Single Crystal Si Layers on Glass Fabricated by Hydrophilic Fusion Bonding and Smart-Cut Technology

A single crystal Si thin film on a glass substrate has been obtained successfully by hydrophilic fusion bonding and the smart-cut technology. Tensile strength testing shows that the bonded interface has strong adhesion and the bonding strength is about 8.7MPa. Crystallinity and microstructure of the samples have been characterized by transmission electron microscopy (TEM). Electrical properties have also been investigated by Hall measurements and four-point probe. The mobility of the transferred Si layer on glass is about 122cm^2//V.s. The results show that the single-crystal silicon layer transferred onto glass by direct bonding keeps good quality for the applications of integrated circuits, transducers, and fiat panel display.     

Growth of Nanocrystalline Silicon Films by Helicon Wave Plasma Chemical Vapour Deposition

Nanocrystalline silicon (nc-Si) thin films have been prepared by a helicon-wave plasma chemical vapour deposition technique on glass-Si substrates. The structural properties and the surface morphology are characterized by Raman spectroscopy, x-ray diffraction and atomic force microscopy. It is proven that the deposited films have the features of high crystalline fraction and large grain size compared with that in the normal plasma-enhanced chemical vapour deposition regime. The crystalline fraction of the deposited films varying from 0%to 72% can be obtained by adjusting the substrate temperature.     

Nanocrystalline silicon films prepared by laser—induced crystallization

The excimer laser-induced crystallization technique has been used to investigate the preparation of nanocrystalline silicon (nc-Si) from amorphous silicon ($\al$-Si) thin films on silicon or glass substrates. The $\al$-Si films without hydrogen grown by pulsed-laser deposition are chosen as precursor to avoid the problem of hydrogen effluence during annealing. Analyses have been performed by scanning electron microscopy, atomic force microscopy, Raman scattering spectroscopy and high-resolution transmission--electron microscopy. Experimental results show that silicon nanocrystals can be formed through laser annealing. The growth characters of nc-Si are strongly dependent on the laser energy density. It is shown that the volume of the molten silicon predominates essentially the grain size of nc-Si, and the surface tension of the crystallized silicon is responsible for the mechanism of nc-Si growth.     

Structure Properties of MgxZn1-xO Films Deposited at Low Temperature

MgxZn1-xO films (x = 0.23) have been prepared on silicon substrates by radio-frequency magnetron sputtering at 80℃. The structure properties of Mgx Zn1-xO films are studied using x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), x-ray photoelectron spectroscopy and Raman spectra. The analysis of XRD and HRTEM indicates that the Mgx Zn1-xO films have hexagonal wurtzite single-phase structures and a preferred orientation with the c axis perpendicular to the substrates. Raman spectra of ZnO and MgxZn1-xO films reveal that the MgxZn1-xO films have not only the hexagonal wurtzite structure but also higher crystalline quality than ZnO films.     

Magnetic Properties of Co-Doped TiO2 Films Grown on TiN Buffered Silicon Substrates

Co-doped TiO2 thin films are grown on TiN buffered silicon substrates by the pulsed laser deposition method and then hydrogenated. Transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy measurements have shown that the TiN buffer layer can suffer a 400℃ deposition temperature and prevent the growth of silicon dioxide on silicon. After that, the room temperature ferromagnetism behaviors are observed in the hydrogenated samples, which are measured by the alternating gradient magnetometer. X- ray photoelectron spectroscopy and x-ray absorption fine structure measurements have revealed the existence of cobalt clusters. According to the material analysis, the magnetic behavior after hydrogenation is suggested to be induced by the enhancement of cobalt dusters.     

Columnar growth of crystalline silicon films on aluminium-coated glass by inductively coupled plasma CVD at room temperature

Silicon films were grown on aluminium-coated glass by inductively coupled plasma CVD at room temperature using a mixture of SiH₄ and H₂ as the source gas. The microstructure of the films was evaluated using Raman spectroscopy, scanning electron microscopy and atomic force microscopy. It was found that the films are composed of columnar grains and their surfaces show a random and uniform distribution of silicon nanocones. Such a microstructure is highly advantageous to the application of the films in solar cells and electron emission devices. Field electron emission measurement of the films demonstrated that the threshold field strength is as low as ～9.8V/μm and the electron emission characteristic is reproducible. In addition, a mechanism is suggested for the columnar growth of crystalline silicon films on aluminium-coated glass at room temperature.     

Temperature-Controllable Preparation of ZnS Nanosaws on Si Substrate

A large number of ZnS nanosaws are synthesized on Si substrates in the presence of Au catalyst by thermally evaporating ZnS powder. Morphologies and structures of thus-grown ZnS nanosaws are characterized by a field emission scanning electron microscopy （FE-SEM） and a transmission electron microscopy （TEM）. The results show that temperature of the Si substrates used for collection of the products is a critical experimental parameter for the formation of ZnS nanostruetures with different morphologies. The growth mechanism of the ZnS nanosaws is discussed on the basis of the experimental findings.     

Laser Molecular Beam Epitaxy Growth of BaTiO3 in Seven Thousands of Unit-Cell Layers

BaTiO3 thin films in seven thousands of unit-cell layers have been successfully fabricated on SrTiO3 （001） substrates by laser molecular beam epitaxy. The fine streak pattern and the undamping intensity oscillation of reflection high-energy electron diffraction indicate that the BaTiO3 film was layer-by-layer epitaxial growth. The measurements of scanning electron microscopy and atomic force microscopy show that surfaces of the BaTiO3 thin film are atomically smooth. The measurements of x-ray diffraction and transmission electron microscopy, as well as selected-area electron diffraction reveal that the BaTiO3 thin film is a c-oriented epitaxial crystalline structure.     

Growth of high-crystallinity uniform GaAs nanowire arrays by molecular beam epitaxy

The self-catalyzed growth of Ga As nanowires(NWs) on silicon(Si) is an effective way to achieve integration between group III–V elements and Si. High-crystallinity uniform Ga As NW arrays were grown by solid-source molecular beam epitaxy(MBE). In this paper, we describe systematic experiments which indicate that the substrate treatment is crucial to the highly crystalline and uniform growth of one-dimensional nanomaterials. The influence of natural oxidation time on the crystallinity and uniformity of Ga As NW arrays was investigated and is discussed in detail. The Ga As NW crystallinity and uniformity are maximized after 20 days of natural oxidation time. This work provides a new solution for producing high-crystallinity uniform III–V nanowire arrays on wafer-scale Si substrates. The highly crystalline uniform NW arrays are expected to be useful for NW-based optical interconnects and Si platform optoelectronic devices.     

Comparisons of Structural and Optical Properties of ZnO films Grown on Sapphire and Si（001）

Zinc oxide films were grown on sapphire and Si(001) substrates by reactive electron beam evaporation at low substrate temperatures,Atomic force microscopy(AFM),x-ray diffraction(XRD),and photoluminescence excitation(PLE) are employed to characterize the as-grown films.The AFM measurements have shown that all of the ZnO films present pillar-like growth properties.but the dimensional uniformity of the ZnO crystal pillars grown on sapphire was better than that on Si(001),The XRD results indicated that the prepared ZnO films both on sapphire and Si(001) were all highly c-axis oriented.the linewidths of ZnO(002)are only 0.19 and 0.28,respectively,The PLE characterizations revealed the continum absorption of the samples grown on sapphire,However,in the PLE spectra of the ZnO films grown on Si(001) substrates,a broad peak appears at the high-energy region,which indicates the formation of ZnO quantum dot structures on Si(001).     

ON THE STUDY OF SILICON NANO-WIRES SELF-ASSEMBLED AS PARTICLES

Two different types of Silicon nano-wires (SiNWs) have been observed by scanning and transmission electron microscopy. One are of free standing SiNWs deposited uniformly on the surface of silicon substrates, and the other are self-assembled into special shaped particles. These SiNWs were synthesized by thermal evaporation of SiO amorphous powders without any metal catalysts in the temperature range of 900-1250℃. Growth history reveals that the self-assembled SiNWs are formed by original nucleation from the surface of amorphous SiO_{x particle matrices through phase separation and silicon precipitation followed by further growth through oxide-assisted vapor-solid reactions. The above results provide a solid experimental support for the oxide-assisted growth model of SiNWs.}     

Preparation and Thermal Characterization of Diamond-Like Carbon Films

Diamond-like carbon （DLC） films are prepared on silicon substrates by microwave electron cyclotron resonance plasma enhanced chemical vapor deposition. Raman spectroscopy indicates that the films have an amorphous structure and typical characteristics. The topographies of the films are presented by AFM images. Effective thermal conductivities of the films are measured using a nanosecond pulsed photothermal reflectance method. The results show that thermal conductivity is dominated by the microstructure of the films.     

A CMOS Compatible Si Template with (111) Facets for Direct Epitaxial Growth of Ⅲ–Ⅴ Materials

Ⅲ-Ⅴ quantum dot(QD) lasers monolithically grown on CMOS-compatible Si substrates are considered as essential components for integrated silicon photonic circuits.However,epitaxial growth of Ⅲ-Ⅴ materials on Si substrates encounters three obstacles:mismatch defects,antiphase boundaries(APBs),and thermal cracks.We study the evolution of the structures on U-shaped trench-patterned Si(001) substrates with various trench orientations by homoepitaxy and the subsequent heteroepitaxial growth of GaAs film.The results show that the formation of(111)-faceted hollow structures on patterned Si(001) substrates with trenches oriented along [110] direction can effectively reduce the defect density and thermal stress in the GaAs/Si epilayers.The(111)-faceted silicon hollow structure can act as a promising platform for the direct growth of Ⅲ-Ⅴ materials for silicon based optoelectronic applications.     

ZnO nanorod arrays with tunable size and field emission properties on an ITO substrate achieved by an electrodeposition method

In the present work,vertically aligned ZnO nanorod arrays with tunable size are successfully synthesized on nonseeded ITO glass substrates by a simple electrodeposition method.The effect of growth conditions on the phase,morphology,and orientation of the products are studied in detail by X-ray diffraction(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).It is observed that the as-prepared nanostructures exhibit a preferred orientation along c axis,and the size and density of the ZnO nanorod can be controlled by changing the concentration of ZnCl2.Field emission properties of the as-synthesized samples with different diameters are also studied,and the results show that the nanorod arrays with a smaller diameter and appropriate rod density exhibit better emission properties.The ZnO nanorod arrays show a potential application in field emitters.     

Investigation of natural contamination layer growth on optical substrates

The surface contamination layer on mirrors can cause significant degradation of the optical performance,which is widely observed in applications, particularly in the fabrication of X-ray focusing telescopes. In this paper,we study the natural contamination layer arising from adsorption precipitation of hydrocarbons or other organic and water molecules in the absence of any external factor. Temporal evolution of the layer formed on super-smooth fused silica, borosilicate glass, and silicon substrates is studied by X-ray reflectometry, atomic force microscopy,and transmission electron microscopy for a one-year period after surface cleaning. The general characteristics of adhesion layer growth are established and discussed. The reconstructed dielectric constant profiles demonstrate that an increase in the adhesion layer thickness, deposited mass and density over time obeys power laws with extremely small exponents. Therefore, the adhesion layer growth is rapid immediately after surface cleaning, with a～1 nm thick layer formed within the first day on all three substrates studied, while the layer density is low(～1 g/cm~3). The layer growth on the fused silica and silicon substrates became very slow in the succeeding days, with only a 1.4–1.5 nm thick layer and 1.2–1.3 g/cm~3 density after one year of storage in air. At the same time, the adhesion layer growth on the glass substrate showed unexpected acceleration about two months after cleaning, so that the layer thickness reached～2.2 nm after one year of storage. The reason for this effect, which is connected with leaching of the glass,is discussed briefly.     

Growth and characterization of ZnO multipods on functional surfaces with different sizes and shapes of Ag particles

Three-dimensional ZnO multipods are successfully synthesized on functional substrates using the vapor transport method in a quartz tube. The functional surfaces, which include two different distributions of Ag nanoparticles and a layer of commercial Ag nanowires, are coated onto silicon substrates before the growth of ZnO nanostructures. The structures and morphologies of the ZnO/Ag heterostructures are investigated using X-ray diffraction and field emission scanning electron microscopy. The sizes and shapes of the Ag particles affect the growth rates and initial nucleations of the ZnO structures, resulting in different numbers and shapes of multipods. They also influence the orientation and growth quality of the rods. The optical properties are studied by photoluminescence, UV-vis, and Raman spectroscopy. The results indicate that the surface plasmon resonance strongly depends on the sizes and shapes of the Ag particles.     

Structural properties of polycrystalline silicon films formed by pulsed rapid thermal processing

A novel pulsed rapid thermal processing (PRTP) method has been used for realizing solid-phase crystallization of amorphous silicon films prepared by plasma-enhanced chemical vapour deposition.The microstructure and surface morphology of the crystallized films were investigated using x-ray diffraction and atomic force microscopy.The results indicate that PRTP is a suitable post-crystallization technique for fabricating large-area polycrystalline silicon films with good structural quality,such as large grain size,small lattice microstrain and smooth surface morphology on low-cost glass substrates.     

Strained and strain-relaxed epitaxial Ge1-xSnx alloys on Si（100） substrates

Epitaxial Ge1-xSnx alloys are grown separately on a Ge-buffer/Si(100) substrate and directly on a Si(100) substrate by molecular beam epitaxy (MBE) at low temperature. In the case of the Ge buffer/Si(100) substrate, a high crystalline quality strained Ge0.97Sn0.03 alloy is grown, with a χmin value of 6.7% measured by channeling and random Rutherford backscattering spectrometry (RBS), and a surface root-mean-square (RMS) roughness of 1.568 nm obtained by atomic force microscopy (AFM). In the case of the Si(100) substrate, strain-relaxed Ge0.97Sn0.03 alloys are epitaxially grown at 150°C-300°C, with the degree of strain relaxation being more than 96%. The X-ray diffraction (XRD) and AFM measurements demonstrate that the alloys each have a good crystalline quality and a relatively flat surface. The predominant defects accommodating the large misfit are Lomer edge dislocations at the interface, which are parallel to the interface plane and should not degrade electrical properties and device performance.     

Non-homogeneous SiGe-on-insulator formed by germanium condensation process

Ge condensation process of a sandwiched structure of Si/SiGe/Si on silicon-on-insulator （SOI） to form SiGe-on- insulator （SGOI） substrate is investigated. The non-homogeneity of SiGe on insulator is observed after a long time oxidation and annealing due to an increased consumption of silicon at the inflection points of the corrugated SiGe film morphology, which happens in the case of the rough surface morphology, with lateral Si atoms diffusing to the inflection points of the corrugated SiGe film. The transmission electron microscopy measurements show that the non-homogeneous SiGe layer exhibits a single crystalline nature with perfect atom lattice. Possible formation mechanism of the non-homogeneity SiGe layer is presented by discussing the highly nonuniform oxidation rate that is spatially dependent in the Ge condensation process. The results are of guiding significance for fabricating the SGOI by Ge condensation process.     

Effect of CO2 Addition on Preparation of Diamond Films by Direct-Current Hot-Cathode Plasma Chemical Vapor Deposition Method

Diamond films are deposited on Mo substrates by dc hot-cathode plasma chemical vapor deposition method using a CH4-H2-CO2 gas mixture. Adjusting the flow of CO2, we study the relevant influence on surface morphology, grain orientation and crystalline quality of films with scanning electron microscopy, x-ray diffraction, Raman spectroscopy, respectively. The results show that grain orientation of the films has a transition with the increasing CO2 addition, from （100） orientation to （110） orientation and then （111） orientation. The crystalline quality is improved but the growth rate is decreased by raising the flow of CO2. The experimental results are also discussed briefly.