Equilibrium Dependence of the Conductivity of Pure and Tin‐Doped Indium Oxide on Oxygen Partial Pressure and Formation of an Intrinsic Defect Cluster

Abstract

The dependence of the electrical conductivity of pure (99.999%) and tin‐doped indium oxide (In2O3) ceramics on oxygen partial pressure was investigated at 800° and 850°C. The doping amount of tin was 100–1000 ppm, which is within the solubility limit at the temperatures measured. The conductivity of doped ceramics was independent of , and the carrier concentration was almost the same as the estimated value from the tin content. The conductivity of the pure In2O3 ceramic was proportional to. By considering a singly charged defect cluster of interstitial indium and interstitial oxygen, , the conductivity dependence is deduced to be proportional to. There are large and three adjacent vacant sites, 8a and 16c, in the In2O3 structure to enter indium and oxygen.

Deep vs shallow nature of oxygen vacancies and consequentn-type carrier concentrations in transparent conducting oxides

“…At about T = 600 K, the charge state V + O becomes populated as well as V 2+ O , which leads to a greater increase in n 0 with T . That increase then slows down at higher T , where E F and T are high enough that a significant concentration of V [32,62,63,191]. Of course, we have not considered other intrinsic defects, such as oxygen interstitials or cation vacancies, which may be present and act as electron killers, resulting in a lower n 0 .…”

“…Varying P O 2 will change the concentrations of oxygen vacancies, which may act as donors, and interstitials, which may compensate n-type carriers, in a manner that depends on the defect chemistry of the system. It has been observed that, in undoped In 2 O 3 samples, the conductivity increases significantly as P O 2 is reduced [62]. Concurrently, the mobility decreases [21,63], which suggests that it is an increase in vacancy donor concentration, rather than a decrease of the concentration of compensating interstitials, that effects this increase in conductivity.…”

Macro- and microscopic properties of strontium doped indium oxide

“…A special condition for realization of n-p transition in ITO film was found by authors of Ref. [27] at high temperature T>950 0 C. Minimum concentration of free electrons in polycrystalline samples prepared by using very pure components is not less than 10 17 cm -3 [4]. Doping of indium oxide by Sn can increase the density of free electrons up to 10 21 cm -3 .…”

“…Here we have accounted for the fact that, after doping with Sr, the density of electrons in In 2 O 3 was reduced by about 6 orders of the magnitude which can be inferred from the correspondent increase in resistance. Keeping in mind the concentration of free electrons of 10 17 cm -3 in undoped In 2 O 3 [4] and the above evaluated density of oxygen vacancies of about 10 19 cm -3 in oxygen deficient In 2 O 3 :(SrO) x , we assume that, in the latter compound, the major contribution in the number of electrons is due to oxygen vacancies as donors.…”

“…Thereby, the corrections in band structure become feasible for explanation of various experimental data, but they still do not resolve another problem -the absence of the dielectric state in samples of indium oxide at room temperature, expected from the wide band gap. This problem manifests itself in investigations of materials of different kinds and quality, including polycrystalline samples [4], single crystals [3], and high quality films [5,6]. Hence, attention should be focused on the electrical activity of surface states and crystal defects.…”