Mechanism of silicon implant-deposition for surface modification of stainless steel 304 using KrF-excimer laser

Simultaneous implantation and deposition of Si by KrF-excimer-laser (248 nm) irradiation in an ambient silane (SiH₄) gas realize the surface modification of stainless steel (SUS) 304 at room temperature. This process is referred to as the Laser Implant-Deposition (LID). Depth profiles of Si concentration in the modified layers and the total quantities of supplied Si (Si dose) are analyzed by Rurtherford Backscattering Spectroscopy (RBS) measurements. The Si supply mechanism of LID is discussed with variations of the Si dose as a function of laser fluence, gas pressure, and the number of laser pulses. The calculation of temperature along the depth during the LID process suggests that the Si atoms diffuse into the SUS304 in a liquid phase. Fitting of the calculated depth profile to the experimental data, using the interdiffusion theory, gives an interdiffusion coefficient between Si and SUS304 as high as 2.8×10^–6 cm²/s. A simplified model for simulation, by which well agreed depth profiles of Si can be simulated for various experimental conditions, is proposed.     

Long-time stabilization of porous silicon photoluminescence by surface modification

We present results on the photoluminescence (PL) properties of porous silicon (PS) as a function of time. Stabilization of PL from PS has been achieved by replacing silicon-hydrogen bonds terminating the surface with more stable silicon-carbon bonds. The composition of the PS surface was monitored by transmission Fourier transform infrared (FTIR) spectroscopy at intervals of 1 month in ageing time up to 1 year. The position of the maximum PL peak wavelength oscillates between a blue-shift and a red-shift in the 615-660 nm range with time.     

Preparation and surface modification of silicon nanowires under normal conditions

Preparation and surface modification of silicon nanowires (SiNWs) grown by the metal catalyzed solution method under normal conditions (room temperature, 1 atm) had been studied in this paper. Firstly, SiNWs using a simple solution method via electroless metal deposition (EMD) of silver under room temperature, standard pressure had been prepared. The influence of the growth parameters such as solution concentration, etching time on the SiNWs formation had been studied. Secondly, the surface modification of SiNWs with platinum and copper had been investigated. The results indicated that the SiNWs modified with Pt and Cu showed different surface morphologies. Pt modification on SiNWs presented in the form of nanoparticles, whereas Cu modification in the form of membrane. Therefore, the Pt modified SiNWs have more vast surface-to-bulk ratio than the unmodified ones, and SiNWs modified with copper nanoparticles will lead to the smaller surface-to-bulk ratio. So the platinum-modified SiNWs have a promising application in sensors’ field.     

Plasma modification of self-assembled structures of CoTMPP molecules

Plasma-treated cobalt metalloporphyrins have recently been proposed as electrocatalysts for the oxygen and oxygen peroxide reduction reaction. Whereas the effects of plasma treatment on the elemental composition of the surface of catalysts have been investigated, the effects of plasma treatment on the morphology of catalysts have not yet been studied. In this study, plasma modified nanosized structures of cobalt tetramethoxyphenylporphyrin (CoTMPP) molecules arising from the deposition of a porphyrin solution on an a-C:H film are investigated using an atomic force microscope (AFM). Additionally, the effects of plasma treatment on the structure of porphyrin molecules are studied by using ultra violet visible (UV-vis) absorption analysis. The investigations reveal the morphological changes which accompany the transformation of CoTMPP into the final catalytic material. First, the large CoTMPP aggregates are split into smaller ones. Second, the CoTMPP layer appears to be sublimated after plasma treatment. Sublimated CoTMPP molecules can be decomposed by plasma and after redeposition can form catalytic active fragments.     

Infrared spectroscopy of self-assembled monolayer films on silicon

Infrared vibrational spectroscopy in an attenuated total reflection (ATR) geometry has been employed to investigate the presence of organic thin layers on Si-wafer surfaces. The phenomena have been simulated to show there can be a field enhancement with the presented single-reflection ATR (SR-ATR) approach which is substantially larger than for conventional ATR or specular reflection. In SR-ATR, a discontinuity of the field normal to the film contributes a field enhancement in the lower index thin film causing a two order of magnitude increase in sensitivity. SR-ATR was employed to characterize a single monolayer of undecylenic acid self-assembled on Si(1 1 1) and to investigate a two monolayer system obtained by adding a monolayer of bovine serum albumin protein.     

响应面方法的硅刻蚀工艺优化分析（英）

利用响应面分析方法优化了用于压力传感器硅敏感芯体的刻蚀操作条件。主要考虑了温度、KOH浓度和腐蚀时间三个操作参数,将它们的范围分别设定为40~60 ℃,0.4~0.48 mol/L 和 5~12.5 h,并设定各向异性腐蚀速率为响应值。通过建立二次方模型,分析这些参数的单独影响以及多个操作条件之间对腐蚀速率的相互交叠作用。分析结果表明：模型可以精确预测99%的响应值,相比于腐蚀时间,溶液浓度和工作温度对刻蚀速率的影响更为明显。     

Fabrication of nanostructured silicon surface using selective chemical etching

A two-stage process based on selective chemical etching induced by metal nanoclusters is used to fabricate nanostructured surfaces of silicon plates with a relatively low reflectance. At silicon surfaces covered with silver nanoclusters, the SERS effect is observed for rhodamine concentrations of about 10^–12 M. At certain technological parameters, the depth of the nanostructured layer weakly depends on the conditions for the two-stage etching, in particular, etching time. Under otherwise equal conditions for etching, the rate of the formation of textured layer in the p-type silicon is two times greater than the formation rate in the n-type silicon.     

响应面方法的硅刻蚀工艺优化分析（英）

利用响应面分析方法优化了用于压力传感器硅敏感芯体的刻蚀操作条件。主要考虑了温度、KOH浓度和腐蚀时间三个操作参数,将它们的范围分别设定为40~60 ℃,0.4~0.48 mol/L 和 5~12.5 h,并设定各向异性腐蚀速率为响应值。通过建立二次方模型,分析这些参数的单独影响以及多个操作条件之间对腐蚀速率的相互交叠作用。分析结果表明:模型可以精确预测99%的响应值,相比于腐蚀时间,溶液浓度和工作温度对刻蚀速率的影响更为明显。     

Patterning and modification of PDMS surface through laser micromachining of silicon masters and molding

We describe preparation of micro patterned PDMS sample surfaces and their chemical modification for the purposes of increased hydrophobicity. The process includes ablation of micrometer sized patterns on a silicon master by pulsed radiation from a Nd:YAG laser, transfer of the patterns to PDMS through molding, and chemical modification of the topmost surface layers of the polymer sample by further laser irradiation and UV/ozone treatment. The samples were characterized by XPS, FTIR, contact angle measurements, optical microscopy and SEM. The study shows the feasibility of the method to manufacture regular patterns with micron-sized cylindrical pillars and to control surface composition. In the absence of chemical modification of the surfaces due to preparation, we compare the effect of increased roughness on the contact angle with theoretically predicted values. Samples with patterned and chemically modified surfaces due to UV/ozone treatment show reduced hydrophobicity. PACS 52.38.Mf; 81.65.Cf; 81.05.Lg     

Computing surface dipoles and potentials of self-assembled monolayers from first principles

We discuss methodological aspects of first principles calculations of surface dipoles and potentials in general, and surface-adsorbed self-assembled monolayers in particular, using density functional theory with a slab/super-cell approach. We show that calculations involving asymmetric slabs may yield highly erroneous results for the surface dipole and demonstrated the efficacy of a simple dipole correction scheme. We explain the importance of the electrostatic dipole distribution, show how to compute it, and establish conditions for the equivalence of calculations for the dipole distribution and the electrostatic potential distribution.     

自组生长的硅纳米管的稳定性研究

文章作者的研究小组在世界上首次合成自组生长的硅纳米管（SiNTs）后,对它的稳定性研究又获得进展.采用5wt%的HF酸对自组生长的硅纳米管的稳定性进行了研究,研究表明HF酸可以去除硅纳米管的氧化物外层,只剩下晶体硅纳米管,说明所得到的硅纳米管是一种稳定结构,因而使其应用研究开发成为可能.研究表明,硅纳米管的稳定性与其生长形成过程密切相关。     

自组生长的硅纳米管的稳定性研究

文章作者的研究小组在世界上首次合成自组生长的硅纳米管（SiNTs）后,对它的稳定性研究又获得进展.采用5wt%的HF酸对自组生长的硅纳米管的稳定性进行了研究,研究表明HF酸可以去除硅纳米管的氧化物外层,只剩下晶体硅纳米管,说明所得到的硅纳米管是一种稳定结构,因而使其应用研究开发成为可能.研究表明,硅纳米管的稳定性与其生长形成过程密切相关.     

Tribological behaviors of self-assembled 3-aminopropyltriethoxysilane films on silicon

3-Aminopropyltriethoxysilane (APTES) thin films were prepared on the hydroxylated silicon substrate by a self-assembling process from formulated solution. Chemical compositions of the films were detected by X-ray photoelectron spectrometry (XPS). The thickness of the films was determined with an ellipsometer, while the morphologies of the original and worn surfaces of the samples were analyzed by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The tribological properties of APTES thin films sliding against GCr15 steel ball were evaluated on a UMT-2MT reciprocating friction and wear tester. It was found that the macroscopic friction coefficients for coating times more than 1 h ranged from 0.177 to 0.3 whereas the value for short coating time was as high as 0.8. It was also found that the tribological behaviors of APTES films were sensitive to normal load and sliding velocity. SEM observation of the morphologies of worn surfaces indicates that the wear of silicon is characteristic of brittle fracture and severe abrasion. Differently, abrasion and micro-crack dominate the wear of APTES–SAM. The superior friction reduction and wear resistance of APTES films compared to the silicon substrate are attributed to good adhesion of the films to the substrate.     

两种常用碳化硅反射镜基底表面改性的研究

利用霍尔离子源辅助电子束蒸发方法,分别在反应烧结碳化硅(RB-SiC)和常压烧结碳化硅(Sintered SiC,S-SiC)基底材料上制备了Si改性膜层,并进行了相关性能测试和分析。经过表面改性,两种基底的表面粗糙度(rms)大幅地降低,镀银后的反射率有较大地提高,基底表面光学质量已满足工程应用要求。在相同工艺条件下,S-SiC基底改性后效果好于RB-SiC基底的情况,主要是因为Si膜在两种基底表面生长情况不同所致。     

Hybrid surface from self-assembled layer and its effect on protein adsorption

We synthesized hybrid self-assembled monolayer (SAM) with short chain hydrophobic and hydrophilic groups on the same molecule. The physical characteristics such as surface roughness and surface energy of the synthesized hybrid SAM were compared with mono SAMs of amine, octyl and mixed amine-octyl SAM. We also compared the response of the surfaces towards adsorption of bovine serum albumin (BSA) using quartz crystal microbalance (QCM). We determined adsorbed amount (Γ) of BSA on the various surfaces from its various bulk concentrations. It follows the Langmuir adsorption isotherm in the concentration range of our study. The strength of adsorbed protein was characterized from the dissipation factor (ΔD). The highest ΔD value of adsorbed BSA was observed for the adsorption on hybrid surface. The arrangement of BSA on hybrid surface such that it leaded to soft layer, corresponded to the highest ΔD value. These findings suggest that the hybrid surface is a potential surface modifying agent of biomaterials.     

Anchoring of alkyl chain molecules on oxide surface using silicon alkoxide

Chemical states of the interfaces between octadecyl-triethoxy-silane (ODTS) molecules and sapphire surface were measured by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) using synchrotron soft X-rays. The nearly self-assembled monolayer of ODTS was formed on the sapphire surface. For XPS and NEXAFS measurements, it was elucidated that the chemical bond between silicon alkoxide in ODTS and the surface was formed, and the alkane chain of ODTS locates upper side on the surface. As a result, it was elucidated that the silicon alkoxide is a good anchor for the immobilization of organic molecules on oxides.     

Synthesis and surface characterization of alkylthioacetyl-capped self-assembled monolayers on gold surface

A novel alkylthioacetyl-capped hydroxyethyl methacrylate monomer and its corresponding homopolymer have been synthesized and characterized. Direct chemisorption of these moieties have been carried out on gold-coated substrate and found to form a strong surface bonding. The surface coverage and the properties of the resultant self-assembled layers have been investigated by multiple surface characterization techniques (i.e. ellipsometry, GA-FTIR, XPS, AFM, and contact angle measurements). These analyses have all confirmed the occurrence of complete chemisorption reactions with typical n-alkanethiol self-assembled characteristics.     

Effect of surface modification by thermally oxidization and HF etching on UV photoluminescence emission of porous silicon

Photoluminescence of porous silicon (PS) is instable due perhaps to the nanostructure modification in air. The controllable structure modification processes on the as-prepared PS were conducted by thermal oxidization and/or HF etching. The PL spectra taken from thermally oxidized PS showed a stable photoluminescence emission of 355 nm. The photoluminescence emission taken from both of PS and oxidized porous silicon (OPS) samples etched with HF were instable, which can be reversibly recovered by the HF etching procedure. The mechanism of UV photoluminescence is discussed and attributed to the transformation of luminescence centers from oxygen deficient defects to the oxygen excess defects in the thermal oxidized PS sample and surface absorbed silanol groups on PS samples during the chemical etched procedure.