Academic literature on the topic 'Undoped Semiconductor Nanocrystals'

Author: Grafiati

Published: 7 September 2023

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Journal articles on the topic "Undoped Semiconductor Nanocrystals"

Akshay, V. R., B. Arun, Shubhra Dash, Ajit K. Patra, Guruprasad Mandal, Geeta R. Mutta, Anupama Chanda, and M. Vasundhara. "Defect mediated mechanism in undoped, Cu and Zn-doped TiO2 nanocrystals for tailoring the band gap and magnetic properties." RSC Advances 8, no. 73 (2018): 41994–2008. http://dx.doi.org/10.1039/c8ra07287f.

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Oxide based dilute magnetic semiconductor materials are of great interest and this study focusses on the optical and magnetic behavior of non-magnetic element doped TiO₂ nanocrystals which provides a significant reduction in bandgap with enhanced magnetization.

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Mittova, Irina Ya, Boris V. Sladkopevtsev, and Valentina O. Mittova. "Nanoscale semiconductor and dielectric films and magnetic nanocrystals – new directions of development of the scientific school of Ya. A. Ugai “Solid state chemistry and semiconductors”. Review." Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases 23, no. 3 (August 17, 2021): 309–36. http://dx.doi.org/10.17308/kcmf.2021.23/3524.

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New directions of development of the scientific school of Yakov Aleksandrovich Ugai “Solid state chemistry and semiconductors” were considered for the direction “Study of semiconductors and nanostructured functional films based on them”, supervised by I. Ya. Mittova. The study of students and followers of the scientific school of Ya. A. Ugai cover materials science topics in the field of solid-state chemistry and inorganic and physical chemistry. At the present stage of research, the emphasis is being placed precisely on nanoscale objects, since in these objects the main mechanisms of modern solid-state chemistry are most clearly revealed: the methods of synthesis - composition - structure (degree of dispersion) - properties. Under the guidance of Professor I. Ya. Mittova DSc (Chem.), research in two key areas is conducted:“Nanoscale semiconductor and dielectric films” and “Doped and undoped nanocrystalline ferrites”. In the first area, the problem of creating high-quality semiconductor and dielectric nanoscale films on AIIIBV by the effect reasonably selected chemostimulators on the process of thermal oxidation of semiconductors and/or directed modification of the composition and properties of the films. They present the specific results achieved to date, reflecting the positive effect of chemostimulators and modifiers on the rate of formation of dielectric and semiconductor films of the nanoscale thickness range and their functional characteristics, which are promising for practical applications.Nanomaterials based on yttrium and lanthanum orthoferrites with a perovskite structure have unique magnetic, optical, and catalytic properties. The use of various approaches to their synthesis and doping allowing to control the structure and properties in a wide range. In the field of magnetic nanocrystals under the supervision of Prof. I. Ya. Mittova studies of the effect of a doping impurity on the composition, structure, and properties of nanoparticles of yttrium and lanthanum orthoferrites by replacing the Y(La)3+ and Fe3+ cations are carried out. In the Socialist Republic of Vietnam one of the talented students of Prof. I. Ya. Mittova, Nguyen Anh Tien, performs studies in this area. To date, new methods for the synthesis ofnanocrystals of doped and undoped ferrites, including ferrites of neodymium, praseodymium, holmium, etc. have been developed.

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Xin, Mei, Dong Ping Liu, Nai Sen Yu, Xiao Hui Qi, and Hui Li. "Luminescence Properties of ZnS:Cu,Tm Semiconductor Nanocrystals Synthesize by a Hydrothermal Process." Advanced Materials Research 415-417 (December 2011): 499–503. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.499.

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ZnS:Cu,Tm nanocrystal with 15nm cubic structures have been synthesized by hydrothermal approach at 200°C. The photoluminescence (PL) properties and the effect of hydrothermal treatment time on the structure, morphology and PL spectra of ZnS:Cu,Tm samples have been studied. The as-obtained samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectra.The result indicated that the PL emission spectrum of codoped with Cu and Tm sample compares with undoped ZnS and doped with Cu alone samples has a significant changes, while the PL emission peak has red shift and PL emission intensity increased. The samples size and crystallization are increase with extending of the treatment time. However, when the hydrothermal treatment time is too long(>12h), the PL emission intensity of sample instead of decreased. Demonstrated changes in surface state of nanomaterials have a greater impact on its luminescence properties.

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Yeltik, Aydan, Murat Olutas, Manoj Sharma, Kivanc Gungor, and Hilmi Volkan Demir. "Nonradiative Energy Transfer between Doped and Undoped Flat Semiconductor Nanocrystals of Colloidal Quasi-2D Nanoplatelets." Journal of Physical Chemistry C 123, no. 2 (December 21, 2018): 1470–76. http://dx.doi.org/10.1021/acs.jpcc.8b10177.

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Sana, Prabha, Lubna Hashmi, and M. M. Malik. "Luminescence and Morphological Kinetics of Functionalized ZnS Colloidal Nanocrystals." ISRN Optics 2012 (February 2, 2012): 1–8. http://dx.doi.org/10.5402/2012/621908.

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This paper reports functionalized zinc sulphide (ZnS) semiconductor nanocrystals (quantum dots, approx., 2.5 nm) which are an important building block in self-assembled nanostructures. ZnS is functionalized by organic stabilizer Thio glycolic acid (TGA). The samples have been synthesized by colloidal technique at relatively low temperature (below 100°C) at an atmospheric pressure of 10−3 torr. Manganese (Mn) doping ions have been incorporated (doped) in ZnS host lattice and observed its effect on growth morphology and optical properties of ZnS colloidal nanocrystals. By XRD, SEM, TEM, and PL, the obtained cubic phase nanosized TGA-capped ZnS materials were characterized. The morphology of ZnS obtained at different temperatures are analyzed by SEM. The crystallite size of the ZnS nanoparticles was estimated from the X-ray diffraction pattern by using Scherrer’s formula (approximately 2.5 nm) which is confirmed by TEM. The estimated bandgap value of ZnS NC’s by ()2 versus plot was 4.89 eV. Gaussian fitting curve in photoluminescence (PL) spectra indicated room temperature emission wavelength range from 300 to 500 nm in undoped and Mn-doped ZnS, with different emission peak intensities, and suggested the wide band emission colours in visible and near UV region which has wider applications in optical devices.

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Rahdar, A., M. Aliahmad, and H. Asnaashari. "Effect of Different Capping Agents on the Undoped ZnS Semiconductor Nanocrystals: Synthesis and Optical and Structural Characterization." Advanced Science Letters 19, no. 2 (February 1, 2013): 547–49. http://dx.doi.org/10.1166/asl.2013.4740.

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Gayou, V. L., B. Salazar Hernández, R. Delgado Macuil, G. Zavala, P. Santiago, and A. I. Oliva. "Structural Studies of ZnS Nanoparticles by High Resolution Transmission Electron Microscopy." Journal of Nano Research 9 (February 2010): 125–32. http://dx.doi.org/10.4028/www.scientific.net/jnanor.9.125.

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Zinc sulfide (ZnS), a representative of wide band gap semiconductor nanocrystals, has an excitonic Bohr radius (aBZnS ) of 2.5 nm. It makes ZnS nanoparticles (ZnS NP) having such size very interesting as small biomolecular probes for fluorescence and laser scanning microscopy. To date, ZnS NP of diameters larger than aBZnS has been subject of extensive experimental and theoretical studies. However many questions remain open concerning the synthesis of undoped and uncapped ZnS NP of diameters less than 2.5 nm. To further probe into the physical properties of undoped and uncapped ZnS NP, in this work we report on studies of uncapped ZnS nanoparticles synthesized by a wet chemical process at room temperature. Three colloidal suspensions (named A, B and C, respectively) were obtained from 9:1, 1:1 and 1:9 volume mixtures of 1mM ZnSO4 and 0.85mM Na2S aqueous solutions. Qualitative differences in UV-Vis absorption spectra are discussed in the context of Z-contrast scanning transmission electron microscopy (Z-contrast), low and high resolution transmission electron microscopy (TEM) results. Distribution of particle size is dependent on different volumes of source solutions. For the intermediate mixture, it has been found that about 78% of ZnS nanoparticles have a diameter smaller than the excitonic Bohr Radius of 2.5 nm. HRTEM studies have revealed that nanoparticles grow preferentially with hexagonal structure.

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Nawrot, Katarzyna C., Manoj Sharma, Bartłomiej Cichy, Ashma Sharma, Savas Delikanli, Marek Samoć, Hilmi Volkan Demir, and Marcin Nyk. "Spectrally Resolved Nonlinear Optical Properties of Doped Versus Undoped Quasi-2D Semiconductor Nanocrystals: Copper and Silver Doping Provokes Strong Nonlinearity in Colloidal CdSe Nanoplatelets." ACS Photonics 9, no. 1 (January 4, 2022): 256–67. http://dx.doi.org/10.1021/acsphotonics.1c01456.

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Kupchak, I. M., D. V. Korbutyak, and N. F. Serpak. "Electronic characteristics of CdS quantum dots with defects." Технология и конструирование в электронной аппаратуре, no. 3-4 (2020): 28. http://dx.doi.org/10.15222/tkea2020.3-4.28.

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Using the density functional theory and the generalized gradient approximation, we calculated the atomic structure, the density of electronic states, and the optical absorption spectra of CdS quantum dots containing intrinsic defects — a cadmium vacancy VCd and an interstitial sulfur atom SI, and substitutional impurities — zinc and copper in place of the atom cadmium — ZnCd and CuCd, respectively. The calculations were performed for the Cd33S33 cluster corresponding to the so-called “magic” size of the quantum dot. This size has a minimum of dangling bonds at the surface and allows the using of such a cluster without the passivation. The structural relaxation during the formation of such defects and the distribution of the wave function of the state corresponding to the top of the valence band are analyzed in details. It has been shown that the cadmium vacancy forms local states in the band gap of CdS nanocrystals, and can serve as centers of radiative recombination. Other defects form energy levels in the depths of the valence band or near its top, but whose energy positions do not correspond to the band maxima in the experimental photoluminescence spectra of CdS quantum dots, both undoped and doped with zinc. The calculated optical absorption spectra demonstrate a strong peak in the region of fundamental absorption of CdS for a cluster containing a substitutional impurity of CuCd, in contrast to other systems where no such peaks are observed. In addition, the replacement of the cadmium atom with copper leads to a decrease in the number of chemical bonds to three and, accordingly, to the largest relaxation among the systems studied. This feature is caused by the crystal structure inhomogeneity of copper sulfide CuxS, which, depending on stoichiometry, can be either a semiconductor or a metal.

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Ramrakhiani, Meera, Nitendra Kumar Gautam, Kamal Kushwaha, Sakshi Sahare, and Pranav Singh. "Electroluminescence in Chalcogenide Nanocrystals and Nanocomposites." Defect and Diffusion Forum 357 (July 2014): 127–69. http://dx.doi.org/10.4028/www.scientific.net/ddf.357.127.

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Several research groups have reported that nanocrystalline II-VI semiconductors show enhanced luminescence, increased oscillator strength and shorter response time. Nanocrystalline powder samples of CdS, CdSe, ZnS and ZnSe nanocrystals and their composites with PVA and PVK have been prepared by chemical route. SEM. TEM and AFM images indicate agglomeration of particles. XRD reveal the crystal structure and size in nanometer range and absorption spectra show increased band gap due to quantum confinement.The EL studies on nanocrystalline powder samples and nanocrystal/polymer composites have shown that the light emission starts at certain threshold voltage, different for different specimens and then increases with increasing voltage. It is found that smaller nanocrystals have lower threshold voltage and higher EL brightness. It is observed that nanocomposite give much higher electroluminescence starting at lower voltage and increasing very fast with the voltage as compared to nanocrystalline powder. The emission spectra are found to depend on the material, crystalline size and doping. Electroluminescence in undoped and doped chalcogenide nanocrystals and nanocomposites is reviewed in this paper. In nanosize regime, electroluminescence (EL) is governed by the size quantization effect. Contents of Paper

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