1991 Fiscal Year Final Research Report Summary
Metal-Semiconductor Contacts for Sensor Application
| Project/Area Number |
01460138
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
電子材料工学
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| Research Institution | Shinshu University |
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Principal Investigator |
ITO Kentaro Shinshu University, Faculty of Engineering, Professor, 工学部, 教授 (20020977)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAZAWA Tatsuo Nagano National College of Technology, Associate Professor, 助教授 (70126689)
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| Project Period (FY) |
1989 – 1991
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| Keywords | anodization / semiconducting oxide / hydrated tungsten oxide / metal-semiconductor contacts / hydrogen sensor / PTC effect / 水和酸化タングステン / 着色機構 |
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| Research Abstract |
We have investigated metal-semiconducting oxide contacts to develop a highly selective and sensitive hydrogen detector and a positive temperature coefficient (PTC) thermistor. Our purpose in this research is to elucidate fundamental mechanisms for these sensors and optimize process parameters of the device fabrications.
We have found that a forward current of the diode consisting of Pd thin film and semiconducting Sr_xBa_<1-x>TiO_3 ceramics increases on exposure to hydrogen. The barrier height depends on hydrogen concentration in the same way as that of a Pd MOS structure. The reverse currents of Au/anodic oxide/ barium strontium titanate ceramics structure shows the PTC effect and voltage dependence which follows the Fowler-Nordheim equation.
A transmission-type hydrogen sensor is fabricated by using a sputtered amorphous tungsten oxide film which is deposited on the glass substrate and then covered with semitransparent Pd thin film. A decrease in the spectral transmittance by hydrogen has a peak at the wavelength of 900 nm. The response time of the sensor is of the order of 10^2 s. Though the hydrogen sensitivity is considerably degraded after annealing at 200 ﾟC in vacuum, the sensor partially recovers the initial response time after subsequent exposure to water vapor at 100 ﾟC and aging in room air.
A reflection-type hydrogen sensor consists of an anodic oxide film formed on the W sheet and then covered with semitransparent Pd or Pt film. Its response time is of the order of 10 s. It is revealed by X-ray diffraction that the film consists of WO^3・H^2O. Coloration mechanism for the sensor is considered to be based on formation of hydrogen tungsten bronzes and a consequent increase in electron concentration of the film. A rate determining step of the coloration reaction is probably due to water-assisted proton diffusion. The best processes for polishing and anodizing the W sheet are also presented.
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Research Products
(8 results)
