Optical absorption cross section and quantum efficiency of a single silicon quantum dot

Abstract

Optical absorption cross section and quantum efficiency of a single silicon quantum dot.In: Nanotechnology VI (pp. 876607- ABSTRACTDirect measurements of the optical absorption cross section (σ) and exciton lifetime are performed on a single silicon quantum dot fabricated by electron beam lithography (EBL), reactive ion etching (RIE) and oxidation. For this aim, single photon counting using, an avalanche photodiode detector (APD) is applied to record photoluminescence (PL) intensity traces under pulsed excitation. The PL decay is found to be of a mono-exponential character with a lifetime of 6.5 µs. By recording the photoluminescence rise time at different photon fluxes the absorption cross could be extracted yielding a value of 1.46×10 -14 cm 2 under 405 nm excitation wavelength. The PL quantum efficiency is found to be about 9% for the specified single silicon quantum dot.

Effect of X‐ray irradiation on the blinking of single silicon nanocrystals

“…(left). The values of peak position (eV), full‐width half‐maximum (fwhm 130 meV), and PL lifetime (s) are all in accordance with previous works on similar samples , indicating that the emission is originating from quasi‐direct recombination of quantum‐confined excitons in Si . As shown in Fig.…”

“…As a final step, self‐limiting oxidation () at 900C for 5 h reduced the core size of the walls, forming isolated Si‐NCs with a thick oxide shell (10 nm). The crystallinity of the particles was previously confirmed by transmission electron microscope (TEM) () and PL characterization at room temperature showed emission in the range 1.7–2.0 eV, with fwhm around 100–200 meV , and lifetimes between 1 and 20s ().…”

Near-Unity Internal Quantum Efficiency of Luminescent Silicon Nanocrystals with Ligand Passivation

“…Note that these PL decay times are longer than those we previously reported (5À45 μs) for single Si dots with a thick oxide shell 37 where the IQE is ∼9% due to the low oxidation temperature used (900°C). 19 The results of the standard optical and structural characterization of ligand-passivated Si NCs discussed above are typical for this material system. 38 We now turn the discussion to the determination of IQE in the present samples using spectrally resolved PL decay measurements.…”

“…Recently, we obtained a similar value of IQE ≈ 9% for isolated single Si nanoparticles prepared by lithography and oxidation. 19 By a different approach, based on the effect of photonic mode density on the radiative recombination rate, Walters et al 20 and Kalkman et al 21 extracted Γ r and estimated ∼40À80% IQE for Si NCs embedded in SiO 2 prepared by ion implantation and annealing. The exact wavelength dependence of Γ r measured by this technique revealed IQEs approaching even 100% for large nanoparticles emitting in a limited energy range (1.4À1.5 eV).…”

Strong Absorption Enhancement in Si Nanorods

“…We measured absolute values of the absorption cross-section in nanorods and close-to-spherical nanoparticles at α ≈ 70° (Figure , left). For that, we recorded luminescence decay and rise transients for several individual dots from each sample under 405 nm excitation . The linear dependence of eq S1 with experimental data points is shown for one particular dot in the inset (the value at zero photon flux is the luminescence decay rate).…”