氮化硅微金字塔结构化薄膜的分光特性研究

为研究氮化硅微金字塔结构化薄膜的分光特性,使用单点金刚石切削制备微金字塔结构,结合纳米压印技术制备氮化硅微金字塔结构薄膜,对其透射率与散射进行检测。通过对底面角度可变的氮化硅微金字塔结构化薄膜的近场光场分布展开仿真分析与实验研究,基于射线追踪方法建立数值仿真模型分析结构化薄膜的近场光场分布。研究结果表明:通过调整切削方向实现对微金字塔结构阵列底面角度0°～90°的控制,检测结果证明薄膜光学微金字塔结构化薄膜可以实现对光束传播方向与能量分布的调制,改变微金字塔结构的底面角度,可以让光波按照底角的设计传播,这一现象为微光电系统的光路设计提供了更广的自由度。

Fabrication of Bottom-Gate and Top-Gate Transparent ZnO Thin Film Transistors

Transparent zinc oxide thin film transistors （ZnO-TFTs） with bottom-gate and top-gate structures were constructed on 50mm silica glass substrates. The ZnO films were deposited by RF magnetron sputtering and SiO2 films served as the gate insulator layer. We found that the ZnO-TFTs with bottom-gate structure have better electrical performance than those with top-gate structure. The bottom-gate ZnO-TFTs operate as an n-channel enhancement mode, which have clear pinch off and saturation characteristics. The field effect mobility, threshold voltage, and the current on/off ratio were determined to be 18.4cm^2/（V ·s）, - 0. 5V and 10^4 , respectively. Meanwhile, the top-gate ZnO-TFTs exhibit n-chan- nel depletion mode operation and no saturation characteristics were detected. The electrical difference of the devices may be due to the different character of the interface between the channel and insulator layers. The two transistors types have high transparency in the visible light region.

Influence of Pressure on SiNx：H Film by LF-PECVD

Hydrogenated silicon nitride films as an effective antireflection and passivation coating of silicon solar cell were prepared on p-type polished silicon substrate （1.0 f^em） by direct LF-PECVD （low frequency plasma enhanced chemical vapor deposition） of Centrotherm. The preferable passivation effect was obtained and the refractive index was in the range of 2.017-2.082. The refractive index of the hydrogenated silicon nitride films became larger with the increase of the pressure. Fourier transform infrared spectroscopy was used to study the pressure influence on the film structural properties. The results highlighted high hydrogen bond and high Si-N bonds density in the film, which were greatly influenced by the pressure. The passivation effect of the films was infuenced by the Si dangling bonds density. Finally the effective minority liftetime degradation with time was shown and discussed by considering the relationship between the structural properties and passivation.

Microstructure and superhardness effect of VC/TiC superlattice films

Vanadium carbide/titanium carbide （VC/TiC） superlattice films were synthesized by magnetron sputtering method. The effects of modulation period on the microstructure evolution and mechanical properties were investigated by EDXA, XRD, HRTEM and nano-indentation. The results reveal that the VC/TiC superlattice films form an epitaxial structure when their modulation period is less than a critical value, accompanied with a remarkable increase in hardness. Further increasing the modulation period, the hardness of superlattices decreases slowly to the rule-of-mixture value due to the destruction of epitaxial structures. The XRD results reveal that three-directional strains are generated in superlattices when the epitaxial structure is formed, which may change the modulus of constituent layers. This may explain the remarkable hardness enhancement of VC/TiC superlattices.

Formation of nanocrystalline microstructure in arc ion plated CrN films

Applying negative bias voltages caused significant microstructure changes in arc ion plated CrN films. Nanocrystalline microstructures were obtained by adjusting the negative bias voltage. Structural characterizations of the films were carried out using X-ray diffractometry (XRD) and high-resolution transmission electron microscopy (HR-TEM). The results indicated that increasing ion bombardment by applying negative bias voltages resulted in the formation of defects in the CrN films, inducing microstructure evolution from micro-columnar to nanocrystalline. The microhardness and residual stresses of the films were also affected. Based on the experimental results, the evolution mechanisms of the film microstructure and properties were discussed by considering ion bombardment effects.

Effect of the Structure and Valence State on the Properties of VO_2 Thin Films

VO 2 thin films with good switching properties were prepared by controlling the annealing time and the annealing temperature in a vacuum system. The structural, optical and electrical properties of the samples were characterized by using XRD、XPS、UV-VIS and electrical measurements. The switching parameters of VO 2 thin film were investigated too. The results indicate that before and after phase transition the resistance of VO 2 thin films changes about three orders of magnitude, the variation of film transmittance of 40 % has been carried out with the absorptivity switching velocity of about 0.260 7 /min at 900 nm . The structural property of samples has been improved but the phase-transition properties have been decreased by increasing the annealing time and annealing temperature. The valence of V ions and the structure of samples have great effect on phase transition properties of VO 2 thin films. Discussion on the effects of annealing time and annealing temperature on the phase-transition temperature and hysteresis width shows that the best reasonable annealing time and annealing temperature can be achieved.

Facile Synthesis of 3D Porous Flower-like ZnO Micro/nanostructure Films and Their Photocatalytic Performance

3D porous flower-like ZnO micro/nanostructure films grown on Ti substrates are synthesized via a very facile electrodeposition technique followed by heat treatment process. The ZnO architecture is assembled with ultra thin sheets, which consist of numbers of nanoparticles and pores, and the size of the nanoparticles can be controlled by adjusting the electrodepo- sition time or calcination temperature. It is worth noting that this synthetic method can provide an effective route for other porous metal oxide nanostructure films. Moreover, the photocatalytic performance shows the porous ZnO is an ideal photocatalyst.

Theoretical Calculation on Optimum Si-doping Content in Boron Carbide Thin Film

The theoretical expression of the relationship between optimumdoping content and crystal structure is presented as well as thepreparation methods. By using this expression, the optimum dopingcontent of silicon-coped boron carbide thin film is calculated. Thequantitative calculation value is consistent with the experimentalresults. This theoretical expression is also appropriate to resolvethe optimum doping content for Other electric materials.

Effective Pyroelectric Coefficient and Polarization Offset of Compositionally Step-like Graded Ferroelectric Structures

In this paper, the effective pyroelectric coefficient and polarization offset of the compositionally step-like graded multilayer ferroelectric structures have been studied by use of the first-principles approach. It is exhibited that the dielectric gradient has a nontrivial influence on the effective pyroelectric coefficient, but has a little influence on the polarization offset; and the polarization gradient plays an important role in the abnormal hysteresis loop phenomenon of the co.mpositionally step-like graded ferroelectric structures. Moreover, the origin of the polarization offset is explored,which can be attributed to the polarization gradient in the compositionally step-like graded structure.

Optical and electrical properties of room temperature preparedα-IGZO thin films using an In_(2)Ga_(2)ZnO_(7) ceramic target

In this study,a high-purity In_(2)Ga_(2)ZnO_(7) ceramic target was used to deposit indium gallium zinc oxide(IGZO)films by RF magnetron sputtering technology.The microstructure,growth state,optical and electrical properties of the IGZO films were studied.The results showed that the surface of the IGZO film was uniform and smooth at room temperature.As the substrate temperature increased,the surface roughness of the film gradually increased.From room temperature to 300℃,all the films maintained amorphous phase and good thermal stabilities.Moreover,the transmission in the visible region decreased from 91.93%to 91.08%,and the band gap slightly decreased from 3.79 to 3.76 eV.The characterization of the film via atomic force microscope(AFM)and X-ray photoelectron spectroscopy(XPS)demonstrated that the film prepared at room temperature exhibited the lowest surface roughness and the largest content of oxygen vacancies.With the rise in temperature,the non-homogeneous particle distribution,increase in the surface roughness,and reduction in the number of oxygen vacancies resulted in lower performance of theα-IGZO film.Comprehensive analysis showed that the best optical and electrical properties can be obtained by depositing IGZO films at room temperature,which indicates their potential applications in flexible substrates.

Polycrystalline ZnSx Se1—x thin films deposited on ITO glass by MBE

MBE growth of ZnS_xSe_1-x thin films on ITO coated glass substrate s were carried o ut using ZnS and Se sources with the substrate temperature ranging from 270℃ to 330℃. The XRD θ/2θ spectra resulted from these films indicated that the as-gro wn polycrystalline ZnS_xSe_1-x thin films had a preferred orientat ion along the (1 11) planes. The evaluated crystal sizes as deduced from the FWHM of the XRD laye r peaks showed strong growth temperature dependence, with the optimized temperat ure being about 290℃. Both AFM and TEM measurements of these thin films also in dicated a similar growth temperature dependence. High quality ZnS_xSe_1- x thin fil m grown at the optimized temperature had the smoothest surface with lowest RMS v alue of 1.2 nm and TEM cross-sectional micrograph showing a well defined column ar structure.

Microstructure and optical properties of TiO_2 thin films deposited at different oxygen flow rates

To research the influence of oxygen flow rate on the structural and optical properties of TiO2 thin film,TiO2 films on glass were deposited by reactive magnetron sputtering.The microstructure and optical properties were measured by X-ray diffractometry,AFM and UV-VIS transmittance spectroscopy,respectively.The results show that the films deposited at oxygen flow rate of 10 mL/min has the lowest roughness and the highest transmittance.The absorption angle shifts to longer wavelengths as oxygen flow rates increase from 5 to 10 mL/min,then to shorter ones as the oxygen flow rate increase from 10 to 30 mL/min.The band gap is 3.38 eV,which is nearly constant in the experiment.For the TiO2 thin films deposited at 10 mL/min of oxyge flow rate,there are nano-crystalline structures,which are suitable for anti-reflection(AR) coating in the solar cells structure system.

Study on the growth of honeycomb-like film of basic zinc carbonate induced by bovine serum albumin LB film template

Honeycomb-like films of basic zinc carbonate were successfully prepared on FTO(SnO_(2):F)conductive glass using bovine serum albumin(BSA)as a template at room temperature.After low-temperature annealing,a high-specific-surface-area porous ZnO film with excellent electron mobility was obtained.The surface morphology,crystallization performance,and photoluminescence characteristics of basic zinc carbonate thin films and annealed ZnO thin film were analyzed by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),photoluminescence spectroscopy(PL)and UV-Visible spectroscopy(UV-vis).By comparing with those samples prepared without any protein,it was determined that the complexation between BSA molecules and Zn^(2+)ions was the primary factor in the synthesis of porous films of basic zinc carbonate.The experimental results showed that the ZnO thin film samples prepared with this method had high specific surface area and broadband luminescence characteristics in the near ultraviolet range.

Reduced graphene oxide with a highly restored π-conjugated structure for inkjet printing and its use in all-carbon transistors

An inkjet-printed graphene film is of great importance for next-generation flexible, low cost and high performance electronic devices. However, due to the limitation of the inkjet printing process, the electrical conductivity of inkjet-printed graphene films is limited to N10 S＇cm-1, and achieving a high conductivity of the printed graphene films remains a big challenge. Here, we develop a ＂weak oxidation- vigorous exfoliation＂ strategy to tailor graphene oxide （GO） for meeting all the requirements of highly conductive inkjet-printed graphene films, including a more intact carbon plane and suitable size. The -conjugated structure of the resulting graphene has been restored to a high degree, and its printed films show an ultrahigh conductivity of -420 S-cm-I, which is tens of times higher than previously reported results, suggesting that, aside from developing a highly efficient reduction method, tuning the GO structure could be an alternative way to produce high quality graphene sheets. Using inkjet-printed graphene patterns as source/drain/gate electrodes, and semiconducting single-walled carbon nanotubes （SWCNTs） as channels, we fabricated an all-carbon field effect transistor which shows excellent performance （an on/off ratio of -104 and a mobility of -8 cm2＂V-l＇s-1） compared to previously reported CNT-based transistors, promising the use of nanocarbon materials, graphene and SWCNTs in printed electronics, especially where high performance and flexibility are needed.

Influence of Mn-doping concentration on the microstructure and magnetic properties of ZnO thin films

The microstructure and magnetic properties of Mn-doped ZnO films with various Mn contents,synthesized by magnetron sputtering at room temperature,are investigated in detail.X-ray diffraction(XRD) measurement results suggest that the doped Mn ions occupy the Zn sites successfully and do not change the crystal structure of the ZnO films.However,the microstructure of the Mn-doped ZnO films apparently changes with increasing the Mn concentration.Arrays of well-aligned nanoscale rods are found in the Mn-doped ZnO films with moderate Mn concentrations.Magnetic measurement results indicate that the ZnO films doped with moderate Mn concentration are ferromagnetic at room temperature.The possible origin of the ferromagnetism in our samples is also explored in detail.

Towards full repair of defects in reduced graphene oxide films by two-step graphitization

The complete restoration of a perfect carbon lattice has been a central issue in the research on graphene derived from graphite oxide since this preparation route was first proposed several years ago, but such a goal has so far remained elusive. Here, we demonstrate that the highly defective structure of reduced graphene oxide sheets assembled into free-standing, paper-like films can be fully repaired by means of high temperature annealing （graphitization）. Characterization of the films by X-ray photoelectron and Raman spectroscopy, X-ray diffraction and scanning tunneling microscopy indicated that the main stages in the transformation of the films were （i） complete removal of oxygen functional groups and generation of atomic vacancies （up to 1,500 ~C）, and （ii） vacancy annihilation and coalescence of adjacent overlapping sheets to yield continuous polycrystalline layers （1,800-2,700 ~C） similar to those of highly oriented graphites. The prevailing type of defect in the polycrystalline layers were the grain boundaries separating neighboring domains, which were typically a few hundred nanometers in lateral size, exhibited long-range graphitic order and were virtually free of even atomic-sized defects. The electrical conductivity of the annealed films was as high as 577,000 S-m-1, which is by far the largest value reported to date for any material derived from graphene oxide, and strategies for further improvement without the need to resort to higher annealing temperatures are suggested. Overall, this work opens the prospect of truly achieving a complete restoration of the carbon lattice in graphene oxide materials.

Growth and low-energy electron microscopy characteri- zation of monolayer hexagonal boron nitride on epitaxial cobalt

Low-energy electron microscopy （LEEM） has been used to study the structure, initial growth orientation, growth progression, and the number of layers of atomically thin hexagonal boron nitride （h-BN） films. The h-BN films are grown on heteroepitaxial Co using chemical vapor deposition （CVD） at low pressure. Our findings from LEEM studies include the growth of monolayer film having two, oppositely oriented, triangular BN domains commensurate with the Co lattice. The growth of h-BN appears to be self-limiting at a monolayer, with thicker domains only appearing in patches, presumably initiated between domain boundaries. Reflectivity measurements of the thicker h-BN films show oscillations resulting from the resonant electron transmission through quantized electronic states of the h-BN films, with the number of minima scaling up with the number of h-BN layers. First principles density functional theory （DFT） calculations show that the positions of oscillations are related to the electronic band structure of h-BN.

Electrochemical water oxidation by photo-deposited cobalt-based catalyst on a nano-structured TiO_(2) electrode

A cobalt-based catalyst was directly photo-deposited on the surface of a widely used n-type nano-structured semiconductor(TiO_(2)).Different thicknesses of the TiO 2 films as well as different time of photo-deposition of the Co-based catalyst on TiO_(2) films have been optimized.It was found that the electrode with 3 layers of TiO_(2) film(in 8 m thickness) and 1 hour photo-deposition of the cobalt-based catalyst by light irradiation from a 500 W Xenon lamp gave the highest current density(~5 mA/cm^(2)).Using this cobalt-modified TiO_(2) film as a working electrode in an electrochemical device,highly efficient water oxidation has been demonstrated in a pH 7.0 aqueous solution with low overpotential.

TiCl_4 assisted formation of nano-TiO_2 secondary structure in photoactive electrodes for high efficiency dye-sensitized solar cells

A new kind of photoactive electrodes with nanocrystalline TiO2(nano-TiO2)secondary structure is successfully prepared via a simple method of adding a small amount of TiCl4 2-propanol solution in conventional nano-TiO2 paste to form micro-sized nano-TiO2 aggregates.The benefits of this special structure include improved optical absorption,increased light scattering ability,and enhanced electron transport and collection efficiency.Dye-sensitized solar cells(DSCs)based on these photoactive electrodes show improved performance.The power conversion efficiency of the cells can be increased from 5.03%to 7.30%by substituting 6μm conventional nano-TiO2 thin film with the same thickness of as-prepared nano-TiO2 aggregates film in the photoactive electrodes.A higher power conversion efficiency of the cells can be obtained by further increasing the thickness of the nano-TiO2 aggregates film.

Design of molecule-based magnetic conductors

Enabling the use of rationally designed thin films in technological devices is a recognized goal in materials science. However, constructing such thin films using highly ordered supramolecular architectures with well-controlled size and growth direction has remained an elusive target. Here, we introduce a layer-by- layer protocol to grow hybrid thin films of molecule-based magnetic conductors comprising arachidic acid and donor bis（ethylenedioxy）tetrathiafulvalene （BEDO-TTF） as the organic component and Cu/Gd complexes as the inorganic component. The construction of layered hybrid thin films was achieved at ambient conditions by employing the Langmuir-Blodgett method, which provides good control over film thickness and packing of molecules in the monolayer. As demonstrated by X-ray diffraction, these films are crystalline with distinct organic and inorganic sublattices, where the BEDO-TTF molecular layer is interfaced with the inorganic layer. Due to the flexibility of the Langmuir-Blodgett deposition technique, this result indicates a route toward the preparation of well-ordered films with various functionalities, determined by the choice of the inorganic compound that is combined with the π-unit of BEDO-TFF. Moreover, the ability to deposit films on a variety of substrates establishes the potential for lower-cost device fabrication on inexpensive substrates.