Structural, Optical and Electrical Properties of Zinc Oxide Layers Produced by Pulsed Laser Deposition Method
Wisz et al. Nanoscale Research Letters
Structural, Optical and Electrical Properties of Zinc Oxide Layers Produced by Pulsed Laser Deposition Method
G. Wisz 1
I. Virt 1 2
P. Sagan 1
P. Potera 1
R. Yavorskyi 0 1
0 Vasyl Stefanyk PreCarpathian National University , T. Shevchenko, 57, 76018 Ivano-Frankivsk , Ukraine
1 Rzeszow University , Rejtana 16C, 35-959 Rzeszow , Poland
2 Drohobych State University , I. Franko, 24, 82100 Drohobych , Ukraine
The structural, optical, and electrical properties of zinc oxide (ZnO) layers manufactured at different process conditions were investigated. ZnO epitaxial layers were grown on silicon, glass, and ITO/glass substrates by pulsed laser deposition (PLD) technique. The influence of power beam, substrate temperature, and deposition time on films properties was analysed. Morphological features of the film surface were investigated by scanning electron microscopy. A structural study shown planar orientation of films at low temperatures of substrate, but the columnar type of growth originated in temperature enhances. Electrical properties were determined in the temperature range 300-500 K. It was shown that the type of films conductivity is metallic and it is limited by charge transfer across grain boundaries.
Thin film; Zinc oxide; Photoconduction of ZnO; Conductive thin films; Pulse laser deposition
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Background
Zinc oxide is one of the most important group II?VI
semiconductor materials. It is a wide-bandgap oxide
semiconductor with a direct energy gap of about
3.37 eV. ZnO has high chemical and mechanical stability;
furthermore, it is nontoxic and widespread in nature.
Recently, transparent-conducting oxides on the base of
ZnO have been studied well [1?3]. ZnO is one of the most
promising materials for the fabrication of the next
generation of optoelectronic devices in the UV region and
optical or display devices [4]. As a matter of fact,
simultaneous occurrence of both high optical transmittances in
the visible range and low resistivity make ZnO an
important material for manufacturing of heat mirrors used in gas
stoves, conducting coatings in aircraft glasses to avoid
surface icing, and thin film electrodes in amorphous
silicon solar cells. ZnO belongs to hexagonal wurtzite
class; it is a semiconducting, piezoelectric, and optical
waveguide material used in sensors, surface acoustic
devices, transparent electrodes, and solar cells [5?7].
Controlling of ZnO physical properties depending on
various factors, such as doping and temperature growth, is
important for efficient function of devices on the base of
ZnO structures. The existence of both (n and p)
conduction types is of fundamental importance for application in
light-emitting devices [8]. The nanostructures like
nanotubes, nanorods, nanowalls, nanofibers and high-quality
undoped and doped ZnO thin films have been grown with
plasma-assisted molecular beam epitaxy, vapor transport
deposition method, vacuum arc deposition metal organic
chemical vapor deposition (MOCVD), sol?gel process,
and spray pyrolysis [9, 10]. Such nanotubes, nanowires,
nanoribbons, and nanofibers have deserved special
attention for their potential applications in applied fields such as
field emission displays, optical waveguides, solar cells,
ultraviolet photodetectors, optical switches, and gas
sensing [1?8]. The chemical bath deposition and sol?gel
technique are also well known methods of preparation of
ZnO thin films. Among these methods, spray pyrolysis is
useful in wide range of applications [11, 12]. This method
is cheaper, simpler and permits to obtain films for
optoelectronic applications with required properties. Structural,
electrical, and optical properties dependence on thickness
? The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
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of ZnO films has been investigated. The unique and
fascinating properties of nanostructured materials have triggered
tremendous motivation among scientists to explore the
possibilities of using them in technological applications. In
particular, the electronic and optical properties of
nanostructure materials have been of great interest because of
their potential applications in the fabrication of
microelectronic and optoelectronic devices [13].
In this paper, the electrical, structural, and optical
properties of ZnO nanostructured thin film deposited by
PLD method and their changes during annealing have
been investigated.
Methods
The ZnO films grown on silicon, glass, and ITO/glass
were deposited by the PLD method. The YAG: Nd3+
laser with the 532 nm (II harmonics) wavelength, 6 ns
pulse time, and 16 J/cm2 fluence was used. The laser
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