We have measured the thermal properties of an n-type hot-pressed Bi1.8Sb0.2Te3 alloy with a carrier concentration of 3.1×1019 cm-3. With the adjustable parameters determined from these experimental data, the dependence of thermal properties on the carrier concentrations is investigated, using the two-band-conduction model with a mixed scattering mechanism and a small fluctuation theory. The maximum dimensionless figures of merit of the alloy in a carrier concentration range of 0.8–3×1019 cm-3 have values over 0.7 at temperatures between 250 K and 300 K and a minimum thermal conductivity of 1 W/Km. These alloys are comparable to single crystals, showing the possibility that they provide higher thermoelectric performance than the single crystals, since their microstructure can be controlled by hot-press processing.

This study presents an investigation of the band structure in a semimetallic two-dimensional (2D) PtSe2 nanosheet based on thermoelectric transport phenomena. Mechanically exfoliated PtSe2 nanosheets, including naturally doped nonneutral samples, were studied. The gate-tuned electrical conductivity and thermoelectric power were measured by varying the temperature. Based on the combined effects of gate-tuning and shifting of zero-gate energy level, the semimetallic band structure of 2D PtSe2 was confirmed in the band over a wide energy range. Furthermore, the temperature dependence of transport properties was investigated to determine the band structure and intrinsic properties.

Ti-Ni shape memory alloy (SMA) thin films are very attractive material for industrial and medical applications such as micro-actuator, micro-sensors, and stents for blood vessels. An important property besides shape memory effect in the application of SMA thin films is the adhesion between the film and the substrate. When using thin films as micro-actuators or micro-sensors in MEMS, the film must be strongly adhered to the substrate. On the other hand, when using SMA thin films in medical devices such as stents, the deposited alloy thin film must be easily separable from the substrate for efficient processing. In this study, we investigated the effect of substrate roughness on the adhesion of Ti-Ni SMA thin films, as well as the structural properties and phase-transformation behavior of the fabricated films. Ti-Ni SMA thin films were deposited onto etched glass substrates with magnetron sputtering. Radio frequency plasma was used for etching the substrate. The adhesion properties were investigated through progressive scratch test. Structural properties of the films were determined via Feld emission scanning electron microscopy, X-ray diffraction measurements (XRD) and Energy-dispersive X-ray spectroscopy analysis. Phase transformation behaviors were observed with differential scanning calorimetry and low temperature-XRD. Ti-Ni SMA thin film deposited onto rough substrate provides higher adhesive strength than smooth substrate. However the roughness of the substrate has no influence on the growth and crystallization of the Ti-Ni SMA thin films.

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