Hydrogen sulfide is a toxic and flammable gas, usually generated in sewages, swamps, mines etc. Hydrogen sulfide gas detector finds application in petroleum refineries, paper mills, tanneries and other industries, laboratories, and in heavy water plants where it is used as a process gas. It is imperative that the gas should be detected in ppm levels in air by selective and sensitive sensors. We have exploited surface conductivity of hydrogen terminated diamond films to detect trace levels (<1ppm) of hydrogen sulfide at room temperature.

SALIENT FEATURES

• Room temperature operation, hence low thermal budget and low power requirement.
• Stable and long life (> 2 years).
• Suitable to operate at temperatures up to 100°C.

APPLICATIONS

• Environmental monitoring for H₂S in plants.
• H₂S gas detection and alarm systems.

Hydrogen sulfide is a toxic and flammable gas, usually generated in sewages, swamps, mines etc. Hydrogen sulfide gas detector finds application in petroleum refineries, paper mills, tanneries and other industries, laboratories, and in heavy water plants where it is used as a process gas. Hydrogen sulfide reacts strongly with living tissues and attacks the central nervous system. Human nose is sensitive to trace amount (0.2 ppm) of H₂S, which is recognized by a distinctive odor of rotten eggs. Higher concentration or prolonged exposure of H₂S paralyses the olfactory system. Thus it is imperative that the gas must be detected in ppm levels in air by selective and sensitive sensors. 

Diamond is a unique material with a wide range of mechanical, optical, electrical, thermal and chemical properties. Though undoped diamond is an excellent insulator, hydrogen terminated diamond shows p-type surface conductivity, which has been exploited to detect trace levels (<1ppm) of hydrogen sulfide at room temperature.

SALIENT FEATURES

• Room temperature operation, hence low thermal budget and low power requirement.
• Stable and long life (> 2 years).
• Suitable to operate at temperatures up to 100°C.

SPECIFICATIONS

The sensor response is linear from 0.5 to 10 ppm of H₂S. Response time (~80% ) for 1 ppm  is typically < 30s and recovery time (~20%) is ~ 30 min. Though the sensor is operated at room temperature normally, it can reliably operate up to an ambient temperature of 100°C.

APPLICATIONS

• Environmental monitoring for H₂S in plants.
• H₂S gas detection and alarm systems.

REQUIREMENTS

A. Raw Materials :

• CVD diamond thin films on silicon substrate and laboratory chemicals

B. Equipments

1. CVD system for hydrogen plasma treatment
2. Fume hood with accessories for chemical cleaning
3. Physical vapour deposition (PVD) system for contact metallization
4. Diamond scriber for dicing the sensors
5. Wire bonder for bonding
6. Suitable mounting system for packaging
7. Gas testing and calibration facility (Electronics for the sensor is not included)

Equipment no. 4, 5 and 6 are not necessary if dicing, bonding and packaging can be outsourced

C. Space requirements

• The space requirement is approximately 12ft by 15ft to comfortably accommodate the process equipments such as CVD system, Fume hood, PVD system, space for assembling and packaging, testing and calibration setup etc.

D.  Man power

• One technician to carry out the chemical cleaning, CVD processing and metallization and one engineer or physicist to carry out assembling, calibration and quality control.