Local Density of States at Metal-Semiconductor Interfaces: An Atomic Scale Study

Iffländer, Tim; Rolf-Pissarczyk, Steffen; Winking, L.; Ulbrich, R. G.; Al-Zubi, A.; Blügel, Stefan; Wenderoth, M.

doi:10.1103/physrevlett.114.146804

Cited by 19 publications

(18 citation statements)

References 39 publications

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“…The presence of a Schottky barrier (SB) between a semiconductor and a metal is of paramount importance to numerous application fields, including electronics1, photovoltaics23 photocatalysis456 and gas sensors789 Schottky barrier physics has been a subject of intense investigation for several decades, but has recently received renewed substantial attention in two areas: i) the emergence of novel Schottky devices in plasmonics for photocurrent generation, photo detection and solar light harvesting51011 and ii) the development of quantum-scale metal-semiconductor structures, pushed by the ever present need to further minimise and optimise electronic devices121314151617 Continued development of these areas could be greatly facilitated by an atomistic understanding of SB-based processes.…”

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confidence: 99%

Schottky barrier formation and band bending revealed by first- principles calculations

Jiao

Hellman

Fang

et al. 2015

Sci Rep

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The formation of a Schottky barrier at the metal-semiconductor interface is widely utilised in semiconductor devices. With the emerging of novel Schottky barrier based nanoelectronics, a further microscopic understanding of this interface is in high demand. Here we provide an atomistic insight into potential barrier formation and band bending by ab initio simulations and model analysis of a prototype Schottky diode, i.e., niobium doped rutile titania in contact with gold (Au/Nb:TiO2). The local Schottky barrier height is found to vary between 0 and 1.26 eV depending on the position of the dopant. The band bending is caused by a dopant induced dipole field between the interface and the dopant site, whereas the pristine Au/TiO2 interface does not show any band bending. These findings open the possibility for atomic scale optimisation of the Schottky barrier and light harvesting in metal-semiconductor nanostructures.

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confidence: 99%

Schottky barrier formation and band bending revealed by first- principles calculations

Jiao

Hellman

Fang

et al. 2015

Sci Rep

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“…Our results suggest that the pinning of E F in the lower half of the Si band gap at the interface is connected to the insulator-metal transition in ZnO. This lends experimental support to the concept of orbital hybridization and MIGS, wherein extended electronic states in the metal hybridize with the semiconductor, leading to a net transfer of charge and an interface dipole [6,10,12]. We hypothesize that the band alignment could be tuned by controlling the transition between localized and extended states in the oxide, thereby changing the orbital hybridization across the interface.…”

Section: Introductionmentioning

confidence: 55%

“…Microscopic experimental evidence for MIGS contributing to the interface dipole has been shown for an intimate Fe/GaAs interface [12]. On the other hand, a layer of NiO 26 Å thick can reduce the interface dipole at metal/NiO/Si Schottky junctions; this is significantly thicker than the SiO 2 layer used here [4].…”

Section: Discussionmentioning

confidence: 96%

Using Atom-Probe Tomography to UnderstandZnO∶Al/SiO2/SiSchottky Diodes

Jaramillo¹,

Youssef²,

Akey³

et al. 2016

Phys. Rev. Applied

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We use electronic transport and atom-probe tomography to study ZnO∶Al=SiO 2 =Si Schottky diodes on lightly doped n-and p-type Si. We vary the carrier concentration in the ZnO∶Al films by 2 orders of magnitude, but the Schottky barrier height remains nearly constant. Atom-probe tomography shows that Al segregates to the interface, so that the ZnO∶Al at the junction is likely to be metallic even when the bulk of the ZnO∶Al film is semiconducting. We hypothesize that the observed Fermi-level pinning is connected to the insulator-metal transition in doped ZnO. This implies that tuning the band alignment at oxide/Si interfaces may be achieved by controlling the transition between localized and extended states in the oxide, thereby changing the orbital hybridization across the interface.

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“…Another possible application is the study of charge dynamics in the SCR of a Schottky contact, which plays a crucial role in the subject of Spintronics. In our research group and in the thesis of Tim Iffländer 29,38 , a Schottky-contact in form of a thin iron (Fe) film on GaAs was prepared and characterized. A double cleavage process inside the UHV gives access to the cross-section along the Fe-GaAs junction (Fig.…”

Section: )mentioning

confidence: 99%

“…However, in this case, one has to differentiate between "spin-down" and "spin-up" electrons in order to determine the absolute screening efficiency. Theoretical calculations indicate, that the interface region of the Fe-GaAs junction is spin-polarized 29,38 . Consequently, it can be expected that the rates of the corresponding relaxation channels for the optical-generated charge, accumulated at the interface region, are as well spin-dependent.…”

Section: )mentioning

confidence: 99%

Optical Excitation in Scanning Tunneling Microscopy: From Surface Photovoltages to Charge Dynamics oin the Atomic Scale

Kloth¹

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In this thesis, the successful implementation of optical excitation for time-resolved Scanning Tunneling Microscopy (STM) is presented. The fruitful combination of these two experimental methods allows investigating photo-induced dynamic processes on the nanosecond time scale with atomic resolution. The optical setup provides a great versatility regarding the adjustment of excitation parameters such as optical pulse height, pulse width or pulse repetition rate to the experimental needs. Moreover, for the first time, it is possible to disentangle and quantify thermally induced effects, e.g. thermal expansion of the STM tip, from the originally inquired signals, resulting from photo-triggered charge dynamics at the sample surface.Using continuous wave optical illumination at the Gallium-Arsenide(110) (GaAs) surface, it is proven in this thesis, that the presence of excited holes, accumulating in the tip-induced Space Charge Region (SCR) beneath the STM tip not only creates a Surface Photovoltage (SPV) but also opens an additional tunneling channel. Current dependent studies show that this extra tunneling process exhibits a high impact on the charge concentration at the surface. Assuming a steady state between charge generation via optical excitation and charge annihilation via the tunneling process, parameters such as the diffusional or field driven transport rate towards the surface are determined.The build-up and relaxation of an SPV is connected to various microscopic processes, e.g., charge transport or carrier recombination. With pulsed optical excitation, these mechanisms can be probed and disentangled. Whereas for low tunnel rates the decay of the system after optical excitation is mainly determined by the charge annihilation via the tunneling process, for high rates the recharging of dopants becomes visible. Studies of this ionization process for donors, positioned at different depths beneath the surface, reveal a significant local inhomogeneity. By applying a field driven ionization mechanism, it turns out, that the dopants cannot be treated independently from each other. Instead, the ionization dynamics have to be treated as an interacting network of coupled, locally fixed and randomly distributed charge centers.

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Local Density of States at Metal-Semiconductor Interfaces: An Atomic Scale Study

Cited by 19 publications

References 39 publications

Schottky barrier formation and band bending revealed by first- principles calculations

Schottky barrier formation and band bending revealed by first- principles calculations

Using Atom-Probe Tomography to UnderstandZnO∶Al/SiO2/SiSchottky Diodes

Optical Excitation in Scanning Tunneling Microscopy: From Surface Photovoltages to Charge Dynamics oin the Atomic Scale

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