ICAMS / Interdisciplinary Centre for Advanced Materials Simulation

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The path to a porous semiconductor multilayer

Date: 04.06.2013
Place: CECAM Workshop, Lausanne, Switzerland

Ari Harjunmaa

Thin films are the basis of much of recent technological advance, ranging from coatings with mechanical or optical benefits to platforms for nanoscale electronics. In the latter, semiconductors have been the norm ever since silicon became the main construction material for a multitude of electronical components. Semiconductor thin films can be manufactured using many different methods; one emerging field is cluster beam deposition, where aggregates of hundreds or thousands of atoms are deposited one by one to form a layer, the characteristics of which depend on the parameters of deposition. One critical parameter is deposition energy, which dictates how porous, if at all, the layer becomes. Other parameters, such as sputtering rate and aggregation conditions, have an effect on the size and consistency of the individual clusters. In this work, the entire process of cluster beam deposition is explored using molecular dynamics as the principal simulation tool. The process begins with the formation of the clusters, which is investigated for Si(x)Ge(1-x) in an Ar atmosphere. The structure of the clusters is optimized to bring it as close to the experimental ideal as possible. Then, clusters are deposited, one by one, onto a substrate, until a sufficiently thick layer has been produced. Finally, the concept is expanded by further deposition with different parameters, resulting in multiple superimposed layers of different porosities.

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