Reaction with atomic hydrogen

Copper and nickel are also common contaminants in Si and can often be introduced during annealing treatments. Both of these impurities are extremely rapid diffusers and cannot be retained in electrically active form even by rapid quenching of diffused samples (Weber, 1983). Quite often, complexes involving Cu or Fe impurities are observed by DLTS in heat-treated Si. All of these centers are hole traps, with Cu giving rise to levels at Ev + 0.20 eV, Ev + 0.35 eV and Ev + 0.53 eV, whereas Ni is related to levels at Ev + 0.18 eV, Ev + 0.21 eV and Ev + 0.33 eV. All of these levels are passivated by reaction with atomic hydrogen (Pearton and Tavendale, 1983), and are restored by annealing at 400°C. 

A wide variety of process-induced defects in Si are passivated by reaction with atomic hydrogen. Examples of process steps in which electrically active defects may be introduced include reactive ion etching (RIE), sputter etching, laser annealing, ion implantation, thermal quenching and any form of irradiation with photons or particles wih energies above the threshold value for atomic displacement. In this section we will discuss the interaction of atomic hydrogen with the various defects introduced by these procedures. 

VII. REACTION WITH FREE RADICALS A. Reaction with Atomic Hydrogen... 

Reaction with atomic hydrogen 1.6.2.1.1 CAsFjIj CFjAsIj... 

In addition to the formation of normal isotopologues, deuterated species can also be formed, as will be discussed later. This result can happen in two ways. First, in addition to association reactions with atomic hydrogen, there are association reactions with atomic deuterium. For example, the iso-topologue CH2DOH can be formed by the following sequence of reactions ... 

From kinetic analyses of these systems. Barker was able to determine the rate constants for the reactions of ethanol and methanol with both OH- and H-radicals. Values of k were equal for each alcohol, with magnitudes of 2.4 x 10 moP liter s for the reactions with atomic hydrogen and 1.0 x 10 moP liter s for those with the OH- radicals. The constants agree well with pulse radiolysis data, and these chemical reactivity studies provide some of the best evidence for the presence of the solvated electron. The original references should be consulted for a detailed description of these results. 

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