Time-dependent glassy behavior of interface states in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi><mml:mtext>−</mml:mtext><mml:mi mathvariant="normal">Al</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mtext>−</mml:mtext><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow></mml:math>tunnel junctions

Nesbitt, Jeremy R.; Hebard, A. F.

doi:10.1103/physrevb.75.195441

Cited by 15 publications

(14 citation statements)

References 32 publications

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“…As the atomic configurations change, the local electronic states change, resulting in the electrical resistance drift. 11 Typically, during the initial fabrication of AlO x , the aluminum closest to the surface is oxygen-rich compared to deeper in the aluminum. 8,35 Once the oxidation is complete, the oxygen concentration profile relaxes with time and temperature from this asymmetric AlO x towards a more uniform Al 2 O 3 -like stoichiometry throughout the barrier.…”

Section: Resultsmentioning

confidence: 99%

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Reduced resistance drift in tunnel junctions using confined tunnel barriers

Barcikowski

Pomeroy

2017

Journal of Applied Physics

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Metal-insulator-metal (MIM) tunnel junctions with the aluminum oxide tunnel barriers confined between cobalt electrodes exhibit less resistance drift over time than junctions that utilize a thick, unconfined aluminum electrode. The improved long time stability is attributed to better initial oxide quality achieved through confinement (use of a potential energy well for the oxygen) and plasma oxidation. In this work, Co/AlOx/Co and Co/Al/AlOx/Co tunnel junction aging is compared over a period of approximately 9 months using transport measurements and Wentzel-Kramers-Brillouin (WKB) based modelling. The Co/AlOx/Co (confined) tunnel junction resistance increased by (32 ± 6) % over 5400 h, while Co/Al/AlOx/Co (unconfined) tunnel junction resistance increased by (85 ± 23) % over 5200 h. Fit parameters for the tunnel barrier width and potential energy barriers were extracted using WKB transport modelling. These values change only a small amount in the confined Co/AlOx/Co tunnel junction but show a significant drift in the unconfined Co/AlOx/Co tunnel junction.

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Section: Resultsmentioning

confidence: 99%

“…Our confinement strategy is another method to increase the as-formed oxygen concentration. 11,14,18,19 …”

Section: Introductionmentioning

confidence: 99%

Reduced resistance drift in tunnel junctions using confined tunnel barriers

Barcikowski

Pomeroy

2017

Journal of Applied Physics

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“…The role of interface states in the electronic properties of Al-AlO x Al tunnel junctions was also emphasized in Ref. [21]. Capacitive studies on standard Si-SiO 2 wafers covered with an electron-gun evaporated Al layer, indicate typical charge densities about 10 12 e.cm −2 , i.e.…”

Section: B Electrical Measurementsmentioning

confidence: 99%

Coexistence of anomalous field effect and mesoscopic conductance fluctuations in granular aluminium

Delahaye

Grenet

2008

Eur. Phys. J. B

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We perform electrical field effect measurements at 4 K on insulating granular aluminium thin films. When the samples size is reduced below 100µm, reproducible and stable conductance fluctuations are seen as a function of the gate voltage. Our results suggest that these fluctuations reflect the incomplete self-averaging of largely distributed microscopic resistances. We also study the anomalous field effect (conductance dip) already known to exist in large samples and its slow conductance relaxation in the presence of the conductance fluctuations. Within our measurements accuracy, the two phenomena appear to be independent of each other, like two additive contributions to the conductance. We discuss the possible physical meaning of this independence and in particular whether or not this observation is in favor of an electron glass interpretation of slow conductance anomaly relaxations.

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“…Obviously, the transient shape of the current is dominated by the capacitive charging in the first 10 À3 s since the experimental curves and the calculated charging curve coincide quite well. [80][81][82] and was for the first time studied by J. Curie 83 and E. R. von Schweidler. 84 With U step ¼ 0.3 V a detectable current remains even after 10 3 s. With higher step voltages the remanent current increases and reaches a constant level after 10 or 100 s for voltages of 0.5 and 0.4 V respectively (see Fig.…”

Section: 79mentioning

confidence: 99%

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Stella¹,

Kovacs²,

Diesing³

et al. 2011

J. Electrochem. Soc.

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Heterosystems of metal/insulator/gold type with titanium oxide and tantalum oxide as internal barriers are studied using internal photoemission (IPE), field induced current transport (current transients after voltage steps) and chemical reaction induced current transport (chemicurrent). IPE investigations over a broad energy range from 0.8 to 4.5 eV allow a determination of the interstitial layers band gap and the maximum height of the internal tunnel barrier. The built-in field of the heterosystem is derived by the evaluation of the slope in the photoyield versus photon energy plot. Current transients recorded after voltage steps allow the determination of the heterosystems time constants which generally have a value of some milli seconds. In titanium oxide systems additional time constants with values of several 100 s appear for bias voltages >0.5 V. These time constants are assigned to slow processes altering the height of the titanium oxide barriers. and electron sources in spin polarized tunneling. 5 In the present work we present a comparative investigation of charge transport induced by different methods through thin oxide films. Charges are driven through the oxide by: i) application of a device voltage ii) illumination of the samples with monochromatic light at variable photon energies, leading to spectra of internal photoemission, iii) non adiabatic chemical surface reactions. All three methods are combined since it is possible to derive the nature of excited carriers transport through heterosystems.6 For aluminum and tantalum oxide heterosystems it was found, that they form a high pass filter for excited electrons and holes (defect electrons). 4,6 Since the height of the internal barriers for electrons and holes can be modified by an applied bias voltage, it became possible to characterize the spectra of excited charge carriers with energies below the vacuum barrier. Bias voltages of up to 1 V could be applied to the system which had an internal barrier height of 3 eV.To increase the detection efficiency for excited electrons travelling from the surface of a metal towards the bulk, one can either decrease the thickness of the top metal film of a heterosystem or one can reduce the height of the internal barrier. But with a decrease of the internal barrier the method of applying a bias voltage for tuning this barrier might become problematic, since tunnel currents become larger with lower barrier heights. Additionally, the influence of midgap states, impurities and remanent changes of the internal barrier might become more relevant for lower barriers.8,9 These problems are adressed in the present work.A comparison of metal/insulator/metal heterojunctions is presented with potentiostatically formed titanium and tantalum oxide as interjacent insulating layer. Titanium and tantalum oxide were chosen since both have bandgaps smaller than 4.5 eV.10 For amorphous tantalum oxide values of 4.2 eV are typical 11,12 whereas crystalline samples show values of 3.9-4.5 eV.12,13 Bulk titanium oxide values are for rut...

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Time-dependent glassy behavior of interface states inAl−AlOx−Altunnel junctions

Cited by 15 publications

References 32 publications

Reduced resistance drift in tunnel junctions using confined tunnel barriers

Reduced resistance drift in tunnel junctions using confined tunnel barriers

Coexistence of anomalous field effect and mesoscopic conductance fluctuations in granular aluminium

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

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