Electronic surface properties of SrTiO3 derived from a surface photovoltage study

Beyreuther, Elke; Becherer, J.; Thiessen, A.; Grafström, S.; Eng, Lukas M.

doi:10.1016/j.susc.2013.01.022

Cited by 10 publications

(12 citation statements)

References 47 publications

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“…As schematically illustrated in Figure d,e, the shorter lifetime indicates that a larger number of recombination sites exist at the SRO(4 ML)/STO interface, which is confirmed by the higher PES intensities near E F (Figure a). There was a tendency of the shorter lifetime at the higher incident photon flux, which is consistent with the previous reports for semiconductor surfaces …”

supporting

confidence: 92%

“…As a photovoltaic component, STO crystals have a large advantage to be transparent with visible light, which opens new usage or functionality that is fundamentally impossible by silicon‐based solar cells. Concerning the photo‐induced phenomena in technology, generation of the photovoltage is the most fundamental optical response, and therefore extensive studies have been carried out to clarify mechanisms in the surface photovoltage (SPV) effect . The SPV is an effect generated by photo‐induced electron–hole pairs near a surface or an interface.…”

mentioning

confidence: 99%

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Tailoring Photovoltage Response at SrRuO₃/SrTiO₃ Heterostructures

Yukawa

Yamamoto

Akikubo

et al. 2016

Adv Materials Inter

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band diagrams and the optical responses were evaluated by soft X-ray photoelectron spectroscopy (PES) that selectively probes either the SRO overlayer or the STO substrate. Space-charge layers of the STO crystal are controlled between the accumulation-type and the depletion-type by the surface/interface conditions. Then, amount of the photovoltage and lifetime of the photo-excited carriers in the SRO/STO system were traced by the time-resolved measurement. We show that the SPV effect in an STO crystal was drastically dependent on the initial electrostatic potential structure at the SRO/STO interface that is understood from the bulk-band bending effect.The optical responses of the surface/interface systems were induced by irradiation of the second harmonic generation of a Ti:sapphire laser and were monitored by the soft-X ray core-level PES using synchrotron radiation (SR). The time-resolved measurements at the delay time (t) were made by the pump(laser)probe(SR) method. [14] Figure 1a shows time-resolved Sr 3d core-level spectra of the bare STO surface and the SRO/STO interfaces with different SRO thicknesses taken before and after the light irradiation. Taking the Sr 3d 5/2 peak position before the optical pumping as the energy reference, the energy shifts of 15, 180, and 90 meV in binding energies with an uncertainty of ±25 meV were obtained for the STO, SRO(2 ML)/STO, and SRO(4 ML)/ STO surfaces, respectively. The spectral peaks obviously shift to the higher binding energies after the photo-excitation for the SRO/STO heterojunctions but not for the bare STO surface. To assign the energy shift at the SRO/STO interface, time-resolved measurements were made for core-level spectra of Sr 3d and Ti 2p, as shown in Figure 1b. After the optical pumping, both the Sr and Ti spectral peaks shift by the same amount of value (105 ± 25 meV) to the higher binding energy. While the Sr signals originate from both the SRO overlayer and the STO substrate (see the Supporting Information), Ti peak is only from the STO substrate. Therefore, the PES signals of the Ti peak are suppressed as in Figure 1b. Focusing on the Sr core-level peak, one finds a lack of observable broadening of the Sr 3d peak before and after the optical excitation. These facts indicate the simultaneous energy shifts of electronic bands in SRO and STO as well as the drastic change of optical response of the STO substrate with the SRO overlayers.The photo-induced phenomena result from dynamics of the photo-excited carriers that are governed by electronic potential induced by the interface electronic structure. To clarify the electric potential, core-level peak positions and the valence band maxima (VBMs) were obtained. Figure 2a shows a collection of valence band photoelectron spectra of the STO surface and SRO/STO interfaces with 2 ML-and 4 ML-thick SRO films. On Strontium titanate (SrTiO 3 : STO) has been regarded as one of the key materials for the metal oxide industry owing to its chemical stabilities, non-toxic natures, and exotic electron correlation effec...

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supporting

confidence: 92%

mentioning

confidence: 99%

Tailoring Photovoltage Response at SrRuO₃/SrTiO₃ Heterostructures

Yukawa

Yamamoto

Akikubo

et al. 2016

Adv Materials Inter

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“…The intensity of the SPV response gradually increases as the Ni content increases, and reaches a maximum for an Ni content of 2.0 %, that is, the density of the shallow surface states has increased. [43] However, the response intensity began to decrease with further increases in Ni content. This can be attributed to the existence of the I Ni ions due to the high level of Ni doping, which may act as recombination centers.…”

Section: Resultsmentioning

confidence: 99%

Construction of Shallow Surface States through Light Ni Doping for High‐Efficiency Photocatalytic Hydrogen Production of CdS Nanocrystals

Li¹,

Zhang²,

Jiang³

et al. 2013

Chemistry A European J

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Ni-doped CdS nanowires were synthesized by a simple one-step method. X-ray diffraction, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy confirmed that light Ni doping can form shallow surface states due to the presence of substitutional Ni ions, and heavy Ni doping can form deep surface states due to the presence of interstitial Ni ions. Surface photovoltage spectroscopy and transient photovoltage measurements revealed that the shallow surface states can prolong the lifetime of the photogenerated charge carriers, whereas the deep surface states lead to recombination of the photogenerated charge carriers. The relationship between different surface states and the photocatalytic performance of CdS nanocrystals are discussed. The enhanced density of shallow surface states due to light Ni doping significantly promotes photocatalytic H2 production.

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“…A bandgap of 3.2 eV and a relative dielectric permittivity of 100 are used for SrTiO 3 . The effective density of states for conduction band is set to 2.5 × 10 20 cm −3 [9]. Drift-diffusion model is used for transport calculation.…”

Section: Device Fabrication and Simulationmentioning

confidence: 99%

Conduction Mechanism in SrTiO<sub>3</sub>-Based Field-Effect Transistors

Zhu

Zhao

et al. 2015

IEEE Trans. Electron Devices

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In this brief, we find that the previously reported performance improvement of HfO 2 /SrTiO 3 devices after argon bombardment may be attributed to the decrease of interface traps. With the greatly reduced interface trap density, the HfO 2 /SrTiO 3 device after argon bombardment shows remarkable reduction of turn-ON voltage shift with decreasing temperature, which is in contrast with the unbombarded HfO 2 /SrTiO 3 device. Though HfO 2 /SrTiO 3 devices behave like conventional transistors, Al 2 O 3 /SrTiO 3 devices show very different linear transfer characteristics, which may be due to the high density of shallow donor states near the Al 2 O 3 /SrTiO 3 interface. The exhibited SrTiO 3 -based device characteristics are studied by experiments and simulations. The simulations with drift-diffusion model reproduce the experimental results.Index Terms-Al 2 O 3 /SrTiO 3 , HfO 2 /SrTiO 3 , interface traps, oxygen vacancy, transistors.

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Electronic surface properties of SrTiO3 derived from a surface photovoltage study

Cited by 10 publications

References 47 publications

Tailoring Photovoltage Response at SrRuO₃/SrTiO₃ Heterostructures

Tailoring Photovoltage Response at SrRuO₃/SrTiO₃ Heterostructures

Construction of Shallow Surface States through Light Ni Doping for High‐Efficiency Photocatalytic Hydrogen Production of CdS Nanocrystals

Conduction Mechanism in SrTiO<sub>3</sub>-Based Field-Effect Transistors

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Electronic surface properties of SrTiO3 derived from a surface photovoltage study

Cited by 10 publications

References 47 publications

Tailoring Photovoltage Response at SrRuO3/SrTiO3 Heterostructures

Tailoring Photovoltage Response at SrRuO3/SrTiO3 Heterostructures

Construction of Shallow Surface States through Light Ni Doping for High‐Efficiency Photocatalytic Hydrogen Production of CdS Nanocrystals

Conduction Mechanism in SrTiO<sub>3</sub>-Based Field-Effect Transistors

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Tailoring Photovoltage Response at SrRuO₃/SrTiO₃ Heterostructures

Tailoring Photovoltage Response at SrRuO₃/SrTiO₃ Heterostructures