Layer nano-crystalline

The model analytes, which were used to show the sensor performance of the microsystems include carbon monoxide, CO, and methane, CH4. The sensor microsystems were designed for practical applications, such as environmental monitoring, industrial safety applications or household surveillance, which implies that oxygen and water vapors are present under normal operating conditions. In the following, a brief overview of the relevant gas sensor mechanisms focused on nano crystalline tin-oxide thick-film layers will be given. 

Figure 2.3 shows a schematic view of the nano crystalline sensor material. It consists of single-crystalline tin-oxide grains with a typical size of 10 nm and a narrow size distribution [68]. The grains are in loose contact. The lower graph in Fig. 2.3 schematically represents the conduction band of the layer. 

The first device is a circular microhotplate (Sect. 4.1). One important guideline was to implement the microhotplate in CMOS technology with a minimum of post-CMOS micromachining steps. Additionally the hotplate had to be optimized for drop-coating with nano crystalline tin-oxide layers. This microhotplate was cointegrated with circuitry, and the respective monolithic sensor system will be discussed in Sect. 5.1. 

The most recent development which has, in addition, already be applied in industrial scale, is the preparation of superhard nano-crystalline layers by a combined plasma-CVD/PVD method. Two-phase layers of the type neTiN/cBN and neTiN/ aSi3N4 were prepared, where nc denotes nano-erystalline, c cubic, and a amorphous [129-131]. Hardnesses of up to 70GPa were measured. The grain size of the crystalline phases of these materials is of the order of a few nm, whereas the maximum hardnesses are observed at the lower end of grain sizes studied (about 2nm). 

Figure 12. Population density (A) and adhesion area (B) of osteoblast-like MG 63 cells on day 2 after seeding on tissue culture polystyrene dish (TCPS). carbon fibrereinforced carbon composites (CFRC) and CFRC coated with a fullerene layer (CFRC+full). C Growth curves of MG 63 cells on a terpolymer of polytetrafluoroethylene. poljcvinyldifluoride and polypropylene (Ter), terpolymer mixed with 4 wt. % of single-wall carbon nanohorns (SWNH) or 4 wt.% of high crystalline electric arc multi-wall nanotubes (MWNT-A). D Growth curves of MG 63 cells on TCPS. a nanostructured diamond layer (Nano) and a layer with hierarchically organized micro-and nanostructure (Micro-Nano). Mean S.E.M. from 4-12 measurements. ANOVA. Student-Newman-Keuls method. Statistical significance TCPS. CFRC. Ter p<0.05 compared to the values on tissue culture polystyrene, pure CFRC and pure terpolymer [23].

Suitable coatings with a very good adherence were deposited onto Cu substrate. Temperatures of minimum 70°C and current densities of 1 - 1.5 A/ dm2 afford optimum coatings. The deposit entirely covers the metallic copper substrate, with a very good uniformity. Usually metallic grey layers are formed, with a micro/ nano-crystalline structure. 

D layered compounds as well. A related method for the synthesis of WS2 nanotubes is to first synthesize crystalline and long W18049 nanowhiskers, and subsequently sulfidize these nano whiskers (10,31). This method yields large amounts of very long (30 (t) WS2 nanotubes, often with nonclosed caps. 

Several synthetic methods for the preparation of semiconductor nanoparticles have been reported. Colloidal and organometallic routes have probably been identified as the two major methods in use [11-16], although nano dimensional particles have been also synthesized in confined matrices such as zeolites [17], layered solids [18], molecular sieves [19,20], vesicles/micelles [21,22], gels [23,24], and polymers [25]. An ideal synthetic route should produce nanoparticles which are pure, crystalline, reasonably monodisperse and have a surface which is independently derivatized. 

Last, but by no means least, reference should be made to the use of proteins in nano-fabrication [492]. One approach is illustrated by the fabrication of a 1-nm-thick metal film with 15-nm-diameters holes, periodically arranged on a triangular protein lattice [493]. Advantage was taken of the 10-nm-thick, uniformly porous surface (or S) layer of the crystalline protein obtained from the thermophilic bacterium Sulfolobus acidocaldarius. The protein was adsorbed from a dilute solution onto a molecularly smooth carbon-film surface, metal coated by evaporation, and ion milled to give spatial ordering of holes with the same nanometer periodicity as the protein lattice [493]. 

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