Introduction to heat transfer

In this paper, we present a complete characterization of poly SiGe bolometers. Devices having different dimensions and different geometry have been fabricated. The dependence of the low-frequency noise and of the temperature coefficient of resistance (TCR) on resistivity in poly SiGe has been measured and modeled. The impact of resistivity, bias voltage, thermal conductance, thickness, and dimensions of the active element on the device performance has been investigated. It has been demonstrated that, by using the appropriate absorber and by optimizing the device parameters, poly SiGe bolometers are suitable for realizing high-performance focal plane arrays (FPA's).

Characterization and optimization of infrared poly SiGe bolometers

This paper presents a Pirani vacuum gauge based on a micro-hotplate (MHP) supported by six unequal beams. The MHP is fabricated using surface silicon micromachining technique. A thermal model for the gauge is established by means of Fourier analysis, which takes account of internal heat source in the beams and pressure-dependent gaseous heat conduction above and below the MHP. It is applied to determine the MHP operation temperature, temperature distributions along the supporting beams and heat losses through various mechanisms at different vacuum pressure. The measurements of gauge characteristics have been done and the results show good agreements with theoretical analysis. The measured sensitive range of the gauge is 10−1 to 105 Pa when driven by a constant current, 0.8 mA.

A micro-Pirani vacuum gauge based on micro-hotplate technology

Nanostructured vanadium oxide thin film with high TCR at room temperature for microbolometer

Microelectromechanical systems sensors have been intensively developed utilizing various physical concepts, such as piezoresistive, piezoelectric, and thermoresistive effects. Among these sensing concepts, the thermoresistive effect is of interest for a wide range of thermal sensors and devices, thanks to its simplicity in implementation and high sensitivity. The effect of temperature on the electrical resistance of some metals and semiconductors has been thoroughly investigated, leading to the significant growth and successful demonstration of thermal-based sensors, such as temperature sensors, convective accelerometers and gyroscopes, and thermal flow sensors. In this paper, we review the fundamentals of the thermoresistive effect in metals and semiconductors. We also discuss the influence of design and fabrication parameters on the thermoresistive sensitivity. This paper includes several desirable features of thermoresistive sensors and recent developments in these sensors are summarized. This review provides insights into how it is affected by various parameters, and useful guidance for industrial designers in terms of high sensitivity and linearity and fast response. [2017-0022]

Thermoresistive Effect for Advanced Thermal Sensors: Fundamentals, Design Considerations, and Applications

As an extension of previous work in our laboratory, a wide‐range Pirani gauge that is capable of measuring vacuum pressure down to 10−7 Torr reproducibly has been built. The micromachined Pirani sensor used in the experiments has a suspended membrane that is supported by the nearly radiation‐limited, thermally insulating beam leads crossing over a V‐groove cavity. A method of partial dummy compensation, as proposed previously by Weng and Shie for eliminating the ambient drift, is proved here to be very effective with a thermal drift as small as only 5.7 μV/°C. It has also been found that a thermal‐stress‐induced piezoresistive effect, which has a profound influence on the limitation of measurement, appears in the constant‐bias operation wherein the sensor temperature rises with the reduction of gas pressure and therefore thermal conduction. This effect causes the irreproducibility of pressure measurements by the device below 10−5 Torr. In addition to its inherently higher sensitivity, a constant‐temperatu...

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High performance Pirani vacuum gauge

The characteristic thermal parameters of a platinum-film microbolometer are extracted from the data of two measuring methods. A simple and accurate equivalent circuit model, along with its thermal behavior, is proposed for the device. Applying the model to simulate some device circuits results in good agreement with the experimental data. Furthermore, an effective method of ambient temperature compensation, proposed previously by our laboratory, is demonstrated both experimentally and by simulation using the same model. The established electro-thermal model therefore serves as an useful tool for SPICE simulations in the design of microbolometers.

https://ir.nctu.edu.tw:443/bitstream/11536/881/1/A1996VY41300009.pdf

Characterization and modeling of metal-film microbolometer

A sensitive micro-Pirani vacuum sensor has been fabricated. With effective schemes of ambient-temperature compensation and stabilization, it is capable of measuring vacuum pressure linearly from 1 torr down to 10 −7 torr, a three orders-of-magnitude improvement in resolution over conventional gauges. A special electrothermal SPICE model, complementary to the conventional analog representation of thermal parameters, is also proposed. It allows a high-level sensor-circuit integrated simulation based on the most fundamental principle and thermal variables. Good agreement between the measured data obtained from a constant-temperature readout circuit and the simulation result is demonstrated.

https://ir.nctu.edu.tw:443/bitstream/11536/1302/1/A1996UV64900010.pdf

A sensitive Pirani vacuum sensor and the electrothermal SPICE modelling

Obtaining thermal parameters is important in evaluating the performance of thermal microsensors. Two experimental methods are described here for the study of the pressure-dependent thermal behavior of the sensors: a bolometric method that utilizes a chopped light input to obtain a sensor frequency response, and deriving its thermal data therefrom; a.d.c. electrical method that measures the heat required for balance under d.c. bias, and obtaining sensor information. The thermal conductance and capacitance, absorptance, as well as emissivity of a sensor can be extracted from the experimental measurements. These parameters provide the essential data for the electrothermal SPICE program in the related design simulations.

https://ir.nctu.edu.tw:443/bitstream/11536/1167/1/A1996VY35800009.pdf

Parameter extraction of resistive thermal sensors

This paper presents a platform technology with experimental results that show the scientists and biologists a way to rapidly investigate and analyze the biological effects of localized extremely low frequency (ELF) electromagnetic field (EMF) on living cells. The proximity effect of the localized ELF-EMF on living cells is revealed using the bio-compatible microplatform on which an on-glass inductive coil array, the source of the localized ELF-EMF in micro scale, is designed, fabricated and operated with a field strength of 1.2 ± 0.1 mT at 60 Hz for cell culturing study. After a 72 h ELF-EMF exposure, HeLa (human cervical cancer) and PC-12 (rat pheochromocytoma) cells exhibit about 18.4% and 12.9% cell proliferation rate reduction, respectively. Furthermore, according to the presented dynamic model, the reduction of the proliferation can be attributed to the interference of signal transduction processes due to the tangential currents induced around the cells.

https://ir.nctu.edu.tw:443/bitstream/11536/31894/1/000284828500023.pdf

Yeong-Maw Chen

Papers

High performance Pirani vacuum gauge

Characterization and modeling of metal-film microbolometer

A sensitive Pirani vacuum sensor and the electrothermal SPICE modelling

Parameter extraction of resistive thermal sensors

Design and fabrication of a microplatform for the proximity effect study of localized ELF-EMF on the growth of in vitro HeLa and PC-12 cells