Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 6: Quantum dots and wires: preparation and characterization I

HL 6.2: Talk

Monday, March 26, 2007, 11:15–11:30, H15

Templated Selforganization of SiGe Quantumdots — •Christian Dais, Harun Solak, Hans Sigg, Elisabeth Müller, and Detlev Grützmacher — Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, Villigen-PSI, Switzerland

Templated self-organization has been used to prepare samples with regimented arrays of Ge quantum dots. For prepatterning of Si (001) substrates we used extreme ultra-violet interference lithography (EUV-IL) which was performed at the Swiss Light Source (SLS) at the PSI. The EUV-IL technique is based on multiple beam interference to form an interference pattern which is projected onto PMMA resist. EUV-IL allows the definition of patterns of various symmetries with a periodicity smaller than 30 nm over areas as large as 2x2 mm. After the pattern had been transferred into the Si (100) substrate by reactive ion etching, molecular beam epitaxy was employed to grow Si/Ge quantum dot layers on the prepatterned substrates. By choosing appropriate growth conditions, dense packed 2D dot arrays, quantum dot molecule arrays, as well as 3D quantum dot crystals have been realized. AFM surface scans as well as cross-sectional TEM micrographs exhibit a remarkably narrow size distribution of the dots. This is confirmed by X-ray diffraction experiments at symmetric and asymmetric diffraction peaks. Moreover, photoluminescence measurements have been performed giving insights into the bandstructure of the 2-d and 3-d quantum dot crystals. Our results on the fabrication and properties of 2- and 3-dimensional Ge quantum dot crystals may open new routes towards the realization of nanoelectronic and spintronic devices.