Silicon passivity

Other reverse-bias annealing experiments have been published that can be analyzed in the same way. Tavendale et al. (1985) used 10 ft cm boron-doped silicon passivated by exposure to plasmas containing or 2H. Schottky diodes formed with such specimens showed breakup of BH under heating at 80°C with reverse bias however, there was a persistence of passivation in the first two or three microns that must be attributed to some sort of near-surface reservoir of hydrogen. This effect was absent in an annealing experiment on a junction diode with an -type surface... 

Booij, K. Smedes, R van Weerlee, E.M. 2002, Spiking of performance reference compounds in low density polyediylene and silicone passive water samplers. Chemosphere 46 1157—1161. 

Pan LK, Ee YK, Sun CQ, Yu GQ, Zhang QY, Tay BK (2004) Band-gap expansion, core-level shift, and dielectric suppression of porous silicon passivated by plasma fluorination. J Vac Sci Technol B 22(2) 583-587... 

Kim H, Lee C (2008) Enhancement in the photoluminescence of porous silicon deposited by sputtering an ultrathin silver film. J Korean Phys Soc 53 2562 Kim H, Han B, Choo J, Cho J (2008) Three-dimensional porous silicon particles for use in high-performance lithium secondary batteries. Angew Chem-Int Ed 47 10151 Kim H, Hong C, Lee C (2009) Enhanced photoluminescence from porous silicon passivated with an ultrathin aluminum film. Mater Lett 63 434... 

Yellow brass Admiralty brass Aluminum bronze Red brass Copper Silicon bronze 70-30 cupronickel Nickel (passive)... 

In de-aerated 10sulphuric acid (Fig. 3.45) the active dissolution of the austenitic irons occurs at more noble potentials than that of the ferritic irons due to the ennobling effect of nickel in the matrix. This indicates that the austenitic irons should show lower rates of attack when corroding in the active state such as in dilute mineral acids. The current density maximum in the active region, i.e. the critical current density (/ ii) for the austenitic irons tends to decrease with increasing chromium and silicon content. Also the current densities in the passive region are lower for the austenitic irons... 

As silica is not attacked by any acid other than hydrofluoric it might be expected to act as an effective barrier to attack by any other acid solutions, but in fact, while the high-silicon iron is resistant to attack by most acids, it is corroded relatively severely by hydrochloric, hydrobromic and sulphurous acids. The aggressive character of the two halogen acids may be ascribed to the readiness with which their relatively small anions can penetrate a passive film. 

Nitric acid is also withstood by high-silicon iron. The concentrated acid is believed to reinforce the silica film by the formation of a passive iron oxide... 

As can be seen in Fig. 3.67, the corrosion resistance of amorphous alloys changes with the addition of metalloids, and the beneficial effect of a metaU loid in enhancing corrosion resistance based on passivation decreases in the order phosphorus, carbon, silicon, boron (Fig. 3.72). This is attributed partly to the difference in the speed of accumulation of passivating elements due to active dissolution prior to passivation... 

Cihal, etal presented early data on the effects of chromium, nickel, molybdenum, titanium, niobium and silicon on the passive behaviour of stainless steel. 

Another example of a cold-wall reactor is shown in Fig. 5.9. It uses a hot plate and a conveyor belt for continuous operation at atmospheric pressure. Preheating and cooling zones reduce the possibility of thermal shock. The system is used extensively for high-volume production of silicon-dioxide coatings for semiconductor passivation and interlayer dielectrics. 

A widely used glass is phosphosilicate (PSG), which is used extensively in semiconductor devices as a passivation and planarization coating for silicon wafers. It is deposited by CVD by the reaction of tetraethyl orthosilicate (TEOS) (C2H50)4Si, and trimethylphosphate PO(OCH3)3, in a molecular ratio corresponding to a concentration of 5 to 7% P. Deposition temperature is usually 700°C and pressure is 1 atm. 

The uses of CVD silicon dioxide films are numerous and include insulation between conductive layers, diffusion masks, and ion-implantation masks for the diffusion of doped oxides, passivation against abrasion, scratches, and the penetration of impurities and moisture. Indeed, Si02 has been called the pivotal material of IC s.1 1 Several CVD reactions are presently used in the production of Si02 films, each having somewhat different characteristics. These reactions are described in Ch. 11. 

The concepts and basic approach used in studies of electrical fluctuations in corrosion processes proved to be very successful as well in mechanistic studies of electrode reactions taking place at materials covered by passivating films. A typical example is the electrochemical dissolution of silicon. From an analysis of the noise characteristics of this process, it has been possible to identify many features as well as the conductivity of the nanostructures of porous silicon being formed on the original silicon surface. 

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