P.W. Cheung's research while affiliated with The Hong Kong University of Science and Technology and other places
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Publications (12)
The fabrication and characterization of an integrated gas sensor based on tin oxide thin-film and improved micro-hotplate (MHP) are presented in this paper. Tin oxide thin-films are sputtered onto the MHP from tin dioxide target or pure tin metal target under different sputtering conditions. The properties of the films are analyzed by scanning elec...
The fabrication and characterization of an integrated gas sensor based on tin oxide thin-film and improved micro-hotplate (MHP) are presented in this paper. Tin oxide thin-films are sputtered onto the MHP from tin dioxide target or pure tin metal target under different sputtering conditions. The properties of the films are analyzed by scanning elec...
A spectrophotometric method is presented in this paper to demonstrate the authors' experimental results to measure bilirubin in hemolysed whole blood. The absorption spectra were taken using a HELLMA thin (0.1 mm) cuvette. Bilirubin measurement over a concentration range of 0.5 to 10 mg/dl was obtained from the composite absorption spectra with a n...
The sensing mechanism of polymer gas separation membrane to
enhance the selectivity of tin dioxide gas sensors is presented. Two
types of Commercial polymers, XU218 and PMDA-ODA of Ciba-Geigy company,
are used to coat onto the sensing film of FIGARO series tin dioxide gas
sensors TGS800, TGS813 and TGS842. Different gases such as carbon
monoxide, h...
The application of commercial mechanical computer-aided engineering (MCAE) software to the design and analysis of micro-hotplate (MHP) structures is presented. The simulation provides an estimation of heating efficiency and temperature distribution on the hotplate. The analysis is applied to a newly proposed MHP structure during layout design. Nove...
The application of a polymer to enhance the selectivity of a tin
dioxide gas sensor is presented. Commercial polymer, XU218 of Ciba-Geigy
company, is coated on the sensing film of a tin dioxide gas sensor
FIGARO TGS842 which was designed to detect methane. The polymer coated
sensor is calibrated in a high accuracy testing chamber that is
controlled...
The automated gas sensor characterization system is designed for
precision characterization of integrated or discrete gas sensors. Gas
metering and data acquisition are computer controlled. Calibration of
the gas concentration is carried out through the use of a gas analyzer
or gas chromatography (GC). The system has been used to characterize two
t...
To facilitate gas sensor design with the associated signal-conditioning circuitry, a previously developed gas adsorption model is implemented in the popular circuit simulation program SPICE. The model is based on the gas adsorption theory. With the adsorption model implemented in SPICE, the performance of a MOSFET gas sensor integrated with the ass...
A non-conducting polymer membrane can be used as a molecular sieve
to enhance the selectivity of a tin dioxide gas sensor. A commercial
polymer, polyimide XU218 of the Eiba-Geigy company, is coated on the
surface of a tin dioxide gas sensor FIGARO TGS842 which was designed to
detect methane. The polymer coated sensor is calibrated in a high
accurac...
The paper reports a novel approach to fabricate micro-hotplate for thin film gas sensor. The approach uses frontside anisotropic etching of silicon together with special layout to create the thermally isolated structure. Sandwich of inter-dielectric layers and aluminum interconnection provides the supporting material while highly doped boron diffus...
This paper reports a novel approach to fabricate a micro-hotplate
for a thin film gas sensor. The approach uses frontside anisotropic
etching of silicon together with special layout to create the thermally
isolated structure. A sandwich of inter-dielectric layers and aluminum
interconnection provides the supporting material while highly doped
boron...
Citations
... Среди различного рода и видов преобразователей весомую часть составляют преобразователи тепловые, которые представляют собой в основном первичные устройства в системах контроля или измерения [6][7][8][9][10][11][12][13][14]. Они характеризуются тем, что в их функционировании существенную роль играют тепловые процессы, так как применяются для измерения параметров тепловых процессов либо используются при преобразовании измеряемой величины в выходной сигнал [15][16][17][18][19][20][21][22][23][24]. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/276059736244231-1442829178858_Q64/Philip-Chan-20.jpg)
... Another issue of high power consumption can be solved by integrating miniaturized and thermally isolated heater, underneath the sensing material to control the operating temperature, on a sensor chip. Two approaches have been widely used to thermally isolate the heater from bulk silicon, i.e. the surface and bulk micromachining processes [4][5]. In general, surface micromachined release MEMS structures are often touted as being less fragile compared to bulk micromachined released MEMS structures; that are challenging to be packaged [1]. ...
... Innovation of reversible and compassionate ammonia sensing technology is often studied in active areas due to the widespread use of ammonia in industry and its toxic nature to animal and human bodies. Several ammonia monitoring techniques in gas samples have been investigated, including electrochemical sensors [39], optical ammonia sensors based on the up-converting luminescent nanoparticle [40], mobility spectrometry [41], and metal oxide semiconductor detectors [42]. However, these techniques cannot be employed to measure water-soluble ammonia and are only suitable for ammonia gas. ...
... In the case of methane, the risk of explosion starts at concentrations around 4.4 %, which is orders of magnitude higher than ambient concentrations around 1.8 ppm (Forster et al., 2007), and hence such solid-state sensors were not sensitive enough for measurements in ambient air. For example, Wong et al. (1996) reported on earlier TGS sensors that showed almost negligible change in response to non-polar gases such as hy-drogen and methane. A few years later, Brudzewski (1998) reported that an older TGS 813 reacted to pulses of air and methane ranging between 1600 ppm and 4000 ppm, but not at ambient concentrations (≈ 1.8 ppm). ...
... Moreover, since the best sensing temperature varies for different gases, such temperature variations can be also used to improve the selectivity of MOS sensors by choosing the temperature with best sensitivity and response time [38,39]. Catalytic filtering [40] and membrane coatings [41] have been also proposed to improve the selectivity of MOS sensors. ...
... Many different techniques, including introduction of various dopants [1][2][3], catalyst decorations [4][5][6], operating temperature variations [7][8][9], and physical design alterations [10][11][12] have been employed for selectivity enhancement [13][14][15]. Target gas separation by selective diffusion through nano-porous membranes and molecular sieves has also been employed for the fabrication of selective gas sensors [16][17][18][19]. These filters can only select the smallest molecule present in a gas mixture, and are, hence, employed in the fabrication of hydrogen detectors [20,21]. ...
