AFM and XPS Study on the Surface and Interface States of CuPc and SiO_2 Films

A CuPc/SiO2 sample is fabricated. Its morphology is characterized by atomic force microscopy, and the electron states are investigated by X-ray photoelectron spectroscopy. In order to investigate these spectra in detail, all of these spectra are normalized to the height of the most intense peak,and each component is fitted with a single Gaussian function. Analysis shows that the O element has great bearing on the electron states and that SiO2 layers produced by spurting technology are better than those produced by oxidation technology.

Surface and interface chemistry in metal‐free electrocatalysts for electrochemical CO_(2) reduction

The electrochemical reduction of carbon dioxide(CO_(2))into value‐added fuels and chemicals presents a sustainable route to alleviate CO_(2) emissions,promote carbon‐neutral cycles and reduce the dependence on fossil fuels.Considering the thermodynamic stability of the CO_(2) molecule and sluggish reaction kinetics,it is still a challenge to design highly efficient electrocatalysts for the CO_(2) reduction reaction(CO_(2)RR).It has been found that the surface and interface chemistry of electrocatalysts can modulate the electronic structure and increase the active sites,which is favorable for CO_(2) adsorption,electron transfer,mass transport,and optimizing adsorption strength of reaction intermediates.However,the effect of surface and interface chemistry on metal‐free electrocatalysts(MFEs)for CO_(2)RR has not been comprehensively reviewed.Herein,we discuss the importance of the surface and interface chemistry on MFEs for improving the electrochemical CO_(2)RR performance based on thermodynamic and kinetic views.The fundamentals and challenges of CO_(2)RR are firstly presented.Then,the recent advances of the surface and interface chemistry in improving reaction rate and overcoming reaction constraints are reviewed from regulating electronic structure,active sites,electron transfer,mass transport,and intermediate binding energy.Finally,the research challenges and prospects are proposed to suggest the future designs of advanced MFEs in CO_(2)RR.

In situ photoemission study of interface and film formation during epitaxial growth of Er_2O_3 film on Si(001) substrate

Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si（001） imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompanied by a shift in the Er2O3 valence band maximum. This shift depended on the oxide layer thickness and interfacial structure. An interfacial layer was observed at the initial growth of Er2O3 film on Si, which was supposed to be attributed to the effect of Er atom catalytic oxidation effect.

Surface diffraction beamline at the SSRF

BL02U2 of the Shanghai Synchrotron Radiation Facility is a surface diffraction beamline with a photon flux of 5.5×10^(12) photons/s at 10 keV and a beam size of 160µm×80µm at the sample site.It is dedicated to studying surfaces(solid-vacuum,solid-gas)and interfaces(solid-solid,solid-liquid,and liquid-liquid)in nanoscience,condensed matter,and soft matter systems using various surface scattering techniques over an energy range of 4.8-28 keV with transmission and reflection modes.Moreover,BL02U2 has a high energy resolution,high angular resolution,and low beam divergence,which can provide excellent properties for X-ray diffraction experiments,such as grazing incident X-ray diffraction,X-ray reflectivity,crystal truncation rods,and liquid X-ray scattering.Diversity of in situ environments can also be provided for the samples studied.This paper describes the setup of the new beamline and its applications in various fields.

Microstructure and mechanical properties of hot isostatically pressed cermets with TiN coatings

To increase the adhesion strength between the coating and the substrate, sintered Ti（C,N）-based cermets were selected and deposited with monolayer TiN using a multiarc ion-plating technique; subsequently, hot isostatic pressing （HIPhag） treatment was performed at 1000℃ using nitrogen pressure up to 110 MPa. The mechanical properties of cermets after a coating process and subsequent HIPing treatment have been evaluated with respect to the hardness, the residual stress, and the coating adhesion. The results show that atter the HIPing process, there was a higher increase ha critical load ha the TiN-coated cermets with lower surface roughness compared with those with higher surface roughness. In all cases, the residual stress was found to be compressive. The effects of substrate surface roughness and posttreatment on the adhesion strength of the coatings were thus investigated. It was also fotmd that the HIPing posttreatment process is well suited for hacreasing the adhesion strength between the coating and the substrate.

Corrosion behavior of tantalum and its nitride in alkali solution

The corrosion behavior of tantalum and its nitrides in stirring NaOHsolutions was researched by potentiostatic method, cyclic voltammetry and XPS. The results showedthat the corrosion products were composed of Ta_2O_5 and NaTaO_3. The corrosion reaction formula oftantalum and its nitrides was written according to cyclic volt-ampere curves. The electric chargetransfer coefficient and the electric charge transfer number were calculated

Detection and formation mechanism of micro-defects in ultrafine pitch Cu-Cu direct bonding

In this paper, Cu-Cu interconnects with ultrafine pad pitches of 6 p.m, 8 p.m, and 15 p.m are implemented on the 12 inch wafers by a direct bonding process. Defects are not found by traditional non-destructive （NDT） c-mode scanning acoustic microscopy （c-SAM）. However, cross sectional observation of bonding interfaces reveals that micro-defects such as micro seams are located at SiO2 bonding interfaces. In order to examine the micro-defects in the ultra-fine pitch direct bonding process by the NDT technology, a novel ＂defect-enlarged approach＂ is proposed. The bonded dies are first annealed in an N2 oven at 300 ℃ for a few hours and then cooled quickly in air. The c-SAM scanning images show large defects at the place where nothing can be detected by c-SAM before this treatment. Cross sectional observation of the bonding interfaces indicates that these defects consist of large size micro seams at the SiO2 bonding interface, especially near Cu pads with an ultrafine pitch of 6μm. However, these large defects disappear after several hours at room temperature, observed by c-SAM. It is inferred that the disappearance of these defects inspected by the ＂defect-enlarged approach＂ results from the combination of intrinsic micro seams and ＂weak＂ bonds in the silicon oxide layer. Then the underlying physical mechanism of these micro-defects is proposed, which is influenced by Cu pad surface topology and bonding models.

Effect of nano-oxide layers on the magnetoresistance of ultrathin permalloy films

Ta/NiFe/Ta ultrathin films with and without nano-oxide layers （NOLs） were prepared by magnetron sputtering followed by a vacuum annealing process. The influence of NOLs on the magnetoresistance （MR） ratio of ultrathin permalloy films was studied. The results show that the influence of grain size and textures on the MR ratio becomes weak when the thickness of the NiFe layer is below 15 nm. A higher MR ratio was observed for the thinner （〈 15 nm） NiFe film with NOLs. The MR ratio of a 10 nm NiFe film can be remarkably enhanced by NOLs. The enhanced MR ratio for these ultrathin films can be attributed to the enhanced specular reflection of conduction electrons.

Research on Effect of Adding Nanomaterial to Propellant on Gun Barrel

The barrel lifes of three small caliber rifles were tested by using the propellant with nanomaterial and the standard propellant respectively. The test results show that the service life increases observably due to adding nanomaterial to the propellant. Then, the influence of the nanomaterial on the tube was researched by splitting the two barrels tested and detecting their inner surfaces. It was found that the erosion of the barrel bore is reduced observably by using the propellant with nanomaterial. And it makes the volume and the size of the gun chamber change less. Therefore, the barrel life can be prolonged by adding the nanomaterial in the propellant.

Study on the interfacial reactions of Ti/AIN joints

Based on the phase equilibrium calculation of the Ti-Al-N ternary system, the interfacial reactions and the phase formation sequences between different types of joints, （Ti matrix）/（AlN particles）, （Ti particles）/（AlN plate）, and （Ti plate）/（AlN plate）, were analyzed theoretically under the reported experimental conditions, Different phase formation sequences for the three kinds of Ti/AlN joints were obtained, It proved that the different phase sequences of both the phase formation sequences and the apparent spatial phase sequences are dominated by the relative amounts and the distribution of the two pairs in the diffusion couples, The theoretical prediction can explain the experimental observations well.

Thermal stability of HfO_2/Si(001) films prepared by electron beam evaporation in ultrahigh vacuum using atomic oxygen

HfO2 films on silicon substrates have been prepared by electron beam evaporation in ultrahigh vacuum using atomic oxygen. Synchrotron radiation photon-electron spectroscopy was used to investigate the thermal stability of HfO2 films under an ultrahigh vacuum environment. At the temperature of 750 ℃, HfO2 films begin to decompose. After being further annealed at 850℃ for 3 min, HfO2 films decomposes completely, partially to form Hf-silicide and partially to form gaseous HfO. Two chemical reactions are responsible for this decomposition process. A small amount of Hf-silicide, which is formed at the very beginning of growth, may result in the films grown subsequently to be loosened, and thereby leads to a relatively low decomposition temperature.

Effect of direct electric current on wetting behavior of molten Bi on Cu substrate

The effect of direct electric current on the wetting behavior of molten Bi on Cu substrate at 370℃ was investigated by the sessile drop method. The wettability of molten Bi on Cu without an applied current is poor and the spreading time required to form the steady-state contact angle （about 102°） is approximately 30 min. With the increase of the applied electric current, the spreading of molten Bi on Cu is accelerated significantly and the steady-state contact angle decreases considerably. The cross-section SEM micrographs of the solidified Bi droplet on Cu substrate show that the electric current has a marked effect on the convection of melt. Correspondingly, the application of an electric current obviously enhances the dissolution of Cu into Bi melt, which may change the wetting triple line configuration. The improvement of wettability induced by electric current is also related to the additional driving force for wetting provided by the electromagnetic pressure gradient force.

Suppressing byproduct formation for high selective CO_(2) reduction over optimized Ni/TiO_(2) based catalysts

One of the challenges for catalytic CO_(2)reduction is to control product selectivity,and new findings that can modify selectivity would be transformative.Herein,two kinds of TiO_(2)(homemade and commercial)with the same crystal phase but different surface properties are chosen as supports to prepare Ni-based catalysts for CO_(2)reduction,which show distinctly different product selectivity for CO_(2)reduction to CH_(4) or CO,as well as the CO_(2)conversion.The catalysts based on the homemade TiO_(2)support are highly selective for CH_(4) formation,while the latter ones are about 100%selective for CO formation under the same reaction conditions.In addition,the former ones are much active(more than 3 times)than the latter ones.We found that the collaborative contribution of Ti^(3+)and Ni^(2+)species and the electronic metal-support interactions effect maybe the main driving force behind for determining the product selectivity.Methane is almost exclusively produced over the catalysts with abundant Ti^(3+)and Ni^(2+)species and greater electronic metal-support interaction,otherwise,it will give priority to CO generation.The addition of CeO_(2)can reduce the Ni particle size and improve the dispersion of Ni nanoparticles,as well as create more Ti^(3+)species,contributing to the enhancement of CO_(2)conversion,but shows a negligible effect on product selectivity.Furthermore,the in situ DRIFT experiments and kinetic experiments indicate that the CO route is probably involved in the CO_(2)reduction process over the homemade Ni-CeO_(2)/TiO_(2)-CO catalyst with abundant Ti^(3+)and Ni^(2+)species and a strong electronic transform effect.

Plasma-nitriding of tantalum at relatively low temperature

The combined quadratic orthogonal regression method of experiment design wasemployed to explore the effects of process parameters of plasma nitriding of tantalum such as totalpressure, temperature and original hydrogen molar fraction on the hardness, roughness and structureof nitriding surfaces. The regression equations of hardness, roughness and structure were givenaccording to the results of regression and statistic analysis. And the diffusion activation energyof nitrogen in tantalum on plasma nitriding conditions was calculated according to the experimentaldata of hardness of plasma-nitriding of tantalum vs time and temperature. The diffusion activationenergy calculated belongs to (155.49 +- 10.51) kJ/mol (783-983 K).

Characterization of GaSb Films by Metalorganic Chemical Vapour Deposition

GaSb epilayers were grown on GaSb and GaAs substrates by atmospheric pressure metalorganic chemical vapor deposition (MOCVD). The properties of GaSb layers were characterized by low temperature photoluminescence (PL) spectra and scanning electron acoustic microscopy (SEAM) images. The temperature dependence of the PL spectrum was investigated and a red shift of bound excitons was observed in high quality epilayer. The pyramids of the surface and the buried subsurfaces were observed by scanning electron microscopy (SEM) and scanning electron acoustic microscopy (SEAM), and their growth model was discussed.

Electrostatic field effects on three-dimensional topological insulators

Three-dimensional topological insulators are a new class of quantum matter which has interesting connections to nearly all main branches of condensed matter physics. In this article, we briefly review the advances in the field effect control of chemical potential in three-dimensional topological insulators. It is essential to the observation of many exotic quantum phenomena predicted to emerge from the topological insulators and their hybrid structures with other materials. We also describe various methods for probing the surface state transport. Some challenges in experimental study of electron transport in topological insulators will also be briefly discussed.

Study on Al_xNi_y Alloys as Diffusion Barriers in Flexible Thin Film Solar Cells

Co-sputtered AlxNiy thin films were used as diffusion barriers between aluminum and hydrogenated microcrystalline silicon （μc-Si：H） for flexible thin film solar cells. The stoichiometric ratio of AlxNiy showed a significant effect on the structures of the films. The obtained Al3Ni2 film was amorphous, while polycrystalline films were obtained when the ratio of aluminum to nickel was 1：1 and 2：3. An auger electron spectroscope and four-point probe system were applied to test the resistance to the interdiffusion between aluminum and silicon, as well as the conductivities of the AlxNiy barriers. The data of auger depth profile showed that the content of silicon was the minimum in the aluminum layer after sputtering for 4 min using AlNi thin film as the barrier layer. Compared to other AlxNiy alloys, the AlNi thin film possessed the lowest sheet resistance.

Odd-even effects in the structure and properties of aryl-substituted aliphatic self-assembled monolayers

Self-assembled monolayers(SAMs)represent an important tool in context of nanofabrication and molecular engineering of surfaces and interfaces.The properties of functional SAMs depend not only on the character of the tail groups at the SAM-ambient interface,but are also largely defined by their structure.In its turn,the latter parameter results from a complex interplay of the structural forces and a variety of other factors,including so called odd-even effects,viz.dependence of the SAM structure and properties on the parity of the number(odd or even)of individual building blocks in the backbone of the SAM constituents.The most impressive manifestation of the odd-even effects is the structure of aryl-substituted alkanethiolate SAMs on Au(111)and Ag(111),in which,in spite of the fact that the intermolecular interaction is mostly determined by the aryl part of the monolayers,one observes a pronounced dependence of molecular inclination and,consequently,the packing density of the SAM-forming molecules on the parity of number of methylene units in the alkyl linker.Here we review the properties of the above systems as well as address fundamental reasons behind the odd-even effects,including the existence of a so-called bending potential,which is frequently disregarded in analysis of the structure-building forces.The generality of the odd-even effects in SAMs is additionally supported by the recent data for SAMs on GaAs,scanning tunneling microscopy data for SAMs on Ag(111),and the data for the monolayers with selenolate and carboxyl anchoring groups on Au(111)and Ag(111).The implications of these effects in terms of the control over the packing density and orientation of the tail groups at the SAM-ambient interface,structural perfection,polymorphism,temperature-driven phase transitions,and SAM stability toward such factors as ionizing radiation,exchange reaction,and electrochemical desorption are discussed.These implications place the odd-even effects as an important tool for the design of functional SAMs in context of specific applications.

Rational design of nanoarray structures for lithium-sulfur batteries:recent advances and future prospects

Lithium-sulfur(Li-S)batteries are considered as promising candidates for future-generation energy storage systems due to their prominent theoretical energy density.However,their application is still hindered by several critical issues,e.g.,the low conductivity of sulfur species,the shuttling effects of soluble lithium polysulfides,volumetric expansion,sluggish redox kinetics,and uncontrollable Li dendritic formation.Considerable research efforts have been devoted to breaking through the obstacles that are preventing Li-S batteries from realizing practical application.Recently,benefiting from the no additives/binders,buffer of volume change,high sulfur loading and suppression of lithium dendrites,nanoarray(NA)structures have have emerged as efficient and durable electrodes in Li-S batteries.In this work,recent advances in the design,synthesis and application of NA structures in Li-S batteries are reviewed.First,the multifunctional merits and typical synthetic strategies of employing NA structure electrodes for Li-S batteries are outlined.Second,the applications of NA structures in Li-S batteries are discussed comprehensively.Finally,the challenge and rational design of NA structure for Li-S batteries are analyzed in depth,with the aim of providing promising orientations for the commercialization of high-energy-density Li-S batteries.

Water-trapping and drag-reduction effects of fish Ctenopharyngodon idellus scales and their simulations

In the last decades, surface drag reduction has been re-emphasized because of its practical values in engineering applications,including vehicles, aircrafts, ships, and fuel pipelines. The bionic study of drag reduction has been attracting scholars' attentions. Here, it was determined that the delicate microstructures on the scales of the fish Ctenopharyngodon idellus exhibit remarkable drag-reduction effect. In addition, the underlying drag-reduction mechanism was carefully investigated. First,exceptional morphologies and structures of the scales were observed and measured using a scanning electron microscope and3-dimensional(3D) microscope. Then, based on the acquired data, optimized 3D models were created. Next, the mechanism of the water-trapping effect of these structures was analyzed through numerical simulations and theoretical calculations. It was determined that there are many microcrescent units with certain distributions on its surface. In fact, these crescents are effective in generating the "water-trapping" effect and forming a fluid-lubrication film, thus reducing the skin friction drag effectively.Contrasting to a smooth surface, the dynamics finite-element analysis indicated that the maximum drag-reduction rate of a bionic surface is 3.014% at 0.66 m/s flow rate. This study can be used as a reference for an in-depth analysis on the bionic drag reduction of boats, underwater vehicles, and so forth.