Abstract
Si and Ge growth on the stripe-patterned Si (001) substrates is studied using in situ reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). During Si buffer growth, the evolution of RHEED patterns reveals a rapid change of the stripe morphology from a multifaceted “U” to a single-faceted “V” geometry with {119} sidewall facets. This allows to control the pattern morphology and to stop Si buffer growth once a well-defined stripe geometry is formed. Subsequent Ge growth on “V”-shaped stripes was performed at two different temperatures of 520 and 600°C. At low temperature of 520°C, pronounced sidewall ripples are formed at a critical coverage of 4.1 monolayers as revealed by the appearance of splitted diffraction streaks in RHEED. At 600°C, the ripple onset is shifted toward higher coverages, and at 5.2 monolayers dome islands are formed at the bottom of the stripes. These observations are in excellent agreement with STM images recorded at different Ge coverages. Therefore, RHEED is an efficient tool for in situ control of the growth process on stripe-patterned substrate templates. The comparison of the results obtained at different temperature reveals the importance of kinetics on the island formation process on patterned substrates.
Highlights
We report on in situ control of Si and Ge growth on stripe-patterned Si (001) substrates using reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) where large area patterns were produced by holographic lithography
In situ reflection highenergy electron diffraction (RHEED) monitoring of Si and Ge growth on stripe-patterned Si substrates was demonstrated as a sensitive tool for controlling the changes in the pattern structure as well as of the island formation process
This allowed to observe the transformation of the pattern geometry from multifaceted ‘‘U’’ to single-faceted ‘‘V’’ stripes
Summary
Self-assembled growth of Stranski–Krastanow islands on pre-patterned substrates has attracted great interest [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] because it provides an effective route for positioning of quantum dots in nano-electronic devices. We report on in situ control of Si and Ge growth on stripe-patterned Si (001) substrates using reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) where large area patterns were produced by holographic lithography. Because of the simple geometry, stripes represent a model system [4,5,6] for the growth on non-planar substrate templates with complex surface topographies Their one-dimensional structure allows electron diffraction from all parts of the surface when the electron beam is directed parallel to the stripes. To obtain a real space picture of the nucleation process, the epitaxial surfaces were imaged in a step-wise manner using STM, where due to UHV conditions, epitaxial growth could be continued after each imaging step. Due to the low system pressure in the 10-11 mbar regime, growth could be continued afterward after a short annealing for a few minutes at 450°C
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