Microstructure and Optical Properties of E-Beam Evaporated Zinc Oxide Films-Effects of Decomposition and Surface Desorption.

Lukasz Skowronski,Robert Szczesny,Antoni Bukaluk,Marek Trzcinski,Mieczyslaw Naparty,Aleksandra Olszewska,Arkadiusz Ciesielski

doi:10.3390/ma13163510

Abstract

Zinc oxide films have been fabricated by the electron beam physical vapour deposition (PVD) technique. The effect of substrate temperature during fabrication and annealing temperature (carried out in ultra high vacuum conditions) has been investigated by means of atomic force microscopy, scanning electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. It was found that the layer deposited at room temperature is composed of Zn and ZnO crystallites with a number of orientations, whereas those grown at 100 and 200 C consist of ZnO grains and exhibit privileged growth direction. Presented results clearly show the influence of ZnO decomposition and segregation of Zn atoms during evaporation and post-deposition annealing on microstructure and optical properties of zinc oxide films.

Highlights

Zinc oxide exhibits high thermal and chemical stability and has been studied for decades [1,2].ZnO is a semiconductor with a direct band-gap of Eg ∼ 3.3 eV [3,4] similar to the value reported to gallium nitride (Eg ∼ 3.4 eV) [5], the binding energy of zinc oxide exciton (60 meV) [4]is 2.4 times larger than that of GaN (25 meV) [5]
Zinc oxide films were produced by means of the electron beam evaporation method and investigated using atomic force microscopy, scanning electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy and spectroscopic ellipsometry techniques
We have shown that decomposition of ZnO during evaporation and segregation of

Summary

Introduction

Is 2.4 times larger than that of GaN (25 meV) [5] These features indicate that ZnO is a promising material for short-wavelength optoelectronic devices such as light-emitting and laser diodes [6]. Zinc oxide is a very good candidate for space applications due to its stability to high energy radiation [1]. ZnO can be etched in acids and alkali [11]. This feature is commonly used to produce ZnO in form of nanosheeds, nanoshells, multipods, nanorods or nanowires typicaly implemented as periodic structures using a number of methods [2,12]

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Results

Discussion

Conclusion