Melissa S. Sander

Plasmon excitation modes in nanowire arrays

Electron energy loss spectrometry and energy-filtered transmission electron microscopy reveal characteristic plasmon excitations in both isolated Bi nanowires and an array of Bi nanowires within an Al2O3 matrix. As the average nanowire diameter decreases from 90 to 35 nm, both the volume plasmon energy and peak width increase. In addition, a lower-energy excitation is present in a very localized region at the Bi–Al2O3 interface. These results are discussed in the context of quantum confinement and the influence of interfaces on the electronic properties of nanocomposite materials.

Epitaxial growth of skutterudite (CoSb 3 ) thin films on (001) InSb by pulsed laser deposition

Heteroepitaxial growth of the cubic skutterudite phase CoSb 3 on (001) InSb substrates was achieved by pulsed laser deposition using a substrate temperature of 270 °C and a bulk CoSb 3 target with 0.75 at.% excess Sb. An InSb ( a 0 = 4 0.6478 nm) substrate was chosen for its lattice registry with the antimonide skutterudites (e.g., CoSb 3 with a = 0 4 0.9034 nm) on the basis of a presumed 45° rotated relationship with the InSb zinc blende structure. X-ray diffraction and transmission electron microscopy confirmed both the structure of the films and their epitaxial relationship: (001) CoSb 3 ∥ (001) InSb ; [100] CoSb 3 ∥ [110] InSb .

High Spatial Resolution Assessment of the Structure, Composition, and Electronic Properties of Nanowire Arrays

Abstract : We have employed transmission electron microscopy (TEM) and analytical electron microscopy to perform preliminary assessment of the structure, composition and electronic properties of nanowire arrays at high spatial resolution. The two systems studied were bismuth and bismuth telluride nanowire arrays in alumina (wire diameters 40nm), both of which are promising for thermoelectric applications. Imaging coupled with diffraction in the TEM was employed to determine the grain size in electrodeposited Bi2Te3 nanowires. In addition, a composition gradient was identified along the wires in a short region near the electrode by energy-dispersive x-ray spectroscopy. Electron energy loss spectroscopy combined with energy-filtered imaging in the TEM revealed the excitation energy and spatial variation of plasmons in bismuth nanowire arrays.

Electrodeposition of Bi 2 Te 3 Nanowire Composites

Widespread applications of thermoelectric materials are limited due to low efficiency. Currently, the most widely used thermoelectric devices consist of alloys based on Bi 2 Te 3 . In such devices, the thermoelectric figure-of-merit (ZT) of bulk Bi 2 Te 3 has been increased through doping. It is postulated that further enhancements in ZT may be attained by engineering the microstructure of the material to enhance carrier mobility while suppressing the phonon component of the thermal conductivity. This may be achieved by fabricating Bi 2 Te 3 in the form of one-dimensional (1D) nanowires. We have deposited nanowires of Bi 2 Te 3 with two different diameters (200 nm and 40 nm) by electrodeposition into porous anodic alumina. Characterization of the Bi 2 Te 3 /porous Al 2 O 3 composite materials has been accomplished using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive X-ray spectroscopy (EDS) has been used to determine the stoichiometry of the wires.