Electrical field impact on the gas adsorptivity of thin metal oxide films

Bogner, Martin; Fuchs, Anne; Scharnagl, K.; Winter, R.; Doll, Theodor; Eisele, I.

doi:10.1063/1.122503

Cited by 29 publications

(11 citation statements)

References 5 publications

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“…Presently, it is not known how the hydrogen adsorption at the metal-insulator interface of MIS field-effect sensors is influenced by the electric field, but reports on suspended gate field-effect devices show a large dependence on absorptivity from the applied electric field. 23 In our case, however, no obvious trend can be observed supporting such a model.…”

Section: Discussioncontrasting

confidence: 66%

Characterization of the metal–insulator interface of field-effect chemical sensors

Åbom

Haasch

Hellgren

et al. 2003

Journal of Applied Physics

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Characterization of atomic-layer-deposited silicon nitride / SiO 2 stacked gate dielectrics for highly reliable pmetal-oxide-semiconductor field-effect transistors The metal-insulator interface of hydrogen-sensitive metal-insulator-semiconductor capacitors, with SiO 2 as the insulator and Pt as the metal contact, has been studied. The thin Pt films were prepared in ultrahigh vacuum by electron beam evaporation and dc magnetron sputtering. Deposition parameters were substrate temperature and sputtering pressure. The hydrogen responses of the differently prepared devices were measured in a semi-inert ambient ͑and used as a measure of the concentration of available adsorption sites for hydrogen at the interface͒. A large variation of responses was found for differently prepared sensors, and the magnitude of the response was found to increase for decreasing bonding strength between the Pt film and the SiO 2 substrate, as determined by scratch adhesion measurements. The bonding strength was controlled via the energetics of the Pt deposition flux. The largest interfacial roughness, from cavities between noncoalesced metal grains, and the poorest adhesion, was obtained by a reduced surface diffusion during growth and incomplete coalescence of the metal grains on the oxide surface as studied by transmission electron microscopy and atomic force microscopy. From x-ray photoelectron spectroscopy studies it was concluded that no chemical bonds were formed between Pt and SiO 2 . It is inferred that the hydrogen active in the sensor response is adsorbed on the oxide side of the interface in a spillover process. The difference in hydrogen response between differently prepared devices can be explained by a difference in concentration of available adsorption sites giving rise to a detectable dipole moment, on the oxide due to a blocking by Pt atoms in contact with the oxide. Thus, the concentration of Pt atoms in contact with the oxide affects both the hydrogen response and the metal-oxide adhesion.

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Section: Discussioncontrasting

confidence: 66%

Characterization of the metal–insulator interface of field-effect chemical sensors

Åbom

Haasch

Hellgren

et al. 2003

Journal of Applied Physics

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“…15,16 According to the electron theory of chemisorption, the chemical potential controls the catalytic activity on the surface, determining the occupation probability of the chemisorbed states. In addition, it has been observed that a large gate voltage induced field is capable of affecting gas adsorptivity on the ZnO NW significantly.…”

mentioning

confidence: 99%

Gate-refreshable nanowire chemical sensors

Fan¹,

Lu²

2005

Applied Physics Letters

433

250

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ZnO nanowire field effect transistors were implemented as highly sensitive chemical sensors for detection of NO2 and NH3 at room temperature. Due to a Debye screening length comparable to the nanowire diameter, the electric field applied over the back gate electrode was found to significantly affect the sensitivity as it modulates the carrier concentration. A strong negative field was utilized to refresh the sensors by an electrodesorption mechanism. In addition, different chemisorbed species could be distinguished from the “refresh” threshold voltage and the temporal response of the conductance. These results demonstrated a refreshable field effect sensor with a potential gas identification function.

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“…21,23,27,29 High electric field may also shift the adsorbent energy with respect to the solid substrate. 22,30 However, in order to generate a shift of a few mV at least, over a distance of ∼ 0.3 nm, the field strength has to exceed 3 × 10 4 V/cm. These and even higher fields persist at the electrode/SE interface.…”

Section: The Cathode/se Sidementioning

confidence: 99%

Catalytic Requirements for Mixed Reactant Fuel Cells

Riess

2008

Funct. Mater. Lett.

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Significant advantage could be achieved if mixed reactant fuel cells, MR-FC, were functioning. These cells are intended to operate on a mixture of air and fuel introduced into both the cathode and anode compartment. Symmetry is broken by using different electrode materials exhibiting special and different catalytic properties. No high temperature fuel cell was reported to date to function as a true MR-FC and only one, low temperature type, did function properly. We discuss the required catalytic properties which are unique in that they promote electrochemical reactions and suppress chemical ones as well as possible ways to search for them. The chemical reaction which has to be suppressed is the direct reaction of fuel and oxygen as the two components are premixed and the mixture is then introduced into the fuel cell at both electrode compartments. The electrochemical reactions that should be promoted are the reduction of oxygen at the cathode and the oxidation of fuel at the anode only by oxygen ions that emerge from the solid electrolyte. Conditions to promote this selectivity are discussed. These are derived from the theory of chemisorption as applied to heterogeneous catalysis.

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Electrical field impact on the gas adsorptivity of thin metal oxide films

Cited by 29 publications

References 5 publications

Characterization of the metal–insulator interface of field-effect chemical sensors

Characterization of the metal–insulator interface of field-effect chemical sensors

Gate-refreshable nanowire chemical sensors

Catalytic Requirements for Mixed Reactant Fuel Cells

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