Influence of Ca/Al Ratio on Properties of Amorphous/Nanocrystalline Cu–Al–Ca–O Thin Films

Abstract

This article reports the characterization of thin films sputtered from CuAl 1 -x Ca x O targets (x = 0, 0.05, 0.1, 0.15, and 0.2) at room temperature. All films exhibit amorphous/nanocrystalline structures. Their transparency increases slightly with the addition of Ca. Furthermore, the resistivity decreases as the Ca/Al atomic ratio increases. Transmission electron microscopy with energy dispersive spectroscopy mapping indicates that the composition is uniform throughout the films deposited from the highest Ca doping concentration target. Some nanocrystals are present at the top surface of the CuAl 0.8 Ca 0.2 O thin film as well as the interface region between the CuAl 0.8 Ca 0.2 O thin film and the glass substrate, whereas the interior of the film is pretty amorphous with some embedded nanocrystals. X-ray photoelectron spectroscopy shows that the Cu 2+ /Cu + atomic ratio increases with the Ca/Al atomic ratio, indicating the enhancement of p-type conductivity from the nonisovalent Cu-O alloying.

Oriented p–n Heterojunction Ag2O/Zn(O,S) Nanodiodes on Mesoporous SiO2 for Photocatalytic Hydrogen Production

“…The peak with binding energies of 533.2 eV corresponds to the O–Si contribution . The other two peaks of 530.4 and 531.3 eV are contributed from oxygen in the Zn­(O,S) phase as oxygen in the lattice and oxygen vacancy, respectively. , These binding energies have good agreement to early works. − The percentage of oxygen in the lattice and oxygen vacancy are about 70 and 30%, respectively, for Zn­(O,S) phase. On the basis of the peak area, the oxygen ratio between oxygen in SiO 2 and in Zn­(O,S) is 6:1.…”

“…34 The other two peaks of 530.4 and 531.3 eV are contributed from oxygen in the Zn(O,S) phase as oxygen in the lattice and oxygen vacancy, respectively. 32,35 These binding energies have good agreement to early works. 36−38 The percentage of oxygen in the lattice and oxygen vacancy are about 70 and 30%, respectively, for Zn(O,S) phase.…”

Electrohydrodynamic Processing of p‐Type Transparent Conducting Oxides

“…Films and Nanofibers. Due to the poor p-type conductivity of delafossite CuAlO 2 , there have been many attempts to improve the electrical conductivity, such as divalent doping [19][20][21] and nitrogen doping [44]. Trivalent dopant in substitution of Al site has become a new experimental interest in recent years.…”

“…The first reason is its inherently low conductivity and difficulty in degenerate doping. Even though there have been a few reports on using divalent dopants such as Mg and Ca [19][20][21] to increase the hole concentration, the dominant O 2 p states underlying the conduction band may strongly localize the extrinsic hole carriers [22]. The second reason lies in the fact that the conductivity highly depends on processing parameters and usually a wide range of optical bandgap values are reported from different synthesizing methods.…”