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Semiconductor Surfaces (semiconductor + surface)
Selected AbstractsLow- and high-frequency C,V characteristics of the contacts formed by sublimation of the nonpolymeric organic compound on p-type Si substratePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 14 2004C. Temirci Abstract The Sn/pyronine- B/p-Si Schottky structures have been obtained by sublimation of the organic compound pyronine- B onto the top of a p-Si surface. Barrier height and ideality factor value of 0.79 eV and 1.13, respectively, for the device have been determined from the forward-bias current,voltage (I,V) characteristics. The interface state density obtained from the forward bias high and low capacitance,voltage characteristics increases exponentially with bias between the midgap and the top of the valance band, from 2.15 × 1010 cm,2 eV,1 at (0.79,Ev) eV to 1.16 × 1012 cm,2 eV,1 at (0.53,Ev) eV. These values have been compared to those of the metal/Si structures in the literature, and it is seen that the presence of the nonreactive organic materials at the inorganic semiconductor and metal interface may obstruct the generation of the interface states at the semiconductor surface that strongly influence the Schottky barrier formation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrochemical CV-profiling of GaNPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2004T. Wolff Abstract A Schottky-like contact is formed by electrolyte, wetting the area of the semiconductor surface delimited by a sealing ring. In reverse bias with common CV technique the concentration of donors and acceptors can be evaluated. Using a newly developed etch procedure, which we call "cyclic oxidation", n- and p- type nitrides can be etched (photo-)electrochemically (PEC) to yield reproducibly etched surfaces with mirror-like surface morphology at high etch rates (,3 ,m/h). Using this new etch procedure, various MOVPE and HVPE grown samples have been characterized by ECV profiling. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Advances in Photoelectrocatalysis with Nanotopographical PhotoelectrodesCHEMPHYSCHEM, Issue 8 2010A. G. Muñoz Dr. Abstract The design of photoelectrodes for high efficiency solar fuel energy conversion devices is based on the search for adequate surface conditioning to achieve efficient light harvesting, stability, minimized surface recombination losses and high electron-transfer rates at the electrolyte interface. An overview on established and novel approaches is given. A recent viable solution is provided by electroplating of nanoscale catalytic metals on passivated semiconductor surfaces, thereby forming reactive centers and avoiding contact between the semiconductor surface and the electrolyte. At these nano-dimensioned Schottky-type junctions, light-induced excess minority carriers are scavenged and transferred to the electrolyte. Various possible device configurations are outlined and envisaged systems for hydrogen or oxygen evolution and carbon dioxide reduction are presented. The role of ultrathin passivating films is emphasized and methods to fabricate open as well as compact conformal films are described. [source] Probing Biomolecular Interactions at Conductive and Semiconductive Surfaces by Impedance Spectroscopy: Routes to Impedimetric Immunosensors, DNA-Sensors, and Enzyme BiosensorsELECTROANALYSIS, Issue 11 2003Eugenii Katz Abstract Impedance spectroscopy is a rapidly developing electrochemical technique for the characterization of biomaterial-functionalized electrodes and biocatalytic transformations at electrode surfaces, and specifically for the transduction of biosensing events at electrodes or field-effect transistor devices. The immobilization of biomaterials, e.g., enzymes, antigens/antibodies or DNA on electrodes or semiconductor surfaces alters the capacitance and interfacial electron transfer resistance of the conductive or semiconductive electrodes. Impedance spectroscopy allows analysis of interfacial changes originating from biorecognition events at electrode surfaces. Kinetics and mechanisms of electron transfer processes corresponding to biocatalytic reactions occurring at modified electrodes can be also derived from Faradaic impedance spectroscopy. Different immunosensors that use impedance measurements for the transduction of antigen-antibody complex formation on electronic transducers were developed. Similarly, DNA biosensors using impedance measurements as readout signals were developed. Amplified detection of the analyte DNA using Faradaic impedance spectroscopy was accomplished by the coupling of functionalized liposomes or by the association of biocatalytic conjugates to the sensing interface providing biocatalyzed precipitation of an insoluble product on the electrodes. The amplified detections of viral DNA and single-base mismatches in DNA were accomplished by similar methods. The changes of interfacial features of gate surfaces of field-effect transistors (FET) upon the formation of antigen-antibody complexes or assembly of protein arrays were probed by impedance measurements and specifically by transconductance measurements. Impedance spectroscopy was also applied to characterize enzyme-based biosensors. The reconstitution of apo-enzymes on cofactor-functionalized electrodes and the formation of cofactor-enzyme affinity complexes on electrodes were probed by Faradaic impedance spectroscopy. Also biocatalyzed reactions occurring on electrode surfaces were analyzed by impedance spectroscopy. The theoretical background of the different methods and their practical applications in analytical procedures were outlined in this article. [source] Versatile vacuum chamber for in situ surface X-ray scattering studiesJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2008Dina Carbone A compact portable vacuum-compatible chamber designed for surface X-ray scattering measurements on beamline ID01 of the European Synchrotron Radiation Facility, Grenoble, is described. The chamber is versatile and can be used for in situ investigation of various systems, such as surfaces, nanostructures, thin films etc., using a variety of X-ray-based techniques such as reflectivity, grazing-incidence small-angle scattering and diffraction. It has been conceived for the study of morphology and structure of semiconductor surfaces during ion beam erosion, but it is also used for the study of surface oxidation or thin film growth under ultra-high-vacuum conditions. Coherent X-ray beam experiments are also possible. The chamber is described in detail, and examples of its use are given. [source] Selection and mass spectrometry characterization of peptides targeting semiconductor surfacesBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2009Elias Estephan Abstract We report on elaboration of 12-mer peptides that reveal specific recognition for the following semiconductor (SC) surfaces: GaAs(100), InAs(100), GaN(0001), ZnSe(100), ZnTe(100), GaAs(111)A, GaSb(100), CdSe(100). A M13 bacteriophage library was used to screen 109 different 12-mer peptides against these substrates to finally isolate, in maximum six amplification cycles, peptides that bind to the target surfaces. The specific peptides for the InAs and ZnSe surfaces were obtained. Contrary, for the other SC surfaces several peptides with high affinities have been isolated. Aiming for a better specificity, when the phage display has been conducted through six cycles, the screening procedure got dominated by a phage present in the M13 bacteriophage library and the SVSVGMKPSPRP peptide has been selected for different SCs. The high amplification potential of this phage has been observed previously with different targets. Thus, precaution should be undertaken in defining adhesion peptides with the phage display technique and real affinity of the obtained biolinkers should be studied with other methods. We employed mass spectrometry (MALDI-TOF/TOF) to demonstrate the preferential attachment (or not) of the SVSVGMKPSPRP peptide to the different SC surfaces. This allows us to define a realistic selection of the expressed peptides presenting affinity for the studied eight SC surfaces. We demonstrate that with increasing the dielectric constants of the employed solvents, adhesion of the SVSVGMKPSPRP peptide onto GaN(0001) is hindered. Biotechnol. Bioeng. 2009; 104: 1121,1131. © 2009 Wiley Periodicals, Inc. [source] Advances in Photoelectrocatalysis with Nanotopographical PhotoelectrodesCHEMPHYSCHEM, Issue 8 2010A. G. Muñoz Dr. Abstract The design of photoelectrodes for high efficiency solar fuel energy conversion devices is based on the search for adequate surface conditioning to achieve efficient light harvesting, stability, minimized surface recombination losses and high electron-transfer rates at the electrolyte interface. An overview on established and novel approaches is given. A recent viable solution is provided by electroplating of nanoscale catalytic metals on passivated semiconductor surfaces, thereby forming reactive centers and avoiding contact between the semiconductor surface and the electrolyte. At these nano-dimensioned Schottky-type junctions, light-induced excess minority carriers are scavenged and transferred to the electrolyte. Various possible device configurations are outlined and envisaged systems for hydrogen or oxygen evolution and carbon dioxide reduction are presented. The role of ultrathin passivating films is emphasized and methods to fabricate open as well as compact conformal films are described. [source] | |||||||||||||