UA85925U - Resistive ethanol sensor - Google Patents

Abstract

A resistive ethanol sensor includes semiconductor layer applied on insulating carrier with two electrodes, system for gas supply and measuring circuit. Besides that, ZnO nano-structures are used as a sensitive semiconductor layer.

Description

The useful model belongs to the field of metrology and can be used in the food industry to control the content of ethanol in biotechnological processes, namely in the production of alcohol-containing substances and confectionery, in the perfume industry and in the diagnosis of alcohol in human breath.

A resistive gas sensor based on metal oxide (ZpO", or IpOz, or 7p0O) is known, the action of which is based on measuring the change in the resistance of a sensitive element based on metal oxides under the influence of an indicator gas (Vuytsik V., Gotra 3., Grigoryev V. Microelectronic sensors of physical quantities - Lviv: Liga-Press, 2002. - 475 p... Resistive type sensors consist of a sensitive film applied to the substrate, a heater in the form of a resistive film applied on the other side of the substrate, and electrodes.

The disadvantages of such a sensor are high operating temperatures (200-500 "C) and complex designs due to the need to install a heating element.

A known resistive gas sensor type T25 822 for detecting vapors of organic solvents. The sensor is made on the basis of a film of stannous dioxide (ZpOg) applied to an aluminized ceramic tube, inside which a heater is placed. The sensitivity of such a sensor to ethanol vapors is 300 ppt, the sensitivity to resistance changes does not exceed 40.

Iiapaagt Teptv apa Sopainopv oi ZaiIe oi Ridago OA Ips., mlum/. Ridagozepsog.sot/Letptv.pti.

The disadvantages of such a sensor are relatively low sensitivity and the complexity of the design due to the need to use a heating element.

A known gas sensor based on metal oxide nanostructures with n-type conductivity (ZpO", or IpgOz, or 7pO), which has a higher sensitivity and a shorter response time than film sensors.

Compared to the film sensor, the sensor based on nanostructures has better characteristics due to the larger size of its working surface area |(Zsptidi-Mepave I. 7pO-Mapozygisiygez, YuOeyesiv, apa Oeyemisez / I. Zsptidi-Mepaye, U. MasMapyv-Ogizzoi! // Maietia !5 Todau. - 2007. - M. 10. - R. 40-48.

The disadvantages of such sensors are the use of raw materials of high purity and expensive equipment used to obtain nanostructures.

The closest technical solution to the proposed useful model - the prototype is the ethanol sensor based on zinc oxide I.B. Kapustyanik, B.I. Turko, M.R. Panasiuk, M.V. Party,

V.Ya. Kulyk Engineering of sensitive elements of ethanol, ammonia and acetone based vapor sensors

From thin films 2pO:Sy // bBepsog Eiesigopis5 apa Misgozuztet Tesppoiiodiev5. - 2012. - T. 3. - b. 48-52). The sensor consists of a sensor film applied to a mesh substrate, a Nisel chrome heater and aluminum contact pads. The ethanol sensor based on zinc oxide works on surface effects, the operating temperature of which is 200-400 "C. When the film is exposed to 210 ethanol vapors, the conductivity increases, the resistance decreases. The gas-sensitive characteristics of the film are significantly improved when alloying impurities are introduced, for example, copper. The highest sensitivity is achieved for a 7pO:Sy film, with a response time of 100 seconds.

The disadvantages of the ethanol sensor are the energy-consuming technology of manufacturing the sensor film with the use of complex equipment, low sensitivity to small concentrations of ethanol (change in resistance does not exceed 10 times).

The useful model is based on the task of improving the resistive ethanol sensor by using 2pO nanostructures for the sensitive layer, which provide an increase in the size of the working surface area of the sensor, which will make it possible to reduce energy consumption when producing a sensitive element of the sensor and increase its sensitivity.

The problem is solved by the fact that in a resistive ethanol sensor, which contains a sensitive semiconductor layer deposited on a non-conductive substrate with two electrodes and a heating element, a system for supplying ethyl alcohol vapors and a measuring circuit, 2n0 nanostructures are used as a sensitive semiconductor layer.

The proposed sensor and the prototype have significant common features (sensitive element with 7p0, sieve substrate, ohmic contacts and measuring circuit).

The technical result of the claimed sensor is due to the fact that the authors of the useful model used for the first time to create a sensitive element of the ethanol sensor a nanostructure of 2pO with p-type conductivity (Patent for a utility model Mo 78485 Ukraine, IPC СО1с 9/00. The method of obtaining a nanostructured material of 7pO with p-type G.O. Lubochkova, B.Yi.

Turko, O.P. Kregel, V.B. Kapustyanik, I. Kityk, M. Pyasetsky. - MO and 201208985 Application. 07/20/2012;

Publ. 25.03.2013, Bul. Mo 6), which made it possible to indicate small concentrations of ethanol.

Fig. 1. Photomicrograph of the surface of the sensitive sensor element based on zinc oxide nanostructures.

Fig. 2. Schematic image (top view) of a resistive sensor, where 1 is a mesh substrate, 2 is an aluminum contact pad, and C is a sensitive element made of zinc oxide (516) nanostructures.

Fig. 3. Schematic image of the sensor (bottom view): 1 sieve substrate, 2 - nickel-chromium heater.

Fig. 4. The response curve of a sensor created on the basis of 2pO nanostructures to ethanol vapor with a concentration of 100 ppt at an operating temperature of 350 "C. The resistive ethanol sensor consists of 27pO nanostructures obtained by electrodeposition from an aqueous solution in an electrochemical cell with two electrodes, a sieve substrate, with thermal evaporation in a vacuum, two contact aluminum electrodes and a nickel-chromium heater applied to it using the VUP-5M installation.

Deposition of nanostructures is carried out from an aqueous equimolar solution of 7p(MOz)2:bHgO and hexamine SeH:2Ma4 with a concentration of both reagents in the range of 10-30 mM with a solution pH of about 7. A voltage of 0.9 V is applied to the working electrode-substrate. To increase 0.1 M aqueous solution of KSI is added to the electrical conductivity of the solution. A nickel-chromium resistive heater is deposited on the opposite side of the sieve substrate by thermal evaporation in a vacuum.

The aluminum contact pads and the nickel-chromium resistive heater are applied according to certain patterns. Thickness measurements of aluminum and nickel-chromium films are carried out on the MI-4 microinterferometer. The surface area of the sensitive element of the sensor made of 7p0 nanostructures is 1 cm.

The study of sensory properties of nanostructures is carried out using a hermetic chamber with a capillary for supplying the analyzed substance, in which a sample with metal contacts and a heater is placed. The change in resistance is fixed after reaching a stationary value (after 60-120 s). The resistance and operating temperature of the sensor are measured with a multimeter

ВМ859СРа (VKUMEM, Taiwan) with chromel-alumel thermocouple and software. In fig. 4 shows an example of the response of a sensor created on the basis of 27p0 nanostructures to ethyl alcohol vapors, which illustrates its operation. And the table summarizes the comparative properties of ethanol sensors based on zinc oxide.

When the sensor is placed in a gas environment, particles are adsorbed on its surface

С2Н5»ОнН. Under the influence of small concentrations of ethanol vapors of 100 ppt, a significant increase in the resistance of the sensor (Fig. 4), namely - by 55 times, is observed. The response time of the sensor is 10 s, and recovery occurs within 5 minutes of exposure to air (Table).

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Table

Comparative properties of ethanol sensors based on zinc oxide

The useful model provides the expected technical result - a reduction in energy consumption when producing a sensitive element of the sensor and an increase in sensitivity by improving the manufacturing technology of the sensor layer using 2pO nanostructures, which ensures an increase in the size of the working area of the sensor surface.

Claims (1)

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