Blue luminescence of SrTiO3 under intense optical excitation

Rubano, Andrea; Paparo, D.; Miletto, F.; Uccio, U. Scotti di; Marrucci, Lorenzo

doi:10.1063/1.3256140

Cited by 48 publications

(40 citation statements)

References 43 publications

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“…In addition, we observe a quite unusual pump-fluence behavior: at high carrier concentrations, an increase of the lifetime is observed, contrary to a lifetime decrease expected from bimolecular and/or Auger recombination mechanisms. 22 Both observations are consistent with previous studies covering millisecond time windows with nanosecond time resolution. 10,11 The relaxation and recombination mechanism of photogenerated carriers in 3C-SiC is not yet well understood and requires further studies, beyond the scope of the present work.…”

supporting

confidence: 82%

“…By varying the pump fluence, we do not observe a charge-density dependence of the relaxation dynamics. This observation suggests a unimolecular recombination mechanism, for example via defect states: the photoinduced carrier population consists of several distinct subpopulations, each obeying an exponential decay law with different decay constant 22 . Possibly, different excitation mechanisms (for instance nanosecond versus femtosecond pulses) enhance one population with respect to another.…”

mentioning

confidence: 99%

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Terahertz conductivity and ultrafast dynamics of photoinduced charge carriers in intrinsic 3C and 6H silicon carbide

Rubano¹,

Wolf²,

Kampfrath³

2014

Applied Physics Letters

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The terahertz conductivity of photoinduced charge carriers in two common polytypes of silicon carbide, 3C-SiC and 6H-SiC, is studied on picosecond timescales using an optical-pump / THz-probe technique. We find that the conductivity, measured from 0.7 to 3 THz, is well described by the Drude model, and obtain a velocity relaxation time of 75 fs, independent of sample and charge-carrier density. In contrast, the carrier relaxation rates in the two polytypes differ by orders of magnitude: in 6H-and 3C-SiC, recombination proceeds on a time scale of few picoseconds and beyond nanoseconds, respectively.The technological demand for high-power, hightemperature, and high-field electronic devices requires robust base materials. 1 In this respect, silicon carbide (SiC) is one of the most promising candidates owing to its excellent electrical and structural properties. SiC exists in a large number of polytypes that can be all thought of resulting from stacking three types of bilayer structures (A, B and C) in a certain periodic sequence. The most commonly encountered polytypes are 3C-SiC (stacking order ABC) and 6H-SiC (ABCACB), resulting in a zincblende (two atoms per unit cell) and hexagonal structure (twelve atoms per unit cell), respectively. 2 At room temperature, 3C-and 6H-SiC have an an indirect electronic energy gap of 2.36 eV and 3.0 eV, respectively. 2SiC exhibits exceptional properties that are to a large extent related to the Si-C bond, leading to a stronger localization of the charge density and a larger band gap compared to Si. 2,3 For example, the thermal conductivity of 4.9 and 5.0 W/cm K and breakdown electric field of 3.2 and 1.5 MV/cm for 6H-SiC and 3C-SiC, respectively, 4,5 are about 3 to 5 times larger than those of Si. 2 In addition, the various polytypes make SiC an interesting host material for controlling single electron spins. 6 Also, 6H-SiC may serve as suitable starting material for large-scale graphene production. 7 In order to improve the quality and performance of SiC-based devices, knowledge of fundamental parameters such as the mobility of charge carriers is crucial. Moreover, charge transport is also of considerable interest from the perspective of fundamental physics. So far, the carrier mobility has not been measured in the case of intrinsic samples since they are wide band-gap insulators. A possible approach is to create a transient free-carrier population, for instance by exciting the material with a light pulse. The optical generation of charge carriers circumvents complications arising from chemical doping and, in addition, provides the opportunity to measure out-of-equilibrium parameters. a) Electronic mail: rubano@fisica.unina.it So far, the dynamics of photoinduced charge carriers in intrinsic 3C-and 6H-SiC has been studied using pumpprobe experiments 8-10 , however, with a time resolution of nanoseconds and at optical probe frequencies, far above the charge-carrier scattering rates that usually lye in the terahertz (THz) frequency range. 12 Deeper insight could be obtained by per...

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supporting

confidence: 82%

mentioning

confidence: 99%

Terahertz conductivity and ultrafast dynamics of photoinduced charge carriers in intrinsic 3C and 6H silicon carbide

Rubano¹,

Wolf²,

Kampfrath³

2014

Applied Physics Letters

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“…15,16 However, there is still controversy about the underlying luminescence processes responsible for each emission band. 17 The accelerating voltage used to excite the CL signal is directly related to the electron penetration depth below the surface. We have carried out simulations of the penetration depth profiles using the CASINO software package 18 for 5 and 10 keV electrons in STO.…”

Section: Resultsmentioning

confidence: 99%

Anisotropic magnetotransport in SrTiO3surface electron gases generated by Ar+irradiation

et al. 2011

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Metallic surface layers are fabricated by doping (100) SrTiO 3 (STO) single crystals with oxygen vacancies generated by bombardment with Ar ions from an rf plasma source. The presence of oxygen vacancies is confirmed by cathodoluminescence and x-ray photoemission spectroscopy. This technique produces a surface electron gas with high values of the sheet carrier density (n 2D = 2.45×10 17 cm −2 ). A strong increase (300%) of the low-temperature magnetoresistance is observed when the magnetic field is rotated away from the surface, characteristic of orbital effects of confined electrons. We estimate the width of the confinement region to be in the 200-300 nm range. When a magnetic field is applied in the surface plane and parallel to the current direction, a large negative magnetoresistance is found below the structural transition of the STO, which is discussed in terms of spin-orbit scattering. On further reduction of temperature, there is a change to a positive magnetoresistance regime due to the scattering of charge carriers at the disordered surface region.

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“…pairs [49]. Further, the secondary spin 6 ] clusters and so Cr 3? ion tend to occupy octahedral sites [1].…”

Section: Electron Paramagnetic Resonancementioning

confidence: 96%

“…SrTiO 3 has wide band gap (3.2 eV) and further, the optical band gap can be tuned by doping suitable transition metal (TM) ions. The enhancement of optical property of TM doped SrTiO 3 has been extensively studied and elucidated the possibility of the blue, red, green and yellow emission in the SrTiO 3 compounds [6][7][8]. Further, Alvarado et al [9] reported that the electroluminescence spectra of Cr doped SrTiO 3 was arises due to positioning of Cr 3? in an octahedral ligand field which influences the resistive switching process by involving trapping and detrapping of electrons at the Cr site.…”

Section: Introductionmentioning

confidence: 97%

Carrier mediated ferromagnetism in Cr doped SrTiO3 compounds

Muralidharan

Anbarasu

Perumal

et al. 2015

J Mater Sci: Mater Electron

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The carrier doped ferromagnetism in SrTiO 3 compounds has been investigated for the importance in the field of multiferroics and spintronics. Polycrystalline pure and Cr doped SrTiO 3 compounds were synthesized by glycol assisted sol-gel method. Powder X-ray diffraction (XRD) studies reveal the simple cubic perovskite structure of all the prepared compounds. The grain size and lattice strain of the compounds were estimated from the powder XRD pattern which evidences the incorporation of Cr in SrTiO 3 system. The local order and disorder parameter of the compounds was investigated by laser Raman spectroscopy. The change in particles to rod like surface morphology while increasing Cr doping concentration was examined by scanning electron microscope and transmission electron microscopy. The enhancement of oxygen vacancy while increasing Cr doping concentration in SrTiO 3 system and reduction in Ti 4? to Ti 3? states was identified by X-ray photoelectron spectroscopy. The UVVis absorption spectra evidence the distinctive shift of absorption edge exclusively for Cr doped SrTiO 3 compounds. Photoluminescence (PL) spectra of the compounds reveal defective states and decrease in PL intensity due to the influence of Cr in SrTiO 3 . Electron paramagnetic resonance analysis of Cr doped compounds reveals the paramagnetic nature of the dopants. The magnetization studies of all the prepared compounds emphasis carrier mediated diamagnetic to ferromagnetic phase transition in due with the presence of carriers induced by Cr. It is also evident that the highest dopant concentration of Cr in SrTiO 3 system exhibits reversal ferromagnetism. The enhancement of magnetization and ferromagnetic ordering has been understood in terms of carrier-mediated Ruderman-KittelKasuya-Yosida interaction theory. The present work also demonstrates the influence of surface morphology on the occurrence of ferromagnetism in Cr doped SrTiO 3 compounds.

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Blue luminescence of SrTiO3 under intense optical excitation

Cited by 48 publications

References 43 publications

Terahertz conductivity and ultrafast dynamics of photoinduced charge carriers in intrinsic 3C and 6H silicon carbide

Terahertz conductivity and ultrafast dynamics of photoinduced charge carriers in intrinsic 3C and 6H silicon carbide

Anisotropic magnetotransport in SrTiO3surface electron gases generated by Ar+irradiation

Carrier mediated ferromagnetism in Cr doped SrTiO3 compounds

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