ZnO transparent thin films for gas sensor applications (original) (raw)
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Nanocrystalline ZnO thin film for gas sensor application
Journal of Ovonic Research
Nano-crystalline (NC) materials exhibiting small particle size and large surface area may be applied for gas sensors, for which an excellent surface effect is required. Thin films of zinc oxide (ZnO) have been deposited onto glass substrates using a simple and inexpensive ultrasonically spray pyrolysis technique. Aqueous methanolic solution of zinc acetate was used as a spraying solution. The concentration of the solution was 0.1 M. The films prepared at different substrate temperature were uniform and well adherent to the substrates. X-ray diffraction (XRD) studies showed that all the films were polycrystalline in nanosize scale. The SEM photographs reveal the nano-size of the constituents. The electrical resistivity of the films was found to be dependent on the deposition temperature. The room temperature electrical resistivity was found to be varying in the range 10 -5 to 10 -6 Ω cm -2 . The sample resistance is measured with the presence of CH 4 in Ar carrier gas. The obtained responses of the samples were studied where our data were analyezed on the basis Yamoze SnO 2 sensor.
Nanostructured ZnO and ZAO transparent thin films by sputtering-surface characterization
Zinc oxide (ZnO) and aluminum zinc oxide (ZAO) transparent thin films with different thickness were prepared by dc magnetron sputtering technique using metallic targets onto silicon and Corning glass substrates. Surface investigations carried out by Atomic Force Microscopy (AFM) and X-ray Diffraction (XRD) have shown a strong influence of deposition tech-nique parameters on the film surface topography. Film roughness (RMS), grain shape and dimensions were found to correlate with the deposition parameters. The results revealed that the target composition has a radical effect on ZnO and ZAO film characteristics. XRD analysis revealed that all films grown by dc magnetron sputtered are polycrystalline regardless of target composition. The correlation of conductivity measurements with film RMS has shown a strong influence of surface on film electrical properties. Since the film surface characteristics are deter-mined by the growth conditions, the gas sensing characteristics of these film...
Surface characterization of ZnO transparent thin films
Journal of Physics: Conference Series, 2005
Zinc oxide transparent thin films (ZnO) with different thickness were prepared by dc magnetron sputtering and pulsed laser deposition (PLD) techniques using metallic and ceramic targets onto silicon and Corning glass substrates. Structural investigations carried out by Optical Microscopy (OM), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) have shown a strong influence of the target and deposition technique on the film surface topography. Film roughness (RMS), grain shape and dimensions were found to correlate with the applied deposition technique. On the films grown by PLD high oriented nanostructures were identified and XRD measurements proved that they have a polycrystalline structure following the characteristic zincite XRD spectrum, while the dc magnetron sputtered films were amorphous. Results revealed also that the target composition has a radical effect on film characteristics. In the case of thin films sputtered from a ceramic target AFM analysis has shown the presence of hexagonal shaped grains exhibiting a different surface behavior compared with the films grown from metallic target, the first being also the case of the PLD grown film surfaces. This work indicates that the film surface characteristics are strongly influenced by the deposition technique and conditions applied, thus providing a tool for the enhancement of the film sensing capabilities.
Structural characterization of ZnO thin films deposited by dc magnetron sputtering
Thin Solid Films, 2007
In this work we present recent results on ZnO thin films grown by dc magnetron sputtering technique at room temperature (RT), focusing on structural and surface characterization using conventional cross-section transmission electron microscopy (XTEM) and high resolution cross section transmission electron microscopy (HRXTEM) in an attempt to understand the thickness influence on film, mechanical and optical properties as well as photoreduction/oxidation conductivity changes. Films were found to be polycrystalline with a columnar mode of growth. For films with thickness over 100 nm, XTEM and HRTEM analysis evidenced the presence of a small grains transition layer near interface with the substrate, feature which plays an important role in ZnO thin films for gas sensing application. The control of such structural parameters is proved to be critical for the improvement of their gas sensing performance.
Journal of Materials Science: Materials in Electronics, 2020
In this work, ZnO thin films were deposited by ultrasonic spray pyrolysis by utilizing zinc acetate and zinc nitrate as precursors. Deposition substrate temperature, solution precursor and molarity were varied. Molarity was fixed to 0.1 and 0.3 M for each precursor solution. ZnO thin films were deposited at two substrate temperatures, 250 °C and 450 °C. Morphological, structural and chemical characterizations were performed in order to study the effect of experimental conditions such as solution molarity, substrate temperature and precursor type on the ZnO thin films properties. Films deposited with acetate precursor have a polycrystalline structure, contrary to samples deposited with nitrate precursor, which are monocrystalline. Lastly, a total of eight samples with different characteristics mentioned above were utilized for CO 2 detection. Our results let us suggest that sensing response is slightly higher when nitrate precursor solution is utilized. In addition, the fastest response and recovery time were found in samples deposited by nitrate precursor solution. The main objective of this work is the discussion of the increment in response and recovery time as a consequence of the electronic interaction between the CO 2 and the ending (100) crystal plane of ZnO films deposited with nitrate precursor solution, which takes place due to the monodentate and bidentate adsorption path ways.
ZnO thick film gas sensors fabrication and its structural and electrical Properties
In the present work, the ZnO thick films were prepared by a standard screen printing method on alumina substrate. The developed thick films were fired at different temperatures in air atmosphere. The structural and electrical properties were investigated. X-Ray diffraction pattern analysis shows that fabricated films are polycrystalline. Scanning electron microscopy SEM shows that the fabricated ZnO films are granular and porous. The DC resistance of the films was measured by half bridge method in air atmosphere at different temperatures. The films were showing decrease in resistance with increase in temperature indicating semiconductor behavior. The resistivity, activation energy and temperature coefficient of resistance (TCR) are evaluated at different firing temperatures.
Single step deposition of different morphology ZnO gas sensing films
Sensors and Actuators B: Chemical, 2007
Al-doped ZnO thin films were deposited onto fixed silicon substrates by dc reactive sputtering. The inherent lateral inhomogeneity in the deposited film with areas of different morphology and sheet resistance revealed different sensing properties. This novel approach offers the possibility of controllable deposition of ZnO sensing layers for the simultaneous manufacturing of sensors with different properties in an array in a single technological step.
Fabrication, Processing and Characterization of Thin Film ZnO for Integrated Optical Gas Sensors
MRS Proceedings, 2009
Zinc oxide layers deposited on quartz substrates by means of RF reactive magnetron sputtering with subsequent RTP annealing in a nitrogen flow at 400 o C and in an oxygen flow at 500 o C have been investigated in applications to waveguide structures. The ZnO films reveal a highly c-oriented columnar structure with a surface roughness of 4.3 nm. Annealing causes a significant increase of the lattice constant to the value of 5.210±0.001 Å suggesting the relaxation of the stress in the film. The annealing process causes a significant improvement of propagation properties of the fabricated waveguide structures in comparison to structures using as-deposited ZnO films. The minimal attenuation coefficient of the 630 nm thick films was found to be 2.8 and 3.0 dB/cm for TE0 and TM0 modes respectively.
Materials Research Bulletin, 2009
A B S T R A C T Nanostructured ZnO thin films have been deposited using a successive chemical solution deposition method. The structural, morphological, electrical and sensing properties of the films were studied for different concentrations of Al-dopant and were analyzed as a function of rapid photothermal processing temperatures. The films were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron and micro-Raman spectroscopy. Electrical and gas sensitivity measurements were conducted as well. The average grain size is 240 and 224 Å for undoped ZnO and Al-doped ZnO films, respectively. We demonstrate that rapid photothermal processing is an efficient method for improving the quality of nanostructured ZnO films. Nanostructured ZnO films doped with Al showed a higher sensitivity to carbon dioxide than undoped ZnO films. The correlations between material compositions, microstructures of the films and the properties of the gas sensors are discussed. ß
Characteristics of Zinc Oxide Film Prepared by Chemical Spray Deposition as a Gas Sensor
2011
Zinc oxide thin films were deposited by chemical spray pyrolysis onto glass substrates which are held at a temperature of 673 K. Some structural, electrical, optical and gas sensing properties of films were studied. The resistance of ZnO thin film exhibits a change of magnitude as the ambient gas is cycled from air to oxygen and nitrogen dioxide.