A5072122309- Silicon Nanostructures and Photoluminescence
- Nanowire Synthesis and Applications
- Semiconductor materials and devices
- Quantum Dots Synthesis And Properties
- Thin-Film Transistor Technologies
- Photonic and Optical Devices
- Semiconductor materials and interfaces
- Carbon and Quantum Dots Applications
- Semiconductor Quantum Structures and Devices
- Boron and Carbon Nanomaterials Research
- Photonic Crystals and Applications
- Plasma Applications and Diagnostics
- Force Microscopy Techniques and Applications
- Electrohydrodynamics and Fluid Dynamics
- Plasma Diagnostics and Applications
- Molecular Junctions and Nanostructures
- Laser-induced spectroscopy and plasma
- Diamond and Carbon-based Materials Research
- Advanced Optical Sensing Technologies
- ZnO doping and properties
- Ga2O3 and related materials
- TiO2 Photocatalysis and Solar Cells
- Graphene and Nanomaterials Applications
- Advanced Fiber Laser Technologies
- Metal and Thin Film Mechanics
Czech Academy of Sciences, Institute of Physics
2014-2025
Czech Academy of Sciences
2008-2021
Silicon nanocrystals are an extensively studied light-emitting material due to their inherent biocompatibility and compatibility with silicon-based technology. Although they might seem fall behind rival, namely, direct band gap based semiconductor nanocrystals, when it comes the emission of light, room for improvement still lies in exploitation various surface passivations. In this paper, we report on original way, taking place at temperature ambient pressure, replace silicon oxide shell...
In this paper, we discuss the validity of band structure concept in silicon nanocrystals a few nanometers size. We introduce general method which allows reconstruction fuzzy electronic from ordinary real-space calculations. A comprehensive study realistic nanocrystal is given including full geometric and relaxation with surface passivating groups. particular, combine large-scale density functional theory calculations to obtain insight into luminescence properties up 3 nm size depending on...
Silicon, a semiconductor underpinning the vast majority of microelectronics, is an indirect‐gap material and consequently inefficient light emitter. This hampers ongoing worldwide effort towards integration optoelectronics on silicon wafers. Even though nanocrystals are much better emitters, they retain nature. Here, we propose solution to this long‐standing problem: can be transformed into with fundamental direct bandgap via concerted action quantum confinement tensile strain. We document...
Colloidal suspensions of small silicon nanoparticles (diameter around 2 nm) with fast and efficient ultraviolet–blue photoluminescence (PL) band are fabricated by enhanced electrochemical etching Si wafers. The detailed study excitation spectra in a wide range photon energies (270–420 reveals specific behavior the Stokes shift PL that agrees well theoretical calculation optical transitions nanocrystals is distinct from emission dioxide defects.
Small oxidized silicon nanocrystals of average sizes below 3.5 nm are prepared using modified electrochemical etching a wafer. Modifications introduced in the procedure together with postetching treatment H2O2 lead to decrease nanocrystalline core size and also, some extent, changes surface oxide. The interplay between these two factors allows us blueshift photoluminescence (PL) spectrum from 680 down 590 nm, which is accompanied by PL dynamics. This continual development, however, stops at...
We collect a large number of experimental data from various sources to demonstrate that free-standing (FS) oxide-passivated silicon nanocrystals (SiNCs) exhibit considerably blueshifted emission, by 200 meV on average, compared those prepared as matrix-embedded (ME) ones the same size. This is suggested arise compressive strain, exerted their matrix, which plays an important role in light-emission process; this strain has been neglected up now opposed impact quantum confinement or surface...
Abstract Plasma activated water (PAW) is a unique highly reactive medium, traditionally used in medicine and agriculture because of its decontamination disinfection abilities. Recently, we have shown that this medium can also be beneficial for tailoring the surface chemistry semiconductor nanostructures if composition tuned to contain high concentration nitrogen-related species (HiN:PAW). However, pathways leading production HiN:PAW remained unclear, which address article. By monitoring...
Abstract Spectra of individual silicon nanocrystals within porous Si grains are studied by the wide‐field imaging microspectroscopy and their ON – OFF blinking is detected confocal single‐photon‐counting microscopy. Observed spectral properties comprise all features reported before in differently prepared single (SiNCs). Former apparently contradictory results shown to be due different experimental conditions. When effect dark periods ( switching) removed common ultimate photoluminescence...
The storage and release of energy is an economic cornerstone. In quantum dots (QDs), mostly governed by their surfaces, in particular surface chemistry faceting. impact free (SFE) through faceting has already been studied QDs. Here, we introduce dominant representing the structural order surface. particular, propose that realistic QDs attain complicated polyhedral quasi-spherical shapes while keeping dominance a certain type facet. facet determines rates surface-related processes. Therefore,...
In this paper we study the influence of progressing oxidation on photoluminescence spectra small silicon nanocrystals (SiNCs). H-terminated SiNCs exhibit only a fast approximately nanosecond component at ∼525 nm, quenched and redshifted to ∼550 nm by oxidation. At same time new microsecond appears, intensity which progressively increases its peak position redshifts continuously from 575 up 660 nm. We interpret our observations in terms quasidirect core electron-hole pair recombination...
Silicon nanocrystals (SiNCs) smaller than 5 nm are a material with strong visible photoluminescence (PL). However, the physical origin of PL, which, in case oxide-passivated SiNCs, is typically composed slow-decaying red–orange band (S-band) and fast-decaying blue–green (F-band), still not fully understood. Here we present interpretation F-band based on results an experimental study, which combine temperature (4–296 K), temporally (picosecond resolution) spectrally resolved luminescence...
Silicon nanocrystals (Si-ncs) of sufficiently small size, emitting luminescence at short wavelengths (which implies the occurrence quasi-direct radiative recombination) and being densely packed in a planar thin film ensures stimulated emission (StE) lifetime) can become suitable active material for observation StE visible region. In this paper, we describe fabrication method nanostructures type, based on enhanced electrochemical etching silicon wafers followed by embedding porous grains into...
In this paper we present time-resolved optical gain spectroscopy using the variable stripe length technique in combination with shifting excitation spot under pumping nanosecond laser pulses. Measurements reveal positive on a time scale at 430 nm (F-band), accompanied by spectral narrowing and threshold behaviour of amplified spontaneous emission as function intensity. We show that presence slow-red (S-band) component critically influences observation stimulated from F-band.
Strain-engineered silicon nanocrystals (SiNCs) have recently been shown to possess direct bandgap. Here, we report the observation of a rich structure in single-nanocrystal photoluminescence spectra strain-engineered direct-bandgap SiNCs temperature range 9–300 K. The relationship between individual types is discussed, and numerical modeling spectral diffusion experimentally acquired reveals common origin for most types. intrinsic shape be that contains three peaks, approximately 150 meV...
A class of important semiconductors, such as Si, Ge, or C, has an indirect band gap, which critically limits their optical properties. Lack efficient emission is especially unfortunate for silicon, where Si light sources could enable realization the long-awaited on-chip-integrated laser integrated computing CPU architecture. Hence, methods toward improvement properties Si-based materials are in high demand. Unlike most applied light-emitting semiconductor nanocrystals (NCs) with a direct...
We propose an analytical description of the role local depolarization fields in terahertz conductivity nanostructured samples and demonstrate this approach a sample composed silicon nanocrystals. This helps to uncover nature charge carrier transport at nanoscale. Time-resolved is investigated ensemble nanocrystals fabricated by electrochemical etching wafer followed H2O2 oxidizing treatment. The post-etching treatment leads decrease average nanocrystalline Si core size which enhances...
Non-thermal plasma activated water can be used for cheap, easy and chemicals-free surface modification of nanoparticles, with all the reactive species originating solely in air water.
Doping silicon nanocrystals (SiNCs) provides a new way to modify their luminescence properties and tailor them for particular application. We prepared Li-doped SiNCs characterized by neutron depth profiling x-ray diffraction. Our SiNC samples are doped with around 10–100 Li atoms per one nanocrystal lattice slightly expands after lithium insertion. show that the photoluminescence (PL) of distinctly modified compared undoped case. The PL maximum shifts shorter wavelengths decay time...
Silicon nanocrystals are very interesting light‐emitting materials due to the abundance and low inherent toxicity of silicon. Although ability silicon in form emit light has been known for more than 25 years now, fundamental research still not answered all questions regarding origin this emission. In paper, a brief summary what is about emission material provided some recent developments field highlighted.
Silicon quantum dots (SiQDs) represent a perspective light emitting material. Here, we show that their typical long-lived photoluminescence can be fully radiative. However, despite the radiative nature, overall yield of emission from SiQDs is still hindered by dark QDs, understanding which only very limited so far. To address this problem, first, experimentally quantify dependence lifetimes on photon energy and universal across different types samples laboratories. Second, use to internal...
Two-dimensional photonic crystal can be exploited as the top part of a light source in order to increase its extraction efficiency. Here, we report on room-temperature intrinsic photoluminescence (PL) behavior nanocrystalline diamond (NCD) layer with columns prepared and periodically ordered into lattice square symmetry. Angle-resolved far-field measurements Γ–X direction broadband visible PL revealed up six-fold enhancement efficiency compared smooth NCD layer. A band diagram above...