Electrical Properties of Nanocrystalline n-SnO2 to Single Crystal p-Si Interfaces under Gas Adsorption Conditions

Abstract

We present a study of heterostructures based on thin n-SnO 2 layers prepared by means of an aerosol pyrolysis on a single crystalline p-Si substrate. SnO 2 films are composed of 6-8 nm grains segregated into agglomerates of about 0.1 mm providing a porous structure of the film. Currentvoltage (I -V) characteristics are taken in the temperature interval 180-300 K. Capacitance-voltage (C -V) curves are obtained at frequencies of the reference signal varied within 0.5-20 kHz at 300 K. Electrical properties of the structures were examined in air and in gas mixtures N 2 þ 0:1% NO 2 and N 2 þ 1% C 2 H 5 OH. A pronounced non-linearity of the I -V curves is explained in terms of the Schottky equation with high ideality factors b % 7 À 11. The gas sensitivity S depends on the kind of adsorbed gas molecule due to the Schottky barrier variation together with the interface states density change. The SnO 2 doping with Ni induces an increase of S by an order of magnitude.

Inorganic structures as materials for gas sensors

“…64 Nitrogen dioxide molecules are electron acceptors and form a surface level in the band gap. The energy of this level is lower than that of the acceptor level of 93 chemisorbed oxygen. 113 Thus, adsorption of NO 2 molecules causes a decrease in the effective carrier concentration and, correspondingly, a decrease in the barrier height.…”

“…Calculated using the current ± voltage (1, 3) and capacitance ± voltage (2, 4 ) curves. 93 Gas concentration: C2H5OH (1%) and NO2 (0.01%).…”

“…Figure 22. Current ± voltage curves of a SnO2(pyr)/Si heterostructure in different atmospheres: (1) N2, (2) N2 + C2H5OH (1%) and (3) N2 + NO2 (0.1%) 93. …”