Effect of annealing on rectifying contacts on ZnO thin films grown using pulsed laser deposition

Abstract

Zinc oxide (ZnO) is probably the most explored oxide based semiconductors in this century, for its versatile characteristics in number of domains. ZnO has drawn a strong attention in optoelectronics for being transparent as well as highly conducting in nature, making it suitable to be used for transparent electrodes. Having wide optical band gap ∼3.34 eV, ZnO offers promise to be utilized as UV detectors. Also ZnO has tasted some success in the domain of spintronics as well. But in-spite of this fame, the thirst of understanding the basic transport phenomena in ZnO is still in search, as the situation is enough challenging to make good contact on ZnO. Based upon the growth technique a metal-ZnO contact can be ohmic or rectifying in nature. The ultimate hurdle therefore lies to make a stable rectifying contact with metal (Au, Ag, and Pt) and ZnO. In this article we therefore aim to make some systematic study towards the metal (Au, Ag) and ZnO contact, and optimization of the growth parameters. It has been found that inherent oxygen vacancies act as source of conducting nature of ZnO. Here we grow ZnO films in ambient oxygen pressure (5.0 × 10 mbar) at 400°C using pulsed laser deposition technique. The films with (100) preferential growth, are annealed for different time scales in higher oxygen pressure. This makes the carrier concentration of ZnO to reduce from 10 cm to 10 cm or order below that. Thickness of the films were limited to 100 nm, with rms surface roughness ranging 1-5 nm. The ZnO surface was ablated with energy pulses 5 mJ/cm to reduce some surface defects. The transparency of the films grown in ambient oxygen pressure is nearly 85%. Later, Ag and Au electrodes were grown using same technique on the ZnO film. Detailed observations of I-V characteristics with different annealing time, surface roughness, and XRD data will be presented.

Department(s)

Physics, Astronomy, and Materials Science
Center for Applied Science and Engineering

Document Type

Conference Proceeding

Publication Date

12-1-2009

Journal Title

Materials Research Society Symposium Proceedings

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