Showing papers on "Potential well published in 2013"
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TL;DR: It is found that the hydrogen evolution rate from illuminated suspended CdSe quantum dots in aqueous sodium sulfite solution depends on nanocrystal size, which establishes a quantitative experimental basis for quantum-confinement-controlled proton reduction with semiconductor nanocrystals.
Abstract: The ability to adjust the mechanical, optical, magnetic, electric, and chemical properties of materials via the quantum confinement effect is well-understood. Here, we provide the first quantitative analysis of quantum-size-controlled photocatalytic H2 evolution at the semiconductor–solution interface. Specifically, it is found that the hydrogen evolution rate from illuminated suspended CdSe quantum dots in aqueous sodium sulfite solution depends on nanocrystal size. Photoelectrochemical measurements on CdSe nanocrystal films reveal that the observed reactivity is controlled by the free energy change of the system, as determined by the proton reduction potential and the quasi-Fermi energy of the dots. The corresponding free energy change can be fitted to the photocatalytic activity using a modified Butler–Volmer equation for reaction kinetics. These findings establish a quantitative experimental basis for quantum-confinement-controlled proton reduction with semiconductor nanocrystals. Electrochemical data...
224 citations
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TL;DR: In this paper, a microwave-assisted synthesized cobalt oxide nanoparticle appears to be a promising electrode material for supercapacitor application, which exhibits a broad emission in the UV/Violet region.
183 citations
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TL;DR: In this article, the authors used femtosecond transient absorption spectroscopy (TAS) to measure the quantum confinement effect and molecule-like emission in green-fluorescence graphene quantum dots (GQDs), and the two characteristic fluorescence peaks that appear in all samples are attributed to independent moleculelike states.
Abstract: Graphene quantum dots (GQDs) have recently emerged as a promising type of low-toxicity, high-biocompatibility, and chemically inert fluorescence probe with a high resistance to photobleaching. They are a prospective substitution for organic materials in light-emitting devices (LED), enabling the predicted concept of much brighter and more robust carbon LED (CLED). However, the mechanism of GQD emission remains an open problem despite extensive studies conducted so far, which is becoming the greatest obstacle in the route of technical improvement of GQD quantum efficiency. This problem is solved by the combined usage of femtosecond transient absorption spectroscopy and femtosecond time-resolved fluorescence dynamics measured by a fluorescence upconversion technique, as well as a nanosecond time-correlated single-photon counting technique. A fluorescence emission-associated dark intrinsic state due to the quantum confinement of in-plane functional groups is found in green-fluorescence graphene quantum dots by the ultrafast dynamics study, and the two characteristic fluorescence peaks that appear in all samples are attributed to independent molecule-like states. This finding establishes the correlation between the quantum confinement effect and molecule-like emission in the unique green-fluorescence graphene quantum dots, and may lead to innovative technologies of GQD fluorescence enhancement, as well as its broad industrial application.
142 citations
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TL;DR: In this article, a hot-injection method was used to synthesize controllable sizes of quantum dots (QDs) with diameters ranging from 3.2 to 10.1 nm with tunable band gap from 1.27 to 1.54 eV.
Abstract: Cu2ZnSnSe4 quantum dots (QDs) with controllable sizes have been synthesized via a hot-injection method. The diameters of the QDs range from 3.2 to 10.1 nm with the tunable band gap from 1.27 to 1.54 eV by adjusting the reaction temperatures from 180 to 240 °C. Structural and Raman scattering data confirm that Cu2ZnSnSe4 is obtained without other secondary phases. The band gaps of the QDs with diameters less than 4.6 nm show an obvious blue shift to higher energy due to quantum confinement effect. It indicates that the Cu2ZnSnSe4 QDs can be a potential candidate for quantum-dot-sensitized solar cells in the future.
111 citations
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TL;DR: In this paper, an unusual optical bandgap narrowing is observed in undoped SnO2 nanoparticles synthesized by the solution combustion method, which can be attributed to the deep donor levels of oxygen vacancies, owing to the high exothermicity of the combustion reaction and the faster cooling rates involved in the process.
Abstract: Unusual optical bandgap narrowing is observed in undoped SnO2 nanoparticles synthesized by the solution combustion method. The estimated crystallite size is nearly 7 nm. Though the quantum confinement effect predicts a larger optical bandgap for materials with small crystallite size than the bulk, the optical bandgap in the as synthesized materials is found to be 2.9 eV compared to the reported value of 3.6 eV for bulk SnO2 particles. The yellow-green photoluminescence emissions and the observed narrowing of the bandgap can be attributed to the deep donor levels of oxygen vacancies, owing to the high exothermicity of the combustion reaction and the faster cooling rates involved in the process.
72 citations
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TL;DR: In this paper, the quantum confinement effect in strontium oxide (SrO) QDs is discussed through exciton Bohr radius and particle size from UV-VIS analysis is in excellent agreement with fluorescence and TEM.
Abstract: The properties of drastically change when matter makes transition from 1D, 2D, 3D, to 0D. The quantum dots (QDs) of strontium oxide (SrO) were synthesized by one pot chemical precipitation method using hexamethylenetetramine (HMT). The radius of SrO QDs was calculated from hyperbolic band model (HBM). The direct and indirect band gaps of SrO QDs were estimated from UV–VIS analysis. The particle size was found to be 2.48 nm. The quantum confinement effect in SrO QDs is discussed through exciton Bohr radius. The particle size from UV–VIS analysis is in excellent agreement with fluorescence and TEM.
59 citations
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TL;DR: Gharaati and Khordad as mentioned in this paper considered an exciton confined in a spherical quantum dot with the modified Gaussian potential and tried to study the electronic and optical properties of the system by using the numerical diagonalization of the Hamiltonian matrix.
51 citations
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TL;DR: Intense visible photoluminescence tunable within 1.66-2.47 eV, under UV 325 nm excitation, was obtained from nanocrystalline silicon quantum dots obtained from the low temperature and single-step plasma processing and holds great promise for the fabrication of light-emitting devices and flexible flat panel displays.
Abstract: Intense visible photoluminescence (PL) tunable within 1.66–2.47 eV, under UV 325 nm excitation, was obtained from nanocrystalline silicon quantum dots (∼5.72–1.67 nm in diameter) embedded in amorphous silicon-nitride matrix (nc-Si/a-SiNx:H) prepared in RF-ICPCVD (13.56 MHz) at substrate temperatures between 400 to 150 °C. The dominant component of PL, having a narrow band width of ∼0.16–0.45 eV, originates from quasi-direct band-to-band recombination due to quantum confinement effect (QCE) in the nanocrystalline silicon quantum dots (nc-Si QDs) of appropriate size; however, the contribution of defects arose at lower substrate temperatures leading to asymmetric broadening. Intense atomic hydrogen flux in high-density inductively coupled plasmas (ICPs) provides a very high surface coverage, passivates well the nonradiative dangling bonds, and thereby favors the PL intensity. The average size of nc-Si QDs measured by HR-TEM appears consistent with similar estimates from Raman studies. The red shift of the Raman line and corresponding line broadening originates from the confinement of optical phonons within nc-Si QDs. Photoluminescence emerging from nc-Si/a-SiNx:H quantum dots obtained from the low temperature and single-step plasma processing holds great promise for the fabrication of light-emitting devices and flexible flat panel displays.
48 citations
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TL;DR: In this paper, the size-dependent optical band gap and photoluminescence (PL) band shift due to the quantum confinement effect were observed in a noncoordinating solvent.
Abstract: Colloidal ZnCuInS/ZnSe/ZnS core/shell/shell quantum dots (QDs) with average particle sizes of 2.3, 2.7, and 3.3 nm were prepared in a noncoordinating solvent. The size-dependent optical band gap and photoluminescence (PL) band shift due to the quantum confinement effect were observed. Because the PL band showed a large Stokes shifts over 400 meV, the origin of the PL band was related to the electronic transition via defect levels. A time-resolved PL measurement indicated that the PL lifetime of the QDs was a characteristic feature of three dominating transitions from the conduction band to surface defect level, from the conduction band to an acceptor level, and from the donor level to an acceptor level. It was investigated as a function of temperature in the range from 50 to 373 K to understand the radiative and nonradiative relaxation processes and fitted with two empirical expressions, from which the Huang-Rhys factor and the phonon energy were calculated. According to the fitting data, the size-dependent parameters were analyzed including the Huang-Rhys factor, the average phonon energy, and the excitonic-acoustic phonon coupling coefficient. The temperature coefficient was about -2.32 10-4 eV/K. The results showed that, in the temperature range from 50 to 373 K, the variations of the energy band gap and the photoluminescence line broadening were predominantly due to an optical transition from the band edge to the defect-related level and the coupling of the carriers to acoustic phonon, respectively. 2013 American Chemical Society.
42 citations
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TL;DR: In this article, a cubic closed packed (zinc blende) structure and average particle size of 2-3nm was obtained for high luminescent ZnS quantum dots using co-precipitation.
42 citations
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TL;DR: Broadband antireflection of silicon has been realized by combining black silicon, surface passivation and surface plasmons, and the surface plasmon effect of the Ag nanoparticles on the black silicon was demonstrated by surface enhanced Raman scattering.
Abstract: Broadband antireflection of silicon has been realized by combining black silicon, surface passivation and surface plasmons. Black silicon, fabricated by Ag assisted chemical etching, was employed here to reduce the reflection of incident light with wavelengths below 1100 nm. Due to the increased bandgap caused by the quantum confinement effect and enhanced backward-scattering in our black silicon, light trapping was diminished at the wavelengths above 1100 nm. Ag nanoparticles were deposited on black silicon to obtain the lowest reflectivity at the wavelengths above 1100 nm. Compared with traditionally textured multicrystalline silicon, the average reflectivity of passivated black multicrystalline silicon patterned with 5 nm mass thickness of Ag was decreased to 5.7% in the wavelength range from 300 nm to 1100 nm and was reduced by 20.2% in the wavelength range from 1100 nm to 1400 nm. The surface plasmon effect of the Ag nanoparticles on the black silicon was also demonstrated by surface enhanced Raman scattering, which was observed in the Ag nanoparticle patterned black silicon after being immersed in rhodamine 6g.
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TL;DR: In this article, a hierarchical porous silicon with nanopores in macropores structure (NP-MPSi) was fabricated through electro-assisted chemical etching using a silicon wafer as a substrate.
Abstract: In this work, hierarchically porous silicon was fabricated through electro-assisted chemical etching using a silicon wafer as a substrate. Pores with an average diameter of ca. 1200 nm (macropores) were observed and a large number of nanopores with a diameter of less than 5 nm were uniformly distributed over the surface of the macropore, forming the hierarchically porous silicon with nanopores in macropores structure (NP-MPSi). UV–vis diffuse reflection measurements indicated that NP-MPSi has a bandgap of 2.12 eV, which is 1.0 eV higher than that of the original silicon wafer because of the quantum confinement effect caused by the nanopores. Mott–Schottky experiments further demonstrated that the increase in bandgap of NP-MPSi arises from a positive shift of the valence band potential, which improves its capability for photocatalytic oxidation. NP-MPSi exhibited higher photoelectrochemical stability than macroporous silicon (MPSi), a comparison sample lacking nanopores. Using phenol as an example, photocatalytic experiments under irradiation with a Xe lamp demonstrated that the kinetic constants of phenol degradation and total organic carbon removal using NP-MPSi were nearly 3.5 and 8.0 times larger, respectively, than those using MPSi. This unique porous silicon material is therefore an attractive photocatalyst for environmental applications.
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TL;DR: In this paper, a Si QD-based tandem solar cell was fabricated by co-sputtering of thin layers of Si-rich dielectric sandwiched between stoichiometric dielectrics.
Abstract: Silicon quantum dot (QD)-based ‘all-silicon’ tandem solar cells have emerged as a promising third generation photovoltaic approach to realize high-efficiency and cost effective solar cells. This approach exploits the quantum confinement effect of silicon QDs embedded in a dielectric matrix to engineer the effective electronic bandgap of a solar cell material. Research work in our group has shown that such a Si QD solar cell can be fabricated by co-sputtering of thin layers of Si-rich dielectric sandwiched between stoichiometric dielectric layers which crystallize to form Si QDs of uniform size on annealing. The Si-richness in the Si-rich layer plays an important role in formation of uniform size and shape. The matrix and barrier layer materials also affect the formation of Si QDs. The bandgap tunability of such Si QD superlattice structures has been clearly demonstrated by photoluminescence and electroluminescence measurements. Doping of Si QD layers has been achieved by impurity incorporation of P, Sb or B in the Si-rich layers. Strong evidence of effective doping has been demonstrated from the enhanced conductivity, from the dopant concentrations extracted from MOS structures and from the formation of rectifying p–n junctions which give an open circuit voltage (Voc) of 492 mV. The doping mechanism is more likely to be modified interface doping rather than direct doping to the Si QDs.
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TL;DR: In this article, the relationship between the size and the emission was investigated through spectroscopic analyses to reveal the appearance of the quantum confinement effect in germanium nanocrystals (Ge NCs).
Abstract: Highly efficient ‘deep-green’ luminescent germanium nanocrystals (Ge NCs) have been synthesized by a one-step laser ablation process. The NCs are thoroughly characterized by TEM, Raman and optical spectroscopic techniques. The relationship between the size and the emission is investigated through spectroscopic analyses to reveal the appearance of the quantum confinement effect. Due to the strong quantum confinement of photogenerated carriers in diamond cubic Ge NCs and well-controlled size distribution, both a full width half maxima (FWHM) of the photoluminescence (PL) (about 55 nm) and a 17% absolute PL quantum yield (QY) of the Ge NCs in thin film form are drastically improved.
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TL;DR: In this article, an exciton confined in a quantum dot with modified Kratzer potential was considered and the electronic and optical properties of the system were studied by using the numerical diagonalization of the Hamiltonian matrix.
Abstract: In the present work, we have considered an exciton confined in a quantum dot with modified Kratzer potential. We have studied the electronic and optical properties of the system by using the numerical diagonalization of the Hamiltonian matrix. For this purpose, we have calculated the binding energies of the ground and first excited states as functions of the quantum dot size. We have also computed the linear, nonlinear and total absorption coefficients between ground and first excited states. It is found that the quantum dot radius has an important role on the binding energy and absorption coefficient.
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TL;DR: In this article, ultrathin amorphous Ge films (2 to 30 nm in thickness) embedded in SiO2 layers were grown by magnetron sputtering and employed as a light sensitizer in photodetector devices.
Abstract: In this work, ultrathin amorphous Ge films (2 to 30 nm in thickness) embedded in SiO2 layers were grown by magnetron sputtering and employed as proficient light sensitizer in photodetector devices. A noteworthy modification of the visible photon absorption is evidenced due to quantum confinement effects which cause both a blueshift (from 0.8 to 1.8 eV) in the bandgap and an enhancement (up to three times) in the optical oscillator strength of confined carriers. The reported quantum confinement effects have been exploited to enhance light detection by Ge quantum wells, as demonstrated by photodetectors with an internal quantum efficiency of 70%.
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TL;DR: In this paper, high resolution transmission electron microscope image shows that CdS and Gd-doped cdS nanoparticles have particle size lying in the range of 3.5 to 4.0 nm.
Abstract: CdS and Gd-doped CdS nanoparticles have been synthesized by chemical precipitation technique. The X-ray diffraction patterns show that the CdS and Gd-doped CdS nanoparticles exhibit hexagonal structure. The high resolution transmission electron microscope image shows that CdS and Gd-doped CdS nanoparticles have particle size lying in the range of 3.5 to 4.0 nm. Raman spectra show that 1LO, 2LO and 3LO peaks of the Gd-doped CdS nanoparticles are slightly shifted to lower wavenumber side when compared to that of CdS. Optical absorption spectra of Gd-doped CdS nanoparticles shows that absorption edge is slightly shifted towards longer wavelength side (red shift) when compared to that of CdS and this shift is due to the quantum confinement effect present in the samples.
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TL;DR: In this article, the as-synthesized SnS nanoparticles were quantitatively analyzed and characterized in terms of their morpho- logical, structural, and optical properties, which confirmed the ortho- rhombic SnS structure and a strongly blue shifted direct band gap (1.74 eV), for synthesized nanoparticles.
Abstract: Nanocrystalline SnS powder has been prepared using tin chloride (SnCl2) as a tin ion source and sodium sulfide (Na2S) as a sulfur ion source with the help of ultrasound irradiation at room temperature. The as-synthesized SnS nanoparticles were quantitatively analyzed and characterized in terms of their morpho- logical, structural, and optical properties. The detailed structural and optical properties confirmed the ortho- rhombic SnS structure and a strongly blue shifted direct band gap (1.74 eV), for synthesized nanoparticles. The measured band gap energy of SnS nanoparticles is in a fairly good agreement with the results of theoretical calculations of exciton energy based on the potential morphing method in the Hartree-Fock approximation.
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TL;DR: In this paper, a facile method for synthesis of monodispersed, starch-capped ZnSe nanoparticles at room temperature is reported, which exhibited strong quantum confinement effect with respect to the bulk ZnSE.
Abstract: A facile method for synthesis of monodispersed, starch-capped ZnSe nanoparticles at room temperature is being reported. The nanoparticles exhibited strong quantum confinement effect with respect to the bulk ZnSe. The transmission electron microscopy image indicated that the particles were well dispersed and spherical in shape. The X-ray diffraction analysis showed that the ZnSe nanoparticles were of the wurtzite structure, with average particle diameter of about 3.6 nm. The Fourier transform infrared spectrum confirmed the presence of starch as passivating agent.
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TL;DR: In this paper, the first example of single-sized quantum dots (QD) of a III-VI semiconductor, In2Te3, self-assembled in solution was reported.
Abstract: We report the first example of single-sized quantum dots (QD) of a III–VI semiconductor, In2Te3, self-assembled in solution. The nanometer-sized dots (∼1 nm in diameter) with the formula of In8Te12 are arranged into perfectly ordered arrays via an organic passivating and structure-directing molecule (triethylenetetramine or trien) resulting in a single crystal structure of [In8Te12(trien)4] (monoclinic crystal system, space group C2/c). The In8Te12 dots in the [In8Te12(trien)4] structure show a remarkably strong structure-induced quantum confinement effect which results in a very large blue shift of 2.1 eV in the optical absorption spectrum. The observed increase in the band gap is substantially higher than that of the smallest colloidal quantum dots reported to date. The In8Te12 dots are readily dispersible in suitable solvents to form nanoparticles of an average size of ∼8 to 10 nm. The capability of forming periodic crystal lattices of semiconductor quantum dots offers an attractive way to tune the electronic and optical properties in the same (or larger) extent as those of the smallest nanoparticles while having the advantages of precisely controlling the size and stoichiometry. Such a crystal assembly of QDs may find utility as a new type of molecular-based precursors for the fabrication of energy- and cost-effective solution-processed thin film devices.
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TL;DR: Direct band photoluminescence peak significantly shifts to longer wavelength as compared to that from bulk Ge due to a combination of strain-induced band gap reduction and quantum confinement effect.
Abstract: We present a method to introduce a large biaxial tensile strain in an ultra-thin germanium-on-insulator (GOI) using selective oxidation of SiGe epilayer on silicon-on-insulator (SOI) substrate. A circular patterned Si0.81Ge0.19 mesa on SOI substrate with the sidewall protected by Si3N4 or SiO2 is selectively oxidized to generate local 12 nm GOI with high crystal quality, which shows enhanced photoluminescence due to large tensile strain. Direct band photoluminescence peak significantly shifts to longer wavelength as compared to that from bulk Ge due to a combination of strain-induced band gap reduction and quantum confinement effect.
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TL;DR: In this paper, a time-integrated as well as time-resolved photoluminescence (TRPL) spectroscopy was used to study the lifetime of ZnO nanoparticles.
Abstract: ZnO nanoparticles with controlled sizes produced by a sol-gel method are studied by means of time-integrated as well as time-resolved photoluminescence (TRPL) spectroscopy. Room-temperature photoluminescence spectra show a blueshift of the excitonic emission with the decreasing particle size, which is attributed to the quantum confinement effect. The temperature dependence of the exciton lifetimes deduced from the TRPL results contains two components: the fast decay is attributed to surface trapping of exciton and the slow decay is mainly representative of the radiative processes involving the bound or free excitons.
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TL;DR: The first observation of room-temperature quantum-confined photoluminescence from low-dimensional Ge(1-x)Sn(x)/Ge superlattices (SLs) up to a high Sn content is reported, suggesting that Sn-based low- dimensional structures are promising material for efficient Si-based lasers.
Abstract: We report the first observation of room-temperature quantum-confined photoluminescence (PL) from low-dimensional Ge1−xSnx/Ge superlattices (SLs) up to a high Sn content of 6.96%. Both direct and indirect emissions associated with the interband transitions between minibands in the conduction bands and valence band were observed at room temperature. As the Sn content is increased, the energy difference between the lowest direct and indirect transitions is reduced, indicating an effective modification of the band structure desired for optoelectronics. The integrated PL intensity ratio of direct to indirect recombinations is significantly enhanced with increasing Sn content due to the reduced Γ-L energy separation and quantum confinement effect. Those results suggest that Sn-based low-dimensional structures are promising material for efficient Si-based lasers.
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TL;DR: In this paper, the ground state binding energy of a hydrogenic donor impurity in square quantum well and V-shaped quantum well as a function of the well width in the presence of magnetic fields with both constant and position dependent effective mass was calculated.
Abstract: In this paper we have calculated variationally the ground state binding energy of a hydrogenic donor impurity in square quantum well and V-shaped quantum well as a function of the well width in the presence of magnetic fields with both constant and position dependent effective mass. The wave function of electrons confined to donor impurity within the quantum well is considered as the two dimensional and three dimensional trial wave functions. It has been found that by increasing the well width, the binding energy decreases smoothly to bulk values while its steepness is sharper in square quantum well in comparison with V-shaped quantum well. Increasing the magnetic field leads to the enhancement of binding energy. At higher magnetic fields, by increasing the well width, binding energy tends to a constant value. The effect of position dependent effective mass on the enhancement of binding energy is more evident in comparison with constant effective mass one.
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TL;DR: In this article, the authors used Rietveld refinement technique to extract the microstructural parameters of thioglycolic acid capped CdSe quantum dots and showed that Schnakenberg model provides good fit to the non-linear region of the variation of dc conductivity with temperature.
Abstract: We have used Rietveld refinement technique to extract the microstructural parameters of thioglycolic acid capped CdSe quantum dots. The quantum dot formation and its efficient capping are further confirmed by HR-TEM, UV-visible and FT-IR spectroscopy. Comparative study of the variation of dc conductivity with temperature (298 K ≤ T ≤ 460 K) is given considering Arrhenius formalism, small polaron hopping and Schnakenberg model. We observe that only Schnakenberg model provides good fit to the non-linear region of the variation of dc conductivity with temperature. Experimental variation of ac conductivity and dielectric parameters with temperature (298 K ≤ T ≤ 460 K) and frequency (80 Hz ≤ f ≤ 2 MHz) are discussed in the light of hopping theory and quantum confinement effect. We have elucidated the observed non-linearity in the I-V curves (measured within ±50 V), at dark and at ambient light, in view of tunneling mechanism. Tunnel exponents and non-linearity weight factors have also been evaluated in this regard.
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TL;DR: In this paper, the magnetic field and impurity's position effects on the ground-state shallow-donor binding energy in a spherical quantum dot-quantum well (SQDQW) were investigated.
Abstract: Simultaneous study of magnetic field and impurity's position effects on the ground-state shallow-donor binding energy in GaN│InGaN│GaN (core│well│shell) spherical quantum dot–quantum well (SQDQW) as a function of the ratio of the inner and the outer radius is reported. The calculations are investigated within the framework of the effective-mass approximation and an infinite deep potential describing the quantum confinement effect. A Ritz variational approach is used taking into account of the electron-impurity correlation and the magnetic field effect in the trial wave-function. It appears that the binding energy depends strongly on the external magnetic field, the impurity's position and the structure radius. It has been found that: (i) the magnetic field effect is more marked in large layer than in thin layer and (ii) it is more pronounced in the spherical layer center than in its extremities.
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TL;DR: In this paper, a systematic size dependence study of visible photoluminescence (PL) from laser-etched silicon nanostructures has been performed, which is attributed to the quantum confinement effect and calculated values of oscillator strength and radiative lifetime show that PL is due to radiative recombination of confined excitons.
Abstract: Visible photoluminescence (PL) from laser-etched silicon nanostructures has been analysed. A systematic size dependence study of PL from silicon nanostructures has been performed. The PL from these structures is attributed to the quantum confinement effect. Different quantum confinement models have been used for PL and Raman lineshape fitting to calculate the mean size and size distribution of silicon nanostructures and the results are comparatively studied. Calculated values of oscillator strength and radiative lifetime show that PL is due to radiative recombination of confined excitons.
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TL;DR: The growth mechanisms for the two samples were discussed; this proved that the high coordination ability of ethylenediamine to zinc played an important role in the final phase of the products as mentioned in this paper.
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TL;DR: In this article, thermal annealing of annealed Si quantum dots (QDs)/SiC multilayered structures was investigated by Raman scattering, cross-sectional transmission electron microscopy, and Fourier transform infrared spectroscopy.
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TL;DR: In this paper, the size and shape of ZnS nanocrystals can be tuned by adjusting the surfactant and its feed, and the UV-Vis absorption spectra of quasispherical and one-dimensional quantum-sized nanocrystal all showed a blue-shift from the bulk counterpart, indicating large quantum confinement effects.
Abstract: With the features of convenience and eco-friendly, the low-temperature solid-state
reaction synthesis was successfully developed as a new approach to prepare quantum-sized
ZnS nanocrystals. One major achievement is that the size and shape of ZnS nanocrystals
can be tuned by adjusting the surfactant and its feed. The UV-Vis absorption spectra
of quasispherical and one-dimensional quantum-sized ZnS nanocrystals all showed
a blue-shift from the bulk counterpart, indicating large quantum confinement effects
of ZnS nanocrystals. These ZnS nanocrystals all showed well-defined excitonic emission
features. Contrastive studies on photoluminescence performances
indicated that the bandedge emission experienced only the size-dependent quantum
confinement effect, while the trap-state emission experienced the size- and shape-dependences.
So we can design a purposeful synthesis route to ZnS nanocrystals with target luminescence
emission performances.