Femtosecond Spectroscopy of Porous Silicon

Kovalenko, Sergey A.; Dobryakov, A. L.; Karavanskiĭ, V. A.; Lisin, D. V.; Merkulova, S. P.; Lozovik, Yu. E.

doi:10.1238/physica.regular.060a00589

Cited by 5 publications

(5 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22 Silicon grains showed a fast decay component of 400 fs, attributed to the quenching of the interior exciton radiative recombination by carrier trapping, 23 while another study found a 500 fs component attributed to nanocrystallite defect scattering. 24 Other investigations observed a femtosecond component that was proposed to be due to molecule-like silicon complexes or clusters in the material. 25,26 Additionally, a feature that decayed in ∼3 ps was monitored and found to be dependent on the porosity of the sample.…”

mentioning

confidence: 99%

Ultrafast Exciton Dynamics in Silicon Nanowires

Wheeler

Huang

Newhouse

et al. 2012

J. Phys. Chem. Lett.

View full text Add to dashboard Cite

Ultrafast exciton dynamics in one-dimensional (1D) silicon nanowires (SiNWs) have been investigated using femtosecond transient absorption techniques. A strong transient bleach feature was observed from 500 to 770 nm following excitation at 470 nm. The bleach recovery was dominated by an extremely fast feature that can be fit to a triple exponential with time constants of 0.3, 5.4, and ∼75 ps, which are independent of probe wavelength. The amplitude and lifetime of the fast component were excitation intensity-dependent, with the amplitude increasing more than linearly and the lifetime decreasing with increasing excitation intensity. The fast decay is attributed to exciton-exciton annihilation upon trap state saturation. The threshold for observing this nonlinear process is sensitive to the porosity and surface properties of the sample. To help gain insight into the relaxation pathways, a four-state kinetic model was developed to explain the main features of the experimental dynamics data. The model suggests that after initial photoexcitation, conduction band (CB) electrons become trapped in the shallow trap (ST) states within 0.5 ps and are further trapped into deep trap (DT) states within 4 ps. The DT electrons finally recombine with the hole with a time constant of ∼500 ps, confirming the photophysical processes to which we assigned the decays.

show abstract

mentioning

confidence: 99%

Ultrafast Exciton Dynamics in Silicon Nanowires

Wheeler

Huang

Newhouse

et al. 2012

J. Phys. Chem. Lett.

View full text Add to dashboard Cite

show abstract

“…The time evolution of the PIA and PIB, shown in Figure , has been extracted from the biexponential curve fitting model given by eq : normalΔ A = normalΔ A 0 + A 1 * exp ( prefix− t τ 1 ) + A 2 * exp ( prefix− t τ 2 ) where τ 1 and τ 2 are defined as states decay lifetimes with their respective amplitude weights A 1 and A 2 given as a percentage with the lifetime in Table S1. Figure shows the decay dynamics of various states for transient absorption at the 400 nm excitation wavelength . The transient absorption dynamics results have been divided into two distinct regions: the cavity mode (λ cav ) in Figure a, and the band-edge regions in Figure b–d.…”

Section: Resultsmentioning

confidence: 99%

Ultrafast Dynamics, Optical Nonlinearities, and Chemical Sensing Application of Free-Standing Porous Silicon-Based Optical Microcavities

Shanu,

Acharyya,

Kuriakose

et al. 2024

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

The present work demonstrates the ultrafast carrier dynamics and third-order nonlinear optical properties of electrochemically fabricated free-standing porous silicon (FS-PSi)-based optical microcavities via femtosecond transient absorption spectroscopy (TAS) and single-beam Z-scan techniques, respectively. The TAS (pump: 400 nm, probe: 430−780 nm, ∼70 fs, 1 kHz) decay dynamics are dominated by the photoinduced absorption (PIA, lifetime range: 4.7−156 ps) as well as photoinduced bleaching (PIB, 4.3−324 ps) for the cavity mode (λ c ) and the band edges. A fascinating switching behavior from the PIB (−ve) to the PIA (+ve) has been observed in the cavity mode, which shows the potential in ultrafast switching applications. The third-order optical nonlinearities revealed an enhanced two-photon absorption coefficient (β) in the order of 10 −10 mW −1 along with the nonlinear refractive index (n 2 ) in the range of 10 −17 m 2 W −1 . Furthermore, a real-time sensing application of such FS-PSi microcavities has been demonstrated for detecting organic solvents by simultaneously monitoring the kinetics in reflection and transmission mode.

show abstract

“…Although the main "red" fluorescence band of PS is known to originate from silicon nanocrystallites [19][20][21][22][23], the mechanism behind slower relaxation at longer detection wavelength in this band is still debatable. The wavelength dependent relaxation rate could be attributed to the size distribution of nanocrystallites, because fluorescence wavelength and probably its lifetime increase with the nanocrystallite size [25].…”

Section: Ps/r6gmentioning

confidence: 99%

“…Red fluorescence band usually attributed to nanometer sized Si nanocrystallites [19][20][21][22][23] is also inhomogeneous: fluorescence at different wavelengths decays with different rates and is attributed to nanocrystallites of different dimensions. Such behavior is also ambiguous -increasing relaxation times with longer detection wavelength could also be explained as a result of energy migration between nanocrystallites [14].…”

mentioning

confidence: 99%

Excitation energy transfer in porous silicon/laser dye composites

Pranculis

Šimkienė

Treideris

et al. 2013

Phys. Status Solidi A

View full text Add to dashboard Cite

Excited state relaxation and energy transfer in porous silicon (PS)/laser dye [oxazine 1 (Ox1), rhodamine 6G (Rh6G)] composites have been studied by means of steady-state and time-resolved fluorescence. Fluorescence decay kinetics reveals the nonradiative energy transfer from PS to the dye. Increased decay rate of the dye luminescence in the composite indicates that opposite energy transfer is also likely. Analysis of the time-resolved fluorescence of the PS/R6G composite also shows that there is no energy transfer from silicon oxide responsible for the "blue" fluorescence band to silicon nanocrystalites, and that interaction between Si nanocrystals responsible for the "red" PS fluorescence is absent or weak. 1 Introduction Since its discovery, porous silicon (PS) proved to be a non-trivial fluorescent system. Having many different energy levels, each with its own relaxation time and at least two distinct fluorescence mechanisms (surface oxide and Si nanocrystallites) PS is still not fully understood.PS/organic material composites were first investigated few years after the discovery of the visible luminescence of PS. Polymers were spin-coated onto PS in order to produce hybrid LEDs with variable fluorescence spectra [1-3], while laser dye impregnation into the pores was motivated by possible application of such composites in laser physics [4][5][6][7]. One of the key processes in such systems -energy transfer, attracted most of the researcher's attention because of its natural complexity resulting from intricate fluorescence of PS.In 1993 Canham [8] reported impregnation of PS with laser dye in order to get a solid state host for optically active media -a goal of great interest still. In his work Canham examined possible energy transfer in such composites. Since then, driven by possible applications of such materials in optoelectronics, a number of researchers investigated PS/ laser dye composites using different techniques and reported energy transfer from PS to the dye as their main findings [9][10][11][12][13].Time-gated fluorescence of PS reveals two bands -high energy "blue" fluorescence, which is intensive but decays in less than 5 ns, and low energy "red" fluorescence, which is

show abstract

Femtosecond Spectroscopy of Porous Silicon

Cited by 5 publications

References 18 publications

Ultrafast Exciton Dynamics in Silicon Nanowires

Ultrafast Exciton Dynamics in Silicon Nanowires

Ultrafast Dynamics, Optical Nonlinearities, and Chemical Sensing Application of Free-Standing Porous Silicon-Based Optical Microcavities

Excitation energy transfer in porous silicon/laser dye composites

Contact Info

Product

Resources

About