Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 31: Poster II

HL 31.35: Poster

Tuesday, February 26, 2008, 16:30–19:00, Poster D

Kinetics of Si quantum dot formation in thermally deposited SiO_x layers upon vacuum annealing — •Bert Stegemann, Daniel Sixtensson, Andreas Schöpke, and Manfred Schmidt — Hahn-Meitner-Institut Berlin, Abt. Silizium-Photovoltaik, Kekuléstraße 5, 12489 Berlin

Si quantum dots embedded in an amorphous SiO₂ matrix were prepared under ultrahigh vacuum conditions by thermal annealing of evaporated substoichiometric SiO_x (x = 1.3) layers with thicknesses between 3 and 10 nm. By codeposition of Si or O atoms the initial amount of O was varied between x=0.9 and 1.5. An ultrathin SiO₂ capping layer grown by plasma oxidation with atomic oxygen turned out to prevent SiO_x sublimation upon annealing. The kinetics of the decomposition of the constituting suboxides into Si and SiO₂ was analyzed by X-ray photoelectron spectroscopy as a function of the post deposition annealing temperature. Peak analysis of the Si 2p transition revealed the evolution of relative fractions of the different oxidation states Siⁿ⁺ (n = 0...4) with increasing temperature. For all investigated initial compositions phase separation started at about 600^∘C and was completed at 850^∘C. Annealing temperature also controls the quantum dot structure: crystallization sets on above 800^∘C as evidenced by cross-sectional TEM and photoelectrical measurements.