(a) SEM image (30° tilt angle) of GaAs/GaSb core/shell NWs (shell growth time of 600 s). (b)–(e) BF TEM images of the top regions of four NWs with four beam orientations.
HAADF image of a middle section of a GaAs/GaSb core/shell NW (a1) with corresponding EDS scans ((a2) and (a3)) along the lines indicated in (a1). HAADF image of the top region of two GaAs/GaSb core/shell NW (b1) with corresponding EDS scan (b2) along the line shown in (b1).
(a) BF TEM image of a GaAs/GaSb core/shell NW (b) with corresponding SADP along 〈123〉 zone axis. (c) HRTEM image of the GaAs/GaSb interface. Arrows on both sides of the HRTEM image indicate the GaAs/GaSb interface. The dotted lines indicate the extra planes in the GaAs region terminating at the interface.
Plot of the relative strain relaxation as a function of NW core diameter. Shell thickness was 9 ± 3 nm for all NWs. The inset shows the NW density vs. core NW diameter along with a Gaussian fit to the data.
BF TEM image (a) and associated SADP (b). (c) HRTEM image of the GaAs/GaSb interface. The arrows in (c) indicate the approximate location of the GaAs/GaSb interface.
(a) BF, (b) SADP, and (c) (111) DF TEM images of a GaP/GaSb core/shell NW. HRTEM images of the regions indicated by boxes in (a) and (c) are shown in (d) and (e), respectively.
Room temperature Raman spectra from an ensemble of GaAs/GaSb core/shell NWs (core diameter of 34 ± 5 nm) with shell growth times of 100 s (shell thickness of ∼1.8 nm) (solid curve) and 600 s (shell thickness of 9 ± 3 nm) (dotted curve). Raman spectra from GaSb substrate (dashed line) and GaAs NWs (dotted-dashed curve) are shown for comparison.
Lorentzian fits of the Raman spectrum from GaAs/GaSb core/shell NWs with a shell growth time of 100 s (shell thickness of ∼1.8 nm).
Summary of the Raman peak positions (cm−1) of a GaSb substrate, GaAs NWs, and GaAs/GaSb core/shell NWs with shell growth times of 100 s (shell thickness of ∼1.8 nm) and 600 s (shell thickness of 9 ± 3 nm). The peak position of the GaP NWs and GaP/GaSb core/shell NWs are also summarized for comparison. The peak positions were determined by fitting the data with Lorentzians. Also, the values of p + 2q (1028 s−2) for GaSb (Ref. 31 ), GaAs (Ref. 31 ), and GaP (Ref. 32 ) are summarized.
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