Laser selective spectromicroscopy of myriad single molecules: tool for far-field multicolour materials nanodiagnostics

In this Colloquium, we discuss the main principles, achievements and perspectives in the field of highly parallel luminescence spectroscopy and imaging of single molecules (SM) in transparent solids. Special attention will be given to SM detection at low temperatures, where ultranarrow and bright zero-phonon lines (ZPL) of emitting centres are achievable for observation. Frequency of ZPL can be used as an additional property for separation of multiple SM images within diffraction limited volume, thus realising “multicolour” super-resolution microscopy. The extreme sensitivity of ZPL parameters to SM local environment allows application of SM spectromicroscopy for the study of structure and dynamics of doped solids on the nanometre scale. We show that the way to “bridge” the accidental rare events detected by SM probes to general material properties is a statistical analysis of spectral-spatial data obtained by a separated detection of all effectively fluorescing dye centres in a bulk sample. First experimental realisation of three-dimensional phononless luminescence SM spectromicroscopy with modification of SM point-spread function is demonstrated

Lack of Photon Antibunching Supports Supertrap Model of Photoluminescence Blinking in Perovskite Sub-Micrometer Crystals

Antibunching effect is typically observed in individual systems possessing photoluminescence (PL) blinking and vice versa. Contrary to this common perception, absence of antibunching in strongly blinking methyl ammonium led tri-iodide (MAPbI3) perovskite crystals of sizes from tens to hundreds of nanometers regardless of the excitation power density is observed. Antibunching effect does not appear even when photon statistics are analyzed for bright and intermediate PL intensity levels independently. This shows that there is no directional energy funneling and accumulation of charge carriers in the small local regions in MAPbI3 crystals where an Auger recombination can potentially suppress the simultaneous emission of two photons. This result allows for the exclusion of the PL blinking mechanism based on the idea of emitting sites previously hypothesized for perovskites. Therefore, the model of PL blinking in perovskite crystals based on the presence of a metastable non-radiative recombination center (the supertrap) is the only one proposed so far which explains blinking without conflicting with the absence of photon correlations

Detection of Single Charge Trapping Defects in Semiconductor Particles by Evaluating Photon Antibunching in Delayed Photoluminescence

Time-resolved analysis of photon cross-correlation function g(2)(τ) is applied to photoluminescence (PL) of individual submicrometer size MAPbI3 perovskite crystals. Surprisingly, an antibunching effect in the long-living tail of PL is observed, while the prompt PL obeys the photon statistics typical for a classical emitter. We propose that antibunched photons from the PL decay tail originate from radiative recombination of detrapped charge carriers which were initially captured by a very limited number (down to one) of shallow defect states. The concentration of these trapping sites is estimated to be in the range 1013-1016 cm-3. In principle, photon correlations can be also caused by highly nonlinear Auger recombination processes; however, in our case it requires unrealistically large Auger recombination coefficients. The potential of the time-resolved g(2)(0) for unambiguous identification of charge rerecombination processes in semiconductors considering the actual number of charge carries and defects states per particle is demonstrated

Spontaneous transitions to enhanced fluorescence for GeV centers in a single microcrystalline diamond

We propose a theoretical explanation of spontaneous transitions between dim and bright fluorescence intensity states observed experimentally in a microcrystal of diamond with germanium-vacancy colour centres driven by a continuous wave laser. We use a generalized system of optical Maxwell-Bloch equations derived for an emitter in an ensemble of motionless similar particles embedded in a dielectric medium, which is transparent for the incident light. A numerical analysis of transient regimes and several models of slow damping of the bright luminescence mode are reported

Spontaneous transitions to enhanced fluorescence for GeV centers in a single microcrystalline diamond

We propose a theoretical explanation of spontaneous transitions between dim and bright fluorescence intensity states observed experimentally in a microcrystal of diamond with germanium-vacancy colour centres driven by a continuous wave laser. We use a generalized system of optical Maxwell-Bloch equations derived for an emitter in an ensemble of motionless similar particles embedded in a dielectric medium, which is transparent for the incident light. A numerical analysis of transient regimes and several models of slow damping of the bright luminescence mode are reported

AFM Characterization of Track-Etched Membranes: Pores Parameters Distribution and Disorder Factor

The structural characteristics of polymer track-etched membranes (TM) were obtained by atomic force microscopy (AFM) for a set of samples (polypropylene, polycarbonate, polyethylene terephthalate, with average pore diameters ~183, 375, and 1430 nm, respectively). The analysis of AFM experimental data was performed by using a specially developed technique for computer analysis of AFM images. The method allows one to obtain such parameters of TM as distribution of pore diameters, distribution of the minimum distances between the nearest pores, pore surface density, as well as to identify defective pores. Spatial inhomogeneities in the distribution of pore parameters were revealed. No anisotropy (some specific selected direction) was found in the surface distribution of the pores in the samples under study