Very thin (111) NiO epitaxial films grown on c-sapphire substrates by pulsed laser deposition technique

Yadav, Santosh Kumar; Dhar, Subhabrata

doi:10.1088/1361-6641/abed8e

Cited by 9 publications

(6 citation statements)

References 34 publications

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“…In both the cases, (2 20) reflection is the only visible feature associated with NiO phase, suggesting epitaxial nature of the NiO films. Note that a detailed study of the crystalline quality of the NiO layers grown by this technique has already been reported [23]. In no-oxygen cooled sample, an additional feature arises, which can be assigned to (220) plane of Ni-crystals.…”

Section: Growth Temperature Variationmentioning

confidence: 84%

Oriented assembly of Ni-clusters embedded in semi-insulating NiO epitaxial films

Yadav¹,

Sahu²,

Dhar³

2021

J. Phys. D: Appl. Phys.

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(111) NiO epitaxial layers embedded with crystallographically oriented Ni-clusters are grown on c-sapphire substrates using pulsed laser deposition technique. It has been found that certain growth and post-growth cooling conditions can be adjusted to vary the size, shape and density of these clusters. (111) Ni epitaxial layer can also be deposited on c-sapphire substrate by this technique when no oxygen is supplied into the chamber during growth. Structural and magnetic properties of the clusters are examined by a variety of techniques including atomic probe tomography and superconducting quantum interference device magnetometry. All cluster embedded films are found to exhibit ferromagnetic behaviour even at room temperature. Magnetic characteristics of these films depend strongly on the density, size and shape of the clusters. It has also been observed that electrical conductivity of these samples enhances by several orders of magnitude when the cluster density crosses the percolation threshold. While, strong ferromagnetic behaviour is maintained even in highly resistive samples. Therefore, the material system has a potential to serve as an efficient spin-injector, the missing link for the realization of semiconductor based spintronics.

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Section: Growth Temperature Variationmentioning

confidence: 84%

Oriented assembly of Ni-clusters embedded in semi-insulating NiO epitaxial films

Yadav¹,

Sahu²,

Dhar³

2021

J. Phys. D: Appl. Phys.

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“…In all cases, the broadening of the central peak, which is found to be as narrow as ∼0.08 • , can be attributed to the screw dislocations. Narrowness of the feature suggests that the density of screw dislocations in these films is significantly less and it remains to be so even after annealing up to 900 • C. Two satellite features, on the other hand, can be assigned to 60 • dislocations [30,40]. It is interesting to note that the satellites are becoming more prominent as the T A increases for both the samples.…”

Section: Crystallinitymentioning

confidence: 91%

“…NiO epitaxial films were grown on c-sapphire substrates using a PLD technique, where the NiO pellet was ablated by an excimer KrF laser of a wavelength of 248 nm and a pulse width of 25 ns. Details of the growth process and the characterization of the samples can be found elsewhere [30,31]. Two types of samples were investigated here.…”

Section: Methodsmentioning

confidence: 99%

“…NiO epitaxial films have been reported to be grown on various substrates, such as sapphire, cubic yttria-stabilized zirconia, and MgO, using pulsed laser deposition (PLD) [15,24,25], magnetron sputtering [26], and mist chemical vapour deposition [27], chemical solution [28], and molecular beam epitaxy [29] techniques. Very recently, we reported the growth of [111] oriented NiO epitaxial layers on c-sapphire substrates using a PLD technique and demonstrated the important role played by the growth temperature, oxygen pressure, and layer thickness in governing the crystalline quality and strain in the film [30]. It has also been shown that (111) NiO epitaxial layers embedded with crystallographically oriented Ni clusters can be grown under oxygen-deficient conditions.…”

Section: Introductionmentioning

confidence: 99%

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Annealing-dependent changes in the structural and electrical properties of NiO epitaxial films

Sahu¹,

Yadav²,

Dhar³

2022

Semicond. Sci. Technol.

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NiO and Ni cluster embedded NiO epitaxial films grown on c-sapphire substrates by PLD technique are annealed at different temperatures in oxygen environment. Structural, morphological and electrical properties of these samples are investigated as functions of the annealing temperature. It has been observed that in all cases, sample surface becomes smoother with the increase in annealing temperature. Resistivity of the Ni-cluster free NiO epilayers is found to decrease with the increase in annealing temperature beyond ~300℃. Annealing at 450℃, results in about two orders of magnitude decrease of resistivity from the highly insulating state of the as grown. Resistivity shows a gradual increase when annealed at temperatures higher than 450℃. Reduction of resistivity with annealing can be attributed to the enhancement of the density of Ni-vacancy, which are known to act as shallow acceptors in NiO. Formation energy of the Ni-vacancies, which has been estimated from the ln⁡(ρ^(-1) ) versus 1/T_A plot, comes out to be 623 meV. Density of 60°-dislocations in these films increases sharply when annealed above 500℃. Reduction of conductivity of these films for annealing above 500℃ can thus be explained in terms of the enhancement of the rate of scattering of carriers by these defects. Resistivity of the Ni-cluster embedded highly conducting NiO epilayers are found to increase rapidly by more than several orders of magnitude beyond an annealing temperature of ~200℃. This has been ascribed to percolation driven metal-to-insulator transition arising as a result of the reduction of the cluster density with annealing.

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“…The p-type conduction in the film can be ascribed to the nickel vacancies (V Ni ) [17][18][19][20]. It is noteworthy that NiO epitaxial films with high crystalline quality have been reported by different growth techniques such as pulsed laser deposition [8,21,22], mist chemical vapor deposition [23], RF magnetron sputtering [24] and molecular beam epitaxy [5] on various substrates, such as sapphire, cubic yttria-stabilized zirconia and MgO. In fact, films with improved crystallinity do not show p-type conductivity, rather these are found to be highly resistive.…”

Section: Introductionmentioning

confidence: 99%

Study of lithium incorporation in (111) NiO epitaxial layers grown on c-sapphire substrates using the pulsed laser deposition technique

Sahu

Yadav

Arora

et al. 2023

J. Phys. D: Appl. Phys.

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Incorporation of Lithium in (111)NiO epitaxial layers grown by pulsed layer deposition (PLD) technique on c-sapphire substrates is studied as functions of growth conditions. The effect of Li-inclusion on the structural, morphological, electrical and optical properties of the films have been systematically investigated. It has been found that the concentration of Li in the film is more at lower growth temperatures. However, the crystalline quality deteriorates as the growth temperature is lowered. The investigation suggests that there is a miscibility limit of Li in NiO. Beyond a critical concentration of Lithium, Li-clusters are detected in the films. Further, it has been found that inclusion of Li gives rise to hydrostatic tensile strain in the NiO lattice that results in the reduction of the bandgap. The study also suggests that Li incorporation improves the electrical conductivity of NiO layers. Ni-vacancy defects also play important role in governing the conductivity of these samples.

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Very thin (111) NiO epitaxial films grown on c-sapphire substrates by pulsed laser deposition technique

Cited by 9 publications

References 34 publications

Oriented assembly of Ni-clusters embedded in semi-insulating NiO epitaxial films

Oriented assembly of Ni-clusters embedded in semi-insulating NiO epitaxial films

Annealing-dependent changes in the structural and electrical properties of NiO epitaxial films

Study of lithium incorporation in (111) NiO epitaxial layers grown on c-sapphire substrates using the pulsed laser deposition technique

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