Photoinduced hole trapping in single semiconductor quantum dots at specific sites at silicon oxide interfaces

Abstract

Blinking dynamics of CdSe/ZnS semiconductor quantum dots (QD) are characterized by (truncated) power law distributions exhibiting a wide dynamic range in probability densities and time scales both for off-and on-times. QDs were immobilized on silicon oxide surfaces with varying grades of hydroxylation and silanol group densities, respectively. While the off-time distributions remain unaffected by changing the surface properties of the silicon oxide, a deviation from the power law dependence is observed in the case of on-times. This deviation can be described by a superimposed single exponential function and depends critically on the local silanol group density. Furthermore, QDs in close proximity to silanol groups exhibit both high average photoluminescence intensities and large on-time fractions. The effect is attributed to an interaction between the QDs and the silanol groups which creates new or deepens already existing hole trap states within the ZnS shell. This interpretation is consistent with the trapping model introduced by Verberk et al. (R. Verberk, A. M. van Oijen and M. Orrit, Phys. Rev. B, 2002, 66, 233202).

Influence of the Dielectric Environment on the Photoluminescence Intermittency of CdSe Quantum Dots

“…As described recently by Crouch et al,18 the power‐law behaviour for on‐times and its truncation are strongly affected by the number of observed on‐events and the choice of binning time and intensity threshold separating the on and off‐events. We have also reported similar effects 16. In short, three important parameters should be considered to get reliable results and fit parameters.…”

“…All the embedding materials investigated reveal a very similar value of α on , as shown in Table 1. In the case of PVA, the truncated power law is possibly superimposed by an additional exponential contribution, as reported recently 16. 20 Using the simple Equation (1a) for fitting such more complex statistics, this will artificially flatten the distribution explaining the smaller α on value and the related large error for this matrix.…”

“…As already suggested by Verberk et al,6 this contradiction can be overcome by assuming, that also the hole can tunnel out of and back to the core of the QD. If the hole is outside the core of the QD, PL intensity may be at least partly retained 16. Since semiconductor QDs, as well as organic molecules, are supposed to form charge‐separated states under laser irradiation, the charged quantum objects will interact with the local dielectric environment by inducing an electric reaction field in the matrix 3.…”

Influence of the Inner‐Shell Architecture on Quantum Yield and Blinking Dynamics in Core/Multishell Quantum Dots

“…Some extensions have also been added to explain deviations in this behavior, such as the exponential cutoff in observing long on times and changes in the power‐law slope at short timescales . Further deviations from power‐law behavior have been reported upon varying the local environment of the QD, such as changing the immobilization matrix and the proximity of the silanol groups, leading to exponential terms in the distribution function of the on times . Recently, a multiple recombination centers model has been proposed to describe blinking, in which the on times can be fit to a multiexponential decay function rather than a (truncated) power law .…”

Self‐Assembly of Ordered Colloidal Nanoparticle Films in Few‐Micron Wide Laser‐Desorbed Lines of Octadecylsiloxane Monolayers on Silicon Oxide Surfaces

“…5 min and dried in a nitrogen flow. Before SAM preparation, the samples were immersed in piranha solution (i.e., hydrogen peroxide (Sigma-Aldrich, 30%) and sulfuric acid (Merck KGaA, 96%) 1:1, details in literature [64] ) at 100°C for 1 h in an ultrasonic bath, for a controlled and homogeneous hydroxylation of the silicon oxide surface. Finally, the samples were washed with deionized water and dried in nitrogen flow.…”