SnO thin films for gas sensors modified by hexamethyldisilazane after rapid thermal annealing (original) (raw)
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Sensors and Actuators B: Chemical, 2003
The performance of metal oxide gas sensors is affected by their surface states, elemental composition, electronic and morphologic structures. Films of tin oxide were deposited onto silicon substrates using reactive radio frequency sputtering and drop-coating. In order to understand how the deposition procedure affects the morphology of the films, a structural characterisation based on atomic force microscopy was performed. The differences in elemental composition were analysed by X-ray photoemission spectroscopy. For sensors deposited by sputtering, a granular morphology and the presence of stannic sub-oxide (SnO) was observed. Sensors deposited by drop coating had a granular morphology but no stannic sub-oxide was present. The sensitivity of the drop-coated sensors to ethanol was found to be up to five times higher than the one of sputtered sensors. This difference can be associated to the presence of the stannic sub-oxide, grain size and intergranular coupling. #
SnO 2 films for thin film gas sensor design
Materials Science and Engineering B-advanced Functional Solid-state Materials, 1999
In this report we present the results of the study of the influence of the parameters of SnO2 thin films on their basic gas sensitive characteristics such as kinetics and absolute gas sensitivity. We have particularly investigated the influence of the film thickness, structure, concentration of charge carriers, and presence of uncontrolled impurities in the SnO2 films, which were deposited
Microstructural properties and sensing behaviour of SnO 2 gas sensor
Cadmium sulphide (CdS) doped tin oxide (SnO 2) thick film sensors is fabricated using screen printing technology for the detection of acetone and liquid petroleum gas. Undoped tin oxide paste prepared using ball mixing and then screen-printed on alumina substrate (sensor S 1). Further, we fabricated a 2wt% CdS doped tin oxide thick film sensor (sensor S 2) in the laboratory following mixing, firing and other treatment as applied in undoped paste. The fabricated undoped (SnO 2) and doped (CdS-SnO 2) thick films are characterized using XRD and atomic force microscope (AFM). It is found from XRD analysis that the crystallite size decreases with CdS content and it is 17 nm and 12 nm for undoped and 2wt% CdS doped SnO 2 respectively. The grain size was about 75 nm and 46 nm for undoped and CdS doped tin oxide thick films were obtained by AFM investigation. The sensing response of the fabricated sensor (S 1 , S 2) is measured with varying concentration (0-5000 ppm) of acetone and LPG in air ambient at 200 0 C. Measurement reveals that the S 2 sensor is more suitable for the detection of acetone over LPG.
Undoped and Pd-doped SnO2 thin films for gas sensors
Sensors and Actuators B: Chemical, 1993
Undoped and Pd-doped SnO, thin films for gas sensors The aim of this work is the study of the structure and temperature dependence on the conductance and sensitivity of undoped and Pd-doped Snot thin films (0..5-2 pm}. Polycrystalline SnO, thin films have been synthesized by pyrolysis, cm a heated substrate (oxidized silicon (IOO}), of an aerosol produced by ultra-high frequency spraying of a volatile precursor solution. A mixture of two precursors is used to obtain Pddoped SnO,. Growth rate and microstructure of the films are particularly well controlled by the deposition temperature (460-560 "C). Conductivity measurements wem performed between 50 and 500 "C, alternately under pure air (GJ and polluted air fG) (ethanol or CO), using gold layers as electrodes. The pure SnO, sensitivity (C -Q/G, to ethanol increases when the elaboration temperature decreases, in connection with the specific area increase. P~ladium ~n~~~tjon sjgni~~ntly promotes the sensitivity. CO ~nsjt~vit~ is increased by 30 when palladium is inco~amt~ into the SnO, thin fiims and exhibits a marked Peak at low t~m~ratum. The sen~tiv~ty stability is better when the deposition temperature is higher, according with a better stability of the microstructure. A variable frequency elect&at study was carried out using complex impedance spectroscopy ( 1 mHz-20 MHz). Ethanol and CO reactions were observed and the role of grain boundaries studied.
Gas sensing properties of epitaxial SnO 2 thin films prepared by atomic layer deposition
Sensors and Actuators B-chemical, 2003
Undoped SnO 2 thin films are grown on a-Al 2 O 3 (0 1 2) (r-cut sapphire) substrates by gas phase atomic layer deposition (ALD). Two precursor pairs, SnI 4 -O 2 and SnCl 4 -H 2 O 2 , both new for ALD, are used. The films have a cassiterite structure and are [1 0 0] sapphire oriented. A good epitaxial quality and the conductivity acceptable from the standpoint of semiconductor gas sensors are achieved for ultrathin films grown from SnI 4 -O 2 at 600 8C. The sensitivity of these films to CO in air has a maximum at a thickness of about 10 nm. Response rise and decay times belonging to a several seconds interval are measured. The films are assumed to function as a single grain. #
Fabrication and Testing of SnO 2 Thin Films as a Gas Sensor
Archives of Applied Science Research, 2012
Tin dioxide ( SnO 2) thin films were prepared using the thermal spray p yrolysis method from SnCl2.2H 2O isopropyl mixing with water solution on the glass substrate h eated at 450 ◦ C. The films were characterized by X-ray diffractio n (XRD), The crystallite size was evaluated to be 4.4 13 nm by using the Scherrer’s equation. Atomic For ce Microscope (AFM) and optical absorption spectra wer e taken to examine the surface morphology and opt ical properties to determine the band gap energy 3.9 eV, increase in band gap energy is revealed that nan ostructure SnO 2 films. These films were tested in butane gas at op erating temperature 470 ◦ C. The response and recovery time is 13 sec, 63 sec respectively. Keyword: SnO 2 Thin films; spray pyrolysis; butane gas sensing; s ensitivity.
Gas sensing properties of SnO2 thin films grown by MBE
Sensors and Actuators B: Chemical, 2006
A comparative study of the gas sensing properties between mono-and poly-crystalline tin dioxide thin films has been carried out. SnO 2 films of thickness range 30-100 nm were deposited on r-axis sapphire substrate in temperature range 260-550 • C using the molecular beam epitaxy (MBE) technique. The crystalline structure of the resulting films was examined by using in situ high energy electron diffraction (RHEED), X-ray diffraction (XRD) and atomic force microscopy (AFM). The electrical properties of the films were characterized by using a Hall effect measurement system. Sensitivity towards different gases was tested and a comparison between mono-and poly-crystalline films is presented. Monocrystalline films were found to exhibit greater potential for continuous gas detection.
Response to oxygen and chemical properties of SnO2 thin-film gas sensors
Vacuum, 2008
The measurements of the response-in terms of the conductance changes-to oxygen adsorption of tin dioxide (SnO 2) thin-film-based gas sensors were performed. The sensing SnO 2 layers were obtained by means of the rheotaxial growth and thermal oxidation (RGTO) method. The sensor responses were measured under a dry gas flow containing oxygen in nitrogen, within the range of temperature from 25 to 540 1C. For comparison, similar studies were performed for a commercial SnO 2 thick-film (TGS 812) gas sensor. The in-depth profiles of the chemical composition of the RGTO SnO 2 layers were determined from the scanning Auger microprobe experiment. The changes in concentration ratios [O]/[Sn] and [C]/[Sn] from the near-surface region towards the grain bulk were shown.
Gas sensing properties of SnO2 thin films and binary systems compounds
Journal of Physics: Conference Series
Fe2O3 were prepared by pulsed laser deposition technique using (Nd:YAG) laser of λ=1064 nm average frequency (6) Hz and pulse duration (10 ns) under vacuum of 10-2 mbar)deposited on glass, n-Si single crystals substrate room temperature with thickness of (100±10) nm. The structures of pure SnO2 and ,SnO2:TiO2 , SnO2:MoO3 , SnO2:WO3 , SnO2:Cr2O3 , SnO2:Co3O4 compounds were studied by X-ray diffraction .the results showed that there was red shift accompanied addition of MoO3 and TiO2 while a blue shift accompanied the addition of WoO3 , Cr2O3 , Fe2O3 to tin oxide. The gas sensing measurements of NO2 gas showed that SnO2:TiO2 thin films prepared on n-Si substrate have better sensitivity than thin films from the other binary compounds. Maximum sensitivity (231.4%) was obtained from SnO2:TiO2 thin film prepared on n-Si substrate at operating temperature 373K .
SnO2 sol–gel derived thin films for integrated gas sensors
Sensors and Actuators B: Chemical, 2001
In this paper, we present for the ®rst time the compatibility of sol±gel method for SnO 2 thin ®lm preparation with the silicon technology for integrated gas sensor microfabrication. An integrated circuit (IC) compatible test structure of medium power consumption equipped with boron-doped silicon heater and Au/W metallization is developed. The acid composition of the (liquid) sol phase, the thermal budget of sensing layer structuring, selective wet etching of SnO 2 sensing ®lm, thickness uniformity and step coverage of SnO 2 sol±gel ®lms are ®tted with the requirement of above test structure where metal layer is deposited before SnO 2 ®lm. Nanometric grain sizes of undoped and antimony doped polycrystalline SnO 2 ®lms are obtained, as revealed by XRD investigations. The AFM measurements of SnO 2 thin ®lms deposited on existing Au/W metallization shown the excellent step coverage and morphology of SnO 2 ®lms used for gas sensing applications. Low temperature gas sensing properties of our SnO 2 sol±gel derived thin ®lms in reducing (CH 4 , CH 3 COOH) and oxidizing (NO 2) are preliminary reported by using our integrated test structure.