RU2565361C1 - Semiconductor carbon monoxide gas analyser - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: sensor consists of a semiconductor base in the form of a polycrystalline film of a solid solution of (ZnTe)_0.68(CdSe)_0.32, and a nonconducting substrate.

EFFECT: sensor according to the invention enables to determine content of carbon monoxide with sensitivity which is several times higher than that of existing sensors with a significantly simple technique of making the sensor.

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Description

The invention relates to the field of gas analysis, in particular to detecting devices used for recording and measuring the content of trace amounts of carbon monoxide and other gases. The invention can be used in ecology.

A known sensor (detector) for thermal conductivity, the action of which is based on the difference in thermal conductivity of the vapor of the substance and the carrier gas (Vyakhirev D.A., Shushukova A.F. Guide to gas chromatography. M .: Higher school, 1987. - 287 p. ) However, such a sensor (detector) is sensitive only to substances with thermal conductivity close to the thermal conductivity of the carrier gas.

Also known is a semiconductor gas sensor based on indium oxide (In ₂ O ₃ ) doped with alkali metal oxides (γamaura Hiroyuki, Tamaki Jun, Moriya Koji, Miura Norio, Yamazoe Noboru // J. Electrochem. Soc. - 1996. - V.43 . N 2. P. 36-37). It allows you to detect 6.7 - 0.05 Pa WITH in moist air at 300 ° C. The disadvantage of this device is the lack of sensitivity to control the content of carbon monoxide, a high operating temperature of 300 ° C and the complexity of manufacturing.

The closest technical solution to the invention is a gas gas humidity sensor, consisting of a polycrystalline film of indium antimonide doped with zinc selenide, coated with metal electrodes and a non-conductive substrate (Patent RU No. 2206083, Mcl 7 G01N 27/12, publ. 06/10/2003).

A disadvantage of the known device is its lack of sensitivity in the control of trace amounts of carbon monoxide. In addition, the design of the sensor involves the operation of deposition of metal electrodes and direct adsorption measurements during its manufacture.

The technical result of the invention is to increase the sensitivity and manufacturability of the sensor.

The specified technical result is achieved by the fact that in the known gas sensor containing a semiconductor base deposited on a non-conductive substrate, according to the invention, the semiconductor base is made in the form of a polycrystalline film of a solid solution (ZnTe) _0.68 (CdSe) _0.32 .

The invention is illustrated by drawings, which are presented in FIG. 1 - design of the inventive sensor, FIG. 2 - curves of the dependence of the pH value of the surface isoelectric state (pH _iso ) of ZnTe - CdSe semiconductors exposed in air (a) and in a carbon monoxide atmosphere (b), on their composition; in FIG. 3 - the calibration curve of pH changes isoelectric surface state (ΔrN _iso) semiconductor base in the adsorption process at room temperature from an initial pressure of CO (P _co). Curves a, b in FIG. 2 demonstrate a noticeable effect of carbon monoxide on pH _{from the} surface of a semiconductor base — a polycrystalline film of a solid solution (ZnTe) _0.68 (CdSe) _0.32 ; calibration curve in FIG. 3 clearly indicates the high sensitivity of the semiconductor base to carbon monoxide.

The sensor consists of a semiconductor base 1 made in the form of a polycrystalline film of a solid solution (ZnTe) _0.68 (CdSe) _0.32 and a non-conductive substrate 2 (Fig. 1).

The principle of operation of such a sensor is based on adsorption-desorption processes occurring on a semiconductor film deposited on a non-conductive substrate, and causing a change in the pH of the isoelectric state and, accordingly, the strength of the active centers of its surface.

The operation of the sensor is as follows.

The sensor is placed in a chamber at room temperature (it can be an ordinary glass tube) through which the gas analyzed for carbon monoxide content is passed (or in which it is held). Upon contact of the transmitted gas with the surface of the semiconductor film (ZnTe) _0.68 (CdSe) _0.32 , selective adsorption of CO molecules and a change in the pH of the isoelectric state of the surface occur. Using calibration curves, you can determine the content of carbon monoxide in the test medium.

From the analysis of FIG. 3 typical calibration curve obtained using the inventive sensor and expressing the dependence of ΔрН iz _from the content of carbon monoxide (P _co ), follows: the inventive sensor with a significant simplification of its manufacturing technology allows you to determine the content of carbon monoxide with a sensitivity several times higher than the sensitivity of known sensors. A significant simplification of the manufacturing technology of the sensor is due to the exclusion of the operations of applying metal electrodes to the semiconductor base and laborious adsorption measurements.

Small dimensions of the device (working volume less than 0.2 cm ³ ) in combination with a small mass of the adsorbent film can reduce the sensor constant in time to 10-20 ms.

The design of the inventive sensor can also improve other characteristics: speed, regenerability, the ability to work not only in static but also in dynamic mode.

Claims (1)

A gas sensor containing a semiconductor base deposited on a non-conductive substrate, characterized in that the semiconductor base is made of a polycrystalline film of a solid solution (ZnTe) _0.68 (CdSe) _0.32 .

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