Infrared dielectric anisotropy and phonon modes of sapphire

Schubert, M.; Tiwald, Thomas E.; Herzinger, C. M.

doi:10.1103/physrevb.61.8187

Cited by 349 publications

(236 citation statements)

References 39 publications

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“…The two oscillator model of the complex dielectric function is used for the CdO layer, while the factorized model was applied for the sapphire substrate. 17 The high frequency dielectric constant, eð1Þ, for CdO was set to 5.3 18 which is consistent with a recent investigation of optical constants of CdO over a range of energies. 19 The high frequency dielectric constant of 3.06 was used for sapphire.…”

Section: Data Simulation and Analysismentioning

confidence: 81%

Electron mobility in CdO films

Farahani

Veal

King

et al. 2011

Journal of Applied Physics

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Electron mobility in degenerate CdO thin films has been studied as a function of carrier concentration. The "optical" mobility has been determined from infrared reflectance measurements of the conduction band plasmon lifetime. The acquired values vary from $209 to $1116 cm 2 V À1 s À1 for carrier concentrations between 2:5Â10 20 and 2:6 Â 10 19 cm À3 . Ionized impurity scattering is shown to be the dominant effect reducing the intra-grain mobility of the electrons at room temperature. The transport mobilities from Hall effect measurements range between $20 and $124 cm 2 V À1 s À1 which are much lower than the optical mobilities. Simulation of grain boundary scattering-limited mobility is commonly based on models that assume a depletion layer at the boundaries which causes an inter-grain potential barrier. These models are found not to be applicable to CdO as it has been previously shown to have surface electron accumulation. Therefore, simulation of the transport mobility has been performed using the Fuchs-Sondheimer and Mayadas-Shatzkes models to take into account the grain boundary and surface scattering mechanisms, in addition to intra-grain scattering. The results indicate that electron scattering at grain boundaries with $95 % reflection is the dominant mechanism in reducing the mobility across the layer. The effect of surface scattering plays only a minor role in electron transport.

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Section: Data Simulation and Analysismentioning

confidence: 81%

Electron mobility in CdO films

Farahani

Veal

King

et al. 2011

Journal of Applied Physics

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“…The IRSE dielectric functions of sapphire were previously determined and taken without any changes in the current work. 39 The model dielectric functions of GaN and InN included contributions from lattice vibrations (phonons) and FCCs. 40,41 The uncoupled phonon mode parameters and the high-frequency limit of the dielectric function of GaN and InN are taken from our previous works.…”

Section: Experimental and Data Analysismentioning

confidence: 99%

Effect of Mg doping on the structural and free-charge carrier properties of InN films

Xie¹,

Sédrine²,

Schöche³

et al. 2014

Journal of Applied Physics

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We present a comprehensive study of free-charge carrier and structural properties of two sets of InN films grown by molecular beam epitaxy and systematically doped with Mg from 1.0 Â 10 18 cm À3 to 3.9 Â 10 21 cm À3 . The free electron and hole concentration, mobility, and plasmon broadening parameters are determined by infrared spectroscopic ellipsometry. The lattice parameters, microstructure, and surface morphology are determined by high-resolution X-ray diffraction and atomic force microscopy. Consistent results on the free-charge carrier type are found in the two sets of InN films and it is inferred that p-type conductivity could be achieved for 1.0 Â 10 18 cm À3 Շ [Mg] Շ 9.0 Â 10 19 cm À3 . The systematic change of free-charge carrier properties with Mg concentration is discussed in relation to the evolution of extended defect density and growth mode. A comparison between the structural characteristics and free electron concentrations in the films provides insights in the role of extended and point defects for the n-type conductivity in InN. It further allows to suggest pathways for achieving compensated InN material with relatively high electron mobility and low defect densities. The critical values of Mg concentration for which polarity inversion and formation of zinc-blende InN occurred are determined. Finally, the effect of Mg doping on the lattice parameters is established and different contributions to the strain in the films are discussed. V C 2014 AIP Publishing LLC.

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“…Strong light-matter interactions in the near-field for polar dielectrics and other crystalline materials can result in very large scattering amplitudes exceeding highly reflective non-resonant surfaces such as Au. Figure 3b shows the reststrahlen region of c-cut sapphire (Al 2 O 3 ) for its E u and A 2 u optical phonon branches, covering the range where its hyperbolic response is due to an intrinsic optical anisotropy [32].…”

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confidence: 99%

Far Infrared Synchrotron Near-Field Nanoimaging and Nanospectroscopy

et al. 2018

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Scattering scanning near-field optical microscopy (s-SNOM) has emerged as a powerful imaging and spectroscopic tool for investigating nanoscale heterogeneities in biology, quantum matter, and electronic and photonic devices. However, many materials are defined by a wide range of fundamental molecular and quantum states at far-infrared (FIR) resonant frequencies currently not accessible by s-SNOM. Here we show ultrabroadband FIR s-SNOM nanoimaging and spectroscopy by combining synchrotron infrared radiation with a novel fast and low-noise copper-doped germanium (Ge:Cu) photoconductive detector. This approach of FIR synchrotron infrared nanospectroscopy (SINS) extends the wavelength range of s-SNOM to 31 μm (320 cm −1 , 9.7 THz), exceeding conventional limits by an octave to lower energies. We demonstrate this new nanospectroscopic window by measuring elementary excitations of exemplary functional materials, including surface phonon polariton waves and optical phonons in oxides and layered ultrathin van der Waals materials, skeletal and conformational vibrations in molecular systems, and the highly tunable plasmonic response of graphene.

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Infrared dielectric anisotropy and phonon modes of sapphire

Cited by 349 publications

References 39 publications

Electron mobility in CdO films

Electron mobility in CdO films

Effect of Mg doping on the structural and free-charge carrier properties of InN films

Far Infrared Synchrotron Near-Field Nanoimaging and Nanospectroscopy

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