Fundamental and applied investigation of ZnO has been recently experiencing a renaissance due to its prospective use in various technological domains and, in particular, as transparent conductive oxide (TCO) for solar cells applications. In this respect, the present work aims to study the structural and physical properties of ZnO thin films deposited by RF sputtering. Different gas mixtures were explored. Specifically, pure Ar and Ar-H2 at various concentrations were used to grow the films on n-type Si (100) wafers and glass without external heating. The plasma chemical species were followed in function of the different gas mixture settings by optical emission spectroscopy (OES). X-ray photoelectron spectroscopy (XPS) and ATR-FTIR (Attenuated Total Reflection Fourier-Transformed Infrared) spectroscopy were used to study the bulk and surface chemical composition of the films, X-ray Diffraction (XRD) analysis allowed lattice structure and grain size determination while samples morphology was checked with a scanning electron microscope (SEM). The films were also characterized for their electrical and optical properties. The introduction of hydrogen in the plasma phase strongly affected the structural, chemical and physical properties of the films. In particular a pronounced change in the films electrical behaviour was observed which become conductive when H is added in the gas mixture ([H2]>6%). The films transparency was on the other hand maintained. By combining XPS, ATR-FTIR and OES data we could correlate the established conductivity and its variations with intentional hydrogen incorporation in the crystal structure in the form of hydroxide species.

RF sputtering of ZnO films in Ar and Ar-H2 gas mixtures: role of H incorporation in developing transparent conductive coatings

Gottardi, Gloria;Bartali, Ruben;Micheli, Victor;Guarnieri, Vittorio;Luciu, Ioana;Pu, Peng;Pandiyan, Rajesh;Bensaada Laidani, Nadhira
2011

Abstract

Fundamental and applied investigation of ZnO has been recently experiencing a renaissance due to its prospective use in various technological domains and, in particular, as transparent conductive oxide (TCO) for solar cells applications. In this respect, the present work aims to study the structural and physical properties of ZnO thin films deposited by RF sputtering. Different gas mixtures were explored. Specifically, pure Ar and Ar-H2 at various concentrations were used to grow the films on n-type Si (100) wafers and glass without external heating. The plasma chemical species were followed in function of the different gas mixture settings by optical emission spectroscopy (OES). X-ray photoelectron spectroscopy (XPS) and ATR-FTIR (Attenuated Total Reflection Fourier-Transformed Infrared) spectroscopy were used to study the bulk and surface chemical composition of the films, X-ray Diffraction (XRD) analysis allowed lattice structure and grain size determination while samples morphology was checked with a scanning electron microscope (SEM). The films were also characterized for their electrical and optical properties. The introduction of hydrogen in the plasma phase strongly affected the structural, chemical and physical properties of the films. In particular a pronounced change in the films electrical behaviour was observed which become conductive when H is added in the gas mixture ([H2]>6%). The films transparency was on the other hand maintained. By combining XPS, ATR-FTIR and OES data we could correlate the established conductivity and its variations with intentional hydrogen incorporation in the crystal structure in the form of hydroxide species.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11582/25349
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