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Scanning electron micrographs of three InAs nanowire samples grown on SiOx‐masked Si (111) at T = 480 °C and variable In/As ratio yielding different NW diameters, i.e., (a) 135 (±12) nm, (b) 60 (±5) nm, and (c) 40 (±6) nm. The scale bar in all three images is identical. (d) Transmission electron micrograph of a representative InAs NW taken from sample (a) evidencing wurtzite-like (WZ) bilayer stacking intercepted by faults every few MLs to several nm. The diffraction pattern (e) shows reflections which can be all indexed according to WZ structure in [10-10] zone axis (specifically those marked as [1-1-2] and [-11-2]). The diffuse streaks indicate the presence of stacking faults along the NW.
Temperature (T)-dependent PL spectra for (a) the sample with NW diameter of ∼135 nm and (b) the bulk InAs reference (at 284 mW). The spectra arranged from top to bottom correspond to increasing T from 15 K (12 K for bulk) to 130 K (114 K for bulk) with increments of ΔT between 10 and 15 K. (c) Corresponding T-dependent shift in peak energy emission (red‐shift) for these NWs, as compared to the respective shift for the bulk InAs reference (best fitted by Varshni expression). (d) Integrated PL intensity as a function of 1/T (Arrhenius plot) for both NWs and bulk reference, demonstrating the quenching characteristics with best fits using two activation energies (Ea, Eb) for the high- and low-T region.
Excitation power dependent PL spectra recorded at 15 K for the three samples with NW diameters of (a) ∼135 nm, (b) ∼60 nm, and (c) ∼40 nm. Spectra (from bottom to top) correspond to increasing power from 27 to 284 mW in increments of ΔP ∼ 25–50 mW. (d) Integrated PL intensity versus excitation power (log scale) evidencing a transition from linear increase (I(P) ∼ P m with m ∼ 0.97–1.19) to saturation (m ∼ 0.42–0.6).
(a) Direct comparison of low-T PL spectra (taken at 15 K, 85 mW) of the three corresponding NW samples, showing decreased intensities and a pronounced blue-shift with decreasing NW diameter with respect to bulk InAs reference (in grey). (b) Plot of the band‐edge energy shift as a function of NW diameter showing simulated data based on radial quantum confinement of the ground state energy (open symbols) in comparison with as-measured data from PL peak positions (closed symbols).
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