A ‘soft electronic band’ and the negative thermooptic effect in strontium titanate

Трепаков, В. А.; Dejneka, A.; Markovin, P. A.; Lynnyk, Anna; Jastrabı́k, L.

doi:10.1088/1367-2630/11/8/083024

Cited by 25 publications

(19 citation statements)

References 27 publications

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“…This peak is in good agreement with the peak of the dielectric function revealed by ellipsometry data found in literature. 58,59 This finding further confirms the presence of the optical valence-to-conduction band edge in the SHG spectra. From this evidence, it can be safely stated that SHG probes the electronic composition of the STO layers adjacent to the interface and thus the structure of the O(2p) and Ti (3d) orbitals involved.…”

Section: A Shg Spectra Of Lao/sto Interfaces As a Functionsupporting

confidence: 76%

“…The spectra were normalized using the procedure described above and, in addition, accounting for the change of the refractive index in STO at low temperature. 59 No abrupt qualitative and quantitative change of the SHG spectra between 120 and 80 K was observed. Thus, all physical properties probed by SHG are reflected in the spectra taken at 300 and 10 K. Moreover, all qualitative changes between conducting and nonconducting samples are captured by the set of spectra shown in Fig.…”

Section: B Shg Spectra Of Lao/sto Interfaces As a Function Of Tempermentioning

confidence: 97%

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Electronic states at polar/nonpolar interfaces grown on SrTiO3studied by optical second harmonic generation

et al. 2013

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Optical second harmonic generation (SHG) spectra of LaAlO 3 /SrTiO 3 , LaGaO 3 /SrTiO 3 , and NdGaO 3 /SrTiO 3 interfaces with SrTiO 3 substrates have been measured up to 4.2 eV as a function of film thickness and temperature. This spectral range is characterized by two-photon transitions from the valence to conduction bands of SrTiO 3 which are classified with a model based on symmetry, selection rules, and atomic orbital overlaps. This model is further confirmed in spectral measurements as a function of film thickness, material overlayer, and temperature. SHG enhancement at low temperature indicates an increase of the interfacial polarity with decreasing temperature. This confirms the relation between SHG and the spatial translation of Ti ions which are more prone to move at lower temperatures because of the quantum-paraelectric nature of SrTiO 3. We finally show that SHG spectroscopy captures structural details of the interfaces. In particular, we find evidence for proximity effects such as LaAlO 3-induced distortions of the TiO 6 octahedra or bond buckling. We also observe a correlation between SHG and the in-plane lattice mismatch between the SrTiO 3 substrate and the LaAlO 3 , LaGaO 3 , and NdGaO 3 overlayers.

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Section: A Shg Spectra Of Lao/sto Interfaces As a Functionsupporting

confidence: 76%

Section: B Shg Spectra Of Lao/sto Interfaces As a Function Of Tempermentioning

confidence: 97%

Electronic states at polar/nonpolar interfaces grown on SrTiO3studied by optical second harmonic generation

et al. 2013

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“…From these transmission values, the absorption coefficient,

α

, can be calculated () as

α = - \frac{1}{d} ln \frac{\sqrt{false(1 - R)^{4} + 4 {Tr}^{2} R^{2}} - false(1 - R)^{2}}{2 normalTr R^{2}},

where R is the reflectivity, d is the sample thickness and Tr is the transmission. R was approximated from the wavelength dependent room temperature refractive index data reported by Dodge () for the IR spectra while the refractive index data reported by Trepakov et al () was used for the UV/VIS spectra because it is more accurate in this spectral range.…”

Section: Methodsmentioning

confidence: 99%

Temperature-dependent optical absorption of SrTiO₃

Kok

Irmscher

Naumann

et al. 2015

Phys. Status Solidi A

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The optical absorption edge and near infrared absorption of SrTiO 3 were measured at temperatures from 4 to 1703 K. The absorption edge decreases from 3.25 eV at 4 K to 1.8 eV at 1703 K and is extrapolated to approximately 1.2 eV at the melting point (2350 K). The transmission in the near IR decreases rapidly above 1400 K because of free carrier absorption and is about 50% of the room temperature value at 1673 K. The free carriers are generated by thermal excitation of electrons over the band gap and the formation of charged vacancies. The observed temperature-dependent infrared absorption can be well reproduced by a calculation based on simple models for the intrinsic free carrier concentration and the free carrier absorption coefficient. The measured red shift of the optical absorption edge and the rising free carrier absorption strongly narrow the spectral range of transmission and impede radiative heat transport through the crystal. These effects have to be considered in high temperature applications of SrTiO 3 -based devices, as the number of free carriers rises considerably, and in bulk crystal growth to avoid growth instabilities.Temperature dependent optical absorption edge of SrTiO 3 , measured, fitted, and extrapolated to the melting point.

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“…Metals oxides like TiO 2 and SrTiO 3 have been investigated in semiconductor industry as a gate dielectric [15]. These metal oxides also have negative thermo-optic coefficient due to presence of a soft electronic band [16]…”

Section: Introductionmentioning

confidence: 99%

Athermal silicon microring resonators with titanium oxide cladding

2013

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A ‘soft electronic band’ and the negative thermooptic effect in strontium titanate

Cited by 25 publications

References 27 publications

Electronic states at polar/nonpolar interfaces grown on SrTiO3studied by optical second harmonic generation

Electronic states at polar/nonpolar interfaces grown on SrTiO3studied by optical second harmonic generation

Temperature-dependent optical absorption of SrTiO₃

Athermal silicon microring resonators with titanium oxide cladding

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A ‘soft electronic band’ and the negative thermooptic effect in strontium titanate

Cited by 25 publications

References 27 publications

Electronic states at polar/nonpolar interfaces grown on SrTiO3studied by optical second harmonic generation

Electronic states at polar/nonpolar interfaces grown on SrTiO3studied by optical second harmonic generation

Temperature-dependent optical absorption of SrTiO3

Athermal silicon microring resonators with titanium oxide cladding

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Product

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Temperature-dependent optical absorption of SrTiO₃