Mechanisms of nanodot formation under focused ion beam irradiation in compound semiconductors

Joanna Millunchick

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joannamm@umich.edu

2014 HH Dow

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K. A Grossklaus and J. M Millunchick (2011)

JOURNAL OF APPLIED PHYSICS, 109(1).

We have examined the responses of GaAs, InP, InAs, and AlAs to 30 keVfocused ion beam (FIB) irradiation and applied a unified model thatconsistently explains the observed effects. Nanodots were observed toform on GaAs, InP, and InAs under irradiation at normal incidence, whilenanodots are not observed on AlAs. The FIB response and nanodotformation behavior of each material is discussed with regard to a fewbasic material properties and a model for nanodot creation and growth bythe action of preferential sputtering and Ostwald ripening. The modelpredicts the development of a stable average nanodot size withincreasing ion dose, with the average nanodot size depending on theexcess group III adatom yield, adatom surface diffusion rate, andsurface tension. These predictions qualitatively agree with theexperimentally observed trends for GaAs and InP. They also agree for theinitial nanodot formation on InAs, but this material system exhibits asudden transition in the nanodot size distribution. The model predictsthat nanodots will have difficulty forming and growing on AlAs, which isalso in agreement with our experimental results. (C) 2011 AmericanInstitute of Physics. [doi:10.1063/1.3530839]

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