Titanium polycrystalline

Darkowski and Cocivera [94] investigated trialkyl- or triarylphosphine tellurides, as low-valent tellurium sources, soluble in organic solvents. They reported the cathodic electrodeposition of thin film CdTe on titanium from a propylene carbonate solution of tri-n-butylphosphine telluride and Cd(II) salt, at about 100 °C. Amorphous, smooth gray films were obtained with thicknesses up to 5.4 p,m. The Te/Cd atomic ratio was seen to depend on applied potential and solution composition with values ranging between 0.63 and 1.1. Polycrystalline, cubic CdTe was obtained upon annealing at 400 C. The as-deposited films could be either p- or n-type, and heat treatment converts p to n (type conversion cf. Sect. 3.3.2). 

Polycrystalline GaN UV detectors have been realized with 15% quantum efficiency [4], This is about 1 /4 of the quantum efficiency obtained by crystalline devices. Available at a fixed price, however, their increased detection range may well compensate their lack in sensitivity. Furthermore, new semiconductor materials with a matching band gap appear as promising candidates for UV detection if the presumption of the crystallinity is given up. Titanium dioxide, zinc sulfide and zinc oxide have to be mentioned. The opto-electronic properties and also low-cost production processes for these compound semiconductors have already been investigated to some extent for solar cell applications [5]. 

In the near future, UV photodiodes made from polycrystalline wide band-gap semiconductors may fill the gap in the market. Although they have a lower sensitivity (photocurrent per area) they promise to have a better merit-rating in terms of photocurrent per sensor costs. The other major drawback of polycrystalline photodiodes, the risetime of micro- to milliseconds, is not relevant for household applications. Fuji Xerox Laboratories in Japan are developing visible-blind UV photodiodes made from polycrystalline GaN [12], while twlux AG in Berlin, Germany is developing visible-blind UV photodiodes made from polycrystalline titanium dioxide [13]. A prototype is shown in Fig. 5.45. 

Vlachopoulos, N., P. Liska, A. J. McEvoy, and M. Gratzel (1987), "Efficient Spectral Sensitization of Polycrystalline Titanium Dioxide Photoelectrodes", Surface-Science 189/190, 823-831. 

The antenna effect as it is found in natural photosynthetic systems is an attractive tool for increasing light absorption of solar cells. Some of the work done on dye sensitization of polycrystalline titanium dioxide shows aspects of antenna behavior [76,83-87]. Most of the problems in the systems where an electron is injected into the semiconductor arise in the regeneration process of... 

In the sol-gel process, ceramic polymer precursors are formed in solution at ambient temperature shaped by casting, film formation, or fiber drawing and then consolidated to furnish dense glasses or polycrystalline ceramics. The most common sol-gel procedures involve alkoxides of silicon, boron, titanium, and aluminum. In alcohol water solution, the alkoxide groups are removed stepwise by hydrolysis under acidic or basic catalysis and... 

Polycrystalline oxide materials, both undoped and doped, have been extensively examined for use as photoanodes. Ti02 electrodes have been prepared by thermal oxidation of a Ti plate in an electric furnace in air at 300-800°C (15-60 min) and in a flame at 1300°C (20 min) [27-30]. XRD analysis of thermally oxidized samples indicates the formation of metallic sub-oxide interstitial compounds, i.e. TiOo+x (x < 0.33) or Ti20i y (0 < y < 0.33) and Ti30 together with rutile Ti02 [27]. The characteristic reflection of metallic titanium decreases in intensity after prolonged oxidation (60 min) at 800° C indicating the presence of a fairly thick oxide layer (10-15 pm). Oxidation at 900°C leads to poor adhesion of the oxide film... 

Fig. 10.3 Colour contrast of human erythrocytes on different solid reflective substrates Al -polycrystalline aluminum Cu - polycrystalline copper Mo - monocrystalline molybdenum Ni - polycrystalline nickel Pt - chemically polished platinum Si(m) - monocrystalline silicon Si(p) - polycrystalline silicon Ti - chemically polished titanium W- monocrystalline tungsten...

Several fiber types have been mentioned so far, and several other types have been neglected that have been worked on over the past few years. Some of those not discussed may become important fibers for reinforcement in the years ahead. To date though, they have not been available in sufficient quantity for thorough evaluation in composite specimens. Included in this group are boron carbide, spinel, polycrystalline alumina and silica, titanium diboride, and miscellaneous silicides and intermetallics. Ten years from now as we look back on the 70s we no doubt will have an entirely different view of some of these materials. 

It should be noted that all above-mentioned results have been obtained using polycrystalline titanium dioxide (anatase, rutile) [49, 51] on the whole, the same regularities are observed during the control experiments with the monocrystalline rutile. When going from poly- to nanocrystalline Ti02 obtained by zol-gel method, the EER spectrum of the oxide substantially changes [53]. 

Vlachopoulos, N., Liska, P., Augustynski, J. and Gratzel M. 1987. Very efficient visible light energy harvesting and conversion by spectral sensitization of high surface area polycrystalline titanium dioxide films. Submitted for publication. 

Polycrystalline Amorphous Epitaxial silicon Carbon fiber Filaments Carbon nanotubes Silicon dioxide Tungsten Silicon nitride Titanium nitride... 

Semiconductor Electrodes 1. The Chemical Vapor Deposition and Application of Polycrystalline n-Type Titanium Dioxide Electrodes to the Photosensitized Electrolysis of Water Comparison of the behavior of CVD and single crystal n-TiCte presented. 229... 

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