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Intrinsic radiative lifetime derived via absorption cross section of one-dimensional excitons.

Chen S, Yoshita M, Ishikawa A, Mochizuki T, Maruyama S, Akiyama H, Hayamizu Y, Pfeiffer LN, West KW - Sci Rep (2013)

Bottom Line: We experimentally verified our approach for one-dimensional (1D) excitons in high-quality 14 × 6 nm(2) quantum wires by comparing it to the conventional approach.Both independent evaluations showed good agreement with each other and with theoretical predictions.This approach opens a promising path to studying low-dimensional exciton physics.

View Article: PubMed Central - PubMed

Affiliation: Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan. shaoqiangchen@gmail.com

ABSTRACT
Intrinsic radiative lifetime is an essential physical property of low-dimensional excitons that represents their optical transition rate and wavefunction, which directly measures the probability of finding an electron and a hole at the same position in an exciton. However, the conventional method that is used to determine this property via measuring the temperature-dependent photoluminescence (PL) decay time involves uncertainty due to various extrinsic contributions at high temperatures. Here, we propose an alternative method to derive the intrinsic radiative lifetime via temperature-independent measurement of the absorption cross section and transformation using Einstein's A-B-coefficient equations derived for low-dimensional excitons. We experimentally verified our approach for one-dimensional (1D) excitons in high-quality 14 × 6 nm(2) quantum wires by comparing it to the conventional approach. Both independent evaluations showed good agreement with each other and with theoretical predictions. This approach opens a promising path to studying low-dimensional exciton physics.

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Schematics of optical transition processes and cross-sectional transmission electron microscopy (TEM) images of 100-period T-shaped quantum wires.(a) An illustration of the optical emission and absorption processes of a 1D exciton in a quantum wire and the parameters used for calculations. (b) A schematic of optical pumping into 2D continuum states in the arm well, efficient carrier migration, and subsequent luminescence (PL) in T-wires. (c) A TEM image of T-wires. The thicknesses of the stem and arm wells are 14 and 6 nm, respectively. The stem wells and T-wires are uniformly separated by a barrier thickness of 42 nm. The T-wire states are formed at the intersection of the arm well and the stem wells as indicated by the contour curves of the T-wire wavefunction. (d, e) Magnified TEM images demonstrate the high uniformity of the T-wires and the precise replication of the stem wells and T-wires.
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f1: Schematics of optical transition processes and cross-sectional transmission electron microscopy (TEM) images of 100-period T-shaped quantum wires.(a) An illustration of the optical emission and absorption processes of a 1D exciton in a quantum wire and the parameters used for calculations. (b) A schematic of optical pumping into 2D continuum states in the arm well, efficient carrier migration, and subsequent luminescence (PL) in T-wires. (c) A TEM image of T-wires. The thicknesses of the stem and arm wells are 14 and 6 nm, respectively. The stem wells and T-wires are uniformly separated by a barrier thickness of 42 nm. The T-wire states are formed at the intersection of the arm well and the stem wells as indicated by the contour curves of the T-wire wavefunction. (d, e) Magnified TEM images demonstrate the high uniformity of the T-wires and the precise replication of the stem wells and T-wires.

Mentions: The absolute values of the inverse radiative lifetime τK−1 of 1D excitons are scaled and characterized by the inverse intrinsic radiative lifetime τ1D−1 or the averaged τK−1 over all K between 0 and k0, which is given by2345as schematically shown in Fig. 1a. Here, φ(0) is the exciton internal wavefunction φ(z) at an electron-hole relative distance z = 0; μ is the amplitude of the interband-transition dipole moment vector (μx, μy, μz); and ε0 is the vacuum dielectric constant. The key equations, derivations, and related quantities of τ1D−1 shown below are described in detail in the supplementary information. The intrinsic radiative lifetime τ1D has been studied intensively in various 1D systems2345678. In (In)GaAs, the value of τ1D was theoretically calculated to be 150 ps2 in a 10-nm diameter wire; τ1D values in 2D wells and 0D dots have been reported to be shorter (by approximately 10 ps)112 and longer (by approximately 1 ns)13, respectively. For carbon nano-tubes, an ab initio calculation predicted a short τ1D of 8–19 ps6, which is comparable to many experimental results78910.


Intrinsic radiative lifetime derived via absorption cross section of one-dimensional excitons.

Chen S, Yoshita M, Ishikawa A, Mochizuki T, Maruyama S, Akiyama H, Hayamizu Y, Pfeiffer LN, West KW - Sci Rep (2013)

Schematics of optical transition processes and cross-sectional transmission electron microscopy (TEM) images of 100-period T-shaped quantum wires.(a) An illustration of the optical emission and absorption processes of a 1D exciton in a quantum wire and the parameters used for calculations. (b) A schematic of optical pumping into 2D continuum states in the arm well, efficient carrier migration, and subsequent luminescence (PL) in T-wires. (c) A TEM image of T-wires. The thicknesses of the stem and arm wells are 14 and 6 nm, respectively. The stem wells and T-wires are uniformly separated by a barrier thickness of 42 nm. The T-wire states are formed at the intersection of the arm well and the stem wells as indicated by the contour curves of the T-wire wavefunction. (d, e) Magnified TEM images demonstrate the high uniformity of the T-wires and the precise replication of the stem wells and T-wires.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672882&req=5

f1: Schematics of optical transition processes and cross-sectional transmission electron microscopy (TEM) images of 100-period T-shaped quantum wires.(a) An illustration of the optical emission and absorption processes of a 1D exciton in a quantum wire and the parameters used for calculations. (b) A schematic of optical pumping into 2D continuum states in the arm well, efficient carrier migration, and subsequent luminescence (PL) in T-wires. (c) A TEM image of T-wires. The thicknesses of the stem and arm wells are 14 and 6 nm, respectively. The stem wells and T-wires are uniformly separated by a barrier thickness of 42 nm. The T-wire states are formed at the intersection of the arm well and the stem wells as indicated by the contour curves of the T-wire wavefunction. (d, e) Magnified TEM images demonstrate the high uniformity of the T-wires and the precise replication of the stem wells and T-wires.
Mentions: The absolute values of the inverse radiative lifetime τK−1 of 1D excitons are scaled and characterized by the inverse intrinsic radiative lifetime τ1D−1 or the averaged τK−1 over all K between 0 and k0, which is given by2345as schematically shown in Fig. 1a. Here, φ(0) is the exciton internal wavefunction φ(z) at an electron-hole relative distance z = 0; μ is the amplitude of the interband-transition dipole moment vector (μx, μy, μz); and ε0 is the vacuum dielectric constant. The key equations, derivations, and related quantities of τ1D−1 shown below are described in detail in the supplementary information. The intrinsic radiative lifetime τ1D has been studied intensively in various 1D systems2345678. In (In)GaAs, the value of τ1D was theoretically calculated to be 150 ps2 in a 10-nm diameter wire; τ1D values in 2D wells and 0D dots have been reported to be shorter (by approximately 10 ps)112 and longer (by approximately 1 ns)13, respectively. For carbon nano-tubes, an ab initio calculation predicted a short τ1D of 8–19 ps6, which is comparable to many experimental results78910.

Bottom Line: We experimentally verified our approach for one-dimensional (1D) excitons in high-quality 14 × 6 nm(2) quantum wires by comparing it to the conventional approach.Both independent evaluations showed good agreement with each other and with theoretical predictions.This approach opens a promising path to studying low-dimensional exciton physics.

View Article: PubMed Central - PubMed

Affiliation: Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan. shaoqiangchen@gmail.com

ABSTRACT
Intrinsic radiative lifetime is an essential physical property of low-dimensional excitons that represents their optical transition rate and wavefunction, which directly measures the probability of finding an electron and a hole at the same position in an exciton. However, the conventional method that is used to determine this property via measuring the temperature-dependent photoluminescence (PL) decay time involves uncertainty due to various extrinsic contributions at high temperatures. Here, we propose an alternative method to derive the intrinsic radiative lifetime via temperature-independent measurement of the absorption cross section and transformation using Einstein's A-B-coefficient equations derived for low-dimensional excitons. We experimentally verified our approach for one-dimensional (1D) excitons in high-quality 14 × 6 nm(2) quantum wires by comparing it to the conventional approach. Both independent evaluations showed good agreement with each other and with theoretical predictions. This approach opens a promising path to studying low-dimensional exciton physics.

Show MeSH
Related in: MedlinePlus