Hydrogen Gas Sensors

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DEVELOPMENT OF ASEMICONDUCTOR METAL OXIDE

THIN FILM HYDROGEN GASSENSORS

Prepared by:

Manisha Charati1359016

VLSI DESIGN AND EMBEDDED SYSTEM

UNDER THE GUIDANCE OF:

Dr. U.P.SINGH


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Hydrogen Gas sensors Introduction:

Sensor:Latinword santire:- To Percieve

A sensor is a technological device that detects /senses a signal, physical condition and chemicalcompounds.

It is also defined as any device that converts asignal from one form to another.

Sensors are mostly electrical or electronic.


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Hydrogen Gas sensors Introduction:

Sensor:

Applications

Automobiles

Machines Robotics

Industry

Aerospace etc.

Examples of sensors

Thermometer

Thermocouple

Phototransistor

Photo resistor

Microphone

Hydrophone etc.


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Hydrogen Gas sensors Introduction: Gas Sensor:

Gas sensor is a subclass of chemical sensors.

Gas sensor measures the concentration of gas

in its vicinity. Gas sensor interacts with a gasto measure its concentration. Each gas has aunique breakdown voltage i.e. the electricfield at which it is ionized. Sensor identifiesgases by measuring these voltages. The

concentration of the gas can be determinedby measuring the current discharge in thedevice.


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Hydrogen Gas sensors

Gas sensing technologies:

Metal Oxide Based Gas Sensors

Capacitance Based Gas Sensors

Acoustic Wave Based Gas Sensors Optical gas sensors

Electrochemical gas sensors


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Hydrogen Gas sensors Gas sensing technologies:

1. Metal Oxide Based Gas Sensors

Metal oxide sensors are also known as

chemiresistors. The detection principle of resistive sensors is

based on change of the resistance of a thin filmupon adsorption of the gas molecules on thesurface of a semiconductor.

The gas-solid interactions affect the resistanceof the film because of the density of electronicspecies in the film.


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Hydrogen Gas sensors 3. Hydrogen gas sensor

ZnO/SnO with palladium is used to detecthydrogen because palladium selectivelyabsorbs hydrogen gas and forms the

chemical palladium hydride.

Types of hydrogen gas sensor:

Optical fiber hydrogen sensors

Nanoparticle-based hydrogen microsensors


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Hydrogen Gas sensors Principle Of Operation

ZnO/SnO with palladium is used to detecthydrogen because palladium selectivelyabsorbs hydrogen gas and forms the

chemical palladium hydride.

Types of hydrogen gas sensor:

Optical fiber hydrogen sensors

Nanoparticle-based hydrogen microsensors


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MOTIVATIONS

SMO GAS SENSOR ADAVANTAGES Compact small size & Portability

Feasibility of United/combine Control Circuits

Low Cost & long life of around 10 yrs

Maintenance Free

o Drawbackso Lack Of Sensitivity

o

Low Response timeo Broad Selectivity

o Recovery Time/Hysterisis effect


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To Develop a reliable SMO Thin Film H2 Gas Sensor

To maximize sensitivity selectivity byaddition of noble catalyst/activators likePalladium

To study effects of thickness of ZnOFilm/and concentration on sensitivity andresponse time

Explores sensing characteristics,properties and parameters of sensor

Analyze effects of Ti buffering with

palladium for reducing hysteresiseffect


OBJECTIVES


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AIMS


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GAS SENSOR FABRICATION:Schematic Conception

Selection Of Substrate

Substrate Cleaning Procedure

Deposition of Gas sensitive Thin film either by sol gel

or sputteringor spray pyrolysis Surface sensitization of the prepared thin film by

palladium noble metal catalyst.

Deposition of Al/Pt electrodes and attachment of lead

for electrical measurement Buffering of Ti in one sample with palladium for study

effects of recovery time and resistance characteristics
http://d/manisha/thin%20film%20deposition%20methods/thin%20film%20materials%20technology/M061FL02.swfhttp://d/manisha/thin%20film%20deposition%20methods/thin%20film%20materials%20technology/M061FL02.swf


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GAS SENSOR PRINCIPLE

(ZnO)O2 + H2 ZnO + H2O + 2e-

Whenever sensing/reducing gas interactsconduction increses in n-type and decreases

in p

METHODS USED IN CONCERNED


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METHODS USED IN CONCERNEDPAPERS

Thin Film Deposition :

Spray Pyrolysis at a temp of45050c and spray rate of 2-3 ml/min-1 and pr 5kg/cm2

Ofdifferent molar conc of zn(ch3coo)2.2H20 in water

Spray Pyrolysis at a temp of45050c and spray rate of 2-3 ml/min-1 and pr 5kg/cm2

Ofdifferent molar conc of ZnCl2 in water

METHODS USED IN CONCERNED


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METHODS USED IN CONCERNEDPAPERS

THIN FILM DEPOSITIONSol Gel : 1.36 g of ZnCl2 in 100 ml of distilled water and spin coating to

substrate

Sputtering :Sputtering of Commercially avaialable 99.99% pure ZnO and

deposition of different layer thickness.

Pd DepositionSpin Coating/multiple diping/spraying of 1.7 gm PdCl2 in 100 ml ethanol

Sputtering :Sputtering of Commercially avaialable 99.99% pure Pd and

deposition of different layer thickness also use of Ti doped Pd (1% of Ti by wt)


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Conceptual Test System

S h i i d l i l


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Schematic Diagram and Electrical MeasurementCircuit

S h i Di d El i l M


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>Is

Schematic Diagram and Electrical MeasurementCircuit

SENSOR CURRENT LIMITERWITH 2 NO CONTACT

DCPOWERSUPPLY

0-15 v

PARAMETERS FOR STUDY


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PARAMETERS FOR STUDYComparison of ZnO Thin Film and Pd doped ZnO thin film

and ZnO thin film thickness in terms of

Structure and surface Morphology

Electrical Properties

Sensitivity

Selectivity

Response Time

Recovery Time


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Hydrogen Gas sensors LITERATURE REFERRAL:

1. http://scholar.google.com/scholar?hl=en&lr=&q=gas+sensor2. Improvement of ZnO2 and SnO2 sensors bu Q G Hial3. Hydrogen Sensing and Detection by P Sounderrajan4. http://vernier.com/probes/co2-bta.html

5. http://sensors-transducers.globalspec.com/LearnMore/Sensors_Transducers_Detectors/Gas_Sensing/Gas_Sensors

6. Low-Dimensional Palladium Nanostructures for Fastand Reliable Hydrogen Gas DetectionProceeding of the2000 Hydrogen Program Review, NREL/CP-570-28890

7. http://www.gasdetection.com/TECH/sensorprinciple2.htm

8. http://physicsworld.com/cws/article/news/17869

Hydrogen Gas Sensors

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