A. Markowitz et al., Homogeneously size distributed Ge nanoclusters embedded in SiO2 layers produced by ion beam synthesis, NUCL INST B, 147(1-4), 1999, pp. 361-366
500 nm SiO2 layers were implanted with 450 keV (F = 3 x 10(16) at./cm(2)) a
nd 230 keV (F = 1.8 x 10(16) at./cm(2)) Ge ions at room temperature to obta
in an almost constant Ge concentration of about 2.5 at.% in the insulating
layer. Subsequently, the specimens were annealed at temperatures between 50
0 degrees C and 1200 degrees C for 30 min in a dry N-2 ambient atmosphere.
Cross-sectional TEM analysis reveal homogeneously distributed Ge nanocluste
rs arranged in a broad band within the SiO2 layer. Their mean cluster size
varies between 2.0 and 6.5 nm depending on the annealing conditions. Cluste
r-free regions are always observed close to the surface of the specimens in
dependent of the annealing process, whereas a narrow Ge nanocluster band ap
pears at the SiO2/Si interface at high annealing temperatures, e.g. greater
than or equal to 1000 degrees C. The atomic Ge redistribution due to the a
nnealing treatment was investigated with a scanning TEM energy dispersive X
-ray system and Rutherford back scattering(RBS). (C) 1999 Elsevier Science
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