PREPARATION AND PROPERTIES OF Ni-Cr AND Fe-Cr-Al FILMS BY VACUUM EVAPORATION

Ni-Cr and Fe-Cr-Al films deposited on the Al2O3 substrate are studied by a method of vacuum evaporation in this paper. Influence of resistance value on density and evaporation parameters of the films reveals that the resistance of films and the adhesion of films to substrates are determined by the evaporation time and the substrate temperate under the condition of the maximum vacuity of 6.2×10-4 Pa, respectively.

Modeling and Simulation of Lithium Vacuum Evaporation Process Using COMSOL Multiphysics

Based on the COMSOL Multiphysics simulation software,this study carried out modeling and numerical simulation for the evaporation process of liquid metal lithium in the vacuum free molecular flow state.The motion of lithium atoms in the evaporation process was analyzed through a succession of studies.Based on the available experimental values of the saturated vapor pressure of liquid metal lithium,the relationship between saturated vapor pressure and temperature of liquid lithium in the range of 600 K-900 K was obtained.A two-dimensional symmetric model(3.5 mm×20 mm) was established to simulate the transient evaporation process of liquid lithium at wall temperatures of 750 K,780 K,800 K,810 K,825 K,and 850 K,respectively.The effects of temperature,the evaporation coefficient,back pressure,and length-to-diameter ratio on the evaporation process were studied;the variation trends and reasons of the molecular flux and the pressure during the evaporation process were analyzed.At the same time,the evaporation process under variable wall temperature conditions was simulated.This research made the evaporation process of liquid lithium in vacuum molecular flow clearer,and provided theoretical support for the space reactor and nuclear fusion related fields.

In-situ growth of a CdS window layer by vacuum thermal evaporation for CIGS thin film solar cell applications

Highly crystalline and transparent CdS films are grown by utilizing the vacuum thermal evaporation （VTE） method. The structural, surface morphological, and optical properties of the films are studied and compared with those prepared by chemical bath deposition （CBD）. It is found that the films deposited at a high substrate temperature （200 ℃） have a preferential orientation along （002） which is consistent with CBD-grown films. Absorption spectra reveal that the films are highly transparent and the optical band gap values are found to be in a range of 2.44 eV-2.56 eV. Culnl_xGaxSe2 （CIGS） solar cells with in-situ VTE-grown CdS films exhibit higher values of Voc together with smaller values of Jsc than those from CBD. Eventually the conversion efficiency and fill factor become slightly better than those from the CBD method. Our work suggests that the in-situ thermal evaporation method can be a competitive alternative to the CBD method, particularly in the physical- and vacuum-based CIGS technology.

Preparation of large-area isotopic magnesium targets for the 25Mg(p,γ)^26 Al experiment at JUNA

To study the 25Mg(p,y)^26 Al reaction at the Jinping Underground Nuclear Astrophysics laboratory,a large-area 25Mg target with a uniform thickness is needed.A rotating unit is used to ensure the uniformity of the target thickness during evaporation.After many attempts,19 targets with diameters of 40 mm and a non-uniformity of8.4%were prepared simultaneously.The rate of material utilization was approximately 4.7 times higher than that obtained using a conventional evaporation method.

Study on the formation of intermetallic phases in the new type of Zn-Mg coatings on steel sheets

Zn-Mg alloy coatings were obtained by physical vapor deposition （PVD） on electroplated steel sheets. Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction （XRD） ,scanning electron microscope （SEM） and glow discharge optical emission spectrometry （GDOES）. It is found that MgZn2 is the main Zn-Mg alloy phase formed after heat treatment. The formation of Mg-Zn intermetallic phases is controlled not only by thermodynamics, but also by kinetics. MgZn2 has different morphologies, such as laminar structure,porous structure and floc-like structure,which are mainly determined by the annealing temperature. Obvious diffusion of Mg starts at 350 ℃, and the diffusion of iron increases significantly when the temperature is elevated to 380℃.

Interface passivation engineering for hybrid perovskite solar cells

The allure of high efficiency and low-temperature solution-processed organic-inorganic hybrid perovskite solar cells(PSCs)are inspiring scientists to seek for its commercialization.Interface passivation engineering has become an effective way to further enhance the efficiency and stability of PSCs by defect passivation,reduces the charge recombination and ion migration initiation and hysteresis control,etc.Herein,we have summarized the effects and recent research progress of interface passivation engineering in PSCs.Interface passivation layers can be realized by using the solution and/or vacuum evaporation processes which are very adaptable to varied materials with different properties and fabrication processes for enhanced photovoltaic performance and stability.

Recent progress in upgrading metallurgical-grade silicon to solar-grade silicon via pyrometallurgical routes

Si-based photovoltaic solar power has been rapidly developed as a renewable and green energy source.The widespread use of Sibased solar cells requires large amounts of solar-grade Si(SoG-Si)to manufacture Si wafers.Chemical routes,mainly the modified Siemens process,have dominated the preparation of polycrystalline SoG-Si;however,traditional chemical techniques employ a series of complex chemical reactions involving various corrosive and hazardous reagents.In addition,large amounts of complex waste solar cells and Si kerf slurry waste gradually accumulate and are difficult to recycle using these approaches.New methods are required to meet the demand for SoGSi preparation and Si waste recycling.The metallurgical route shows promise but is hindered by the problem of eliminating B and P from metallurgical-grade Si(MG-Si).Various pyrometallurgical treatments have been proposed to enhance the removal of B and P from MG-Si.This article reviews Si refining with slag treatment,chlorination,vacuum evaporation,and solvent refining,and summarizes and discusses the basic principles and recent representative studies of the four methods.Among these,solvent refining is the most promising and environmentally friendly approach for obtaining low-cost SoG-Si and is a popular research topic.Finally,a simple and green approach,i.e.,a combination of solvent refining,slag treatment,or vacuum directional solidification,is proposed for low-cost SoG-Si preparation using MG-Si or Si wastes as raw materials.

Effects of thermal annealing on the properties of N-implanted ZnS films

N-ion-implantation to a fluence of 1 × 1015 ions/cm^2 was performed on ZnS thin films deposited on glass substrates by using the vacuum evaporation method. The films were annealed in flowing nitrogen at 400 ℃-500 ℃ after N-ion-implantation to repair the ion-beam-induced structural destruction and electrically activate the dopants. Effects of ion-implantation and post-thermal annealing on ZnS films were investigated by X-ray diffraction （XRD）, photoluminescence （PL）, optical transmittance, and electrical measurements. Results showed that the diffraction peaks and PL intensities were decreased by N-ion-implantation, but fully recovered by further annealing at 500 ℃. In this experiment, all films exhibited high resistivity due to the partial dopant activation under 500 ℃.

Low-dimensional phases engineering for improving the emission efficiency and stability of quasi-2D perovskite films

The two-dimensional(2 D) Ruddlesden–Popper-type perovskites, possessing tunable bandgap, narrow light emission,strong quantum confinement effect, as well as a simple preparation method, are identified as a new generation of candidate materials for efficient light-emitting diodes. However, the preparation of high-quality quasi-2 D perovskite films is still a challenge currently, such as the severe mixing of phases and a high density of defects within the films, impeding the further promotion of device performance. Here, we prepared the quasi-2 D PEA_(2) MA_(n-1) Pbn Br_(3 n+1) perovskite films by a modified spin-coating method, and the phases with large bandgap were effectively suppressed by the vacuum evaporation treatment. We systematically investigated the optical properties and stability of the optimized films, and the photoluminescence(PL) quantum yield of the treated films was enhanced from 23% to 45%. We also studied the emission mechanisms by temperature-dependent PL spectra. Moreover, the stability of films against moisture, ultraviolet light, and heat was also greatly improved.

Effect of Substrate Nature on the Structural, Optical and Electrical Properties of In2S3 Thin Films

In this study, In2S3 thin films have been deposited on ITO and fluorine-tinoxide FTO coated glass substrates by single source vacuum thermal evaporation annealed in vacuum a 300°C - 400°C for 1 h. The samples structure was characterized by X-ray diffraction, revealing the quadratic structure of In2S3 and the crystallinity depends on the temperature of annealing and nature of substrate. The various structural parameters, such as, crystalline size, dislocation density, strain and texture coefficient were calculated. The optical properties show that the refractive index dispersion data obeyed the single oscillator of the Wemple-DiDomenico model. By using this model, the dispersion parameters and the high-frequency dielectric constant were determined. The Hall Effect has been studied at room temperature. The Hall voltages, the Hall coefficient (RH) and mobility (μH) have been measured at different magnetic and electric fields. The films show n-type behavior irrespective of temperature and composition.

Growth mechanism for zinc coatings deposited by vacuum thermal evaporation

The vacuum thermal evaporation technique was used to simultaneously deposit zinc coatings onto interstitial free steel plates and single-crystal silicon wafers in a high vacuum environment.The effect of substrate temperature on the mor-phology and crystal orientation of zinc coatings was investigated.When the substrate temperature was 25 and 50℃,the zinc crystallites were plate-like and grew under a particular angle to the substrate surface.After the substrate was heated to 100℃,the zinc crystallites were regular hexagonal and arranged almost parallel to the substrate surface.In addition,observation of pure zinc coatings with different thicknesses showed that the growth of zinc coating was mainly in the Volmer-Weber mode.When the process parameters were appropriate,the zinc coating was composed of closely arranged columnar crystallites,and the crystallites grew preferentially along[0001]direction.

Copper-coated Porous Polyimide as Ultralight and Safe Current Collectors for Advanced LIBs

Metallic copper is widely used as current collector(CC) for graphite anode of lithium-ion batteries(LIBs) due to its high electrical conductivity and electrochemical stability. However, the large volume density of commercial copper foil(~8.9 g·cm^(-3)) limits the increase of energy density of battery. Here, copper-coated porous polyimide(Cu@PPI) was prepared by vacuum evaporation as collector for the graphite anode. The sandwich structure connects the copper metal on both sides of the collector with excellent electrical conductivity. Compared to commercial Cu foil, Cu@PPI has lighter mass(≤3.9 mg for disc of 12 mm diameter versus 9.9 mg of ~10 μm Cu foil) and lower volume density(≤3.3 g·cm^(-3)). In addition, the porous structure allows of better adhesion of reactive substances and electrochemical properties than pure Cu foils. It is estimated that the energy density of Cu@PPI should be much higher than that of Cu foil. This strategy should be applicable for other current collectors.

Changes in color and rheological behavior of pineapple concentrate through various evaporation methods

The objective of this study was to investigate the effect of various concentration methods namely microwave vacuum evaporation(MVE),microwave heating evaporation(MHE),and rotary vacuum evaporation(RVE)on the concentrate change,the kinetic of color degradation,and the rheological behavior of pineapple juice.The concentrated behavior of pineapple juice from the experimental data of concentration rate was fitted with three types of exponential models for evaluating a suitable prediction.The four-parameter exponential model was found to agreeably explain the concentrated change of pineapple juice during each concentration methods.The Kinetics of color change during concentration processes was evaluated.The color changing from three different evaporations was measured by lightness values(L*),redness values(a*)and yellowness(b*)values,total color difference(TCD)and brown pigment formation index(A420).The result indicated that the change in Hunter parameters,L*and b*,fitted well with the first-order kinetic model while a*,TCD,and Browning index followed the zero-order kinetic model.The observed apparent viscosities(μa)of pineapple concentrate at 55-85℃through the three different evaporation methods were also measured.In relation to temperature and shear rate,the viscosity decreased as these two parameters increased,for all concentrated pineapple juice.On comparing the values ofμa of pineapple concentrate from different concentration methods,pineapple concentrate from MHE has higher values than those from MVE and RVE.The Duncan test,applied to the experimental results,indicates no significant difference in theμa of pineapple juice concentrate by MVE and by RVE.

Densification and anticorrosion performances of vacuum evaporated aluminium coatings on NdFeB magnets

Al coated NdFeB magnets obtained by vacuum evaporation technique were densified by high energy ball milling method.The surface morphology,metal composition and micro structure of the coatings were characterized by scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy,respectively.The anticorrosive properties were investigated by potentiodynamic polarization curves and neutral salt spray test.The pores in the Al coatings of columnar crystals(Al) induced by the evaporation technique,were apparently filled in the following ball milling process,leading to the densification of Al coatings and the evident improvement of the anticorrosive performances.When treated with ball milling for 30 min,the sample achieves the best anticorrosive performances with the self-corrosion potential of-0.87 V,self-corrosion current density of 1.65 μA/cm^(2) and the neutral salt spray(NSS) time of 144 h(red rust).The improvement of the anticorro sive performances of vacuum evaporated Al coating mainly lies in the densification effect of the coating,which depends on different loading conditions of ball milling process.

Wafer-scale heterogeneous integration of self-powered lead-free metal halide UV photodetectors with ultrahigh stability and homogeneity

Large-scale growth and heterogeneous integration with existing semiconductors are the main obstacles to the application of metal halide perovskites in optoelectronics.Herein,a universal vacuum evaporation strategy is presented to prepare copper halide films with wafer-scale spatial homogeneity.Benefiting from the electric field manipulation method,the built-in electric fields are optimized and further boost the self-powered UV photodetecting performances of common wide-bandgap semiconductors by more than three orders of magnitude.Furthermore,with effective modulation of the interfacial charge dynamics,the as-fabricated GaN-substrate heterojunction photodetector demonstrates an ultrahigh on/off ratio exceeding 107,an impressive responsivity of up to 256 mA W^(-1),and a remarkable detectivity of 2.16×10^(13) Jones at 350 nm,0 V bias.Additionally,the device exhibits an ultrafast response speed(t r/t d=716 ns/1.30 ms),an ultra-narrow photoresponse spectrum with an FWHM of 18 nm and outstanding continuous operational stability as well as long-term stability.Subsequently,a 372-pixel light-powered imaging sensor array with the coefficient of variation of photocurrents reducing to 5.20%is constructed,which demonstrates exceptional electrical homogeneity,operational reliability,and UV imaging capability.This strategy provides an efficient way for large-scale integration of metal halide perovskites with commercial semiconductors for miniature optoelectronic devices.

Behavior of Element Vaporization and Composition Control of Fe-Ga Alloy during Vacuum Smelting

Saturated vapor pressure, critical evaporation temperature and evaporation loss rate of Fe-Ga alloy were calculated under different conditions of Ga and Fe contents with activity coefficients. The relationship between the change of Ga content and melting time was determined. The results demonstrated that saturated vapor pressure of Ga was higher than that of Fe under the same conditions. The difference value of critical evaporation temperature of Ga with and without Ar was nearly 800 K. The critical evaporation temperature of Fe was higher than that of Ga under vacuum, indicating that Ga was more volatile than Fe. At 1800 K, the evaporation rate of Ga was 84 times higher than that of Fe in the melt of Fe81Ga19 alloy. Under this condition, the change of Ga content and smelting time kept a linear relationship. The higher the temperature was, the faster the Ga content decreased, which was consistent with theoretical calculations.

EFFECT OF VACUUM ON THE CRYSTAL FORM AND MORPHOLOGY OF THE EVAPORATED FILM OF COPPER PHTHALOCYANINE

In a previous paper, we have reported the relationship between the crystallite orientation of the evaporated film of copper phthalacyanine （PcCu） （α-form） and the incident angle of molecular beam at 10-5 torr. In this paper, we shall show some research results about vacuum effects on the crystal forms and the morphology of the evaporat-