Metal oxide semiconductor characterization

Palmour, J. W., H. S. Kong, and R. F. Davis, Characterization of Device Parameters in High-Temperature Metal-Oxide-Semiconductor Field-Effect Transistors in fi-SiC Thin Films, J. of Applied Physics, Vol. 64, No. 4, August 15, 1988, pp. 2168-2177. 

There are, however, several fields of current research in which a corresponding level of understanding would be of interest also for large molecular adsorbates. For example, adsorbate-substrate interactions are relevant in the general areas of biocompatibility [51] and chemical sensors [52]. The requirement of dye-sensitization of metal oxide semiconductors also makes this an important aspect of many molecular photovoltaic devices. In fact, a good interfacial contact between dye and substrate, characterized by long-term stability and intimate electric contact, is vital for the efficiency of e.g. the dye-sensitized solar cells which have been at the center of our attention for the last five years. 

D. Schmidt, H. Niimi, B. J. Hinds, D. E. Aspnes, and G. Lucovsky, New approach to preparing smooth Si(lOO) surfaces Characterization hy spectroellipsometry and validation of Si/Si02 interface properties in metal-oxide-semiconductor devices, J. Vac. Sci. Technol. B14(4), 2812, 1996. 

We demonstrate the material and device parameters that need to be determined by way of the metal-oxide-semiconductor tield-effect transistor (MOSFET) in Fig.l. It is meant to be a generic semiconductor device which incorporates many of the device parameters that need to be characterized. Other devices incorporate many of the same parameters and may introduce a few new ones. We will use the MOSFET as an example to point out the characterization techniques typically used to measure these parameters. 

Kou, C.T., and T.R. Lion. 1996. Characterization of metal-oxide-semiconductor field-effect transistor (MOSFET) for polypyrrole and poly(N-alkylpyrrole)s prepared by electrochemical synthesis. Synth Met 82 167. 

Template-based synthesis involves the fabrication of the desired material within the pores or channels of a nanoporous template. A template may be defined as a central structure within which a network forms in such a way that removal of the template creates a filled cavity with morphological and/or stereochemical features related to those of the template. Track-etch membranes, porous alumina, and other nanoporous structures have been characterized as templates. Electrochemical and electroless depositions, chemical polymerization, sol-gel deposition, and chemical vapor deposition have been presented as major template synthetic strategies. Template-based synthesis can be used to prepare nanostructures of conductive polymers, metals, metal oxides, semiconductors, carbons, and other solid matter... 

In recent development of the semiconductor industries, thermal oxide film thickness of less than 5 nm has been used in semiconductor devices such as metal-oxide-semiconductor (MOS) structures. Thickness of less than 5 nm is almost near the thickness of a native oxide film on the surface of silicon wafer. Therefore the characterization of ultra thin native oxide film is important in the semiconductor process technology. The secondary electron microscopy (SEM), the scanning Auger electron microscopy (SAM), the atomic force microscopy (AFM) and the X-ray photoelectron spectroscopy (XPS) might be the useful characterization method for the surface of the silicon wafers. 

Comini, E., Baratto, C., Faglia, G., Ferroni, M., Vomiero, A., and Sberveg-lieri, G. [2009] Quasi-one dimensional metal oxide semiconductors Preparation, characterization and application as chemical sensors. Prog. 

Comini E, Baratto C, Faglia G, Ferroni M, Vomiero A, Sbtaveglieri G (2009) Quasi one dimensionale metal oxide semiconductors preparation, characterization and application as chemical sensors. Prog Mat Sci 54 1-67... 

The nature of the electron accepting conduction band of these metal oxide semiconductors can be characterized by the density of states (DOS). The DOS, g E), is related to the effective mass, m, by the following equation ... 

Absorption. Absorption, the attenuation of a beam through a transparent medium, can be characterized by an absorption coefficient. For thin films, such as those of optical oxides, absorption is very small and can usually be ignored. In metallic or semiconductor coatings however, absorption is a major factor. 

We shall briefly discuss the electrical properties of the metal oxides. Thermal conductivity, electrical conductivity, the Seebeck effect, and the Hall effect are some of the electron transport properties of solids that characterize the nature of the charge carriers. On the basis of electrical properties, the solid materials may be classified into metals, semiconductors, and insulators as shown in Figure 2.1. The range of electronic structures of oxides is very wide and hence they can be classified into two categories, nontransition metal oxides and transition metal oxides. In nontransition metal oxides, the cation valence orbitals are of s or p type, whereas the cation valence orbitals are of d type in transition metal oxides. A useful starting point in describing the structures of the metal oxides is the ionic model.5 Ionic crystals are formed between highly electropositive... 

The passive film is composed of metal oxides which can be semiconductors or insulators. Then, the electron levels in the passive film are characterized by the conduction and valence bands. Here, we need to examine whether the band model can apply to a thin passive oxide film whose thickness is in the range of nanometers. The passive film has a two-dimensional periodic lattice structure on... 

Since the first synthesis of mesoporous materials MCM-41 at Mobile Coporation,1 most work carried out in this area has focused on the preparation, characterization and applications of silica-based compounds. Recently, the synthesis of metal oxide-based mesostructured materials has attracted research attention due to their catalytic, electric, magnetic and optical properties.2 5 Although metal sulfides have found widespread applications as semiconductors, electro-optical materials and catalysts, to just name a few, only a few attempts have been reported on the synthesis of metal sulfide-based mesostructured materials. Thus far, mesostructured tin sulfides have proven to be most synthetically accessible in aqueous solution at ambient temperatures.6-7 Physical property studies showed that such materials may have potential to be used as semiconducting liquid crystals in electro-optical displays and chemical sensing applications. In addition, mesostructured thiogermanates8-10 and zinc sulfide with textured mesoporosity after surfactant removal11 have been prepared under hydrothermal conditions. 

Molecular self-assembly is a technique to form highly ordered, closely packed mono-layers on various substrates via a spontaneous chemisorption process at the interface.11,12 Earlier research done in this field includes the self-assembly of fatty acids monolayers on metal oxides,14,15 SAMs of organosilicon derivatives on metal and semiconductor oxides,16,17 and organosulfur SAMs on metal and semiconductor surfaces.18,19 Among the organosulfur SAMs, the most thoroughly investigated and characterized one is alkanethiol SAM formed on Au(l 11) surfaces.12... 

Since the electrode has to be transparent, the electrode material is limited to thin films of metals or semiconductors deposited on a transparent substrate (for example a thin film of tin(IV) oxide or platinum on quartz) or to very fine grids of the electrode material, as shown in Fig. 9.13. The first of these two options is preferable, since the transmission coefficient is uniform and the electrode can be truly planar, and as such can be used as a hydrodynamic electrode, for example. The change in absorbance with time due to one of the reagents or products of the electrode reaction characterizes the mechanism. 

Thin-lilm photoelectrodes are needed in photoelectrocatalytic systems to apply a bias potential, either for the photoelectrode characterization or to facilitate the photocatalytic reactions. However, to be able to present a more comprehensive view on the performance of different materials, our subsequent discussions will focus on particulate semiconductor photocatalysts since the latter have been much more extensively investigated. Their electronic band structure (i.e., both the bandgap energy and the positions of CB and VB) is the key factor to determine whether or not a semiconductor material is suitable for a specific photocatalytic reaction, as will be demonstrated by reviewing a number of selected metal oxides and cou-pled/composite materials based on various semiconductors. 

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