Two-body decay of thermalized excitons in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:math>

Warren, J. T.; O’Hara, K. E.; Wolfe, J. P.

doi:10.1103/physrevb.61.8215

Cited by 56 publications

(65 citation statements)

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“…The peak at 932 eV is assigned to Cu or a small amount of Cu 2 O. Although Cu 2 O is a luminescent material, 15 its effect can be excluded since the blue emission disappears after acetone rinsing. The peak at 934.2 eV is assigned to CuO or Cu(OH) 2 .…”

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confidence: 99%

Blue photoluminescence from in situ Cu-doped porous silicon

Suh

Kim

Lee

2002

Journal of Applied Physics

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We have observed weak blue photoluminescence from in situ Cu-doped porous silicon formed by electrochemical etching with a low etching current density that is aided by cuprous chloride ͓Cu͑I͒Cl͔. Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and Auger electron spectroscopy reveal that the blue emission is associated with formation of the carbonyl group that is catalyzed by Cu on the surface of the porous silicon. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1476961͔The observation of visible room-temperature photoluminescence ͑PL͒ from porous silicon ͑PS͒ 1 has stimulated many studies for potential applications in silicon-based optoelectronics. Metal deposition on PS is needed to realize potential applications in optoelectronics. There are many techniques available for the deposition such as vapor deposition, sputtering, electrodeposition, and immersion plating. Immersion or electroless plating refers to the plating of soluble metal ions onto a base material without applying a bias. Several authors have investigated the PL properties and chemical composition of metal-doped ͑Cu, Ag, and Au͒ PS, 2-9 in particular by the immersion plating method. Typical metal content is about 10 at. %. Often, the PL of PS is quenched by the deposition, and the oxidation of PS occurs simultaneously with the metal deposition. 2,3,6 Recently, we reported ambient full-color PL from PS that was obtained through electrochemical etching aided by an ''oxidative'' metal such as Zn without any postanodizing treatment. 10 In the course of the etching, Zn deposition does not take place and therefore Zn plays a role in altering the luminescence characteristics. If we use a ''reductive'' metal such as Cu, which has a higher reductive potential than hydrogen, it is expected that PL quenching occurs during etching due to the deposition of Cu ion unto the surface.Copper is known to promote chemisorption of carbon dioxide at room temperature with the aid of adsorbed oxygen to give a surface carbonate. 11 In addition, adsorbed carbon compounds such as alkanes could be more easily oxidized because of the ''reductive'' nature of copper. Once PS is formed and exposed to air, it undergoes aging with some regions attacked by carbon compounds. As PS has a large surface area, the formation of carbonyl group (CvO) could be facilitated under the catalytic action of copper. Huang 7 has given an experimental evidence for the formation of carbonyl group. He reported that two new peaks appeared at 1720.3 cm Ϫ1 and 2949.2 cm Ϫ1 from Fourier transform infrared spectroscopy ͑FTIR͒ measurements when the as-prepared PS sample was dipped into a dilute aqueous CuF 2 solution. Although the two new peaks were not discussed, it is clear that they originate from carbon contamination ͑CvO for 1720.3 cm Ϫ1 and CH x for 2949.2 cm Ϫ1 ͒. When carbon is incorporated into PS, PL properties do change and frequently blue PL is detected from carbonyl (CvO) compounds. 12,13 In this communication, we report weak blue PL from in situ Cu-doped PS fo...

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confidence: 99%

Blue photoluminescence from in situ Cu-doped porous silicon

Suh

Kim

Lee

2002

Journal of Applied Physics

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“…But there is a substantial discrepancy between theory and time-resolved photoluminescence (which measures the decay of exciton number following short optical pulse excitation). The calculated direct (2 Â 10 À21 cm 3 /ns at a temperature of 70 K) [7] and phonon-assisted Auger decay rates (3 Â 10 À22 cm 3 /ns) [8,9] are orders of magnitude smaller than measured decay rate (10 À16 cm 3 /ns) [3]. Moreover, conventional Auger theory predicts a linear increase of the Auger rate with temperature, whereas experiment [7] shows an inverse temperature dependence.…”

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confidence: 84%

“…Usually, this undesirable effect is attributed to an exciton Auger process, i.e., upon collision one of the excitons recombines and contributes its band-gap energy to the kinetic energy of the remaining electron and hole [2][3][4][5][6]. But there is a substantial discrepancy between theory and time-resolved photoluminescence (which measures the decay of exciton number following short optical pulse excitation).…”

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confidence: 98%

“…Here 2C ¼ 10 À16 cm 3 =ns is the average recombination (capture) coefficient; t A ¼ 70 ns is the biexciton lifetime [3]; t is the exciton life time which is mostly defined by impurities and assumed to be much lager then the Auger life time t A . Note that C is much lager than the conventional exciton (biexciton) Auger rate.…”

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confidence: 99%

“…Recently some novel 2D correlation spectroscopic techniques have been applied to study exciton and biexciton formation, their dynamics and transport in bulk semiconductors, quantum wells and quantum dots [11][12][13][14]. In these time domain experiments, a train of well separated optical pulses excites the sample and the generated x (3) signal is heterodyne detected in one of the possible phase matching conditions.…”

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Coherent manipulation of quadrupole biexcitons in cuprous oxide by 2D femtosecond spectroscopy

Roslyak

Aparajita

Birman

et al. 2011

Physica Status Solidi (b)

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We propose using coherent optical spectroscopy to study and control optically-forbidden (dark) biexciton states in crystals of cuprous oxide. These states are revealed in the correlation spectra cross resonances due to coherence with the quadrupole allowed 1S exciton manifold. The signal is obtained by means of sum-over-state formalism and comparing equations of motion for the weakly interacting quadrupole excitons with their analogue of non-interacting quasiparticles. The dephasing mechanisms include rapid Auger relaxation of biexcitons which allegedly impedes the Bose-Einstein condensation of quadrupole excitons. An interesting effect attributed to the deviation of the quadrupole excitons from the ortho-para excitons picture is that the positions of the biexciton resonances are defined by the energy splitting between G þ 5;yz and G þ 5;xz excitons and can be tuned by an external perturbation. Possible quantum computing and lasing applications of the quadrupole induced chirality effects of the excitons and biexcitons, and coherence between exciton/biexciton manifolds are discussed. '' Equal parity of the conduction and valence band states produces dipole-forbidden, quadrupole-allowed 1S exciton which is characterized by a long radiative life-time depending on a dominating dephasing mechanism and varies from ns to ps. At low exciton density the measured life-time (%1.7 ns) is determined by phononassisted non-radiative transitions between ortho (J ¼ 1) and optically forbidden para (J ¼ 0) excitons separated by 12 meV due to spin-orbit interaction. Thanks to the small radius, the exciton gas saturation density n s ¼ 10 20 cm À3 is much higher than the critical density n c ¼ 10 17 cm À3 needed for the quadrupole exciton BEC at T ¼ 2 K.Unfortunately, BEC turned out to be an elusive goal due to a strong recombination process that becomes effective at gas densities above %10 14 cm À3 . Usually, this undesirable

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Molding 2D Exciton Flux toward Room Temperature Excitonic Devices

Dai

Luo

et al. 2022

Adv Materials Technologies

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optoelectronic elements and devices. Owing to the unique talents of electrons and photons, the efficient photonic communication and electronic processing of signals have been proved as the essential and core components the information technology. Electrons as charged particles are sensitive to surroundings because of strong Coulomb interaction, leading to the bottleneck of nanosecond response time for integrated electric devices. The electronic response time and the conversation between photonic and electronic systems inevitably limit the operation speed in the conventional optoelectronic. [1] Thus developing compact photonic devices performing the essential logic operations is promising to accelerate information transmission and processing. In this direction, some simple prototypes, including optoelectronic transistor, compact microring resonator-based modulator, and Mach-Zehnder modulator, have been demonstrated. [2][3][4] The high integration of photonic devices is challenging due to the optical diffraction limit. Although the latter devices have achieved switching speeds exceeding several gigahertz, high packing density is greatly limited by their active-region dimensions of 10-100 µm. Excitons, or bound electron−hole pairs, Devices operating with excitons have promising prospects for overcoming the dilemma of response time and integration in current generation of electron-or/and photon-based elements and devices. In combination with the advantages of emerging twistronics and valleytronics, the atomically thin transition metal dichalcogenide semiconductors open up new opportunities for pursuing practical excitonic devices, where the strong exciton binding energy enables operating exciton at room temperature. The essential and foremost step toward exciton devices is the control of spatiotemporal exciton flux, which is density-dependent and affected by the complex many-body interactions. It can be effectively controlled by the strain, electric field, electron-doping, and local dielectric environment. Intriguingly, exotic phenomena such as exciton condensation, electron-hole liquid, exciton Hall effects, and exciton halo effects can be occurred in 2D exciton system, providing new possibilities for excitonic devices. Up to now, the proof-of-principle of room temperature exciton devices, including excitonic switching and transistor, exciton guides, and excitonic nanolaser, have been realized. Here the authors review the recent advances in molding 2D exciton flux from basic principle, manipulation, exotic phenomena to promising applications and discuss the opportunities and challenges in pushing the frontiers of room temperature excitonic devices.

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Two-body decay of thermalized excitons inCu2O

Cited by 56 publications

References 15 publications

Blue photoluminescence from in situ Cu-doped porous silicon

Blue photoluminescence from in situ Cu-doped porous silicon

Coherent manipulation of quadrupole biexcitons in cuprous oxide by 2D femtosecond spectroscopy

Molding 2D Exciton Flux toward Room Temperature Excitonic Devices

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