Effects of an External Electric Field from a Substrate on Conductance of SnO2 Thin Films

Abstract

Thin Sn02 films of about 10 nm thickness were prepared by sputtering on Si02/Si substrates, and the effects of an external electric field from the substrate on the conductance of the SnO., film were investigated at 26°C and up to 300°C. The apparent conductance of the Sn02 film increased with a positive substrate bias and decreased with a negative substrate bias. These field effects became more evident with larger bias and in 5n02 films with a lower carrier concentration. By using metal oxide semiconductor theory, the results are attributed to the formation of a depletion and an accumulation layers in the Sn02 film under a negative and a positive bias, respectively. The influence of electron traps in the Sn02 film on its apparent conductance was suggestectfrom calculations of these field effects. At temperatures above 150°C, slow changes in the conductance with time were observed under a constant negative bias. From the results measured in N2 and in air, it was suggested that the amount or types of surface oxygen adsorbates changed under a negative electric field. These results indicate the possibility of controlling the electrical properties and the surface reactions of Sn02 films by an external electric field.

Control of Catalytic Reactions at the Surface of a Metal Oxide Nanowire by Manipulating Electron Density Inside It

“…[15][16][17][18][19] This subject was revisited in connection with the development of FET-based gas sensors. [20][21][22][23] The latter property was inferred from the field dependence of the work function…”

“…Experimental observations, supported by calculations, suggest that the availability of electrons at the vacancy site affects the chemical activity of the oxide surface. ,, The influence of an electrostatic field (and the concomitant change in the near-surface electron density) on adsorption and catalysis occurring on macroscopic semiconductor surfaces was predicted and experimentally verified long ago. − This subject was revisited in connection with the development of FET-based gas sensors. − The latter property was inferred from the field dependence of the work function (or channel conductance) change upon the adsorption of a molecule to an oxide surface configured as a field-effect transistor (FET) with a chemically active gate.…”

Effects of the external electric field from a substrate on Cl2 gas adsorption on SnO2 thin films

“…The electron mobility should, consequently, be considered. In the previous letter, 12 it was suggested that a decrease of the current under a negative substrate bias is caused by a high resistive depletion layer formed at SnO 2 /SiO 2 interface. However, it was not confirmed whether the electron mobility is kept constant or not.…”