Influence of Surface Processes on Electrical, Photochemical, and Thermodynamical Properties of Zinc Oxide Films

Conductivity investigations have been performed at highly pure zinc oxide films under equilibrium conditions in the temperature range from 300 to 1000 K in oxygen (1 to 150 mbar). The conductivity behavior has to be divided into two temperature ranges. Above 800 K, the slope of vs. corresponds to 1.6 eV and the oxygen pressure dependence is , while at low temperatures (>500 K) the respective values are 0.8 eV and This behavior is interpreted as an incongruent decomposition at high temperatures and oxygen chemisorption of O − (electrons from frozen‐in donors) at low temperatures. This concept is further supported by the results of photoconductivity measurements. The temperature and pressure dependence of the conductivity σ in the whole measuring range can be expressed by , , and are adjusting parameters, is a normalized pressure. The carrier concentrations are ranging from 10 8 to 10 15 cm −3 in the temperature range from 500 to 1000 K. The maximum concentration of uncompensated donor impurities is about 10 12 cm −3 .