A-Gallium -oxide

In some cases a reactive site is needed to initiate desorption. For example, the native oxide on GaAs wafers, typically a gallium oxide, desorbs very abruptly. After considerable study it has been shown that the oxide desorption requires a nucleation step creating holes in the layer. These then expand rapidly as the desorption occurs. The desorption reaction can be nucleated by adsorption of a variety of species on the surface. The desorption temperature also depends somewhat on how the oxide is formed and its thickness. When desorption is nucleation-limited there may be a considerable delay in its onset if it is not significantly superheated. 

Only thallium of the Group III elements is affected by air at room temperature and thalliumflll) oxide is slowly formed. All the elements, however, burn in air when strongly heated and, with the exception of gallium, form the oxide M2O3 gallium forms a mixed oxide of composition GaO. In addition to oxide formation, boron and aluminium react at high temperature with the nitrogen in the air to form nitrides (BN and AIN). 

With gallium arsenide, additional elements, such as Si, S, and Cl, are of interest because of their doping character. Impurity levels on the order of lO cm are encountered with commercial substrates, which can be readily assessed using direct TXRF." VPD-TXRF is not possible in this case because of the lack of a native oxide layer on gallium arsenide. 

Preadsorption of oxygen at 30°C on the surface of a gallium-doped nickel oxide produces, for instance, a considerable increase of the differ-... 

Fig. 25. Differential heats of adsorption of carbon monoxide at 30°C on fresh (A) or oxygenated (B) samples of a gallium-doped nickel oxide. Reprinted from (63) with permission J. Chim. Phys.

Shimizu, K Takamatsu, M Nishi, K Yoshida, H Satsuma, A Tanaka, T Yoshida, S Hattori, T. Alumina-supported gallium oxide catalysts for NO selective reduction Influence of the local structure of surface gallium oxide species on the catalytic activity, J. Phys. Chem., B, 1999, Volume 103, Issue 9, 1542-1549. 

Chemical properties of gallium fall between those of aluminum and indium. It forms mostly the binary and oxo compounds in -i-3 oxidation state. It forms a stable oxide, Ga203 and a relatively volatile suboxide, Ga20. 

The finding of the low-temperature activation of propane on zeolite Ga/HZSM-5 indicates a bifunctional reaction mechanism 179,181. The highly dispersed gallium oxide species in close vicinity to the Bronsted acid sites promote the initial activation of propane. Derouane et al. 179,181 further showed that hydrogen inhibits the activation of propane. This effect was explained by a competitive adsorption of hydrogen on the gallium species or even by a reduction of Ga to Ga species. 

A. The Oxide Fluorides of Boron, Aluminium, Gallium, Indium, and Thallium... 

The chemistry of gallium is very similar to that of aluminum, its congener. Compounds of gallium almost always have a +3 oxidation state. While a few compounds with a +1 and +2 state have been postulated, these are controversial. 

Possible choices of semiconductor material for the SPICE design include gallium arsenide, silicon, and germanium. In the work described here, silicon was chosen as a reflection of its commercial importance, however this choice brings with it materials compatibility issues and surface chemistry complications. Silicon has a native oxide SiC>2 that is typically 2 nm thick which makes an inefficient spin injection tunnel barrier. 

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