Ag Deposition Forms and Uniformity on Porous Silicon by Electrochemical Method

The electrochemical deposition technique was applied to achieve porous silicon （PS） surface passivated with Ag deposition for improving the properties of PS photoluminescence. The relation of Ag depositing forms to current density and the effect of PS hydrophilic surface on deposition uniformity were investigated. The experimental results indicated that there were two critical current densities （maximum and minimum） in which Ag was absent and electroplated on PS surface correspondingly, and the range of current density for deposition of Ag on porous silicon was from 50 μA/cm^2 to 400 μA/cm^2. The process of changing PS surface from hydrophobic into hydrophilic had positive effect on Ag deposition uniformity. Under the same experimental conditions, PS hydrophobic surface presented uneven Ag deposition.However, hydrophilic surface treated with SC-1 solution was even. Finally, the effect of PS surface passivation with Ag even deposition on photoluminescence intensity and stabilization of PS was studied. It was discovered that Ag passivation inhibited the degradation of PL intensity effectively. In addition, excessive Ag deposition had a quenching effect on room-temperature visible photoluminescence of PS.

Improving the surface flashover performance of epoxy resin by plasma treatment:a comparison of fluorination and silicon deposition under different modes

This work treats the Al_(2)O_(3)-ER sample surface using dielectric barrier discharge fluorination(DBDF),DBD silicon deposition(DBD-Si),atmospheric-pressure plasma jet fluorination(APPJ-F)and APPJ silicon deposition(APPJ-Si).By comparing the surface morphology,chemical components and electrical parameters,the diverse mechanisms of different plasma modification methods used to improve flashover performance are revealed.The results show that the flashover voltage of the DBDF samples is the largest(increased by 21.2%at most),while the APPJ-F method has the worst promotion effect.The flashover voltage of the APPJ-Si samples decreases sharply when treatment time exceeds 180 s,but the promotion effect outperforms the DBD-Si method during a short modified time.For the mechanism explanation,firstly,plasma fluorination improves the surface roughness and introduces shallow traps by etching the surface and grafting fluorine-containing groups,while plasma silicon deposition reduces the surface roughness and introduces a large number of shallow traps by coating Si Oxfilm.Furthermore,the reaction of the DBD method is more violent,while the homogeneity of the APPJ modification is better.These characteristics influence the effects of fluorination and silicon deposition.Finally,increasing the surface roughness and introducing shallow traps accelerates surface charge dissipation and inhibits flashover,but too many shallow traps greatly increase the dissipated rate and facilitate surface flashover instead.

<100> Textured Diamond Film on Silicon Grown by Hot Filament Chemical Vapor Deposition

The <100> textured growth of diamond film on HF eroded silicon wafer has been studied by HFCVD. The evolution of grain size and sudece morphology vs deposition time is presented and the <100> textured thick diamond film (80μm) with smooth surface, desirable for practical application in many fields is obtained

Effect of Cumulative Nanosecond Laser Pulses on the Plasma Emission Intensity and Surface Morphology of Pt-and Ag-Ion Deposited Silicon

In this work, the laser induced plasma plume characteristics and surface morphology of Pt- and Ag-ion deposited silicon were studied. The deposited silicon was exposed to cumulative laser pulses. The plasma plume images produced by each laser shot were captured through a computer controlled image capturing system and analyzed with image-J software. The integrated optical emission intensity of both samples showed an increasing trend with increasing pulses. Agion deposited silicon showed higher optical emission intensity as compared to Pt-ion deposited silicon, suggesting that more damage occurred to the silicon by Ag ions, which was confirmed by SRIM/TRIM simulations. The surface morphologies of both samples were examined by optical microscope showing thermal, exfoliational and hydrodynamical sputtering processes along with the re-deposition of the material, debris and heat affected zones＇ formation. The crater of Ption deposited silicon was deeper but had less lateral damage than Agion deposited silicon. The novel results clearly indicated that the ion deposited silicon surface produced incubation centers, which led to more absorption of incident light resulting into a higher emission intensity from the plasma plume and deeper crater formation as compared to pure silicon. The approach can be effectively utilized in the laser induced breakdown spectroscopy technique, which endures poor limits of detection.

Formation of Epitaxial Heavy-doped Silicon Films by PECVD Method

Plasma-enhanced CVD（PECVD） epitaxy at 200℃ was used to deposit heavy doped n-type silicon films. Post-annealing by rapid thermal processing was applied to improve the properties of the epitaxial layer. By analyzing the Raman spectra and the imaginary part of the dielectric constant spectra of the samples, it was found that high-quality heavy-doped epitaxial n-type silicon layer can be obtained by optimizing the parameters of the PECVD depositing process. Reducing the electrodes distance of the PECVD had a great effect on the crystallzation of the epitaxialed n-type silicon films. Sillicon films with high-crystallization were obtained with the electrodes distance of 18 mm. Post-annealing process can improve the crystallization and reduce the resistance of the epitaxial films. In our research, it was found that the sheet resistance（R□） of the post-annealed films with thickness of about 50 nm has a simple relationship with RPH3/SiH4（ratio of the flow rate of PH3 and SiH4） of the PECVD processing： R□=-184-125 lg（R（PH3/SiH4））. In the end, high-quality epitaxial n-type silicon film was obtained with R□ of 15 Ω/□ and thickness of ~50 nm.

Epitaxial n- and p-type Emitters for High Efficiency Solar Cell Concepts

Reducing the module prices by increasing the efficiency of solar cells is one of the major challenges in today＇s photovoltaic research. The emitter formation by epitaxial growth offers a cost-efficient and faster alternative to the standard furnace diffusion process. The efficiency potential of epitaxial emitters 〉 22% has already been proven using a single wafer, low pressure, chemical vapour deposition tool. The purpose of this work is to show the potential of epitaxially grown emitters by APCVD （atmospheric pressure chemical vapour deposition） compared to diffused emitters. The APCVD formation of epitaxial emitters at 1,050 ~C can be realised as high throughput inline process and only takes 1-2 min, whereas the diffusion process using POCI3 takes up to 60 min. Simulations show an increase in voltage of AVoc = ＋10 mV and a reduction in saturation current ,1o of 30% for the epitaxial emitter. The lifetime experiments of solar cells with epitaxial emitter exhibit a diffusion length Leff〉 750μm and an emitter saturation current of Joe 〈 50 fA/cm2 on a planar 10 Ω2cm p-type FZ wafer. Another important aim of this work is to evaluate the limitations of epitaxial emitters due to high thermal budget, interface recombination and the change of reflective properties on textured wafers due to the deposition process. Solar cell efficiencies up to 18.4% on p-type and 20.0% on n-type wafers presented in this paper underline that the emitter epitaxy by APCVD is a competitive process for the emitter formation.

Carrier Transport Properties in the Doped Micro - crystalline Silicon Films

Doped micro-crystalline silicon films are deposited at temperatures as low as 400 ℃ by the catalytic chemical vapor deposition method using a silane and hydrogen gas mixture. Electrical properties such as the carrier concentration and the Hall mobility are investigated for various measuring temperatures. It is found that the grains of micro-crystalline silicon are preferentially oriented along the (220) direction , and that the Hall mobility is larger than 8 cm 2·V -1 ·s -1 , the carrier concentration is about 1×10 17 cm -1 ～1×10 19 cm -3 at room temperature.

Fe-doped TiO_2/SiO_2 nanofibrous membranes with surface molecular imprinted modification for selective photodegradation of 4-nitrophenol

In this study, Fe-doped TiO2/SiO2 （Fe@TS） nanofibrous membranes with molecular imprinted modification, were fabricated by a combination of sol-gel process, electrospinning, calcination and liquid phase deposition techniques, The precursor sol was prepared from one-pot condensation of poly （vinylpyrrolidone）, ferric chloride hexahydrate, tetraethyl orthosilicate and titanium n-butoxide in the mixture solvents of N,N-dimethylformamide and ethyl alcohol. Fibrous membrane wasthen fabricated by electrospinning, followed by calcination to form the Fe@TS composite. The physicochemical properties of Fe@TS were characterized. Thereafter, 4-nitrophenol （4NP） was used as the template to deposit onto nanofibrous Fe@TS membranes, with a thin layer of molecular imprinted polymer in liquid phase. The photodegradation capabilities of 4NP and methyl orange wereexamined in both single and binary systems. The results demonstrated that molecular imprinted Fe@TS membranes exhibited excellent selectivity for photodegradation of 4NP.