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Controlling surface morphology and sensitivity of granular and porous silver films for surface-enhanced Raman scattering, SERS
摘要： The design of efficient substrates for surface-enhanced Raman spectroscopy (SERS) for large-scale fabrication at low cost is an important issue in further enhancing the use of SERS for routine chemical analysis. Here, we systematically investigate the effect of different radio frequency (rf) plasmas (argon, hydrogen, nitrogen, air and oxygen plasma) as well as combinations of these plasmas on the surface morphology of thin silver films. It was found that different surface structures and different degrees of surface roughness could be obtained by a systematic variation of the plasma type and condition as well as plasma power and treatment time. The differently roughened silver surfaces act as efficient SERS substrates showing greater enhancement factors compared to as prepared, sputtered, but untreated silver films when using rhodamine B as Raman probe molecule. The obtained roughened silver films were fully characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron (XPS and Auger) and ultraviolet–visible spectroscopy (UV–vis) as well as contact angle measurements. It was found that different morphologies of the roughened Ag films could be obtained under controlled conditions. These silver films show a broad range of tunable SERS enhancement factors ranging from 1.93 × 102 to 2.35 × 105 using rhodamine B as probe molecule. The main factors that control the enhancement are the plasma gas used and the plasma conditions, i.e., pressure, power and treatment time. Altogether this work shows for the first time the effectiveness of a plasma treatment for surface roughening of silver thin films and its profound influence on the interface-controlled SERS enhancement effect. The method can be used for low-cost, large-scale production of SERS substrates.
关键词： plasma treatment,sputtering,surface-enhanced Raman spectroscopy (SERS),silver,surface roughening
更新于2025-09-23 15:21:21
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Surface Roughening of Silicon Wafer Solar Cell by Using ECDM Method
摘要： This research proposes surface roughening of silicon wafer solar cell by electrochemical discharge machining (ECDM). The stainless steel was used as negative electrode. The graphite was used as the positive electrode acting as the auxiliary electrode. The potassium hydroxide was used as the electrolyte. The processing parameters include the machining voltage, the processing time, the machining gap, the electrolyte concentration, the additive agent concentration, pulse frequency and duty factor, etc. The result of experiments reveals that appropriate concentrations of ethanol can expand the size of the pores and enhance surface roughening effect. The appropriate processing parameters are a machining gap of 200μm, voltage of 48V, concentration of potassium hydroxide of 3M, concentration of ethanol of 4%. The electrochemical discharge machined surface roughness was increased from 0.417μm to 0.915μm using one minute processing time. The average reflectance rate of the textured surface was decreased from 29.6% to 12.7%. This study reveals that ECDM method has the advantage of short processing time and can generate a higher surface roughness and the porous structure.
关键词： Electrical chemical discharge machining,Reflectance rate,Surface roughening,Silicon wafer solar cell
更新于2025-09-16 10:30:52
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Model for black silicon formation just from surface temperature non-uniformities
摘要： The scienti?c issue of this paper is the formation of the initial surface roughening during black silicon (b-Si) preparation by maskless SF6/O2 plasma texturing. In detail, the authors investigate a novel approach whether merely substrate temperature dependent surface mechanisms and plasma particle diffusion are suf?cient to theoretically obtain anisotropic etching. For that, a quasi-2D model is developed including the relevant mechanisms such as (i) etching, (ii) the deposition of the masking layer SiOxFy, (iii) plasma particle transport, and (iv) heat diffusion. Further on, a linear stability analysis is applied, ?rstly, to reveal theoretical conditions for anisotropic etching and, secondly, to qualitatively evaluate the impact of the model parameters on the texturing range. The evaluation shows that plasma particle diffusion along the surface is the main factor for nano-roughening. Additionally, the experimentally expected strong dependency of the texturing on the substrate temperature is con?rmed and other extracted dependencies can be correlated to experimental observations. With that, a novel model is introduced explaining the initial b-Si roughening without taking into account surface removal by directed ions.
关键词： surface roughening,anisotropic etching,black silicon,plasma texturing,temperature non-uniformities
更新于2025-09-04 15:30:14