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(Color online) (a) TEM picture of a Si NW array sample representative for ESR observations, showing the c-Si NW cores (dark profiles) with surrounding thermal oxide shells (dark grey) and filling CVD oxide (light grey). (b) A schematic representation of the (100)Si substrate and a NW on top, together with the applied magnetic field B configuration.
(Color online) (a) First-derivative low temperature K-band spectra (Pμ = 8 × 10−7 mW; Bm = 0.7-1 G) taken for four orientations of B on a Si NW array subjected to VUV irradiation. The spectra were normalized to equal marker intensity. (b) Inferred angular g map of Pb0 centers pertaining to Si/SiO2 interfaces in the Si NW arrays. The curves represent optimized fittings for trigonal symmetry,7 yielding g‖ (‖〈111〉) = 2.0020 and g‖ = 2.0082, corresponding to Pb0 centers at 〈110〉 and/or 〈100〉Si/SiO2 interfaces. The numbers marked near the various branches indicate expected relative signal intensity (area under absorption curve), in agreement with experimental observation.
(Color online) K-band ESR spectra taken at 4.2 K on sample 2 after vacuum anneal at 610 °C (top curve), after subsequent VUV irradiation (middle curve), and after etching off most of the Si NWs (bottom curve, five times enlarged). The spectra were normalized to equal marker intensity and sample area. The small signal, labeled DD, in the bottom spectrum stems from a double donor center, correlating with the surface charging.
Overview of treatments performed on studied Si NW arrays, together with the densities of observed paramagnetic defects, given per cm2 of Si substrate. Indicated errors represent the spreads over a set of measurements.
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