Developing of N‐(4‐methylpyrimidine‐2‐yl)methacrylamide Langmuir–Blodgett thin film chemical sensor via quartz crystal microbalance technique

In the present work, the characterization and gas sensing properties of newly synthesized N‐(4‐methylpyrimidine‐2‐yl)methacrylamide ( N‐MPMA ) monomer Langmuir–Blodgett (LB) thin films were investigated. The UV–visible spectroscopy, quartz crystal microbalance (QCM), and atomic force microscopy were utilized to characterize N‐MPMA LB thin films. The surface behavior of N‐MPMA monolayer was stable and allowed an effective transfer at a surface pressure of 14 mN/m. The mass change/unit area value of the N‐MPMA LB thin film deposited quartz crystal surfaces was investigated. The amount of N‐MPMA LB thin film deposited on the substrate for bilayer was calculated as 228.72 ng (86.31 ng/mm²) and 12.5 Hz frequency shift was observed for each layer of the N‐MPMA film. The kinetic responses of N‐MPMA LB film against chloroform, dichloromethane, benzene, and toluene were measured via QCM system at room temperature. N‐MPMA QCM sensor results displayed that chloroform has the largest frequency shifts compared with the other vapors used in the present work and these results can be illuminating in terms of physical properties of organic vapors.     

Mirrorlike pulsed laser deposited tungsten thin film

Mirrorlike tungsten thin films on stainless steel substrate deposited via pulsed laser deposition technique in vacuum (10(-5) Torr) is reported, which may find direct application as first mirror in fusion devices. The crystal structure of tungsten film is analyzed using x-ray diffraction pattern, surface morphology of the tungsten films is studied with scanning electron microscope and atomic force microscope. The film composition is identified using energy dispersive x-ray. The specular and diffuse reflectivities with respect to stainless steel substrate of the tungsten films are recorded with FTIR spectra. The thickness and the optical quality of pulsed laser deposition deposited films are tested via interferometric technique. The reflectivity is approaching about that of the bulk for the tungsten film of thickness ～782 nm.     

Real time in situ ellipsometric and gravimetric monitoring for electrochemistry experiments

This work describes a new system using real time spectroscopic ellipsometer with simultaneous electrochemical and electrochemical quartz crystal microbalance (EQCM) measurements. This method is particularly adapted to characterize electrolyte/electrode interfaces during electrochemical and chemical processes in liquid medium. The ellipsometer, based on a rotating compensator Horiba Jobin-Yvon ellipsometer, has been adapted to acquire Psi-Delta spectra every 25 ms on a spectral range fixed from 400 to 800 nm. Measurements with short sampling times are only achievable with a fixed analyzer position (A=45 degrees ). Therefore the ellipsometer calibration is extremely important for high precision measurements and we propose a spectroscopic calibration (i.e., determination of the azimuth of elements according to the wavelength) on the whole spectral range. A homemade EQCM was developed to detect mass variations attached to the electrode. This additional instrument provides further information useful for ellipsometric data modeling of complex electrochemical systems. The EQCM measures frequency variations of piezoelectric quartz crystal oscillator working at 5 MHz. These frequency variations are linked to mass variations of electrode surface with a precision of 20 ng cm(-2) every 160 ms. Data acquisition has been developed in order to simultaneously record spectroscopic ellipsometry, EQCM, and electrochemical measurements by a single computer. Finally the electrodeposition of bismuth telluride film was monitored by this new in situ experimental setup and the density of electroplated layers was extracted from the optical thickness and EQCM mass.     

射频磁控溅射法制备MoS2/SiC双层薄膜

采用射频磁控溅射法在室温、500℃的单晶硅和GCr15钢基体上制备了MoS2/SiC双层薄膜,并借助X射线衍射仪、扫描电子显微镜、摩擦磨损试验机以及划痕仪等研究了薄膜的结构、形貌、成分、摩擦学性能以及薄膜与基体的结合力。结果表明:当衬底温度为500℃时制备的MoS2/SiC双层薄膜表面致密平整,两层薄膜之间界面平直,膜厚约为0.8μm;该双层膜的摩擦因数低,耐磨性好;添加中间层可提高薄膜与基体的结合力。     

Automated apparatus for evaporation and in situ measurements of multiple thin films

We describe a system for vacuum deposition which measures as well as controls substrate temperature, film thickness, and rate of evaporation. By measuring the resonant frequency of a quartz crystal oscillator which has been calibrated for thickness, we produce films of 11 different thicknesses in a single evaporation. The system is then capable of immediately initiating four-probe resistivity measurements on the evaporated films every 90 s, allowing the measurement of rapid structural changes. The system is calculator-based and interfacing is achieved with plug-in compatible instrumentation using the IEEE standard 488-1975 interface bus.     

深紫外倍频用KBBF晶体光栅耦合器设计

分析了氟硼铍酸钾(KBe2BO3F2,KBBF)晶体的倍频特性,结合基波光光栅耦合和KBBF晶体内全反射特性设计了新型KBBF晶体光栅耦合器。介绍了KBBF晶体光栅耦合器设计原理。在KBBF晶体表面制作光栅结构,使其衍射级次满足匹配角进而产生倍频光;结合在KBBF晶体内的全反射传输,增大光程,获得高的倍频转化效率。通过计算晶体匹配角、走离角、倍频系数等参数,获得合适的光栅匹配类型。优化设计匹配光栅参数,获得了槽型参数及较高的衍射效率;基于光栅衍射效率与倍频转化率的关系获得了KBBF晶体光栅耦合器的倍频转化率计算公式,并给出它们的适用范围。最后,基于5.2mm×5.2mm×1mm KBBF晶体研制了晶体光栅耦合器,该光栅耦合器能够实现深紫外波段倍频光的输出,总倍频转化效率达到了16.86%     

On the design of capacitive sensors using flexible electrodes for multipurpose measurements

This article evaluates the potential of capacitive measurements using flexible electrodes to access various physical quantities. These electrodes are made of a thin metallic film, typical thickness 0.2 microm, evaporated on a plastic substrate. Their large flexibility enables them to be mounted in complex geometries such as curved surfaces. In the configuration of planar condensers, using a very sensitive commercial capacitive bridge and a three-terminal measurement method, several measurements are presented. A relative resolution of 10(-8) for the thermal expansion of samples is obtained at low temperature in a differential configuration. The same technique adopted for pressure gauge measurements at low temperature led to a typical 0.1 Pa resolution over a dynamic range of 10(4) Pa. In the configuration of interleaved electrodes, condensers have been used to measure wetting by either bulk liquid helium or by thin continuous helium films in a cylindrical pipe. Both experimental and numerical evidence is provided, showing that the close proximity of a reference ground potential significantly increases the relative sensitivity to fluid wetting. Further, interleaved electrodes can be used to access both the area that is covered by a liquid film but also to determine the thickness of this film, provided it is comparable to the periodicity of the electrode pattern.     

Study on the c-axis preferred orientation of ZnO film on various metal electrodes

ZnO thin film was deposited on various metal electrodes by reactive sputtering, and c-axis preferred orientation of the film has been studied. ZnO, which has high piezoelectricity, is promising for oscillators or filter devices such as surface acoustic wave (SAW) device, gas sensor, and film bulk acoustic resonator (FBAR). But, for the application of ZnO film for these devices, the film should be grown with c-axis normal to the electrode. In this study, Pt, Al, and Au were deposited on Si wafer, and the surface roughness and crystal structure of the ZnO film on the electrode were investigated using AFM, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Columnar structures of ZnO films were grown with c-axis normal to all electrodes, and among them Pt electrode showed the highest preferred orientation of ZnO film.     

Study on the c-axis preferred orientation of ZnO film on various metal electrodes

ZnO thin film was deposited on various metal electrodes by reactive sputtering, and c-axis preferred orientation of the film has been studied. ZnO, which has high piezoelectricity, is promising for oscillators or filter devices such as surface acoustic wave (SAW) device, gas sensor, and film bulk acoustic resonator (FBAR). But, for the application of ZnO film for these devices, the film should be grown with c-axis normal to the electrode. In this study, Pt, Al, and Au were deposited on Si wafer, and the surface roughness and crystal structure of the ZnO film on the electrode were investigated using AFM, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Columnar structures of ZnO films were grown with c-axis normal to all electrodes, and among them Pt electrode showed the highest preferred orientation of ZnO film.     

Geometric analysis of surface resonance conditions in reflection high energy electron diffraction

A three-dimensional analysis in reciprocal space is used to analyse reflection high energy electron diffraction (RHEED) patterns. Particular emphasis is placed on investigating the surface resonance phenomenon, the resonance conditions, and the diffraction mechanisms. The surface resonance regions defined by the resonance beam threshold conditions are related to the limits for the specular reflection spot in the diffraction pattern. The introduction of an Ewald sphere of varying radius is shown to be useful in understanding the surface phenomenon. Simulations based on the geometric theory, taking account of the surface refraction effect, describe very well the RHEED pattern geometry from the (111) surface of a platinum single crystal.     

应用L-MBE方法制备ZnO薄膜的结构和光学特性

用激光分子束外延(Laser Molecular Beam Epitaxy,L-MBE)设备在p型Si(111)衬底上制备了不同衬底温度和不同氧压的ZnO薄膜,用X射线衍射仪(XRD)和原子力显微镜(AFM)分别对薄膜的结构和形貌进行了分析,用He-Cd激光(325nm)激发的光致发光测试系统对薄膜进行了荧光光谱分析。研究发现,在衬底温度为400℃,氧压1Pa左右所制备的ZnO薄膜表面比较均匀致密,晶粒生长较充分,有较高的结晶质量和发光强度。ZnO薄膜的近带边发射与薄膜的结晶质量和化学配比均有关系。     

Thin lubricant films confined between crystalline surfaces: Gold versus mica

In this paper we report molecular dynamics simulation results of lubricant films only a few nanometres thick confined between atomically smooth gold or model mica surfaces. We have studied dodecane (C₁₂H₂₆) of various film thicknesses. We show below a critical film thickness structural transitions take place with the formation of crystal bridges. We demonstrate this critical film thickness is larger with Au(1 0 0) surface. Below this critical film thickness we observe a large enhancement of apparent shear viscosity. This enhancement, however, is much lower for films confined by gold. We find the extrapolated zero shear viscosity of a ∼2.4-nm-thick film confined by gold is almost two orders of magnitude lower than that of a film, of the same thickness, confined by model mica. We find the source of this difference is the weaker pinning of the layers next to the surface of the gold. This leads to stronger slip, at the lubricant-gold interface, which persists at solid-like and liquid-like states. For mica a larger part of shearing takes place inside the film. The solid-like structure of the films confined by gold shows stronger resilience to shear and melt at considerably larger shear rates than those confined by model mica surfaces. These differences could be important in developing low friction devices at microscale.     

Tribological characteristics of gold films deposited on metals by ion plating and vapor deposition

Recent work on the graded interface between an ion-plated film and a substrate is discussed as well as the friction and wear properties of ionplated gold. X-ray photoelectron spectroscopy, depth profiling and microhardness measurements were used to investigate the interface. The friction and wear properties of ion-plated and vapor-deposited gold films were studied both in an ultrahigh vacuum system to maximize adhesion and in oil to minimize adhesion. The results of the investigation indicate that the solubility of gold in the substrate material controls the depth of the graded interface. Thermal and chemical diffusion mechanisms are thought to be involved in the formation of the Au-Ni interface. In the Fe-Au graded inter- face, gold was slightly dispersed in the iron and formed only a physically bonded interface. The hardness of the gold film was influenced by the thickness and was also related to the composition gradient between the gold and the substrate. A graded Ni-Au interface exhibited the highest hardness because of an alloy hardening effect. The effects of film thickness on adhesion and friction were established. A minimum coefficient of friction was found in the thin film region. No graded interfaces were detected in this investigation between vapor-deposited gold films and substrates.     

Description of a polarized source of He i radiation for surface studies

A polarized radiation source has been designed and built for use in angular-resolved photoelectron spectroscopy on surfaces of single crystals under ultrahigh vacuum. The light from a discharge in helium is polarized by a triple reflection from a series of gold mirrors, producing a plane-polarized beam of He i radiation (21.22 eV) with a polarization of 80%. The plane of polarization can be rotated through more than 180 degrees without breaking vacuum. Details of the construction of the lamps are given, together with how it is integrated into the overall operation of the electron spectrometer. As an illustration of the lamp's potential, data are shown on the photoemission studies of the (110) and (111) faces of copper as a function of both the orientation angle of the crystal and the polarization vector. A brief discussion of the future development and possible uses of the lamp is included.     

Influence of zero-loss filtering on electron optical phase contrast

Complex scattering amplitudes are used to calculate the phase contrast of colloidal gold particles. Comparison of measurements of the phase contrast intensity at the centre of the gold particle as a function of defocus for unfiltered and zero-loss filtered images demonstrates the increase in phase contrast achieved by zero-loss filtering even for a thick carbon substrate film. The granulation of amorphous germanium films is measured by the spatial rms (root mean square) values of image intensity in a defocus series.     

一种同时测量液体粘密度的传感器研究

液相环境下振荡的压电石英晶体传感器的谐振频率变化主要受液体性质和表面质量负载的影响。通过将一表面抛光和一表面有沟槽的石英晶体传感器置于测量池,前者在液体中的谐振频移反映了液体粘密度之积的变化,而两晶体的谐振频差则反映了液体的密度变化。从而使该装置可同时用于液体的粘度与密度的测量。实验结果表明,该装置具有简单、灵敏度高和线性关系好等优点。     

Calculation of concentration depth profiles in electron probe microanalysis

Based on a multiple reflection model, the concentration depth profiles of gold diffused into a silver substrate are determined. To conclude the structure of the sample from the measured intensity of radiation, an accurate correction procedure is necessary. A new model was developed for this purpose. Since the new electron probe microanalysis (EPMA) correction procedure is also valid for tilted samples, measurements with different geometries could be performed. The different angles of incidence and take-off angles allow for a better comparison of theory with experiment. One advantage of the applied multiple reflection model is that it can be extended comparatively easily with the analysis of layered specimens. Measurements of some specimens with one layer on a substrate are reported. The mean deviation of calculated thicknesses is about 10%. To calculate depth profiles, gold was evaporated with physical vapor deposition on silver foils. The thicknesses of evaporated gold films were 50 and 100 nm. Then the specimens were annealed at a temperature of approximately 400°C. Finally, the concentration depth profiles were quantified with EPMA. The shape of the profiles was derived from a simple diffusion model valid for the samples under consideration. To check the shape of the functions obtained, a comparison with measurements by secondary ion mass spectrometry was performed.     

Structural, optical and mechanical properties of nanostructure diamond synthesized by chemical vapor deposition

Nanostructure diamond (NSD) films on Si substrate are prepared by microwave plasma enhanced chemical vapor deposition (MPECVD) using methane and hydrogen as the reactants with two-step negative substrate bias (SB). The dependencies of the NSD film morphology, grains, surface roughness, crystal and bonding structures and hardness on the negative SB at the bias-enhanced growth (BEG) step and substrate temperature during growth have been investigated by conducting atomic force microscopy (CAFM), X-ray diffraction (XRD), Raman spectroscopy and nanoindentation. The hardness of the NSD film is found to be as high as 80 GPa with CAFM average and root mean square roughness of 7 and 9 nm, respectively, under optimal negative SB at the BEG step. From the studies of substrate temperature effect, the hardness of the NSD film is as high as 70 GPa, with average and root mean square CAFM roughness of 9 and 11 nm, respectively, which were obtained at a substrate temperature of 500 °C. In both cases, the film hardness was found to be affected by the size of clusters, which are composed of many small NSD particles, the amount of NSD in an amorphous matrix as well as surface roughness. We also synthesized transparent NSD films by MPECVD under optimized single-step growth conditions on quartz substrates, which are scratched with several micrometers diamond powder. A hardness as high as 60 GPa and a maximum transmittance of 60% in the visible light region are achieved for an NSD coating of 1.0 μm thickness with small surface roughness.     

Microstructure and Magnetic Properties of Sputtered Co5 Sm Films

Co5Sm/Cr bilayer films were deposited on Si and glass slides by means of a Direct-Current(DC)magnetron sputtering system with substrate heating.Magnetic properties measurements show that the sample with glass substrate has a comparatively large coercivity(Hc=2 141.2 Oe)with a relatively low optimal temperature(Ts=350 ℃).X-ray diffraction patterns indicate that Cr presents a hexagonal-close-packed(hcp)texture on Si,while a body-centered-cubic(bcc)structure on glass substrate,which leads to Co5Sm films having different lattice constants on Si and glass substrates.At their optimal temperature,the grain size of the sample on glass slide is smaller with its size distribution more uniform.Concurrently,the shape of magnetic domain is more regular and ordered.The value of magnetic switching volume(V)for the film on glass is 1.65×10-18 cm3,smaller than that for films on Si.For the film on glass,the magnetization reversal mechanism is mainly influenced by magnetocrystalline anisotropy,the shape of the crystal grain and the stress in the film.     

Analysis of thermal diffusivity of Ti thin film by thermoreflectance and periodic heating technique

Thermal diffusivity of Ti thin film with several hundred nanometers thickness has been measured by means of thermoreflectance (TR) technique and periodic heating using front heating and front detection configuration. Ti thin films were prepared on Si substrates by dc sputtering method. Then thin Mo layers as reflection layers were coated on Ti thin films. Surface of the Mo layer is irradiated by sinusoidally intensity modulated heating laser. Temperature response at the heated area is measured by a probe laser beam with constant intensity, as a TR signal. Phase lag between the phase of TR signal and that of heating laser beam was obtained from 100 kHz to 2.6 MHz. To analyze thermal diffusivity of Ti thin films using the phase lag data, we developed a three-layer analytical model such as Mo coating (100 nm)∕thin film∕semi-infinite substrate. The calculated phase lag using analytical model is in good agreement with the experimental data for the whole frequency range. The thermal diffusivity of two Ti thin films is determined to be 5 × 10(-6) m(2)∕s, which is 53% of the bulk one.