The influence of capping layers on pore formation in Ge during ion implantation

• Ion induced porosity in Ge has been investigated with and without a cap layer for two ion species, Ge and Sn, with respect to ion fluence and temperature. Results without a cap are consistent with a previous work in terms of an observed ion fluence and temperature dependence of porosity, but with a clear ion species effect where heavier Sn ions induce porosity at lower temperature (and fluence) than Ge. The effect of a cap layer is to suppress porosity for both Sn and Ge at lower temperatures but in different temperatures and fluence regimes. At room temperature, a cap does not suppress porosity and results in a more organised pore structure under conditions where sputtering of the underlying Ge does not occur. Finally, we observed an interesting effect in which a barrier layer of a-Ge that is denuded of pores formed directly below the cap layer. The thickness of this layer (∼ 8 nm) is largely independent of ion species, fluence, temperature, and cap material, and we suggest that this is due to viscous flow of a-Ge under ion irradiation and wetting of the cap layer to minimize the interfacial free energy.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Nyckelord

porosity

ion implantation

free energy

surface energy

ion beam effects

elemental semiconductors

wetting

germanium

Fysik

Physics

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