界面微分电容法单晶硅表面单分子膜质量的检测

有机嫁接;分析;界面微分电容法单晶硅表面单分子膜质量的检测     

醇类在Si-H表面形成单分子膜的特性

以界面电容分析法为主并结合XPS、AFM技术研究了醇类分子在Si(111)-H表面上形成的有机单分子膜的特性。并探讨了嫁接反应中影响单分子膜特性的某些因素和单分子膜的稳定性及其对硅表面氧化的钝化作用。在所选择的反应条件下，不同链长醇分子修饰的硅表面上，嫁接分子所占体积分数约为80％，平带电位约为-1．00V(vs.SSE)。研究表明，这类膜稳定性和对硅表面氧化的钝化作用非常有限。     

有机分子修饰硅表面*

硅作为一种重要的半导体材料,在微电子领域发挥着极其重要的作用。有机分子修饰硅表面是近年来硅表面化学领域的一个研究热点,引起了研究者的广泛重视。以共价键嫁接在硅表面的有机单分子层能形成稳定、高质量的杂化连接,将赋予传统的硅材料更多新的功能,具有许多其它表面难以比拟的优点。本文针对有机分子修饰硅表面的方法、单层膜的表征和应用,对近年来的最新研究进展进行了综述,并对该方向的今后的发展进行了展望。     

硅表面嫁接有机单分子膜的研究近况

由于在微电子、化学 /生物化学传感器、纳米技术及太阳能等领域具有潜在的应用价值 ,通过 Si— C键在硅表面上直接嫁接有机单分子膜 ,已成为近几年新开展的研究热点 .对这一研究领域进行了概要综述     

硅表面有机单分子膜的新表征方法──界面微分电容测量法

提出一种表征硅表面有机单分子膜的新方法界面微分电容测量法.通过对新制备的H-Si(111)表面和一系列烯烃分子修饰的硅表面/电解液界面的微分电容的研究,建立了硅表面有机膜结构和性质与界面电容之间的联系.实践证明这是一个简便、快速和有效的实验技术,为硅表面化学修饰与功能化研究提供了一个非常有力的工具.     

介孔分子筛在生物酶固定化中的应用

综述了MCM-48和SBA-15等新型介孔分子筛用生物酶固定化载体研究的新进展。介孔分子筛由于拥有巨大的比表面积(~1000m2/g)、纳米尺寸孔道(2~50m)和较大的孔容(~1.0 cm3/g),因此以分子筛为载体利用物理吸附制备的固定化酶呈现出高的催化活性,但固定化酶操作稳定性较低,在使用过程中部分酶分子发生了脱落,其原因是分子筛表面自由的硅羟基通过物理吸附或氢键作用固定酶分子。借助介孔分子筛自身的自由硅羟基在表面嫁接-COOH、-NH2、-CH=CH2等有机官能团来构筑酶固定化的微环境,改善酶分子和载体的亲和作用,提高固定化酶的活性。目前,利用有机官能团功能化介孔分子筛固定化酶是研究发展的趋势。     

聚苯胺类/n-Si(111)单晶硅复合电极:制备与光电性质

在过氧化月桂酰作用下,于n-Si(111)型单晶硅表面上分别嫁接苯胺及烷基取代苯胺,进而实现晶体硅表面上聚苯胺和烷基取代聚苯胺的原位聚合,制备得到了系列聚苯胺(或烷基取代聚苯胺)/n-Si(111)单晶硅复合电极。此外,对上述合成电极表面苯胺链进行磺化,得到系列磺酸基化的单晶硅复合电极。电化学研究结果显示,聚苯胺直接嫁接于晶体硅表面所得到的复合电极光电转化效率最高,苯胺聚合链通过碳碳双键桥连于单晶硅表面所得到复合电极的光电转化效率高于通过碳碳单键桥连得到的复合电极,但其光电转化效率低于苯胺聚合链直接桥连于晶体硅表面而得到的复合电极。另外发现,苯环磺酸基化有利于提高复合电极的光电转化效率。     

聚苯胺类/n-Si(111)单晶硅复合电极:制备与光电性质

在过氧化月桂酰作用下,于n-Si(111)型单晶硅表面上分别嫁接苯胺及烷基取代苯胺,进而实现晶体硅表面上聚苯胺和烷基取代聚苯胺的原位聚合,制备得到了系列聚苯胺(或烷基取代聚苯胺)/n-Si(111)单晶硅复合电极。此外,对上述合成电极表面苯胺链进行磺化,得到系列磺酸基化的单晶硅复合电极。电化学研究结果显示,聚苯胺直接嫁接于晶体硅表面所得到的复合电极光电转化效率最高,苯胺聚合链通过碳碳双键桥连于单晶硅表面所得到复合电极的光电转化效率高于通过碳碳单键桥连得到的复合电极,但其光电转化效率低于苯胺聚合链直接桥连于晶体硅表面而得到的复合电极。另外发现,苯环磺酸基化有利于提高复合电极的光电转化效率。     

通过硅烷偶联剂在硅和铟锡氧化物(ITO)表面嫁接寡聚芴分子

通过硅烷偶联剂γ-氨丙基三乙氧基硅烷(3-aminopropyl-triethoxysilane,APTES)的“分子桥梁”作用,采用两种不同的方法,把修饰后的寡聚芴分子键联到硅表面和铟锡氧化物(ITO)表面上。X射线光电子能谱(XPS)、原子力显微镜(AFM)和循环伏安(CV)方法等的表征证实了通过硅烷偶联剂在硅表面和ITO表面嫁接寡聚芴分子可行性。     

多孔硅的光电化学特性研究

研究了多孔硅的光电化学特性和溶液中的光致电荷转移机一，由Ｐ型单晶硅制备的多孔硅具有Ｐ型半导体的光电性质，且光电流响应高于单晶硅，由于多孔硅表面态能级对光致电荷的陷阱作用，多孔硅呈现了独特的光电流响应和光致电荷转移性质。     

A non-oxidative approach toward chemically and electrochemically functionalizing Si(111)

A general method for the non-oxidative functionalization of single-crystal silicon(111) surfaces is described. The silicon surface is fully acetylenylated using two-step chlorination/alkylation chemistry. A benzoquinone-masked primary amine is attached to this surface via Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition ("click" chemistry). The benzoquinone is electrochemically reduced, resulting in quantitative cleavage of the molecule and exposing the amine terminus. Molecules presenting a carboxylic acid have been immobilized to the exposed amine sites. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and contact angle goniometry were utilized to characterize and quantitate each step in the functionalization process. This work represents a strategy for providing a general platform that can incorporate organic and biological molecules on Si(111) with minimal oxidation of the silicon surface.     

The molecular orientation of para-sexiphenyl on Cu(110) and Cu(110) p(2x1)O.

Controlling the molecular growth of organic semiconductors is an important issue to optimize the performance of organic devices. Conjugated molecules, used as building blocks, have an anisotropic shape and also anisotropic physical properties like charge transport or luminescence. The main challenge is to grow highly crystalline layers with molecules of defined orientation. The higher the crystallinity, the closer these properties reach their full intrinsic potential, while the orientation determines the physical properties of the film. Herein we show that the molecular orientation and growth can be steered by the surface chemistry, which tunes the molecule-substrate interaction. In addition, the oxygen reconstruction of the surface, demonstrates the flexibility of the organic molecules to adopt a given surface corrugation and their unique possibility to release stress by tilting.     

Mechanically induced generation of highly reactive excited-state oxygen molecules in cluster scattering

Molecular electronic excitation in (O(2))(n) clusters induced by mechanical collisions via the "chemistry with a hammer" is investigated by a combination of molecular dynamics simulations and quantum chemistry calculations. Complete active space self-consistent field augmented with triple-zeta polarizable basis set quantum chemistry calculations of a compressed (O(2))(2) cluster model in various configurations reveal the emergence of possible pathways for the generation of electronically excited singlet O(2) molecules upon cluster compression and vibrational excitation, due to electronic curve-crossing and spin-orbit coupling. Extrapolation of the model (O(2))(2) results to larger clusters suggests a dramatic increase in the population of electronically excited O(2) products, and may account for the recently observed cluster-catalyzed oxidation of silicon surfaces, via singlet oxygen generation induced by cluster impact, followed by surface reaction of highly reactive singlet O(2) molecules. Extensive molecular dynamics simulations of (O(2))(n) clusters colliding onto a hot surface indeed reveal that cluster compression is sufficient under typical experimental conditions for nonadiabatic transitions to occur. This work highlights the importance of nonadiabatic effects in the "chemistry with a hammer."     

Highly stable organic monolayers for reacting silicon with further functionalities: the effect of the C-C bond nearest the silicon surface

Crystalline Si(111) surfaces have been alkylated in a two-step chlorination/alkylation process using various organic molecules having similar backbones but differing in their C-C bond closest to the silicon surface (i.e., C-C vs C=C vs C[triple bond]C bonds). X-ray photoelectron spectroscopic (XPS) data show that functionalization of silicon surfaces with propenyl magnesium bromide (CH3-CH=CH-MgBr) organic molecules gives nearly full coverage of the silicon atop sites, as on methyl- and propynyl-terminated silicon surfaces. Propenyl-terminated silicon surface shows less surface oxidation and is more robust against solvent attacks when compared to methyl- and propynyl-terminated silicon surfaces. We also show a secondary functionalization process of propenyl-terminated silicon surface with 4'-[3-Trifluoromethyl-3H-diazirin-3-yl]-benzoic acid N-hydroxysuccinimide ester [TDBA-OSu] cross-linker. The Si-CH=CH-CH3 surfaces thus offer a means of attaching a variety of chemical moieties to a silicon surface through a short linking group, enabling applications in molecular electronics, energy conversion, catalysis, and sensing.     

Effects of surface chemical composition on the early growth stages of alpha-sexithienyl films on silicon oxide substrates

In organic field effect transistors, charge transport is confined to a narrow region next to the organic/dielectric interface. It is thus extremely important to determine the morphology and the molecular arrangement of the organic films at their early growth stages. On a substrate of technological interest, such as thermally grown silicon oxide, it has been recently found that alpha-sexithienyl aggregates made of flat-lying molecules can simultaneously nucleate besides islands made of molecules standing vertical. In this paper, we investigate the effects due to variations in surface chemical composition on alpha-sexithienyl ultrathin film formation. Flat-lying molecules are no longer detected when Si-OH groups present at the surface are chemically removed but also when the Si-OH or Si-H group density is maximized. This gives evidence that variations in the surface chemical composition can largely affect the nucleation and growth processes of organic/dielectric interfaces. We hypothesize that isolated OH groups can interact with alpha-sexithienyl molecules and anchor them down flat with respect to the surface.     

Self-assembled and self-sorted array of chemically active beads for analytical and biochemical screening

A technique for generating a general screening platform consisting of dots of immobilized beads on silicon has been developed via self-sorting and -assembly of different kinds of beads. The dots are defined by a teflon-like film, which due to its hydrophobic characteristics also prevents cross-contamination of liquid from different dots. To enable functionalization of individual dots with different target molecules simultaneously a new way of microcontact printing has been explored where different target solutions are printed in parallel using one stamp. In order to show that this platform can be designed for both biochemical assays and organic chemistry, streptavidin-, amino- and hydroxy-functionalized beads have been self-sorted and -assembled both on separate and common platforms. The self-sorting and -arrangement are based on surface chemistry only, which has not previously been reported. Beads of different sizes and material have successfully been immobilized in line patterns as narrow as 5 mum. Besides silicon, quartz and polyethylene have also been used as substrates.     

Molecular structure of organic micro-crystals characterised by atomic force microscopy

In this study we show that the spin-coating technique can be used to prepare micrometer-sized crystals of organic molecules. Hydrophilic silicon wafers were spin-coated with chloroform solutions of rodlike bicyclohexylidene oximes 1–3. Atomic force microscopy images show that well-defined micro-crystals of 1 and 3 deposit on the silicon surface, which can be imaged with molecular resolution. The crystallographic dimensions derived from the atomic force microscope images correspond well with single crystal X-ray diffraction data.     

Functionalization of acetylene-terminated monolayers on Si(100) surfaces: a click chemistry approach

In this article, we report the functionalization of alkyne-terminated alkyl monolayers on Si(100) using "click" chemistry, specifically, the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction of azides with surface-bound alkynes. Covalently immobilized, structurally well-defined acetylene-terminated organic monolayers were prepared from a commercially available terminal diyne species using a one-step hydrosilylation procedure. Subsequent derivatization of the alkyne-terminated monolayers in aqueous environments with representative azide species via a selective, reliable, robust cycloaddition process afforded disubstituted surface-bound [1,2,3]-triazole species. Neither activation procedures nor protection/deprotection steps were required, as is the case with more established grafting approaches for silicon surfaces. Detailed characterization using X-ray photoelectron spectroscopy and X-ray reflectometry demonstrated that the surface acetylenes had reacted in moderate to high yield to give surfaces exposing alkyl chains, oligoether anti-fouling moieties, and functionalized aromatic structures. These results demonstrate that click immobilization offers a versatile, experimentally simple, chemically unambiguous modular approach to producing modified silicon surfaces with organic functionality for applications as diverse as biosensors and molecular electronics.