Germanium surface morphology

A rough surface presents more surface area on which physical absorption can occur. More protein might have been expected to adsorb on the copper and nickel films as compared to germanium due to the granular nature of these films. Only at pH 7.4 did copper and nickel accumulate more albumin than did germanium, however. Despite the macroscopic differences in surface morphology copper and nickel appeared to accumulate the same quantity of albumin. 

As shown in Fig. 9.18, there is a quite uniform deposition of copper on both n-and p- germanium substrates. However, these images clearly show that larger particles of Cu are produced on n- germanium substrates in comparismi to that of the p-Ge, leading in this way to a different surface morphology. The differences in the surface morphology of these two samples were attributed to the presence of different dopants (impurities) in the n- and p- Ge substrates [12]. 

The surface morphology of deposited copper onto germanium substrates is as well very much influenced by pH [12]. As shown by the SEM images in Figs. 9.18 and 9.19, the surface morphology of the deposited copper from alkaline solutions (pH 14) is quite different than that obtained from the acidic Cu (II) solutions (pH 2). 

Although not of primary concern in this review a number of experimenters have developed information on the oxidation rates of amorphous and polycrystalline films of germanium. While there is some disagreement on the role of porosity in the oxidation rate of such films, (17,18) the kinetics of the reaction appear to be strongly dependent on the morphology of the films and the ambient atmospheres to which they are initially exposed. Based on that information it would appear that implant areas should be annealed in situ or at least removed from vacuum to a controlled environment until final surface preparation is affected. This is particularly true of photovoltaic and photo-conductive devices where the uniformity of oxide, interface moisture content, uptake of carbon complexes etc. strongly affect the surface recombination currents and hence the device performance (77). 

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