Performance analysis of an interacting quantum dot thermoelectric system

We analyze the nanocaloritronic performance of an interacting quantum dot that is subject to an applied bias and an applied temperature gradient. It is now well known that, in the absence of phonon contribution, a weakly coupled non-interacting quantum dot can operate at thermoelectric efficiencies approaching the Carnot limit. However, it has also been recently pointed out that such peak efficiencies can only be achieved when operated in the reversible limit, with a vanishing current and hence a vanishing power output. In this paper, we point out three fundamental results affecting the thermoelectric performance due to the inclusion of Coulomb interactions: a) The reversible operating point carries zero efficiency, b) operation at finite power output is possible even at peak efficiencies approaching the Carnot value, and c) the evaluated trends of the the maximum efficiency deviate considerably from the conventional {\it{figure of merit}} $zT$ based result. Finally, we also analyze our system for thermoelectric operation at maximum power output.Comment: 10 pages, 6 figures, Resubmission- to be published in Phys. Rev.

Accurate estimation of low [< (10^-8) ohm . cm²] values of specific contact resistivity

Advancements in nanotechnology have created the need for efficient means of communication of electrical signals to nanostructures, which can be addressed using low resistance contacts. In order to study and estimate the resistance of such contacts or the resistance posed by the interface(s) in such contacts, accurate test structures and evaluation techniques need to be used. The resistance posed by an interface is quantified using its specific contact resistivity (SCR), and although multiple techniques have been utilized, inaccuracies of such techniques in measuring values of SCR lesser than ( < 10-8 Ω ldr cm2 ) have been reported. In this letter, an approach for estimating very low values of SCR (lower than the previously limiting ( < 10-8 Ω ldr cm2 )) using a cross Kelvin resistor test structure is demonstrated using aluminum to titanium silicide ohmic contacts, with a minimum estimated SCR value of 6.0 times 10-10 Ω ldr cm2

RF magnetron sputtered perovskite-oriented PSZT thin films on gold for piezoelectric and ferroelectric transducers

Conditions for depositing perovskite-oriented Pb0.92Sr0.08(Zr0.65Ti0.35) O-3 thin films on gold by RF magnetron sputtering are investigated. Deposition results were analysed by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffractometry. It was found that the desired perovskite phase can be obtained at a substrate temperature of 300 degrees C, much lower than the typically reported 650 degrees C for deposition on platinum

Nanoscale characterization of energy generation from piezoelectric thin films

We report on the use of nanoindentation to characterize in situ the voltage and current generation of piezoelectric thin films. This work presents the controlled observation of nanoscale piezoelectric voltage and current generation, allowing accurate quantification and mapping of force function variations. We characterize both continuous thin films and lithographically patterned nanoislands with constrained interaction area. The influence of size on energy generation parameters is reported, demonstrating that nanoislands can exhibit more effective current generation than continuous films. This quantitative finding suggests that further research into the impact of nanoscale patterning of piezoelectric thin films may yield an improved materials platform for integrated microscale energy scavenging systems

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Composition analysis of nickel silicide formed from evaporated and sputtered nickel for microsystem devices

Nickel silicide (NiSi) is highly suitable for microsystem fabrication, exhibiting suitable mechanical properties and good resistance to bulk micromachining etchants. Conditions for the formation of nickel silicide by vacuum annealing thin films of nickel deposited on silicon substrates are investigated. Nickel silicide thin films formed using sputtered and evaporated nickel films were analysed using Auger electron spectroscopy, which has shown that evaporated thin films of nickel tend to form nickel silicide more readily and with less thermal effort

Reversal and pinning of Curie point transformations in thin film piezoelectrics

The Curie point for a rhombohedral piezoelectric thin film was established by in situ micro-Raman spectroscopy. The hysteresis in phase reversal and specific thermal conditions for disrupting such reversal were determined

Response of oceanic cyclogenesis metrics for NARGIS cyclone:a case study

In this study, variability of two oceanic cyclogenesis metrics, tropical cyclone heat potential (TCHP) and effective oceanic layer for cyclogenesis (EOLC) in the Bay of Bengal (BoB) during NARGIS cyclone is investigated. EOLC represents the geopotential thickness of near surface stratified layer forms because of the spread of low salinity waters due to fresh water influx from rivers and precipitation. Climatological fields of TCHP and EOLC reveal that NARGIS translated towards the region of higher EOLC as seen in the observations. A maximum daily sea surface cooling of 2 °C is observed along the right and rear side of NARGIS track

Microstructural and compositional analysis of strontium-doped lead zirconate titanate thin films on gold-coated silicon substrates

This article discusses the results of transmission electron microscopy (TEM)-based characterization of strontium-doped lead zirconate titanate (PSZT) thin films. The thin films were deposited by radio frequency magnetron sputtering at 300°C on gold-coated silicon substrates, which used a 15 nm titanium adhesion layer between the 150 nm thick gold film and (100) silicon. The TEM analysis was carried out using a combination of high-resolution imaging, energy filtered imaging, energy dispersive X-ray (EDX) analysis, and hollow cone illumination. At the interface between the PSZT films and gold, an amorphous silicon-rich layer (about 4 nm thick) was observed, with the film composition remaining uniform otherwise. The films were found to be polycrystalline with a columnar structure perpendicular to the substrate. Interdiffusion between the bottom metal layers and silicon was observed and was confirmed using secondary ion mass spectrometry. This occurs due to the temperature of deposition (300°C) being close to the eutectic point of gold and silicon (363°C). The diffused regions in silicon were composed primarily of gold (analyzed by EDX) and were bounded by (111) silicon planes, highlighted by the triangular diffused regions observed in the two-dimensional TEM image