Recently SnSe, a layered chalcogenide material, has attracted a great deal of attention for its excellent p-type thermoelectric property showing a remarkable ZT value of 2.6 at 923 K. For thermoelectric device applications, it is necessary to have n-type materials with comparable ZT value. Here, we report that n-type SnSe single crystals were successfully synthesized by substituting Bi at Sn sites. In addition, it was found that the carrier concentration increases with Bi content, which has a great influence on the thermoelectric properties of n-type SnSe single crystals. Indeed, we achieved the maximum ZT value of 2.2 along b axis at 733 K in the most highly doped n-type SnSe with a carrier density of −2.1 × 1019 cm−3 at 773 K. The good thermoelectric figures of merit of p-type tin selenide single crystals are actively studied. Here, the authors show that n-type SnSe can also reach a figure of merit of around 2, at high temperatures, when doped with bismuth.

/pdf/achieving-zt-2-2-with-bi-doped-n-type-snse-single-crystals-1ws4ftemn6.pdf

Achieving ZT=2.2 with Bi-doped n-type SnSe single crystals

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

This review provides a comprehensive survey of noise research in MEMS. Some background on noise and on MEMS is provided. We review noise production mechanisms, and highlight work on the theory and modeling of noise in MEMS. Then noise measurements in the specific types of MEMS are reviewed. Inertial MEMS (accelerometers and angular rate sensors), pressure and acoustic sensors, optical MEMS, RF MEMS, surface acoustic wave devices, flow sensors, and chemical and biological MEMS, as well as data storage devices and magnetic MEMS, are reviewed. We indicate opportunities for additional experimental and computational research on noise in MEMS.

Noise in MEMS

A framework for beef traceability from farm to slaughter using global standards: An Irish perspective

Magnetostriction and magnetostrictive materials for sensing applications

A novel magnetic field sensor is presented in this paper. It combines the classical Fluxgate principle with the anisotropic magneto-resistance (AMR) effect exhibited by barber-pole biased AMR film-resistors. It is shown that such film-resistors can be used as Fluxgate magnetic cores, because they exhibit one high-resistivity state and one low-resistivity state depending on the film magnetization polarity. Periodical alteration of the magnetization polarity, forced by an excitation field, makes the film-resistivity become a rectangular function of time, whose duty-cycle is proportional to the measured ambient field intensity. The proposed design helps with the suppression of repeatability and time-drift errors that are common in AMR sensors; the excitation field enhances the spin-alignment along the easy-axis of the film-resistor. The design also provides excellent temperature stability. Moreover, it is shown how a single AMR film-resistor can be employed for simultaneous sensing of two field components (i.e. on a x – y plane); the first component modulates the duty-cycle of the rectangular function (Fluxgate principle) and the latter its amplitude (conventional AMR effect). A complete mathematical modeling of the proposed sensor is presented in this work. The theoretical results have been verified by the use of a Honeywell HMC1021 single-chip sensor. The calibration data fairly agrees with the theory.

A novel micro-Fluxgate sensor based on the AMR effect of ferromagnetic film-resistors

In the present work, a new monolithic capacitive pressure sensor is being introduced. The sensor is manufactured according to a custom, 15-step SOI process. The process primarily offers great flexibility as far as sensor design is concerned. Absolute or differential pressure sensing is possible by simply arranging proper sensor package. Measurement sensitivity and span are easily regulated over a wide range of values by setting one-single design parameter. Attention is paid to avoid p–n junction formation in order to improve the sensor robustness against temperature increase and allow high-temperature post-processing without doping profile degradation. The presented design allows the implementation of an ordinary p-well CMOS post-process. Sensitivity of 2 mV/kPa, within a span of 180 kPa (2%) and a bandwidth of 25 kHz, is achievable by means of a CMOS switched-capacitor ASIC that is developed and presented here. Significant care has been taken for the ASIC performance to depend as less as possible on CMOS process and transistor-parameter variations that increase due to poor uniformity of the transistor substrate. Moreover, a state-of-the-art design is implemented for the circuit to provide robustness against parasitic capacitance s connected in parallel with sensing capacitors. Implementation of additional analog signal processing improves the aforementioned accuracy at a significant extend. The sensors main applications include medical devices such as sphygmomanometers and respirators that require high reliability and biocompatibility. © 2005 Elsevier B.V. All rights reserved.

A new SOI monolithic capacitive sensor for absolute and differential pressure measurements

Analytical modeling of classical fluxgate sensor function is presented, accompanied by computer simulation results for numerous actual core hysteresis loops that enables theoretical verification of fluxgate limitations which obstruct efficient miniaturization. This mathematical analysis leads to the proposition and experimental verification of two alternative fluxgate signal extraction techniques that can be optimally utilized with conventional thin film and fine wire cores, and which may improve miniature sensor characteristics, thus enabling micro-system fabrication without performance degradation. Two fluxgate systems which meet the theoretically predicted performance, based on these techniques have been developed.

Boosting the performance of miniature fluxgates with novel signal extraction techniques

A switched-capacitor integrated system is presented in this work that attains sub-fF measurement resolution in integrated capacitive sensors, with 1.5-kHz bandwidth and 50-muW average power consumption in continuous function mode. The proposed design employs a pair of nonoverlapping clocks and an operational transconductance amplifier (OTA) that can be made as simple as a basic differential pair. The system exhibits 0.8% linearity error and 0.01 fF/degC temperature drift. It is appropriate for differential, absolute, and ratiometric capacitance measurements, and shows robustness against interconnection parasitics, transistor dimensional mismatch, and process variations, which are an important feature in the case of sensor-die CMOS postprocessing

A low-power/low-noise readout circuit for integrated capacitive sensors

A completely scalable lumped-circuit model for horizontal Hall devices is presented therein that can be efficiently implemented in SPICE-like simulators. The model has been employed for the quantitative analysis of: a) geometrical, b) temperature, and c) fieId-dependent mobility effects, as well as for d) the dynamic response and e) the noise behavior of Hall sensors.

P.D. Dimitropoulos

Papers

A novel micro-Fluxgate sensor based on the AMR effect of ferromagnetic film-resistors

A new SOI monolithic capacitive sensor for absolute and differential pressure measurements

Boosting the performance of miniature fluxgates with novel signal extraction techniques

A low-power/low-noise readout circuit for integrated capacitive sensors

Horizontal Hall Devices: A Lumped-Circuit Model for EDA Simulators