One-step Fabrication of Nanoporous Black Silicon Surfaces for Solar Cells using Modified Etching Solution

Currently, a conventional two-step method has been used to generate black silicon （BS） surfaces on silicon substrates for solar cell manufacturing. However, the performances of the solar cell made with such surface generation method are poor, because of the high surface recombination caused by deep etching in the conventional surface generation method for BS. In this work, a modified wet chemical etching solution with additives was developed. A homogeneous BS layer with random porous structure was obtained from the modified solution in only one step at room temperature. The BS layer had low reflectivity and shallow etching depth. The additive in the etch solution performs the function of pH-modulation. After 16-min etching, the etching depth in the samples was approximately 200 nm, and the spectrum-weighted-reflectivity in the range from 300 nm to 1200 nm was below 5%. BS solar cells were fabricated in the production line. The decreased etching depth can improve the electrical performance of solar cells because of the decrease in surface recombination. An efficiency of 15.63% for the modified etching BS solar cells was achieved on a large area, p- type single crystalline silicon substrate with a 624.32-mV open circuit voltage and a 77.88% fill factor.

TREATMENT OF METALS, POLYMER FILMS, AND FABRICS WITHA ONE ATMOSPHERE UNIFORM GLOW DISCHARGE PLASMA(OAUGDP) FOR INCREASED SURFACE ENERGY AND DIRECTIONAL ETCHING

Direct exposure of samples to the active species of air generated by a One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) has been used to etch and to increase the surface energy of metallic surfaces, photoresist, polymer films, and nonwoven fab- rics. The OAUGDP is a non-thermal plasma with the classical characteristics of a DC normal glow discharge that operates in air (and other gases) at atmospheric pres- sure. Neither a vacuum system nor batch processing is necessary. A wide range of applications to metals, photoresist, films, fabrics, and polymeric webs can be accom- modated by direct exposure of the workpiece to the plasma in parallel-plate reactors. This technolopy is simple, it produces effects that can be obtained in no other way at one atmosphere; it generates minimal pollutants or unwanted by-products; and it is suitable for individual sample or online treatment of metallic surfaces, wafers, films, and fabrics. Early exposures of solid materials to the OAUGDP required minutes to produce rela- tively small increases of surface energy. These durations appeared too long for com- mercial application to fast-moving webs. Recent improvements in OAUGDP gas com- position, power density, plasma quality, recireulating gas flow, and impedance match- ing of the power supply to the parallel plate plasma reactor have made it possible to raise the surface energy of a variety of polymeric webs (PP, PET PE etc.) to levels of 60 to 70 dynes/cm with one second of exposure. In air plasmas, the high surface ener- gies are not durable, and fall to 50 dynes/cm after periods of weeks to months. Here, we report the exposure of metallic surfaces, photoresist, polymeric films, and nonwo- ven fabrics made of PP and PET to an impedance matched parallel plate OAUGDP for durations ranging from one second to several tens of seconds. Data will be re- ported on the surface energy, wettability, wickability, and aging effect of polymeric films and fabrics as functions of time of exposure, and time after exposure; the rate and uniformity of photoresist etching; and the production of sub-micron structures by OAUGDP etching at one atmosphere.

Recent advances in preparation of metallic superhydrophobic surface by chemical etching and its applications

In the past few decades,inspired by the superhydrophobic surfaces(SHPS)of animals and plants such as lotus leaves,rose petals,legs of water striders,and wings of butterflies,preparing metal materials with metallic SHPS(MSHPS)have attracted great research interest,due to the great prospect in practical applications.To obtain SHPS on conventional metal materials,it is necessary to construct rough surface,followed by modification with low surface energy substances.In this paper,the action mechanism and the current research status of MSHPS were reviewed through the following aspects.Firstly,the model of wetting theory was presented,and then the progress in MSHPS preparation through chemical etching method was discussed.Secondly,the applications of MSHPS in self-cleaning,anti-icing,corrosion resistance,drag reduction,oil-water separation,and other aspects were introduced.Finally,the challenges encountered in the present application of MSHPS were summarized,and the future research interests were discussed.

Reduction of Reactive-Ion Etching-Induced Ge Surface Roughness by SF6/CF4Cyclic Etching for Ge Fin Fabrication

An SF6/CF4 cyclic reactive-ion etching （RIE） method is proposed to suppress the surface roughness and to opti- mize the morphology of Ge fin, aiming at the fabrication of superior Ge FinFETs for future CMOS technologies. The surface roughness of the Ge after RIE can be sufficiently reduced by introducing SF6-O2 etching steps into the CF4-O2 etching process, while maintaining a relatively large ratio of vertical etching over horizontal etching of the Ge. As a result, an optimized rms roughness of 0.9nm is achieved for Ge surfaces after the SF6/CF4 cyclic etching with a ratio of greater than four for vertical etching over horizontal etching of the Ge, by using a proportion of 60% for SF6-O2 etching steps.

Etching‑Induced Surface Reconstruction of NiMoO_(4) for Oxygen Evolution Reaction

Rational reconstruction of oxygen evolution reaction(OER)precatalysts and performance index of OER catalysts are crucial but still challenging for universal water electrolysis.Herein,we develop a double-cation etching strategy to tailor the electronic structure of NiMoO_(4),where the prepared NiMoO_(4) nanorods etched by H_(2)O_(2) reconstruct their surface with abundant cation deficiencies and lattice distortion.Calculation results reveal that the double cation deficiencies can make the upshift of d-band center for Ni atoms and the active sites with better oxygen adsorption capacity.As a result,the optimized sample(NMO-30M)possesses an overpotential of 260 mV at 10 mA cm−2 and excellent long-term durability of 162 h.Importantly,in situ Raman test reveals the rapid formation of high-oxidation-state transition metal hydroxide species,which can further help to improve the catalytic activity of NiMoO_(4) in OER.This work highlights the influence of surface remodification and shed some light on activating catalysts.

Fabrication of Superhydrophobic Aluminum Plate by Surface Etching and Fluorosilane Modification

Superhydrophobic aluminum surfaces with a high water contact angle and low sliding angle on aluminum plate substrate were fabricated by means of surface etching with sodium hydroxide under ultrasonic bathing and then modification with fluorosilane. Scanning electron microscopy（SEM） showed a honeycomb-like structure on aluminum substrate surface after etching under ultrasonic bathing. And the surface was rendered from superhydrophilicity to superhydrophobicity after further modification with fluorosilane.

Effect of gear teeth finishing method on properties of teeth surface layer and its resistance to pitting wear creation

This work presented the characteristics of two gear teeth finishing methods, due to the properties of gear teeth surface layer obtained at the tooth working depth. These methods are: 1) the teeth carburization, hardening to a hardness of HRC 60-62 and then grinding, 2) the soft gear shaving as the final mechanical treatment and then carburizing and hardening to the hardness of HRC60-62. This work included the test results of the contact fatigue strength carried out on the circulating power system. The Wohler curves were plotted due to the obtained results, as the basis for the practical evaluation of the considered gear finishing methods. The parameters like volume distribution of the voids, content of the retained austenite, compressive residual stress value, but also the results of contact fatigue strength tests, are more favorable for the teeth shaving method than for the teeth grinding method.

Improving the surface insulation of epoxy resin by plasma etching

Epoxy resin(EP)tends to accumulate a large amount of charge on its surface when exposed to a high-voltage DC electric field,which leads to a reduction in its insulative performance and an increase in potential safety risks in power systems.To suppress charge accumulation,improve the flashover voltage of the EP,and reduce the risk of gas insulated switchgear(GIS)/gas insulated transmission line(GIL)failure,we used two plasma-etching methods,i.e.,atmospheric-pressure dielectric barrier discharge(DBD)and the atmospheric-pressure plasma jet(APPJ),to modify the surface of the EP.The surface morphology and electrical properties of the modified materials were explored as a function of time.The results show that after DBD treatment,the roughness of the sample increases by 103.9 nm,the conductivity increases by3.9×10^(-18)S,and the flashover voltage increases by 14.4%;after APPJ treatment,the roughness of the sample increases by 223.5 nm,the conductivity increases by 3.4×10^(-17)S,and the flashover voltage increases by 18%.This shows that both plasma-etching methods can improve the insulation properties of materials by improving the surface-charge characteristics.The two methods are compared with each other:the APPJ treatment method is better at improving the surface roughness and electrical properties of materials,and this flexible treatment method has greater potential in industrial applications.

Understanding of surface pit formation mechanism of GaN grown in MOCVD based on local thermodynamic equilibrium assumption

Frank’s theory describes that a screw dislocation will produce a pit on the surface,and has been evidenced in many material systems including GaN.However,the size of the pit calculated from the theory deviates significantly from experimental result.Through a careful observation of the variations of surface pits and local surface morphology with growing temperature and V/III ratio for c-plane GaN,we believe that Frank’s model is valid only in a small local surface area where thermodynamic equilibrium state can be assumed to stay the same.If the kinetic process is too vigorous or too slow to reach a balance,the local equilibrium range will be too small for the center and edge of the screw dislocation spiral to be kept in the same equilibrium state.When the curvature at the center of the dislocation core reaches the critical value 1/r0,at the edge of the spiral,the accelerating rate of the curvature may not fall to zero,so the pit cannot reach a stationary shape and will keep enlarging under the control of minimization of surface energy to result in a large-sized surface pit.

Etching characteristics and surface modification of InGaSnO thin films under Cl_(2)/Ar plasma

Indium gallium tin oxide(IGTO)thin films have the potential for high mobility and lowtemperature processing,which makes them suitable for applications such as display backplanes and high-voltage switching devices.However,very few studies have investigated the plasmaetching characteristics of IGTO and changes in its properties after etching.In this study,the etching characteristics of IGTO were investigated using Cl_(2)/Ar plasma,and changes in surface properties were analyzed.Results showed that the etch rate increased with an increase in the proportion of Cl_(2),with the highest etch rate observed at 69 nm min^(-1)in pure Cl_(2)plasma with a gas flow rate of 100 sccm.Furthermore,increased radio-frequency power caused a rise in the etch rate,while a process pressure of 15 m Torr was optimal.The primary etching mechanism for IGTO thin films under Cl_(2)plasma was a chemical reaction,and an increased work function indicated the occurrence of defects on the surface.In addition,the etching process reduced the surface roughness of Cl_(2)-containing plasma,whereas the etching process in pure Ar plasma increased surface roughness.This study contributes to a better understanding of the plasmaetching characteristics of IGTO and changes in its properties after etching,providing valuable insights for IGTO-based applications.

The Effect of Surface Pit Treatment on Fretting Fatigue Crack Initiation

This paper analyses the effect of surface treatment on fretting fatigue specimen by numerical simulations using Finite Element Analysis.The processed specimen refers to artificially adding a cylindrical pit to its contact surface.Then,the contact radius between the pad and the specimen is controlled by adjusting the radius of the pit.The stress distribution and slip amplitude of the contact surface under different contact geometries are compared.The critical plane approach is used to predict the crack initiation life and to evaluate the effect of processed specimen on its fretting fatigue performance.Both crack initiation life and angle can be predicted by the critical plane approach.Ruiz parameter is used to consider the effect of contact slip.It is shown that the crack initial position is dependent on the tensile stress.For same type of model,three kinds of critical plane parameters and Ruiz method provide very similar position of crack initiation.Moreover,the improved sample is much safer than the flat-specimen.

Steering surface reconstruction of hybrid metal oxides for efficient oxygen evolution reaction in water splitting and zinc-air batteries

Surface reconstruction yields real active species in electrochemical oxygen evolution reaction(OER)conditions;however,rationally regulating reconstruction in a targeted manner for constructing highly active OER electrocatalysts remains a formidable challenge.Here,an electrochemical activation strategy with selective etching was utilized to guide the reconstruction process of a hybrid cobalt-molybdenum oxide(CoMoO_(4)/Co_(3)O_(4)@CC)in a favorable direction to improve the OER performance.Both in-situ Raman and multiple ex-situ characterization tools demonstrate that controlled surface reconstruction can be easily achieved through Mo etching,with the formation of a dynamically stable amorphous-crystalline heterostructure.Theoretical calculations together with experimental results reveal that the synergistic effects between amorphous CoOOH and crystalline Co_(3)O_(4) are crucial in enhancing the catalytic performance.Consequently,the reconstructed CoMoO_(4)/Co_(3)O_(4)@CC exhibits a low overpotential of 250 mV to achieve a current density of 10 mA cm^(-2) in 1 M KOH,and more importantly it can be practiced in electrolytic water splitting and rechargeable zinc-air batteries devices,achieving ultra-long stability for over 500 and 1200 h,respectively.This work provides a promising route for the construction of high-performance electrocatalysts.

Superhydrophobic surface of Mg alloys:A review

In the present review,the formation of superhydrophobic(SHP)structures on the surface of Mg alloys was investigated.Different methods including hydrothermal technique,chemical and electrochemical deposition,conversion and polymer coating,and etching routes were discussed.The superhydrophobicity could form on the surface of Mg alloys by the application of different chemical,electrochemical,and physical methods followed by the immersion of these alloys in the solution containing modifying agents including fatty acids or long-chain molecules.The formed morphology,composition,and contact angle were reported and the effect of synthesis route on these characteristics was reviewed.

Laser Surface Modification of Lean-alloyed Austenitic Stainless Steel for Corrosion Resistance

In order to reduce the cost of the austenitic stainless steels(ASSs),the expensive austenite former(nickel) is often substituted by manganese.However,manganese is generally seen to have a detrimental effect on the corrosion resistance.In the present study,the feasibility of laser surface modification of a lean-alloyed ASS(FeCrMn) for enhancing pitting corrosion resistance was investigated.Laser surface modification of FeCrMn was successfully achieved by a 2.3 kW high power diode laser(HPDL).Cyclic polarization tests for FeCrMn after laser surface modification in 3.5% NaCl solution at 25 ℃ were performed by using a potentiostat.The pitting resistance of the laser-modified specimens was found to be significantly improved as reflected by the noble shift in pitting potential.This could be attributed to redistribution of manganese sulphide leading to a more homogenous and refined microstructure.Pitting corrosion resistance of the laser-treated FeCrMn followed by subsequent citric acid passivation was found to be further improved as reflected by the noble shift in pitting potential to 0.18 V.

Osteoblast Behavior on Hierarchical Micro-/Nano-Structured Titanium Surface

In the present work, osteoblast behavior on a hierarchical micro-/nano-structured titanium surface was investigated. A hi- erarchical hybrid micro-/nano-structured titanium surface topography was produced via Electrolytic Etching （EE）. MG-63 cells were cultured on disks for 2 h to 7 days. The osteoblast response to the hierarchical hybrid micro-/nano-structured titanium surface was evaluated through the osteoblast cell morphology, attachment and proliferation. For comparison, MG-63 cells were also cultured on Sandblasted and Acid-etched （SEA） as well as Machined （M） surfaces respectively. The results show signifi- cant differences in the adhesion rates and proliferation levels of MG-63 cells on EE, SLA, and M surfaces. Both adhesion rate and proliferation level on EE surface are higher than those on SLA and M surfaces. Therefore, we may expect that, comparing with SLA and M surfaces, bone growth on EE surface could be accelerated and bone formation could be promoted at an early stage, which could be applied in the clinical practices for immediate and early-stage loadings.

Optimization principle of combined surface and underground mining and its applications

The pit limit optimization is discussed, which is one of the most important problems in the combined min-ing method, on the basis of the economic model of ore-blocks. A new principle of the limit optimization is put for-ward through analyzing the limitations of moving cone method under such conditions. With a view to recovering asmuch mineral resource as possible and making the maximum profit from the whole deposit, the new principle is tomaximize the sum of gain from both open-pit and underground mining. The mathematical models along the horizon-tal and vertical directions and modules for software package (DM&MCAD) have been developed and tested inTonglushan Copper Mine. It has been proved to be rather effective in the mining practice.

Characterization and chemical surface texturization of bulk ZnTe crystals grown by temperature gradient solution growth

Using tellurium as a solvent, we grew ZnTe ingots of 30 mm in diameter and 70 mm in length by a temperature gradient solution growth method. Hall tests conducted at 300 K indicated that the as-grown ZnTe exhibits p-type conductivity, with a carrier concentration of approximately 10^14cm^-3, a mobility of approximately 300 cm^2·V·s^-1, and a resistivity of approximately 10^2 Ω·cm. A simple and effective method was proposed for chemical surface texturization of ZnTe using an HF：H2O2：H2O etchant. Textures with the sizes of approximately 1μm were produced on {100}, {110}, and { 111}zn surfaces after etching. The etchant is also very promising in crystal characterization because of its strong anisotropic character and Te-phase selectivity.

Study on Surface Treatments on CdSe Wafers

The surface treatments on CdSe wafers were studied by means of SEM,XPS and micro-current test instrument.The relations between electrical properties of CdSe wafers and surface topography,composition and structure were analyzed.The results show that the change of surface composition by etching is beneficial to decrease leakage current.Meanwhile,the increase of oxygen on surface caused by passivation can largely decrease leakage current.When passivating time is 40 min,the wafers surface appears smooth and compact,which will decrease the density of surface state,the optimal electrical property of the wafer is therefore obtained.

Effect of Krypton Addition on Electron Cyclotron Resonance-Radio Frequency Hybrid Oxygen Plasma for Patterning Diamond Surfaces

Electron cyclotron resonance radio frequency （ECR-rf） hybrid krypton-diluted oxygen plasmas were used to pattern the surfaces of diamond films with the assistance of a physical mask, while optical emission spectroscopy was employed to characterize the plasma. It was found that with krypton dilution the etching rate decreased, and also the aspect ratios of nanotips formed in micro-holes were significantly modified. The oxygen atomic densities were estimated by oxygen atom optical emission and argon actinometry. Under a microwave power of 300 W and rf bias of-300 V, the absolute density of ground-state oxygen atoms decreased from 1.3×10^12 cm^-3 to 1.4×10^11 cm^-3 as the krypton dilution ratio increased to 80%, accompanied by the decrease in the plasma excitation temperature. It is concluded that oxygen atoms play a dominant role in diamond etching. The relative variations in the horizontal and vertical etching rates induced by the addition of krypton are attributed to the observations of thicker nanotips at a high krypton dilution ratio.

Effect of Sliding Wear on Surface Microstructure and Wear Property of D2 Wheel Steel

In this paper, the surface microstructure and wear property of D2 wheel steel under sliding wear condition were studied by MRH-30 sliding wear tester. After testing, a transmission electron microscope (TEM), scanning electron microscope (SEM) with electron backscatter diffraction (EBSD), and micro-hardness testers were used to characterize the surface microstructure of samples with different cycles. The results show that the wear losss samples are increased as the increase of cycles, and the wear loss of wheel samples is higher than that of rail samples. The surface hardness and thickness of deformation layer of wheel samples are increased as the cycles increase. After sliding wear, the samples surfaces form the white etching layer with the thickness of several microns. Through the analysis of surface microstructure of sample with 12,000 cycles, the lamellar cementite in pearlite is fragment into cementite particles with the decrease of depth from surface, and the cementite is dissolved at surface to lead to the form of white etching layer. The ferrite grains are refined gradually and the fraction of high angle grain boundary is increased with the decrease of depth from surface. The nanosgrains layer of ferrite grains with 5 μm thickness is formed. According to the result of finite element simulation of contact surface temperature, the formation of surface nanograins and the dissolution of cementite are caused by the severe plastic deformation. The fiber structure of samples is formed after sliding wear, with direction of .