We report the evolution of high temperature thermoelectric properties of SrTiO3 thin films doped with Nb and oxygen vacancies. Structure-property relations in this important thermoelectric oxide are elucidated and the variation of transport properties with dopant concentrations is discussed. Oxygen vacancies are incorporated during growth or annealing in Ar/H2 above 800 K. An increase in lattice constant due to the inclusion of Nb and oxygen vacancies is found to result in an increase in carrier density and electrical conductivity with simultaneous decrease in carrier effective mass and Seebeck coefficient. The lattice thermal conductivity at 300 K is found to be 2.22 W m(-1) K(-1), and the estimated figure of merit is 0.29 at 1000 K.

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In this study, the temperature dependent thermoelectric properties of sol-gel prepared ZnO and 3% Ga-doped ZnO (GZO) thin films have been explored. The power factor of GZO films, as compared to ZnO, is improved by nearly 17% at high temperature. A stabilization anneal, prior to thermoelectric measurements, in a strongly reducing Ar/H 2 (95/5) atmosphere at 500 C was found to effectively stabilize the chemically derived films, practically eliminating hysteresis during thermoelectric measurements. Subtle changes in the thermoelectric properties of stabilized films have been correlated to oxygen vacancies and excitonic levels that are known to exist in ZnO-based thin films. The role of Ga dopants and defects, formed upon annealing, in driving the observed complex temperature dependence of the thermoelectric properties is discussed.

In the field of optomechanics, radiation forces have provided a particularly high level of control over the frequency and dissipation of mechanical elements. Here we propose a class of optomechanical systems in which light exerts a similarly profound influence over two other fundamental parameters: geometry and mass. By applying an optical trap to one lattice site of an extended phononic crystal, we show it is possible to create a tunable, localized mechanical mode. Owing to light's simultaneous and constructive coupling with the structure's continuum of modes, we estimate that a trap power at the level of a single intracavity photon should be capable of producing a significant effect within a realistic, chip-scale device.Solid state mechanical systems are ubiquitous throughout society, from oscillators in time-keeping devices to accelerometers and electronic filters in automobiles and cell phones. They also comprise an indispensable set of tools for fundamental and applied science. For example, using tiny mechanical systems, it is possible to "feel around" surfaces at the atomic scale [1], detect mass changes from adsorbed chemicals with single-proton resolution [2], and sense the gentle magnetic "tugs" from individual electron spins [3], persistent currents in a normal-metal ring [4], or even element-specific nanoscale clusters of nuclei [5]. Meanwhile, human-scale masses (positioned kilometers apart) currently "listen" for gravitational waves emitted by violent events across the universe [6].In the field of optomechanics, the forces generated by light provide a means of tuning the fundamental properties -namely frequency, dissipation, normal mode geometry, and effective mass -of mechanical systems at every size scale [7]. The frequency and dissipation have been particularly well-controlled, often tuned by many orders of magnitude using feedback techniques [8], bolometric effects [9][10][11], or radiation pressure [12][13][14][15][16][17]. The geometry and mass have also been tuned via opticallymediated normal mode hybridization [17-23], but not so profoundly: only a few (essentially two) normal modes are involved, and the resulting hybridized modes therefore exhibit a mass and spatial extent comparable to that of the unperturbed modes.Here we propose to exploit radiation pressure's simultaneous influence over a continuum of modes to strongly tune the geometry and mass of a mechanical system. The basic idea is to fabricate an extended phononic crystal structure [24] and apply an optical trap to one lattice site, thereby creating a defect that exponentially localizes one or more mechanical modes. Unlike structurally defined defect modes [24] -realized some time ago [25] and currently exploited with extraordinary success in optomechanics [26-34] -we show that the spatial extent and mass of optically defined defect modes can be tuned by many orders of magnitude using a realistic, chip-scale optomechanical geometry. Additionally, despite the comparatively weak optomechanical interaction with each of the unperturbe...

In the present work, bismuth borate glass samples with the composition of (99-x) B2O3 + 1Cr2O3 + (x) Bi2O3 (x = 0, 5, 10, 15, 20, and 25 wt %) were prepared using the melt quenching technique. The mass attenuation coefficient (MAC) of the prepared glass samples was measured through a narrow beam technique using a NaI(Tl) scintillation detector. Four point sources were used (241Am, 133Ba, 152Eu, and 137Cs) to measure the MAC for the prepared glasses. The experimental data were compared with the theoretical results obtained from the XCOM, and it was shown that for all samples at all tested energies, the relative deviation between the samples is less than 3%. This finding signifies that the experimental data can adequately be used to evaluate the shielding ability of the glasses. The MAC of the sample with x = 25 wt % was compared with different lead borate glasses and the results indicated that the present sample has high attenuation which is very close to commercial lead borate glasses. We determined the transmission factor (TF), and found that it is small at low energies and increases as the energy increases. The addition of Bi2O3 leads to reduction in the TF values, which improves the shielding performance of the glass system. The half value layer (HVL) of the BCrBi-10 sample was 0.400 cm at 0.595 MeV, 1.619 cm at 0.2447 MeV, and 4.946 cm at 1.4080 MeV. Meanwhile, the HVL of the BCrBi-20 sample is equal to 0.171 and 4.334 cm at 0.0595 and 1.4080 MeV, respectively. The HVL data emphasize that higher energy photons tend to penetrate through the glasses with greater ease than lower energy photons. Furthermore, the fast neutron removable cross section (FNRC) was determined for the present samples and compared with lead borate glass and concrete, and the results showed a remarkable superiority of the bismuth borate glass samples.