Macro- and microscopic properties of strontium doped indium oxide

Abstract

Solid state synthesis and physical mechanisms of electrical conductivity variation in polycrystalline, strontium doped indium oxide In 2 O 3 :(SrO) x were investigated for materials with different doping levels at different temperatures (T=20-300 0 C) and ambient atmosphere content including humidity and low pressure. Gas sensing ability of these compounds as well as the sample resistance appeared to increase by 4 and 8 orders of the magnitude, respectively, with the doping level increase from zero up to x=10%. The conductance variation due to doping is explained by two mechanisms: acceptor-like electrical activity of Sr as a point defect and appearance of an additional phase of SrIn 2 O 4 . An unusual property of high level (x=10%) doped samples is a possibility of extraordinarily large and fast oxygen exchange with ambient atmosphere at not very high temperatures (100-200 0 C). This peculiarity is explained by friable structure of crystallite surface. Friable structure provides relatively fast transition of samples from high to low resistive state at the expense of high conductance of the near surface layer of the grains. Microscopic study of the electrodiffusion process at the surface of oxygen deficient samples allowed estimation of the diffusion coefficient of oxygen vacancies in the friable surface layer at room temperature as 3×10 -13 cm 2 /s, which is by one order of the magnitude smaller than that known for amorphous indium oxide films.

"Отрицательная" щель в спектре локализованных состояний (In-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-)-=SUB=-0.9-=/SUB=-(SrO)-=SUB=-0.1-=/SUB=-

“…Энергия ионизации глубоких акцепторных состояний δε ≫ kT , и точная компенсация здесь не нужна. Это положение под-тверждается прямыми экспериментами [28], в которых показано, что с увеличением концентрации стронция в In 2 O 3 от 0 до 1% удельное сопротивление образцов увеличивается на 3−4 порядка, наглядно иллюстрируя процесс компенсации донорных состояний кислородных вакансий акцепторными состояниями стронция.…”

Facile synthesis and gas-sensing performance of Sr- or Fe-doped In2O3 hollow sub-microspheres

“…24 Zhang and coworkers 25 have demonstrated a single In 2 O 3 nanowire transistor to work as a chemical sensor for detecting of NO 2 and NH 3 at room temperature. [28][29][30][31][32][33][34][35][36][37][38][39] Generally, the doped or loaded components can act as catalysts or sensitizers for sensing reaction, thus providing improved sensing performances. 26 Based on In 2 O 3 truncated octahedron, Hu et al fabricated a gas sensor for detecting formaldehyde.…”

“…27 Besides pure In 2 O 3 materials, In 2 O 3 -based composites through doping or loading by a secondary component are also investigated for gas sensing. [28][29][30][31][32][33][34][35][36][37][38][39] Generally, the doped or loaded components can act as catalysts or sensitizers for sensing reaction, thus providing improved sensing performances. For example, Pd-loaded In 2 O 3 nanowire-like networks exhibit superior sensitivity with short response and recovery times for detection of NO 2 gas.…”