Developing thermoelectric materials with superior performance means tailoring interrelated thermoelectric physical parameters – electrical conductivities, Seebeck coefficients, and thermal conductivities – for a crystalline system. High electrical conductivity, low thermal conductivity, and a high Seebeck coefficient are desirable for thermoelectric materials. Therefore, knowledge of the relation between electrical conductivity and thermal conductivity is essential to improve thermoelectric properties. In general, research in recent years has focused on developing thermoelectric structures and materials of high efficiency. The importance of this parameter is universally recognized; it is an established, ubiquitous, routinely used tool for material, device, equipment and process characterization both in the thermoelectric industry and in research. In this paper, basic knowledge of thermoelectric materials and an overview of parameters that affect the figure of merit ZT are provided. The prospects for the optimization of thermoelectric materials and their applications are also discussed.

A review on thermoelectric renewable energy: Principle parameters that affect their performance

Thermoelectric (TE) materials have the capability of converting heat into electricity, which can improve fuel efficiency, as well as providing robust alternative energy supply in multiple applications by collecting wasted heat, and therefore, assisting in finding new energy solutions. In order to construct high performance TE devices, superior TE materials have to be targeted via various strategies. The development of high performance TE devices can broaden the market of TE application and eventually boost the enthusiasm of TE material research. This review focuses on major novel strategies to achieve high-performance TE materials and their applications. Manipulating the carrier concentration and band structures of materials are effective in optimizing the electrical transport properties, while nanostructure engineering and defect engineering can greatly reduce the thermal conductivity approaching the amorphous limit. Currently, TE devices are utilized to generate power in remote missions, solar-thermal systems, implantable or/wearable devices, the automotive industry, and many other fields; they are also serving as temperature sensors and controllers or even gas sensors. The future tendency is to synergistically optimize and integrate all the effective factors to further improve the TE performance, so that highly efficient TE materials and devices can be more beneficial to daily lives.

https://espace.library.uq.edu.au/view/UQ:722903/UQ722903_OA.pdf

High Performance Thermoelectric Materials: Progress and Their Applications

This paper reviews recent achievements in the technology and design of fluxgate sensors and magnetometers. The major recent trends were decreasing of the sensor size, power consumption and price, and, on the other hand, increasing of the precision in the large range of the measured fields. The potential frequency range was increased up to units of kHz. Present fluxgate sensors have a resolution comparable with high-temperature superconducting quantum interference devices (SQUIDs), while their precision is the best of vectorial field sensors.

Advances in fluxgate sensors

An integrated circuit (IC) approach to thermal microsensors is presented. The focus is on thermal sensors with on-chip bias and signal conditioning circuits made by industrial complementary metal-oxide-semiconductor (CMOS) IC technology in combination with post-CMOS micromachining or deposition techniques. CMOS materials and physical effects pertinent to thermal sensors are summarized together with basic structures used for microheaters, thermistors, thermocouples, thermal isolation, and heat sinks. As examples of sensors using temperature measurement, we present micromachined CMOS radiation sensors and thermal converters. Examples for sensors based on thermal actuation include thermal flow and pressure sensors, as well as thermally excited microresonators for position and chemical sensing. We also address sensors for the characterization of process-dependent thermal properties of CMOS materials, such as thermal conductivity, Seebeck coefficient, and heat capacity, whose knowledge is indispensable for thermal sensor design. Last, two complete packaged microsystems-a thermoelectric air-flow sensor and a thermoelectric infrared intrusion detector-are reported as demonstrators.

Micromachined thermally based CMOS microsensors

The thermal conductivities /spl kappa/ of the dielectric and conducting thin films of three commercial CMOS processes were determined in the temperature range from 120 to 400 K. The measurements were performed using micromachined heatable test structures containing the layers to be characterized. The /spl kappa/ values of thermally grown silicon oxides are reduced from bulk fused silica by roughly 20%. The /spl kappa/ of phosphosilicate and borophosphosilicate glasses are 0.94/spl plusmn/0.08 W m/sup -1/ K/sup -1/ and 1.18/spl plusmn/0.06 W m/sup -1/ K/sup -1/, respectively, at 300 K. A plasma-enhanced chemical-vapor-deposition silicon-nitride layer has a thermal conductivity of 2.23/spl plusmn/0.12 W m/sup -1/ K/sup -1/ at 300 K. This value is between published data for atmospheric-pressure CVD and low-pressure CVD nitrides. For the metal layers, we found thermal conductivities between 167 W m/sup -1/ K/sup -1/ and 206 W m/sup -1/ K/sup -1/, respectively, at 300 K, to be compared with 238 W m/sup -1/ K/sup -1/ of bulk aluminum. The temperature-dependent product /spl kappa//spl rho/ of /spl kappa/ with the electrical resistivity /spl rho/ agrees better than 8.2% between 180-400 K with that of pure bulk aluminum. The /spl kappa/ values of the polysilicon layers are between 22.4 W m/sup -1/ K/sup -1/ and 37.3 W m/sup -1/ K/sup -1/ at 300 K. They are reduced from similarly doped bulk silicon by factors of between 2.0-1.3. The observed discrepancies between thin film and bulk data demonstrate the importance of determining the process-dependent thermal conductivities of CMOS thin films.

Process-dependent thin-film thermal conductivities for thermal CMOS MEMS

We report on a miniaturized magnetic-field sensor system consisting of a fluxgate sensor fabricated in CMOS-compatible planar technology and a CMOS-ASIC for sensor supply, readout and signal processing using the second-harmonic principle with a feedback loop for zero-field operation. The system exhibits a sensitivity of 9.2±0.1 mV μT−1 for a magnetic field range of ±90 μT and a temperature range of 0 to 70 °C. The 3 dB bandwith is 300 Hz and a noise value of 30 nT Hz −1 2 has been estimated. Using 5 V supply voltage, the power consumption of the system is measured to be 160 mW.

A miniaturized magnetic-field sensor system consisting of a planar fluxgate sensor and a CMOS readout circuitry

We report on a monolithic integrated infrared sensor system consisting of a thermopile, a sensor measuring the chip temperature and an amplifier stage fabricated in a CMOS process on SIMOX (separation by implanted oxygen) wafers. A responsivity of 209 V W−1 and a normalized detectivity D ∗ of 1.3 × 108 cm Hz 1 2 W−1 are found for thermopiles with single-crystalline p-Si/n-polysilicon thermocouples on silicon oxide/silicon nitride membranes. A first analysis of the thermal influence of the power consumed by the circuitry on the thermopile voltage indicates that the sensor performance is not deteriorated by the integrated electronic circuitry.

A thermoelectric infrared radiation sensor with monolithically integrated amplifier stage and temperature sensor

We report on a monolithic integrated infrared sensor system consisting of a thermopile, a sensor measuring the chip temperature and an amplifier stage fabricated in a CMOS process on SIMOX (Separation by Nplanted mygen) wafers. A responsivity of 209 V/W and a normalized detectivity D*d 1.3*108 cm-HzlnlW were found for thermopiles with single crystalline p-Sun-Polysilicon thermocouples on silicon oxide/silicon nitride membranes. A first analysis of the thermal influence of the power consumed by the circuitry on the thermopile voltage indicates, that the sensor performance is not deteriorated by the integrated electronic circuitry.

A Thermoelectric Infrared Radiation Sensor With Monolithically Integrated Amplifier Stage And Temperature Sensor

This paper investigates the feasibility of realization of analog microwave circuits in submicron CMOS technologies, particularly in bulk-CMOS and CMOS/SIMOX. The investigation concentrates on implementation of wideband amplifiers operating from DC to RF frequencies in the GHz range at power supplies /spl les/5 V.

http://ieeexplore.ieee.org/iel3/3909/11339/00535516.pdf

Microwave wideband amplifiers in bulk-CMOS and CMOS/SIMOX technologies

We report on a monolithically integrated two-axis magnetic field sensor system consisting of two fiuxgate sensors and a CMOS driver- and readout circuitry. The system exhibits a sensitivity of 12mV/?T over a magnetic field range of +/-150?T. The 3dB bandwidth of the system is 300Hz. The sensor system drains 20mA from a 5V power supply.

http://ieeexplore.ieee.org/iel5/5468575/5468576/05468609.pdf

W. Budde

Papers

A miniaturized magnetic-field sensor system consisting of a planar fluxgate sensor and a CMOS readout circuitry

A thermoelectric infrared radiation sensor with monolithically integrated amplifier stage and temperature sensor

A Thermoelectric Infrared Radiation Sensor With Monolithically Integrated Amplifier Stage And Temperature Sensor

Microwave wideband amplifiers in bulk-CMOS and CMOS/SIMOX technologies

A Monolithically Integrated Two-Axis Magnetic Field Sensor System