Oxygen rich p-type ZnO thin films using wet chemical route with enhanced carrier concentration by temperature-dependent tuning of acceptor defects.

This paper reports the temperature-dependent tailoring of acceptor defects in oxygen rich ZnO thin films, for enhanced p-type conductivity. The oxygen rich p-type ZnO thin films were successfully grown by pulsed laser deposition on silicon substrate at different postdeposition annealing temperatures (500-800 °C). The oxygen rich ZnO powder was synthesized by wet chemical method using zinc acetate dihydrate [Zn(CH3COO)2·2H2O] and potassium hydroxide (KOH) as precursors. The powder was then compressed and sintered to make pellets for pulsed laser deposition system. The x-ray diffraction analysis exhibits an improved crystallinity in thin films annealed at elevated temperatures with a temperature-dependent variation in lattice constants. An analysis of Auger Zn L3M4,5M4,5 peak reveals a consistent decrease in interstitial zinc (Zni) exhibiting its temperature-dependent reversion to zinc lattice sites. Room temperature photoluminescence of the p-type ZnO shows a dominant deep level emission peak at ∼3.12 eV related to oxygen interstitials (acceptors). The relative concentration of oxygen interstitials (Oi) increases with increase in annealing temperature, resulting in enhanced hole carrier concentration. The maximum hole carrier concentration of 6.8 × 1014 cm-3 (indicating p-type conductivity) was estimated using Hall probe measurements for the thin film sample annealed at 700 °C. [ABSTRACT FROM AUTHOR]