Stegemann, B.; Lussky, T.; Schöpke, A.; Cermak, J.; Rezek, B.; Kocka, J.; Schmidt, M.: Formation kinetics and electrical transport of silicon quantum dot layers. In: De Santi, G.F. [u.a.] [Eds.] : 25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain. EU PVSEC. Munich: WIP, 2010. - ISBN 3-936338-26-4, p. 260-264
ABSTRACT: Two-dimensional layers of Si quantum dots (QDs) are synthesized under ultrahigh vacuum (UHV) conditions by self-organized growth from thermally deposited SiOx (x<2) precursor layers, which are thermodynamically unstable and therefore undergo phase separation upon appropriate in situ post-annealing. QD density and size are adjusted by variation of the layer thickness and the stoichiometry x, allowing for a tuning of the quantization energies and of the interlayer transport properties. For all investigated initial compositions (x ranging from 0.9 to 1.5) and layer thicknesses (3 to 10 nm), phase separation was completed at 850°C. The kinetics of the thermal decomposition of the constituting suboxides (Sin+, n = 0 … 4) into Si QDs and the surrounding SiO2 matrix was analyzed in situ by X-ray photoelectron spectroscopy (XPS) as a function of the annealing temperature. The gradual phase separation revealed by XPS is directly correlated with electrical properties as derived from atomic force microscopy measurements detecting surface potentials (KFM) and local conductivities (CS-AFM) across individual QDs.