atoms or phenyl rings, which are present in the precursor material. A structural model of Si-DLC is proposed based on XAS findings. Simulated X-ray absorption spectra of the model produced by FEFF8 show a good resemblance to the experimental data.     

H2C2O4稳定剂对SOl-Gel法制备LiNbO3薄膜的影响

研究了分别以H2C2O，HNO3，HCOOH和CH3COOH作稳定剂的LiNbO3薄膜先驱液的稳定性，发现H2C2O4作稳定剂的先驱液的稳定性最好，用sol-gel法在Si(110)基板上制备了以H2C2O4作稳定剂的LiNbO3薄膜，并对LiNbO3薄膜进行了IR，XRD和SEM表征，结果表明，生成的LiNbO3为多晶，与HNO3相比，以H2C2O4作稳定剂制备的LiNbO3薄膜形貌较差。     

BiFeO3 films doped in the A or B sites: effects on the structural and morphological properties

Metal-Organic Chemical Vapor Deposition (MOCVD) has been applied to the fabrication of BiFeO3 films undoped and doped with Ba or Ti on SrTiO3 (100) and YSZ (100) substrates. The films have been deposited using a multi-metal source, consisting of the Bi(phenyl)3, Fe(tmhd)3 and Ba(hfa)2 tetraglyme or Ti(tmhd)2(O-iPr)2 (phenyl = -C6H5, H-tmhd = 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr = iso-propoxide; H-hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme = CH3O(CH2CH2O)4CH3) precursor mixture. The structural and morphological characterization of films has been carried out using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Chemical compositional studies have been performed by energy dispersive X-ray (EDX) analysis. Structural and morphological characterizations point to the formation of homogeneous and flat surfaces for both undoped and doped BiFeO3 films.     

In situ X‐ray Measurements to Probe a New Solid‐State Polycondensation Mechanism for the Design of Supramolecular Organo‐Bridged Silsesquioxanes

A long‐range ordered organic/inorganic material is synthesized from a bis‐silane, (EtO)₃Si? (CH₂)₃? NHCONH? C₆H₄? NHCONH? (CH₂)₃? Si(OEt)₃. This crosslinked sol–gel solid exhibits a supramolecular organization via intermolecular hydrogen bonding interactions between urea groups (? NHCONH? ) and covalent siloxane bonding, ?Si? O? Si?. Time‐resolved in situ X‐ray measurements (coupling small‐ and wide‐angle X‐ray scattering techniques) are performed to follow the different steps involved in the synthetic process. A new mechanism based on the crystallization of the hydrolyzed species followed by their polycondensation in solid state is proposed.     

Surface modification and patterning using low-energy ion beams: Si-O bond formation at the vacuum/adsorbate interface.

Modification of hydroxyl-terminated self-assembled monolayer (HO-SAM) surfaces by collision of low-energy (15 eV) hyperthermal Si(CH3)3+ ions is shown to lead to Si-O bond formation and terminal trimethylsilyl ether formation. Modification was verified by in situ mass spectrometry using chemical sputtering with CF3+ ions (70 eV), ex situ secondary ion mass spectrometric analysis (12 kV Ga+ primary ion beam), and through X-ray photoelectron spectroscopy by monitoring Si (2s). The nature of the surface modification was further established by analysis of synthetic SAM surfaces made up of mixtures of the trimethylsilyl-11-mercapto-1-undecane ether and various proportions of the hydroxyl-terminated mercaptan (11-mercapto-1-undecanol). These mixed surfaces, as well as the spectroscopic data, indicate that ca. 30% of the hydroxyl chains are covalently modified at saturation coverage. Analogous surface transformations are achieved using Si(CH3)2F+ and Si(CH3)2C6H5+.     

Mg2Si薄膜的磁控溅射制备及表征

采用直流磁控溅射的方法在Si(100)衬底上制备了Mg2Si外延半导体薄膜。通过XRD和FESEM对Mg2Si薄膜的晶体结构和表面形貌进行了表征,分析了溅射功率对Mg2Si薄膜制备的影响,得到了Mg2Si薄膜在不同溅射功率下的外延生长特性。结果表明,在Si(100)衬底上,Mg2Si薄膜具有(220)的择优生长特性,并且在50~80W的溅射功率范围内,随着溅射功率的增加,Mg2Si外延薄膜的衍射峰强度逐渐增强。     

Pulsed laser deposition of silicon-substituted hydroxyapatite coatings

Thin films of Si-substituted hydroxyapatite (Si-HA) were deposited on Si and Ti substrates by pulsed laser deposition (PLD), in the presence of a water vapour atmosphere. The PLD ablation targets were made with different mixtures of commercial carbonated HA and Si powder, in order to produce the Si-HA thin films. The physicochemical properties of the coatings and the incorporation of the Si into the HA structure was studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Si atoms were successfully incorporated into the HA structure, and were found to be in the form of SiO₄⁴⁻ groups, principally displacing carbonate groups off the HA structure.     

Reflection high energy electron diffraction and X-ray studies of AlN films grown on Si(111) and Si(001) by organometallic chemical vapour deposition

The crystallinity of AlN films on silicon substrates grown by organometallic chemical vapour deposition was investigated using X-ray diffraction and reflection high energy electron diffraction (RHEED). Single-crystal films of good quality with atomically smooth surfaces can be epitaxially grown on Si(111) substrates. Epitaxial films can also be grown on Si(001) substrates. These films have previously been reported to have a fibre structure. Different RHEED patterns were observed from the films on Si(111) and Si(001). It is established that the films grown on Si(001) consist of two types of crystallite with the following orientations: [11$\text{2}$0]_AlN//[110]_Si and [11$\text{2}$0]_AlN//[1$\text{1}$0]_Si The thickness dependence of the crystallinity was also investigated. The standard deviation σ of the X-ray rocking curve for the films grown on Si(111) is less than that for the films on Si(001) and is independent of the film thickness. The σ values for the films on Si(001) decrease markedly with increasing film thickness. On the basis of these observations, the growth mechanism of AlN epitaxial films on Si(111) and Si(001) is discussed.     

Atomic vapor deposition approach to In2O3 thin films

In2O3 thin films were grown by atomic vapor deposition (AVD) on Si(100) and glass substrates from a tris-guanidinate complex of indium [In(N(i)Pr2guanid)3] under an oxygen atmosphere. The effects of the growth temperature on the structure, morphology and composition of In2O3 films were investigated. X-ray diffraction (XRD) measurements revealed that In2O3 films deposited in the temperature range 450-700 degreesC crystallised in the cubic phase. The film morphology, studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM), was strongly dependent on the substrate temperature. Stoichiometric In2O3 films were formed under optimised processing conditions as was confirmed by X-ray photoelectron and X-ray excited Auger electron spectroscopies (XPS, XE-AES), as well as by Rutherford backscattering spectrometry (RBS). Finally, optical properties were investigated by photoluminescence (PL) measurements, spectroscopic ellipsometry (SE) and optical absorption. In2O3 films grown on glass exhibited excellent transparency (approximately 90%) in the Visible (Vis) spectral region.     

Polymer-assisted deposition of co-doped zinc oxide thin films for the detection of aromatic organic compounds

Co-doped Zinc oxide thin films are deposited onto SiO2/Si substrate by polymer-assisted deposition method. The surface morphology, structures and chemical states of the thin films are examined by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The gas-sensing properties of the thin films upon exposure to aromatic organic compound vapors are also investigated. Co-doping is shown to be very effective in enhancing the response of ZnO thin film to aromatic organic compound.     

Fe/Si多层膜经快速热退火合成β-FeSi_2薄膜的研究

采用磁控溅射仪在高阻Si(100)衬底上沉积了[Fe(0.5nm)/Si(1.6nm)]120和[Fe(1nm)/Si(3.2nm)]60多层膜,并在Ar气气氛下进行了1000℃,10s的快速热退火。为了比较,也进行了880℃,30min的常规退火。采用X射线衍射仪、原子力显微镜、光谱仪和霍尔效应仪分析了样品的晶体结构、表面形貌、光吸收特性和电学性能。结果表明:Fe/Si多层膜法合成的样品均为β-FeSi2相且在(220)/(202)方向择优生长;经快速热退火合成的β-FeSi2薄膜光学带隙约为0.9 eV。[Fe(1nm)/Si(3.2nm)]60多层膜经快速热退火合成的β-FeSi2薄膜表面粗糙度最小,该薄膜样品为p型导电,载流子浓度为4.1×1017cm-3,迁移率为48cm2/V.s。     

Synthesis of β-Mo(2)C thin films

Thin films of stoichiometric β-Mo(2)C were fabricated using a two-step synthesis process. Dense molybdenum oxide films were first deposited by plasma-enhanced chemical vapor deposition using mixtures of MoF(6), H(2), and O(2). The dependence of operating parameters with respect to deposition rate and quality is reviewed. Oxide films 100-500 nm in thickness were then converted into molybdenum carbide using temperature-programmed reaction using mixtures of H(2) and CH(4). X-ray diffraction confirmed that molybdenum oxide is completely transformed into the β-Mo(2)C phase when heated to 700 °C in mixtures of 20% CH(4) in H(2). The films remained well-adhered to the underlying silicon substrate after carburization. X-ray photoelectron spectroscopy detected no impurities in the films, and Mo was found to exist in a single oxidation state. Microscopy revealed that the as-deposited oxide films were featureless, whereas the carbide films display a complex nanostructure.