Growth and characterization of TbAs:GaAs nanocomposites

Cassels, Laura E.; Buehl, Trevor E.; Burke, Peter G.; Palmstrøm, C. J.; Gossard, A. C.; Pernot, Gilles; Shakouri, Ali; Haughn, Chelsea R.; Doty, Matthew F.; Zide, Joshua M. O.

doi:10.1116/1.3555388

Cited by 20 publications

(15 citation statements)

References 21 publications

(37 reference statements)

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“…First, radiative lifetimes for nanostructures are typically on the order of 1 ns [18], which is significantly longer than the lifetimes observed for τ 1. Second, spectrophotometry and Fourier transform infrared (FTIR) measurements out to 12 μm reveal only one absorption peak for TbAs:GaAs, at 750 meV [14]. However, we observe no photoluminescence associated with this absorption peak, suggesting that this peak could not be associated with a direct band gap.…”

Section: A Fluence Dependence Measurementsmentioning

confidence: 62%

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Charge carrier relaxation processes in TbAs nanoinclusions in GaAs measured by optical-pump THz-probe transient absorption spectroscopy

et al. 2014

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Rare-earth materials epitaxially codeposited with III-V semiconductors form small, spherical rare-earthmonopnictide nanoparticles embedded within the III-V host. The small size of these particles (approximately 1.5 nm diameter) suggests that interesting electronic properties might emerge as a result of both confinement and surface states. However, ErAs nanoparticles do not exhibit any signs of quantum confinement or an emergent band gap, and these experimental observations are understood theoretically. We use ultrafast pump-probe spectroscopy to investigate the electronic structure of TbAs nanoparticles embedded in a GaAs host, which were expected to be similar to ErAs. We study the dynamics of carrier relaxation into the TbAs states, which essentially act as traps, using optical-pump terahertz-probe transient absorption spectroscopy. By analyzing how the carrier relaxation rates depend on pump fluence and sample temperature, we conclude that the TbAs states are saturable. Saturable traps suggest the existence of a band gap for TbAs nanoparticles, in sharp contrast with the results for ErAs.

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Section: A Fluence Dependence Measurementsmentioning

confidence: 62%

“…For this sample, a Tb source temperature of 1345 • C was used, resulting in a TbAs concentration of 2.12%. Based on these growth conditions and using an average nanoparticle diameter of 1.1 nm, measured from samples of similar growths [14], a TbAs nanoinclusion density of 3.2 × 10 19 cm −3 was calculated.…”

Section: A Sample Fabricationmentioning

confidence: 99%

Charge carrier relaxation processes in TbAs nanoinclusions in GaAs measured by optical-pump THz-probe transient absorption spectroscopy

et al. 2014

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“…The time-domain thermoreflectance (TDTR) technique was employed to measure the thermal conductivity of the ScN thin films. [24][25][26] In the TDTR setup, a Ti:sappire laser was used to create femtosecond laser pulses with $12.5 ns repetition rate and a fixed laser power of 25 MW. The laser pulses were split into a pump beam (18 MW) and a probe beam (7 MW).…”

Section: Methodsmentioning

confidence: 99%

“…The thermal conductivity of the ScN thin film was obtained by fitting the measurement data with a 3D thermal model based on thermal quadrupoles. 26 Plane-wave self-consistent field (PWSCF) implementation of DFT was employed with a generalized gradient approximation (GGA) to the exchange correlation energy 27 and ultrasoft pseudopotentials 28 to represent the interaction between ionic cores and valence electrons. Plane-wave basis sets (PWs) with cut-off energies of 30 Ry and 180 Ry were used to represent the electronic wave functions and charge densities, respectively.…”

Section: Methodsmentioning

confidence: 99%

Thermoelectric properties of epitaxial ScN films deposited by reactive magnetron sputtering onto MgO(001) substrates

Burmistrova

Maassen

Favaloro

et al. 2013

Journal of Applied Physics

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102

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Epitaxial ScN(001) thin films were grown on MgO(001) substrates by dc reactive magnetron sputtering. The deposition was performed in an Ar/N 2 atmosphere at 2 Â 10 À3 Torr at a substrate temperature of 850 C in a high vacuum chamber with a base pressure of 10 À8 Torr. In spite of oxygen contamination of 1.6 6 1 at. %, the electrical resistivity, electron mobility, and carrier concentration obtained from a typical film grown under these conditions by room temperature Hall measurements are 0.22 mX cm, 106 cm 2 V À1 s À1 , and 2.5 Â 10 20 cm À3 , respectively. These films exhibit remarkable thermoelectric power factors of 3.3-3.5 Â 10 À3 W/mK 2 in the temperature range of 600 K to 840 K. The cross-plane thermal conductivity is 8.3 W/mK at 800 K yielding an estimated ZT of 0.3. Theoretical modeling of the thermoelectric properties of ScN calculated using a meanfree-path of 23 nm at 300 K is in very good agreement with the experiment. These results also demonstrate that further optimization of the power factor of ScN is possible. First-principles density functional theory combined with the site occupancy disorder technique was used to investigate the effect of oxygen contamination on the electronic structure and thermoelectric properties of ScN. The computational results suggest that oxygen atoms in ScN mix uniformly on the N site forming a homogeneous solid solution alloy. Behaving as an n-type donor, oxygen causes a shift of the Fermi level in ScN into the conduction band without altering the band structure and the density of states. V C 2013 AIP Publishing LLC [http://dx.

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“…A Ti: Sapphire laser was used in the TDTR setup to create short pulsed laser beams with $12.5 ns repetition rate. 26,27 In the measurement, the laser pulses were split into pump beam and probe beam. The pump beam was used to create a temperature rise on the sample surface.…”

Section: B Time-domain Thermoreflectance (Tdtr) Measurementmentioning

confidence: 99%

Phonon wave effects in the thermal transport of epitaxial TiN/(Al,Sc)N metal/semiconductor superlattices

Saha

Koh

Feser

et al. 2017

Journal of Applied Physics

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Epitaxial single crystalline TiN/(Al,Sc)N metal/semiconductor superlattice metamaterials have generated significant interest in recent years for their potential applications in high temperature thermoelectric devices, optical hyperbolic metamaterials in the visible and near infrared-spectral range, and as candidates for solar-thermophotovoltaics and high temperature electronic materials. While significant progress in their structural, mechanical, and optical properties has been made, indepth analysis and detailed understanding of their thermal transport mechanism remain to be addressed. In this article, we show that in short-period epitaxial, lattice-matched TiN/(Al,Sc)N metal/semiconductor superlattices, thermal transport is dominated by phonon wave effects as the wavelengths of phonons that carry significant amounts of heat become comparable to the superlattice period thickness. Due to the increasing contribution of such phonon wave-modes, the crossplane thermal conductivity at short-periods increases with decreasing period thicknesses resulting in a distinct minimum of thermal conductivity at a period thickness of about 4 nm at room temperature. Thermal conductivity of the superlattices also decreases with an increase in the temperatures due to Umklapp scattering, which supports the wave-nature of the phonon transport mechanism. These results show that the lattice-matched, epitaxial TiN/(Al,Sc)N metal/semiconductor superlattices behave as an effective medium with respect to phonon transport at short-periods, and the wave-nature of phonon dominates the heat conduction mechanism at such length scales. Published by AIP Publishing. [http://dx.

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Growth and characterization of TbAs:GaAs nanocomposites

Cited by 20 publications

References 21 publications

Charge carrier relaxation processes in TbAs nanoinclusions in GaAs measured by optical-pump THz-probe transient absorption spectroscopy

Charge carrier relaxation processes in TbAs nanoinclusions in GaAs measured by optical-pump THz-probe transient absorption spectroscopy

Thermoelectric properties of epitaxial ScN films deposited by reactive magnetron sputtering onto MgO(001) substrates

Phonon wave effects in the thermal transport of epitaxial TiN/(Al,Sc)N metal/semiconductor superlattices

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