GdN (111) heteroepitaxy on GaN (0001) by N2 plasma and NH3 molecular beam epitaxy

Scarpulla, Michael A.; Gallinat, Chad S.; Mack, Shawn; Speck, J. S.; Gossard, A. C.

doi:10.1016/j.jcrysgro.2008.12.050

Cited by 71 publications

(108 citation statements)

References 34 publications

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“…The RHEED and XRD results are comparable to those from the best gadolinium nitride films. [10][11][12]14 A range of EuN samples have been grown under conditions similar to those described above, at temperatures between 475 and 590 • C, but a clear correspondence between growth temperature and film quality has not been established. In fact, not all samples grown under nominally similar conditions to the sample described above have yielded epitaxial growth, with some growths instead leading to films with a strong [100] texturing but no evidence of epitaxy in RHEED.…”

Section: A Epitaxial Film Growthmentioning

confidence: 99%

“…For most the magnetic state is known, 8,9 but much less information is available regarding the electronic structure. Recent progress has been made, especially in the case of GdN, with the demonstration of epitaxial film growth, [10][11][12][13][14] and studies of its electronic and magnetic properties. [15][16][17][18][19][20][21] Far fewer experimental data concerning the rest of the series are available.…”

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confidence: 99%

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Electronic structure of EuN: Growth, spectroscopy, and theory

et al. 2011

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We present a detailed study of the electronic structure of europium nitride (EuN), comparing spectroscopic data to the results of advanced electronic structure calculations. We demonstrate the epitaxial growth of EuN films, and show that in contrast to other rare-earth nitrides successful growth of EuN requires an activated nitrogen source. Synchrotron-based x-ray spectroscopy shows the samples contain predominantly Eu 3+ , but with a small and varying quantity of Eu 2+ that we associate with defects, most likely nitrogen vacancies. X-ray absorption and x-ray emission spectroscopies (XAS and XES) at the nitrogen K-edge are compared to several different theoretical models, namely LSDA+U (local spin density functional theory with Hubbard U corrections), dynamic mean field theory in the Hubbard-I approximation, and QSGW (quasiparticle self-consistent GW ) calculations. The DMFT and QSGW models capture better the density of conduction band states than LSDA+U . Only the Hubbard-I model contains a correct description of the Eu 4f atomic multiplets and locates their energies relative to the band states, and we see some evidence in XAS for hybridization between the conduction band and the the lowest lying 8 S multiplet. The Hubbard-I model is also in good agreement with purely atomic mutliplet calculations for the Eu M-edge XAS. LSDA+U and DMFT find a metallic ground state, while QSGW predicts a direct band gap at X for EuN of about 0.9 eV that matches closely an absorption edge seen in optical transmittance at 0.9 eV and a smaller indirect gap. Overall, the combination of theoretical methods and spectroscopies provides insights into the complex nature of the electronic structure of this material. The results imply that EuN is a narrow band-gap semiconductor that lies close to the metal-insulator boundary, where the close proximity to the Fermi level of an empty Eu 4f multiplet raises the possibility of tuning both the magnetic and electronic states in this system.

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Section: A Epitaxial Film Growthmentioning

confidence: 99%

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confidence: 99%

Electronic structure of EuN: Growth, spectroscopy, and theory

et al. 2011

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“…The recent demonstration that a new class of ferromagnetic materials -the rare-earth nitrides (REN) -are epitaxy-compatible with group III-nitrides (GaN, AlN and InN) [1,2,3,4] -the technologically important nonmagnetic semiconductor family for the fabrication of white and blue light emitting diodes and transistors -has raised interest not only for semiconductor-based spintronics but also for the possibility of enhancing the efficiency of GaN-based light emitting diodes [5,6,7]. Success in obtaining REN thin films epitaxially grown on wurtzite (0001) oriented AlN or GaN surfaces has been central in getting a better understanding of their fundamental properties, in particular demonstrating, for most of them, their intrinsic ferromagnetic semiconducting nature with a wide variety and complementary magnetic properties across the series [5].…”

Section: Introductionmentioning

confidence: 99%

“…Success in obtaining REN thin films epitaxially grown on wurtzite (0001) oriented AlN or GaN surfaces has been central in getting a better understanding of their fundamental properties, in particular demonstrating, for most of them, their intrinsic ferromagnetic semiconducting nature with a wide variety and complementary magnetic properties across the series [5]. So far, GdN and SmN thin films, typically of the order of tens nanometers thick, have been the most studied compounds of the series, with several reports on the effect of the growth parameters (growth temperature, RE-nitrogen flux ratio…) on the structural and electronic properties [1,2,8,9].…”

Section: Introductionmentioning

confidence: 99%

AlN interlayer to improve the epitaxial growth of SmN on GaN (0001)

Vézian

Damilano

Natali

et al. 2016

Journal of Crystal Growth

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Abstract:An in situ study of the epitaxial growth of SmN thin films on Ga-polar GaN (0001) templates by molecular beam epitaxy is reported. Using X-ray photoelectron spectroscopy we found that Ga segregates at the surface during the first stages of growth. We showed that the problem related to Ga surface segregation can be simply suppressed by growing a few monolayers of AlN before starting the SmN growth. This results in a significant improvement of the crystallinity of SmN thin films assessed by X-ray diffraction.

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“…Furthermore, the electrotransport of GdN has also remained a debatable issue, due to the difficulty of preparing ordered samples with stoichiometric Gd:N ratios and low oxygen levels. Room-temperature resistivity of GdN is in a wide range from 10 À4 X cm for epitaxial films [10][11][12] to 1 X cm for polycrystalline films. 13,14 The dominant dopants are N vacancies 14 and the carriers with concentrations of 10 20 À10 21 cm À3 are electrons.…”

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confidence: 99%

Large negative magnetoresistance in reactive sputtered polycrystalline GdNx films

Zhong

Duan

et al. 2013

Applied Physics Letters

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Polycrystalline ferromagnetic GdNx films were fabricated at different N2 flow rates (fN2) to modify N-vacancy concentration so as to study its influence on electrotransport. Metal-semiconductor transition appears at Curie temperature (TC) of ∼40 K. Temperature-dependent magnetoresistance (MR) shows a peak at TC. The films at fN2 = 5, 10, 15, and 20 sccm show MR of −38%, −42%, −46%, and −86% at 5 K and 50 kOe, respectively. Above 15 K, MR is from colossal MR and from both colossal and tunneling MR below 15 K. The enhanced MR at fN2 = 20 sccm is attributed to large spin polarization of half-metallicity in GdNx with low N vacancies.

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GdN (111) heteroepitaxy on GaN (0001) by N2 plasma and NH3 molecular beam epitaxy

Cited by 71 publications

References 34 publications

Electronic structure of EuN: Growth, spectroscopy, and theory

Electronic structure of EuN: Growth, spectroscopy, and theory

AlN interlayer to improve the epitaxial growth of SmN on GaN (0001)

Large negative magnetoresistance in reactive sputtered polycrystalline GdNx films

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