Ultrathin magnetic oxide EuO films on Si(001) using SiOx passivation—Controlled by hard x-ray photoemission spectroscopy

Caspers, Christian; Flade, Stanley; Gorgoi, Mihaela; Gloskovskii, A.; Drube, W.; Schneider, Claus M.; Müller, Martina

doi:10.1063/1.4795010

Cited by 27 publications

(32 citation statements)

References 24 publications

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“…The major experimental difficulty relies in synthesizing the metastable oxide EuO in its stoichiometric ferromagnetic phase since off-stoichiometry precludes an epitaxial growth and also reduces ferromagnetic exchange in the ultrathin-film limit, which is, however, essential for efficient spin-filter tunneling. [13][14][15][16][17] In recent years, several growth studies on EuO thin films have been presented, in particular on stoichiometric EuO thin films grown coherently on perfectly lattice-matched yttriastabilized zirconia (YSZ) 14,18 and on different cubic oxides with only a few percent tensile lattice strain. 19,20 The system EuO/MgO (001), however, provides a large compressive lattice mismatch of m = (a MgO − a EuO )/a EuO = −18%.…”

Section: Introductionmentioning

confidence: 99%

Heteroepitaxy and ferromagnetism of EuO/MgO (001): A route towards combined spin- and symmetry-filter tunneling

et al. 2013

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We demonstrate the high-quality heteroepitaxy of ultrathin EuO films with bulklike ferromagnetism directly on MgO (001), an important step towards combining the spin-filter tunnel effect in magnetic insulators and symmetry-filter tunneling through single-crystalline MgO barriers. Despite a large compressive lattice mismatch, EuO grows fully relaxed on MgO (001) and adopts its bulk lattice parameter from the first monolayer on. This initial heteroepitaxial growth mode is discussed in terms of different electrostatic atomic configurations of the oxides interface. Single-crystalline EuO/MgO (001) thus can be envisioned as highly effective double spin-selective tunnel barriers for spintronics applications.

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Section: Introductionmentioning

confidence: 99%

Heteroepitaxy and ferromagnetism of EuO/MgO (001): A route towards combined spin- and symmetry-filter tunneling

et al. 2013

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“…23 Analysis of the EELS line shape can thus produce atomic-resolution information about the oxidation state and bonding information of the constituent species present. [24][25][26][27] While other techniques including X-ray absorption spectroscopy 4,12,28 and hard X-ray photoemission spectroscopy 29 have detected the presence of multiple europium valence states in EuO 1±δ films, electron microscopy is uniquely poised to investigate variations in the interface structure at the atomic scale, which are not discernable by bulk characterization. Transmission electron microscopy on EuO is challenging due to its reactivity with air and we are aware of only one report of its use, 4 though no images were shown in that report.…”

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confidence: 99%

Hetero-epitaxial EuO interfaces studied by analytic electron microscopy

Mundy

Hodash

Melville

et al. 2014

Applied Physics Letters

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With nearly complete spin polarization, the ferromagnetic semiconductor europium monoxide could enable next-generation spintronic devices by providing efficient ohmic spin injection into silicon. Spin injection is greatly affected by the quality of the interface between the injector and silicon. Here, we use atomic-resolution scanning transmission electron microscopy in conjunction with electron energy loss spectroscopy to directly image and chemically characterize a series of EuO|Si and EuO|YAlO 3 interfaces fabricated using different growth conditions. We identify the presence of europium silicides and regions of disorder at the EuO|Si interfaces, imperfections that could significantly reduce spin injection efficiencies via spin-flip scattering. a These authors contributed equally to this work.

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“…Being doped, though, at high temperature, these materials typically enter into dominant states that are not spatially homogeneous due to formation of magnetic polarons -few-body systems comprised of electron and local magnetic moments of the host [20,[24][25][26][27]. However, this unwanted formation does not take place when magnetisation of the lattice is significant, leaving the host material perfectly homogeneous in the region of its employment as a spin injector [25][26][27].Owing its outstanding magnetic and transport properties among other MS, EuO has recently attracted much attention as having tremendous potential for semiconductor spintronics, in particular, when integrated with Si [18,[28][29][30]. Not only does doped EuO exhibit a spin polarization close to 100% due to enormous (~0.6 eV) spin splitting of its conduction band but also it can be conductance-matched with Si by doping with oxygen vacancies or trivalent rare-earth atoms such as Gd, La or Lu [18,[30][31][32][33].…”

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confidence: 99%

“…An intermediate layer, however, reduces the probability of spin-polarized carriers injection exponentially. In particular, an enormous band gap of about 6 eV in SrO makes injection of spin-polarized carriers into Si rather ineffective.The continuing attempts to grow EuO/Si heterojunctions [28][29][30]43,44] are checked by the presence of large amounts of impurity phases at the interface. These phases are not only detrimental to the growth of EuO films; they also prevent spin injection due to spin-flip scattering.…”

mentioning

confidence: 99%

“…Owing its outstanding magnetic and transport properties among other MS, EuO has recently attracted much attention as having tremendous potential for semiconductor spintronics, in particular, when integrated with Si [18,[28][29][30]. Not only does doped EuO exhibit a spin polarization close to 100% due to enormous (~0.6 eV) spin splitting of its conduction band but also it can be conductance-matched with Si by doping with oxygen vacancies or trivalent rare-earth atoms such as Gd, La or Lu [18,[30][31][32][33].…”

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confidence: 99%

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Direct Epitaxial Integration of the Ferromagnetic Semiconductor EuO with Silicon for Spintronic Applications

Averyanov

Sadofyev

Tokmachev

et al. 2015

ACS Appl. Mater. Interfaces

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Materials in which charge and spin degrees of freedom interact strongly offer applications known as spintronics. Following a remarkable success of metallic spintronics based on the giant-magnetoresistive effect, tremendous efforts have been invested into the less developed semiconductor spintronics, in particular, with the aim to produce three-terminal spintronic devices, e.g. spin transistors. One of the most important prerequisites for such a technology is an effective injection of spin-polarized carriers from a ferromagnetic semiconductor into a nonmagnetic semiconductor, preferably one of those currently used for industrial applications such as Si -a workhorse of modern electronics. Ferromagnetic semiconductor EuO is long believed to be the best candidate for integration of magnetic semiconductor with Si. Although EuO proved to offer optimal conditions for effective spin injection into silicon and in spite of considerable efforts, the direct epitaxial stabilization of stoichiometric EuO thin films on Si without any buffer layer has not been demonstrated to date. Here we report a new technique for control of EuO/Si interface on submonolayer level which may have general implications for the growth of functional oxides on Si. Using this technique we solve a long-standing problem of direct epitaxial growth on silicon of thin EuO films which exhibit structural and magnetic properties of EuO bulk material. This result opens up new possibilities in developing all-semiconductor spintronic devices.Modern information technology is based on the fundamental dichotomy: it utilizes charge of electrons to process information in semiconductors and their spin to store information in magnetic materials. Strong correlation of spin and charge degrees of freedom in the same material makes it possible to manipulate magnetically stored information with electric fields and/or modify fast logic gates by changing the magnetisation of their components. In metal multilayers, such effects are manifest in giant magnetoresistance, where the orientations of the macroscopic magnetisation in adjacent layers determine the electrical resistance of the structure [1,2]. Metallic spintronic devices, such as hard disk read heads and magnetic random access memory are among the most successful technologies of the past decades. However, metals cannot enhance signals -the prerequisite for transistor technology readily offered by semiconductors.The development of semiconductor spintronics requires the ability to inject, modulate and detect spin-polarized carriers in a single device, preferably made of technologically important materials currently used in integrated circuits such as Si or GaAs [3,4]. Thus far, the spin of the carriers has played a minor role in semiconductor devices mainly because Si and GaAs are nonmagnetic. On the other hand, the enhanced spin-related phenomena realized in diluted magnetic semiconductors (DMS) (especially 2 GaMnAs films [5]) open the way for applications in spintronics [6]. The interplay between electrical and magneti...

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Ultrathin magnetic oxide EuO films on Si(001) using SiOx passivation—Controlled by hard x-ray photoemission spectroscopy

Abstract: Multilayer approach to the quantitative analysis of x-ray photoelectron spectroscopy results: Applications to ultrathin Si O 2 on Si and to self-assembled monolayers on gold

Cited by 27 publications

References 24 publications

Heteroepitaxy and ferromagnetism of EuO/MgO (001): A route towards combined spin- and symmetry-filter tunneling

Heteroepitaxy and ferromagnetism of EuO/MgO (001): A route towards combined spin- and symmetry-filter tunneling

Hetero-epitaxial EuO interfaces studied by analytic electron microscopy

Direct Epitaxial Integration of the Ferromagnetic Semiconductor EuO with Silicon for Spintronic Applications

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