Gas sensing properties of rf sputtered wo3 thin films
- Autores: Stefanova Stankova Mariana
- Directores de la Tesis: Josep Calderer Cardona (dir. tes.), X. Vilanova (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2004
- Idioma: español
- Tribunal Calificador de la Tesis: Eduard Llobet Valero (presid.), Ángel Rodríguez Martínez (secret.), Albert Cornet i Calveras (voc.), del Carmen Hornillo Maria (voc.), Eduard Figueres (voc.)
- Materias:
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- Resumen
In the last years there has been a growing interest for the control of air pollutants and monitoring of toxic gases, The need of low cost and small size gas sensors increase continuously. Many commercial gas sensors are available, but they usually respond to various compounds. That is why the demand of high sensitive and selective gas sensors grows. On these lines, we develop pure and doped tungsten oxide based sensors based on conventional and microhotplate substrates.
The first part of the work consists in the design and fabrication of thin film gas sensors on conventional silicon substrates, containing all the auxiliary elements (heater, electrodes, etc.). Reactive radio frequency (rf) magnetron sputtering is used as deposition technique for the active layer. The purpose is to obtain small sensors that enabled integrating in sensor arrays. After checking the applicability of the chose technique, it is transferred on microhotplate substrates, diminishing the sensor size and the power consumption of this. To improve the sensitivity and selectivity of the devices different doping materials (such as Pt, Au, Ag, etc.) are deposited by rf sputtering or thermal evaporation.
The second part is centred on the characterization of the tungsten oxide as material for semiconductor gas sensors. Different techniques such as SEM, AFM, XPS, etc. are applied. The objective is to dispose information about the crystalline structure and morphology of the tungsten oxide, which can be related with the mechanism of detection. The distribution and the thickness of the dopant are also checked.
The third part deals with the gas sensing characterization of obtained devices. In the beginning, the sensitivities of the sensors on conventional Si substrates are tested to different gases. Very good responses to nitrogen dioxide, ammonia and ethanol are obtained. Influence of different parameter such as annealing and operating temperatures, humidity and electrode
