Control of defect-mediated tunneling barrier heights in ultrathin MgO films

Kim, D. J.; Choi, Woo Seok; Schleicher, F.; Shin, Ran Hee; Boukari, S.; Davesne, Vincent; Kieber, Christophe; Arabski, J.; Schmerber, G.; Beaurepaire, E.; Jo, William; Bowen, M.

doi:10.1063/1.3531652

Cited by 23 publications

(21 citation statements)

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“…As future experiments on appropriate stacks 24,40,65 (and perhaps those of ref. 43 with high TMR) with possible defect control 27 can now explicitly confirm, we expect that a sufficient density of M centres would lower f P to that centre's energy position of B0.4 eV from E F (see Table 1), thereby yielding f P of AP and larger values of TMR. This shows how the effective barrier height of a MTJ reflects the energy position of all defects within the barrier dielectric relative to E F , as weighed by the thermal activation of a given defect species within a precise temperature range.…”

Section: Discussionmentioning

confidence: 93%

“…We thus resolve the contradiction between low barrier heights and large values of TMR in MgO MTJs. In the process, we provide a very important nuance to the generally accepted, intuitive paradigm 20,27,28 that reducing defect densities will lead to improved TMR ratios. Indeed, as predicted theoretically 25 , certain defect species in MgO (that is, M centres) can actually promote resilient magnetotransport under thermal excitation, while others (that is, F/F þ ) promote a thermally induced TMR decrease due to a more efficient, defect-induced mixing of electronic symmetries.…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, the impact of structural defects in MgO on tunnelling is only emerging in this otherwise widely studied, canonical spintronic system [20][21][22][23][24][25][26] . Indeed, defects have been qualitatively suspected of accounting for much lower tunnelling barrier heights than expected 12,27 . Defects are thus generically considered to hinder magnetotransport 28 .…”

mentioning

confidence: 99%

“…Defects are thus generically considered to hinder magnetotransport 28 . This has spurred efforts to control the density of oxygen vacancies during MgO growth 27 , although a more recent theory suggests that spatially close oxygen vacancies, or even paired oxygen vacancies known as M centres, lead to symmetry-conserving transport 25 . However, without knowing of precisely which defect species is responsible for altering magnetotransport in a given MTJ, it is difficult to understand, let alone control, the impact of defects on magnetotransport.…”

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confidence: 99%

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Localized states in advanced dielectrics from the vantage of spin- and symmetry-polarized tunnelling across MgO

et al. 2014

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Research on advanced materials such as multiferroic perovskites underscores promising applications, yet studies on these materials rarely address the impact of defects on the nominally expected materials property. Here, we revisit the comparatively simple oxide MgO as the model material system for spin-polarized solid-state tunnelling studies. We present a defect-mediated tunnelling potential landscape of localized states owing to explicitly identified defect species, against which we examine the bias and temperature dependence of magnetotransport. By mixing symmetry-resolved transport channels, a localized state may alter the effective barrier height for symmetry-resolved charge carriers, such that tunnelling magnetoresistance decreases most with increasing temperature when that state is addressed electrically. Thermal excitation promotes an occupancy switchover from the ground to the excited state of a defect, which impacts these magnetotransport characteristics. We thus resolve contradictions between experiment and theory in this otherwise canonical spintronics system, and propose a new perspective on defects in dielectrics.

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Localized states in advanced dielectrics from the vantage of spin- and symmetry-polarized tunnelling across MgO

et al. 2014

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“…In particular, adding O2 to the Ar plasma during MgO growth also helps in altering the oxygen population and the barrier performance [24]. It is also worth mentioning that these MgO films show a remarkable structural distortion [25], which is taken as an indication of the existence of cation vacancies in our samples [17].…”

Section: Device Preparation and Characterizationmentioning

confidence: 99%

Resistance switching in transparent magnetic MgO films

Jambois

Carreras

Antony

et al. 2011

Solid State Communications

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We have studied the abrupt and hysteretic changes of resistance in MgObased capacitor devices. The switching behavior is discussed in terms of the formation and rupture of conduction filaments due to the migration of structural defects in the electric field, together with the redox events which affects the mobile carriers. The results presented in this paper suggest that MgO transparent films combining ferromagnetism and multilevel switching characteristics might pave the way for a new method for spintronic multibit data storage.

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Probing a Device's Active Atoms

et al. 2017

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Materials science and device studies have, when implemented jointly as "operando" studies, better revealed the causal link between the properties of the device's materials and its operation, with applications ranging from gas sensing to information and energy technologies. Here, as a further step that maximizes this causal link, the paper focuses on the electronic properties of those atoms that drive a device's operation by using it to read out the materials property. It is demonstrated how this method can reveal insight into the operation of a macroscale, industrial-grade microelectronic device on the atomic level. A magnetic tunnel junction's (MTJ's) current, which involves charge transport across different atomic species and interfaces, is measured while these atoms absorb soft X-rays with synchrotron-grade brilliance. X-ray absorption is found to affect magnetotransport when the photon energy and linear polarization are tuned to excite FeO bonds parallel to the MTJ's interfaces. This explicit link between the device's spintronic performance and these FeO bonds, although predicted, challenges conventional wisdom on their detrimental spintronic impact. The technique opens interdisciplinary possibilities to directly probe the role of different atomic species on device operation, and shall considerably simplify the materials science iterations within device research.

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Control of defect-mediated tunneling barrier heights in ultrathin MgO films

Cited by 23 publications

References 30 publications

Localized states in advanced dielectrics from the vantage of spin- and symmetry-polarized tunnelling across MgO

Localized states in advanced dielectrics from the vantage of spin- and symmetry-polarized tunnelling across MgO

Resistance switching in transparent magnetic MgO films

Probing a Device's Active Atoms

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