Study of Sputtered ZnO:Ga2O3 Films for Energy Harvesting Applications

Abstract

<jats:p>Thin films of ZnO:Ga2O3 (ZGO) were deposited by radio frequency (RF) sputtering at voltages of 0.5, 0.9 and 1.1 kV. The films were studied with respect to their suitability in flexible piezoelectric nanogenerators. The analysis of the spectroscopic and microscopic results showed that piezoelectric features were revealed for the films grown at all sputtering voltages, but the most favorable morphology in terms of low roughness was achieved at 1.1 kV. The effect of the sputtering voltage on the films crystallinity and lattice strain was studied. It was found that the increasing sputtering voltage promoted the films crystallization. Additionally, the presence of oxygen vacancies in the piezoelectric films was negligible as it is not a major factor affecting their performance. The electrical measurements of the Ag/ZnO:Ga2O3/Ag harvester on a flexible substrate in the low-frequency range showed a piezoelectric voltage of 414 mV, a current of 10.4 µA and an electric power output of 1.4 µW at a mass load of 100 g. These results were achieved by a simple architecture of a single piezoelectric layer with a relatively small size of 3 cm2 and small piezoelectric film thickness (600 nm) containing lead-free material. It was proven that the sputtered ZGO films are suitable for energy harvesting elements and their performance could be tuned by the sputtering voltage. Another possible application of the proposed device, excluding low-frequency vibrational harvesting, could be a pressure sensor or strain gauge, due to the good linearity of the electrical parameter dependences on the strain.</jats:p>

Zinc Gallium Oxide—A Review from Synthesis to Applications

“…Bouhemadou et al concluded that the bulk modulus (B 0 ) and elastic constants (C ij ) are linear positive correlations to the pressure for ZnGa 2 O 4 [50]. Their results may be considered as reliable predictions of the pressure dependence of the elastic properties [50] for the ZnGa 2 O 4 material, excluding low-frequency vibrational harvesting, which could be a pressure sensor or strain gauge, due to the good linearity of the electrical parameter dependences on the strain [22]. The values for the elastic constants were C 11 = 228 GPa, C 12 = 120 GPa, C 44 = 107 GPa, and bulk modulus B 0 =156 GPa when the pressure was subjected to zero.…”

“…excluding low-frequency vibrational harvesting, which could be a pressure sensor or strain gauge, due to the good linearity of the electrical parameter dependences on the strain [22]. The values for the elastic constants were C11 = 228 GPa, C12 = 120 GPa, C44 = 107 GPa, and bulk modulus B0 =156 GPa when the pressure was subjected to zero.…”

“…Porous ZnGa 2 O 4 microspheres are synthesized by a facial glucose-mediated microwave hydrothermal method followed by annealing, in order to investigate the photocatalytic degradation of gas-phase aromatic pollutants, where porous ZnGa 2 O 4 microspheres confirmed a much higher activity and stability than TiO 2 under 254 nm UV irradiation [21]. Another possible application of the ZnGa 2 O 4 materials, excluding low-frequency vibrational harvesting, could be a pressure sensor or strain gauge, due to the good linearity of the electrical parameter dependences on the strain [22].…”

Impedance Spectroscopy of Lead-Free Ferroelectric Coatings

“…All piezoelectric samples were fabricated with near to ohmic contacts to avoid a measurement error caused by the interface barriers voltage drop. It was previously established that for piezoelectric films of GZO, the most appropriate electrode material was silver (Ag), for KNbO 3 , aluminum (Al) and for BST:PVDF-TrFE composite, Ag [20,21]. The top electrodes were patterned by lift-off process to produce a variety of similar segments for impedance spectroscopy probing.…”

Advances in wearable flexible piezoelectric energy harvesters: materials, structures, and fabrication

“…RF voltage and post heat treatment temperature have influence on the fabricated 32 film. Aleksandrova et al [184] prepared ZnO/Ga2O3 films at different voltages of 0.5 kV, 0.9 kV and 1.1 kV.…”