book of abstracts - IM2NP

A B S T R A C T S TUESDAY, JUNE 29 N A N O S E A 2 0 1 0
conditions we can form either Ge dots or Ge nanowires. We provide evidence of the preferential nucleation
of Ge nanostructures (dots and wires) on the pre-existing 2D array of AuSi liquid nanodroplets. The
influence of the nanopatterns morphology / shape on the nanostructures nucleation and growth is
demonstrated. The developed process provides a promising way to form large scale 2D-arrays of Ge and
core-shell SiGe nanowires for various micro-nano-electronic and photovoltaic applications.
17H00-17H20
Pit-patterning by UV nanoimprint lithography for the site-controlled selfassembly
of highly-uniform Si/Ge islands
FROMHERZ E. Lausecker1, M. Brehm1, M. Grydlik1, I. Bergmair2, M.
Mühlberger2, T. Fromherz1, G. Bauer1(1 Institute of Semiconductor and Solid State Physics,
University of Linz, 4040 Linz, Austria 2 Functional Surfaces and Nanostructures, Profactor GmbH, 4407 Steyr,
Austria)
1 – Introduction
In the germanium-on-silicon (Ge-on-Si) system, it has been demonstrated that the nucleation sites of Si/Ge
islands can be controlled by pre-structuring the Si substrate, allowing the growth of ordered and addressable
Si/Ge islands. For applications relying on addressability, island-ordering on chip-sized areas and, thus a fast
and inexpensive patterning method suitable for large areas and sub-100 nm structuring is required.
2 – Abstract
Therefore we introduce UV nanoimprint lithography (UV-NIL) for the pit-pattering of molecular-beam
epitaxy (MBE) substrates. Our quartz nanoimprint molds (1" x 1") contain a pillar pattern that is transferred
into the Si substrate by UV-NIL and reactive-ion etching. Four pit-patterned fields extend over an area of 3 x
3 mm 2 . The pits have a depth of 45 nm and a diameter of 200 nm with a period of 400 nm. Six monolayers of
Ge were deposited at 690 °C by MBE. The island surface is passivated by the growth of a thin Si capping
layer. Atomic force microscopy images show extremely well-ordered Si/Ge islands. To the best of our
knowledge, these island arrays represent the largest areas so far reported in literature with coherently ordered
Si/Ge islands, which are addressable by a second lithographical step. The homogeneous island growth results
in a significant improvement of the photoluminescence signal. In spatially resolved PL experiments, we
observe no variation in the PL peak position and linewidth,
3 – Conclusion
Our results suggest that pit-patterning by UV-NIL opens a route to explore the Si/Ge island formation on
high-density pattern in the sub-100 nm regime over large areas. Our Si/Ge islands show excellent
optoelectronic properties and therefore may be integrated as active building blocks in Si based optoelectronic
devices.
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