Comparative study of ZnO layers prepared by PLD from different targets at various oxygen pressure levels |
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Authors: | Daniel Ha??ko Jaroslav Bruncko Andrej Vincze Franti??ek Uherek |
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Institution: | (1) International Laser Centre, Ilkovičova 3, Bratislava, 841 04, Slovak Republic |
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Abstract: | Two series of polycrystalline zinc oxide (ZnO) layers, from Zn or ZnO targets, were grown on silicon (1 1 1) substrates by
pulsed laser deposition (PLD) at ambient oxygen pressure levels, stepwise increased from 1 to 35 Pa. For ablation of targets,
a pulsed Nd:YAG laser was used. The structural and morphological properties of the layers were investigated by scanning electron
microscopy (SEM), atomic force microscopy (AFM), and secondary ion mass spectrometry (SIMS). The SEM images of ZnO layers
in SE mode show a uniform granular structure and modified surface morphology, depending on oxygen pressure. The mean grain
size in height and lateral directions decreases with an increase of oxygen pressure from 1 to 5 Pa, while a subsequent rise
of oxygen pressure from 5 to 35 Pa will cause an increase in the grain size. The AFM measurement revealed that the surface
structures of zinc oxide layers grown from different targets were similar, and the layers formed at an ambient oxygen pressure
of 5 Pa exhibited the smallest values of calculated roughness and granularity. SIMS depth profiling analyses confirmed that
the ZnO composition was homogenous across the layer, up to the abrupt change of chemical composition at the interface between
the ZnO layer and the Si substrate.
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Keywords: | zinc oxide pulsed laser deposition laser ablation surface characterization |
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