Optical response of metal–insulator–metal heterostructures and their application for the detection of chemicurrents

Thissen, Peter; Schindler, Beate; Diesing, Detlef; Hasselbrink, Eckart

doi:10.1088/1367-2630/12/11/113014

Cited by 22 publications

(21 citation statements)

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“…42 However, newer works about the dependence of the internal photoemission on the top electrode's thickness point also to a value of 0.6 until 0.7 eV for E b . 75 So we think that a value of around 0.6 eV for E b might be valid for both oxide systems in all likelihood. For higher photon energies, i.e.…”

Section: -63mentioning

confidence: 94%

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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Section: -63mentioning

confidence: 94%

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Stella¹,

Kovacs²,

Diesing³

et al. 2011

J. Electrochem. Soc.

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“…The electronic structure of the oxide barrier of the MIM sensor was characterised recording I-V curves and its response to optical excitations [45]. The tantalum oxide layer has a band gap of 4.0 eV (Fig.…”

Section: Methodsmentioning

confidence: 99%

Electronic Excitations in the Course of the Reaction of H with Coinage and Noble Metal Surfaces: A Comparison

Schindler

Diesing

Hasselbrink

2013

Zeitschrift für Physikalische Chemie

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The creation of electronic excitations during the reaction of atomic hydrogen on and with coinage and noble metals has been studied using metal-insulator-metal heterostructures. A characteristic current trace is observed when the outer metal surface of the structure is exposed to a 20 s pulse of H atoms. Comparison to the chemical kinetics allows to disentangle the contributions from the different chemical processes to this current. In the case of the coinage metals studied the observation is interpreted to suggest that predominantly electrons excited in connection with the hydrogen recombination reaction are the source of the current. For Pt such phenomenon is not observed. This difference allows insights into the role of the transition state for the non-adiabaticity in this simple chemical reaction.

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“…The thin insulator layer acts as high-pass filter for carrier transport. [18][19][20] Charge transport is limited by the band gap of the insulator, but the small thickness of the oxide layer, and the presence of local defect states in the band gap allow (hot) electrons and holes to tunnel through the oxide barrier. 20 Tunneling from a metal through a thin insulator to another metal has been extensively studied for different material combinations.…”

Section: Binding Energy Of Sn To Sc 2 Omentioning

confidence: 99%

“…[18][19][20] Charge transport is limited by the band gap of the insulator, but the small thickness of the oxide layer, and the presence of local defect states in the band gap allow (hot) electrons and holes to tunnel through the oxide barrier. 20 Tunneling from a metal through a thin insulator to another metal has been extensively studied for different material combinations. [18][19][20][21][22] Noting that the Fermi level remains constant across the interfaces, schematic band diagrams for the different thicknesses of Sc 2 O 3 can be constructed (see Figure 4 To estimate the relative tunnelling rates, we consider a plane wave solution to Schrödinger's equation, ψ Ru = A 1 e ik 1 x + B 1 e −ik 1 x , for an electron traveling in the x direction in the Ru layer, orthogonal to the Ru/Sc 2 O 3 interface.…”

Section: Binding Energy Of Sn To Sc 2 Omentioning

confidence: 99%

“…20 Tunneling from a metal through a thin insulator to another metal has been extensively studied for different material combinations. [18][19][20][21][22] Noting that the Fermi level remains constant across the interfaces, schematic band diagrams for the different thicknesses of Sc 2 O 3 can be constructed (see Figure 4 To estimate the relative tunnelling rates, we consider a plane wave solution to Schrödinger's equation, ψ Ru = A 1 e ik 1 x + B 1 e −ik 1 x , for an electron traveling in the x direction in the Ru layer, orthogonal to the Ru/Sc 2 O 3 interface. Setting the potential of the Ru layer to zero leads to:k 2 1 = K e m e / 2 , where K e is the kinetic energy of the electron, m e is the electron's mass, and the reduced Planck's constant.…”

Section: Binding Energy Of Sn To Sc 2 Omentioning

confidence: 99%

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