Intrinsic gap emission and its geometry dependence of thin-film CdS excited by two-photon absorption

Schroeder, Raoul; Sakai, Hisashi

doi:10.1088/0268-1242/16/12/101

Cited by 13 publications

(5 citation statements)

References 23 publications

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“…Comparing the peak energy locations in Figs. 1 and 2 have been observed by SPL and TPL of thin-film CdS, demonstrating that the red shift is subject to self-absorption [22][23][24]. Equivalent results such as these in Figs.…”

Section: Resultsmentioning

confidence: 67%

Photo-dynamic Burstein-Moss doping of PbS quantum dots in solution by single and two-photon optical pumping

Barik¹,

Singh²,

García-Ramírez³

et al. 2015

Opt. Mater. Express

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We report photo-dynamically provoked photoluminescence blue shifts up to ∼8 meV of oleic acid capped 2.5 nm PbS quantum dots in toluene at room temperature. Exposing the solution to pulsed laser (26 ps, 10 Hz) emissions at 532 nm and 1064 nm, the photo-induced band gap increase is evoked by single and two-photon transitions, respectively. The emission peak blue shifts, recorded in reflection and transmission geometries, show a 2/3 power dependence on the optical stimulus gain, rendering the Burstein-Moss shift to be the underlying inherent n-type doping effect in the quantized colloid.

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Section: Resultsmentioning

confidence: 67%

Photo-dynamic Burstein-Moss doping of PbS quantum dots in solution by single and two-photon optical pumping

Barik¹,

Singh²,

García-Ramírez³

et al. 2015

Opt. Mater. Express

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“…Figure 2(b) displays PL spectra of a sample (thickness ∼3 mm) taken in T-PL and R-PL geometries at 5 K. It is interesting to note that the T-PL shows exactly the same three-peak structure as the R-PL. T-PL is an effective method that reveals reabsorption processes, e.g., if a size distribution of QDs exists [21]. Figure 2(c) shows this for a reference sample with a multimodal size distribution prepared by a gradedannealing process (thickness also ∼3 mm).…”

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confidence: 98%

Experimental observation of exciton splitting and relaxation dynamics from PbS quantum dots in a glass matrix

2014

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Multiple optical transitions from PbS quantum dots (QDs) in glass matrix are observed. Energy separations between them amount up to ∼200 meV. Instead of being due to a size distribution of QDs, they are found to be related to a splitting of the lowest exciton levels. Systematic analysis of the relaxation dynamics reveals the lifetimes of the split states ranging from sub-100-ns to ∼μs. Moreover, we observe excited and "intrinsic" states having a sub-100-ps and ∼ns lifetime, respectively. The behavior of the split structure can be modeled by a phonon-assisted relaxation mechanism. This investigation offers a conclusive interpretation for the wide distribution of experimentally observed nonequilibrium carrier lifetimes in PbS QDs.Lead salt (e.g., PbS) quantum dots (QDs) have been widely investigated for applications in optoelectronic devices [1,2]. The QDs are either colloidal or embedded into a glass matrix. The latter provides substantial advantages in terms of longterm stability [3]. In order to evaluate and improve the properties of materials or devices, the QD size and its distribution as well as the excitonic lifetime are major issues, which should be accurately characterized, e.g., directly by optical methods including steady-state (SS) or transient absorption and photoluminescence (PL) spectroscopy at room temperature [4].However, in rock salt PbS QDs the dimension of the excitonic manifold is theoretically 64 because both the valence-band maximum and the conduction-band minimum originate from the 8-fold (including spin) L valleys in the first Brillouin zone of bulk PbS. The degeneracy of these L valleys becomes lifted due to, e.g., intervalley coupling, interband coupling, and electron-hole Coulomb and exchange interaction [5]. Another mechanism potentially acting into this direction is external forces such as pressure as well as a special chemical surrounding, e.g., in a matrix. The split structure makes the optical transition in QDs complex and affects the characterization of QD features including the lowest excitonic transition energy (for simplicity called E g ) and subsequently the size and distribution of QDs as well as the nonequilibrium carrier recombination mechanism. In spite of the fact that asymmetric-or multi-PL (or absorption) peaks from these kinds of QDs have been observed even at room temperature, no direct reports involve these split states. Typically extrinsic assumptions are made including size distribution (e.g., multimodal QDs) [6], temperature/excitation-induced broadening [7], or defect states [8,9].In this Rapid Communication, PbS QDs embedded in a borosilicate glass matrix are prepared and characterized by SS-or transient-PL spectroscopy at low excitation densities and temperatures. A three-transition structure from the QDs is observed with an energy separation up to 200 meV, in dependence of growth conditions including annealing. The * yue@mbi-berlin.de intrinsic mechanism for this three-transition structure that seems to be sensitive to the host matrix, e.g., with borosilicate b...

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“…- For comparison, figure 4 shows the corresponding LC results for the thin film, i.e., the film side was excited as in [19,20]. The film reflection exhibits almost no modulation, whereas the maximum of the transmission modulation is comparable with the results in figure 3, while, as suspected from the PL results in [27,28], at the interface, more absorption transitions are excited with the same amount of impinging photons as at the film surface itself. Furthermore, from the viewpoint of device engineering, with the employment of the reflected beam effective fan-out is easier to achieve than with the much weaker transmitted signals, which were approximately 0.8% and 0.2% for the red and green lasers, respectively.…”

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confidence: 72%

“…It is worthwhile to note that the motivation for the interface investigations came from photoluminescence (PL) measurements rather than from previous switching experiments. Comparing the PL excited at the surface and through the glass substrate, we recognized that PLD CdS on glass exhibits an increased absorption at the glass/CdS interface with respect to the rest of the film [27,28]. Hence, we presumed that the same might be true for PLD GaAs on glass and enhanced LC modulation amplitudes should be possible by using the rear reflection of the film.…”

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confidence: 87%

Introduction of glass/GaAs interfaces for all-optical and hybrid switch fabrics

Erlacher

Danilov

2006

Semicond. Sci. Technol.

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This paper promotes glass/GaAs interfaces as effective photonic switch media. All-optical and hybrid red laser reflection modulations have been achieved by altering the electronic state of the interface with a green laser. The concept straightforwardly enables the flip from negative to positive logics by solely applying an electric field. Furthermore, reflective femtosecond operations of the interface are demonstrated with pump-probe experiments.

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Intrinsic gap emission and its geometry dependence of thin-film CdS excited by two-photon absorption

Cited by 13 publications

References 23 publications

Photo-dynamic Burstein-Moss doping of PbS quantum dots in solution by single and two-photon optical pumping

Photo-dynamic Burstein-Moss doping of PbS quantum dots in solution by single and two-photon optical pumping

Experimental observation of exciton splitting and relaxation dynamics from PbS quantum dots in a glass matrix

Introduction of glass/GaAs interfaces for all-optical and hybrid switch fabrics

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