Growth of Au Nanoparticles in NiO via Short Annealing of Precursor Material Thin Film and Optimization of Plasmonics

Grammatikopoulos, Spyridon; Stamatelatos, Alkeos; Delimitis, A.; Sousanis, Andreas; Chrisanthopoulou, Athanasia; Trachylis, D.; Politis, Constantinus; Poulopoulos, P.

doi:10.1002/pssa.201700303

Cited by 9 publications

(15 citation statements)

References 38 publications

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“…As we have recently shown for Au–Ni–O films [ 18 ], under such growth conditions in a rough vacuum, a precursor thin film material is formed. This may contain a major part of NiO and to a less extent metallic Ni.…”

Section: Methodsmentioning

confidence: 79%

“…In the present contribution, we present a complete experimental study which is also supported and complemented by theoretical calculation based on the potential morphing method (PMM). We grow ultrathin NiO thin films with an alternative method which starts from the growth of a precursor NiO material in a rough vacuum followed by a short annealing time at 600 °C [ 18 ]. At such elevated temperatures NiO film crystallinity improves [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

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A Study of Quantum Confinement Effects in Ultrathin NiO Films Performed by Experiment and Theory

et al. 2018

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Ultrathin NiO films in the thickness range between 1 and 27 nm have been deposited on high-quality quartz substrates by direct magnetron sputtering under a rough vacuum with a base pressure of 2 × 10−2 mbar. The sputtering target was metallic Ni; however, due to the rough vacuum a precursor material was grown in which most of Ni was already oxidized. Subsequent short annealing at temperatures of about 600 °C in a furnace in air resulted in NiO with high crystallinity quality, as atomic force microscopy revealed. The images of surface morphology showed that the NiO films were continuous and follow a normal grain growth mode. UV-Vis light absorption spectroscopy experiments have revealed a blue shift of the direct band gap of NiO. The band gap was determined either by Tauc plots (onset) or by the derivative method (highest rate of absorbance increase just after the onset). The experimental results are interpreted as evidences of quantum confinement effects. Theoretical calculations based on Hartree Fock approximation as applied for an electron-hole system, in the framework of effective mass approximation were carried out. The agreement between theory and experiment supports the quantum confinement interpretation.

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Section: Methodsmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

A Study of Quantum Confinement Effects in Ultrathin NiO Films Performed by Experiment and Theory

et al. 2018

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“…In ref. 11 , a part of Ni was in the hexagonal hcp phase. Hexagonal Ni in bulk form does not affect the magnetic properties of its environment as it is non-magnetic 12,13 .…”

Section: Resultsmentioning

confidence: 98%

“…For the majority of grey areas, the size of the Au crystals is smaller than the thickness of the TEM lamella and, as a result, the measured distance is averaged between Au and NiO. Note also that HRTEM in a similar but only 10 nm thick film showed the presence of partially amorphous material; only part of Au was in crystalline form with a few isolated grains up to 2 nm in diameter 11 . In the present work, we could not identify amorphous material, so Au is in cubic fcc crystalline form consisting of tiny nanocrystals (smaller than about 4 nm, see Fig.…”

Section: Resultsmentioning

confidence: 98%

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Paramagnetic gold in a highly disordered Au-Ni-O alloy

Stamatelatos

Poulopoulos

Goschew

et al. 2019

Sci Rep

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Magnetic materials are usually classified into a distinct category such as diamagnets, paramagnets or ferromagnets. The enormous progress in materials science allows one nowadays, however, to change the magnetic nature of an element in a material. Gold, in bulk form, is traditionally a diamagnet. But in a ferromagnetic environment, it can adopt an induced ferromagnetic moment. Moreover, the growth of gold under certain conditions may lead to a spontaneous ferromagnetic or paramagnetic response. Here, we report on paramagnetic gold in a highly disordered Au–Ni–O alloy and focus on the unusual magnetic response. Such materials are mainly considered for plasmonic applications. Thin films containing Au, Ni and NiO are fabricated by co-deposition of Ni and Au in a medium vacuum of 2 × 10−2 mbar. As a result, Au is in a fully disordered state forming in some cases isolated nanocrystallites of up to 4 nm in diameter as revealed by high resolution transmission electron microscopy. The disorder and the environment, which is rich in oxygen, lead to remarkable magnetic properties of Au: an induced ferromagnetic and a paramagnetic state. This can be proven by measuring the x-ray magnetic circular dichroism. Our experiments show a way to establish and monitor Au paramagnetism in alloys.

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Analysis of localized surface plasmon resonances in gold nanoparticles surrounded by copper oxides

Stamatelatos

Sousanis

Chronis

et al. 2018

Journal of Applied Physics

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Au-doped Cu thin films are produced by co-deposition of Au and Cu via radiofrequency magnetron sputtering in a vacuum chamber with a base pressure of 1 × 10−7 mbar. After post annealing in a furnace with air, one may obtain either Au-Cu2O or Au-CuO nanocomposite thin films. The presence of Au does not have any considerable influence on the position of the optical band gap of the oxides. Only the Au-CuO system shows well-formed localized surface plasmonic resonances with Gaussian shape. We study systematically the plasmonic behavior of the nanocomposites as a function of the gold concentration, annealing time, and film thickness. The intensity of the resonances, their position, and width are intensely affected by all these parameters. The experimental results are compared with respect to rigorous theoretical calculations. The similarities and differences between experiment and theory are discussed.

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Growth of Au Nanoparticles in NiO via Short Annealing of Precursor Material Thin Film and Optimization of Plasmonics

Cited by 9 publications

References 38 publications

A Study of Quantum Confinement Effects in Ultrathin NiO Films Performed by Experiment and Theory

A Study of Quantum Confinement Effects in Ultrathin NiO Films Performed by Experiment and Theory

Paramagnetic gold in a highly disordered Au-Ni-O alloy

Analysis of localized surface plasmon resonances in gold nanoparticles surrounded by copper oxides

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