Influence of particle size on the conductance of SnO2 thick films

Ponce, Miguel Adolfo; Aldao, C. M.; Castro, Miriam Susana

doi:10.1016/s0955-2219(03)00037-2

Cited by 41 publications

(31 citation statements)

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“…Pastes made up of these powders and an organic binder (glycerol), were prepared, having the solid/ organic binder ratio of 1/2. Using the doctor blade technique 21,22 , thick film sensing devices were made by spreading the obtained paste onto insulating alumina substrate with gold sputtered interdigitated electrodes (Figure 1). Finally, in order to improve the adhesion to the substrate and to promote partial sintering, the samples were thermally treated in an electrical oven for 2 hours at 500 °C, in air at atmospheric pressure.…”

Section: Methodsmentioning

confidence: 99%

“…The interaction of oxygen with grain surfaces produces the transfer of electrons from the bulk to the surface. From this process, the barrier height and the depletion width become larger and, as a consequence, the sample resistance increases 21 . The impedance of polycrystalline samples is described by a complex behavior, due to the contribution of different system components like grain boundaries, grains, pores and metallic contacts.…”

Section: Uras -Materials Researchmentioning

confidence: 99%

“…These parameters are to be controlled by choosing the preparation method, which has to include, among other characteristics, good reproducibility and low cost. The doctor-blade technique has several advantages for producing thick layers suitable for gas sensing applications, such as easy precursor preparation, homogeneous composition, easy control of film thickness and very low cost [18][19][20][21] . Lately, impedance spectroscopy has increasingly been applied for studying a variety of electronic devices, being a unique tool for a detailed characterization of the interaction of gas sensors with the surrounding environment.…”

Section: Introductionmentioning

confidence: 99%

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Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

et al. 2009

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Porous nano and micro crystalline tin oxide films were deposited by RF Magnetron Sputtering and doctor blade techniques, respectively. Electrical resistance and impedance spectroscopy measurements, as a function of temperature and atmosphere, were performed in order to determine the influence of the microstructure and working conditions over the electrical response of the sensors. The conductivity of all samples increases with the temperature and decreases in oxygen, as expected for an n-type semiconducting material. The impedance plots indicated the existence of two time constants related to the grains and the grain boundaries. The Nyquist diagrams at low frequencies revealed the changes that took place in the grain boundary region, with the contribution of the grains being indicated by the formation of a second semicircle at high frequencies. The better sensing performance of the doctor bladed samples can be explained by their lower initial resistance values, bigger grain sizes and higher porosity.

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Section: Methodsmentioning

confidence: 99%

Section: Uras -Materials Researchmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

et al. 2009

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“…This result could be explained by considering that samples S2 are thicker than S1. It has long been suggested that the response time of a semiconductor gas sensor could be related to the reactivity and diffusion of gas molecules inside gas sensing layers [13,14].…”

Section: Resultsmentioning

confidence: 99%

Field‐Assisted and Thermionic Contributions to Conductance in SnO₂ Thick‐Films

et al. 2009

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A deep analysis of conductance in nanostructured SnO 2 thick films has been performed. A model for field-assisted thermionic barrier crossing is being proposed to explain the film conductivity. The model has been applied to explain the behavior of resistance in vacuum of two sets of nanostructured thick-films with grains having two well-distinct characteristic radii (R = 25 nm and R = 125 nm). In the first case the grain radius is shorter than the depletion region width, a limit at which overlapping of barriers takes place, and in the second case it is longer. The behavior of resistance in the presence of dry air has been explained through the mechanism of barrier modulation through gas chemisorption.

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“…Esta difusión aniquila vacantes de oxígeno, ensancha las zonas de agotamiento de las barreras de potencial y en granos de pequeño tamaño puede llegar a producir el solapamiento de las barreras. Como consecuencia de este último efecto la resistencia disminuye [8][9].…”

Section: Resultados Y Discusiónunclassified

Adsorción de oxígeno en sensores de película gruesa de SnO<sub>2</sub> dopados con Pd

Ponce¹,

Aldao²,

Castro³

2004

Bol. Soc. Esp. Ceram. Vidr.

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En este trabajo se estudia la dependencia de la conductividad eléctrica en oxígeno de películas de SnO 2 dopadas con Pd. Los cambios en la conductividad, al modificar la atmósfera de vacío a aire, pueden ser explicados si consideramos que la adsorción de oxígeno produce un incremento en el ancho y en el alto de las barreras de potencial intergranulares. La exposición de las películas a estos gases a temperaturas mayores que 300°C favorece la difusión interna del oxígeno lo que provoca la aniquilación de vacantes de oxígeno y por ende la alteración de las barreras intergranulares. Se analiza en particular la diferencia en el comportamiento eléctrico entre las películas de SnO 2 dopadas y sin dopar. Palabras claves: SnO 2 , películas gruesas, mecanismos de conducción. Oxygen adsorption in Pd-doped SnO 2 thick filmsThe dependence of the electrical conductivity Pd-doped SnO 2 thick films in an oxygen atmosphere is studied. The conduction mechanism when the atmosphere is changed from vacuum to oxygen can be explained considering the modification of the intergranular potencial barriers. The films exposure at temperatures higher than 300°C favors the oxygen indiffusion that causes the annihilation of oxygen vacancies. The difference between thick films doped with Pd and films without additives is analyzed.Keywords: SnO 2 , thick films, conduction mechanisms. INTRODUCCIÓNEn las pasadas dos décadas los sensores de gases basados en SnO 2 se han tornado los dispositivos de estado sólido preponderantes para la detección de gases en alarmas domésticas, comerciales e industriales [1][2]. Generalmente se acepta que la quimisorción de oxígeno produce la transferencia de electrones desde el interior de los granos de SnO 2 a sus superficies lo que da lugar a la modificación de las barreras formadas en los bordes de grano. Las características de estas barreras dependen del contenido de oxígeno intergranular lo que se refleja en un cambio en la resistividad del sensor [3]. En este sentido, diferentes factores, tales como química de defectos, propiedades morfológicas, influencia de aditivos y efectos catalíticos en las reacciones superficiales contribuyen a la respuesta eléctrica del sensor [4].Un método ampliamente utilizado para incrementar la selectividad de los sensores de gases es incorporarle catalizadores al SnO 2 [5]. Morrison [6] determinó que un catalizador puede afectar las propiedades de la superficie de los granos y de los contactos intergranulares. Uno de ellos es el llamado "efecto spillover" en el cual la molécula de oxígeno se disocia para formar una especie de oxígeno más activa. Otro efecto es el llamado "control del nivel de Fermi", en el cual se produce un intercambio electrónico entre el catalizador y el cerámico semiconductor [7].En este trabajo realizamos una serie de experimentos destinados a dilucidar aspectos básicos sobre los efectos de la exposición de la película al vacío y a una atmósfera de oxígeno. En particular, se analiza la respuesta de películas gruesas de SnO 2 con y sin el agregado de Pd ante ...

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Influence of particle size on the conductance of SnO2 thick films

Cited by 41 publications

References 14 publications

Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

Field‐Assisted and Thermionic Contributions to Conductance in SnO₂ Thick‐Films

Adsorción de oxígeno en sensores de película gruesa de SnO<sub>2</sub> dopados con Pd

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Influence of particle size on the conductance of SnO2 thick films

Cited by 41 publications

References 14 publications

Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

Field‐Assisted and Thermionic Contributions to Conductance in SnO2 Thick‐Films

Adsorción de oxígeno en sensores de película gruesa de SnO<sub>2</sub> dopados con Pd

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Field‐Assisted and Thermionic Contributions to Conductance in SnO₂ Thick‐Films