Near-surface hydrogen

Greeley J, Mavrikakis M. 2005. Surface and subsurface hydrogen adsorption properties on transition metals and near-surface alloys. J Phys Chem B 109 3460-3471. 

It was proposed (Johnson et al., 1987a) that this local lattice dilation is stabilized by the direct incorporation of hydrogen atoms through the coordinated formation of Si—H bonds. Results from SIMS (Section III. 1) and Raman spectroscopy (following) are consistent with this view. For example, the 60-min deuterium profile in Fig. 7(b) yields an integrated areal density of D in the near-surface peak of —1.7 x 1014 cm-2. The same deuteration conditions applied to this material produced 5 x 10n platelets per cm2 with an average diameter of 7 nm (Ponce et al., 1987). 

The IBM group (Marwick et al., 1987, 1988) studied both the boron and deuterium sites in B-2H complexes using the 2H(3He, pa) and 11B(1H, a) nuclear reactions respectively. The optimum results were obtained with a 30 keV B implant of 1015 cm-2. Figure 8 shows SIMS profiles of the 2H and nB in a typical sample used in their work. A near-surface layer with excess hydrogen remains even after etching off 1000 A of the surface (the figure shows SIMS data from the etched sample). Deeper in, the B and H concentrations are the same within the error in the SIMS calibration, consistent with B—H pair formation. The horizontal lines on the plot show... 

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... 

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