We present a bottom-up synthesis, spectroscopic characterization, and ab initio simulations of star-shaped hexagonal zinc oxide (ZnO) nanowires. The ZnO nanostructures were synthesized by a low-temperature hydrothermal growth method. The cross-section of the ZnO nanowires transformed from a hexagon to a hexagram when sulfur dopants from thiourea [SC(NH2)2] were added into the growth solution, but no transformation occurred when urea (OC(NH2)2) was added. Comparison of the X-ray photoemission and photoluminescence ...
We provide experimental evidence for direct and indirect excitations of photoluminescence PL from Tm-doped AlxGa1-xN of varying Al content. Direct excitation of Tm3+ ions is observed primarily at 85 K through transitions 3H6-1I6, 3P0, 3P1, and 3P2 when these levels are below the absorption edge of the AlxGa1-xN for a given Al content. Strong ultraviolet emission at 298 nm (1I6-3H6), 355 nm (1I6-3F4), and 371 nm (1D2-3H6), as well as ...
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