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991.
半导体纳米晶是近年来发展起来的一类新型功能材料,因其独特的量子限域效应和光电性质,在太阳电池、发光二极管、光电探测器、生物标记、非线性光学等领域中具有潜在的应用。与目前研究比较多的Ⅱ-Ⅵ和Ⅳ-Ⅵ族纳米晶相比,Ⅰ-Ⅲ-Ⅵ族半导体纳米晶,不含镉和铅等重金属元素,具有毒性小、带隙窄、光吸收系数大、Stokes位移大、自吸收小以及发光波长在近红外区等特点,有望成为新一代低成本太阳电池和低毒荧光量子点生物标记材料, 还可用于发光二极管和光电探测等领域。因此,Ⅰ-Ⅲ-Ⅵ族半导体纳米晶的合成、性质及应用研究成为近期纳米晶研究领域的热点之一。本文将综述Ⅰ-Ⅲ-Ⅵ族半导体纳米晶的研究进展,着重介绍其制备方法、光学性质及其在生物标记、太阳电池等领域的应用。 相似文献
992.
Scaling dependence of memory windows and different carrier charging behaviors in Si nanocrystal nonvolatile memory devices 下载免费PDF全文
Based on the charge storage mode,it is important to investigate the scaling dependence of memory performance in silicon nanocrystal(Si-NC) nonvolatile memory(NVM) devices for its scaling down limit.In this work,we made eight kinds of test key cells with different gate widths and lengths by 0.13-μm node complementary metal oxide semiconductor(CMOS) technology.It is found that the memory windows of eight kinds of test key cells are almost the same of about1.64 V @ ±7 V/1 ms,which are independent of the gate area,but mainly determined by the average size(12 nm) and areal density(1.8×10~(11)/cm~2) of Si-NCs.The program/erase(P/E) speed characteristics are almost independent of gate widths and lengths.However,the erase speed is faster than the program speed of test key cells,which is due to the different charging behaviors between electrons and holes during the operation processes.Furthermore,the data retention characteristic is also independent of the gate area.Our findings are useful for further scaling down of Si-NC NVM devices to improve the performance and on-chip integration. 相似文献
993.
Relative enhancement of photoluminescence intensity of passivated silicon nanocrystals in silicon dioxide matrix 下载免费PDF全文
Photoluminescence (PL) intensity of passivated silicon nanocrystals (Si NCs) embeded in an SiO2 matrix is compared with that of unpassivated ones. We investigate the relative enhancement of PL intensity (IR) as a function of annealing temperature and implanted Si ion dose. The IR increases simultaneously with the annealing temperature. This demonstrates an increase in the number of dangling bonds (DBs) with the degree of Si crystallization via varying the annealing temperature. The increase in IR with implanted Si ion dose is also observed. We believe that the near-field interaction between DBs and neighboring Si NCs is an additional factor that reduces the PL efficiency of unpassivated Si NCs. 相似文献
994.
M. Mahdouani R. Bourguiga S. Jaziri S. Gardelis A.G. Nassiopoulou 《Physica E: Low-dimensional Systems and Nanostructures》2009,42(1):57-62
We study theoretically the optical properties of embedded Ge and Si nanocrystals (NCs) in wide band-gap matrix and compared the obtained results for both NCs embedded in SiO2 matrix. We calculate the ground and excited electron and hole levels in both Ge and Si nanocrystals (quantum dots) in a multiband effective mass approximation. We use the envelope function approximation taking into account the elliptic symmetry of the bottom of the conduction band and the complex structure of the top of the valence band in both Si and Ge (NCs). The Auger recombination (AR) in both nanocrystals is thoroughly investigated. The excited electron (EE), excited hole (EH) and biexciton AR types are considered. The Auger recombination (AR) lifetime in both NCs has been estimated and compared. 相似文献
995.
V. Hizhnyakov I. Tehver G. Benedek 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(4):507-512
We investigate, using first-principles calculations, the electronic
structure of substitutional and vacancy defects in a boron nitride
monolayer. We found that the incorporation of a substitutional carbon atom
induces appreciable modification on the electronic properties, when compared
to a non-defective boron nitride sheet. The incorporation of substitutional
carbon impurity also induces a significant reduction of the work function.
In addition, we found that defects introduce electronic states in the
energy-gap region, with strong impact on the optical properties of the
material. The calculation results indicate that spin polarization is
obtained when substitutional impurities or vacancy defects are introduced in
the structure 相似文献
996.
Curvature and external electric field effects on the persistent current in chiral toroidal carbon nanotubes 总被引:1,自引:0,他引:1
N. Xu J. W. Ding H. B. Chen M. M. Ma 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(1):71-75
Taking into account the intrinsic curvature, we calculate the persistent currents (Ipcs) in chiral toroidal carbon nanotubes (TCNs) by developing the supercell approach. It is shown that in the presence of curvature,
the typical current (Ity) oscillates with the unit cell number (P) and tends to be zero, while it damps exponentially in the absence of curvature.
Due to the curvature effects, especially, a paramagnetism-diamagnetism transition is observed in chiral TCNs, depending on
the ring diameter and chirality. In addition, the effect of external electric field energy (Eef) on persistent current is also explored. It is shown that in the presence of electric field, Ity vary unmonotonously with Eef. A pronounced peak of Ity is obtained at high Eef region. By modulating the value of Eef, a paramagnetism-diamagnetism or diamagnetism- paramagnetism transition is observed. 相似文献
997.
The optical waveguide behaviors of CdS and CdS
x
Se1−x
nanostructures are studied using near-field optical microscopy. Optical measurements demonstrate that light may be guided
on sub-wavelength scales along CdS nanoribbons in straight or bent structures. The photoluminescence (PL) spectra from nanoribbon
emission using scanning near-field optical microscopy are analyzed under different incident laser intensities. The PL spectra
along Se-doped and undoped CdS nanoribbons at different propagation distances are investigated. Both the guided PL spectra
of Se-doped and undoped CdS nanoribbons show red-shifts because of the band-edge absorption. Our results are useful for the
development of new kinds of functional nano devices.
Supported by the National Natural Science Foundation of China (Grant Nos. 10574002, 90406007, and 50602015) and the National
Basic Research Program of China (Grant No. 2007CB936800) 相似文献
998.
CdS/α-Fe2O3 hierarchical nanostructures, where the CdS nanorods grow irregularly on the side surface of α-Fe2O3 nanorods, were synthesized via a three-step process. The diameters and lengths of CdS nanorods can be tuned by changing the
ethylenediamine (EDA) and Cd ion concentrations. The magnetic investigations by superconducting quantum interference device
indicate that the hierarchical nanostructures have an Morin transition at lower temperature (230 K) than that of the single
bulk α-Fe2O3 materials (263 K). Importantly, the hierarchical nanostructures exhibit weakly ferromagnetic characteristics at 300 K. A
sharp peak assigned to the surface trap induced emission are observed in room temperature PL spectra. Combining with the optoelectronic
properties of CdS, the CdS/α-Fe2O3 hierarchical nanostructures may be used as multi-functional materials for optoelectronic and magnetic devices.
Supported by the National Natural Science Foundation of China (Grant Nos. 50772025 and 50872159), the Ministry of Science
and Technology of China (Grant No. 2008DFR20420), the China Postdoctoral Science Foundation (Grant Nos. 20060400042 and 200801044),
the Natural Science Foundation of Heilongjiang Province, China (Grant No. F200828), the Specialized Research Fund for the
Doctoral Program of Higher Education of China (Grant No. 20070217002), and the Innovation Foundation of Harbin City (Grant
No. RC2006QN017016) 相似文献
999.
Renjia Zhou Minmin Shi Dr. Xiaoqiang Chen Mang Wang Prof. Hongzheng Chen Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(19):4944-4951
From nanocrystals to atomic clusters : Fluorescent gold clusters (Au8) are synthesized by etching gold nanocrystals with the assistance of biomolecules, such as amino acids, peptides, proteins, and DNA (see picture). The gold clusters exhibit strong blue fluorescence as well as solvent‐dependent emission properties when dissolved in various organic solvents. They show potential applications in biological labeling and photoluminescence‐based sensors.
1000.
Mustafa S. Yavuz Weiyang Li Younan Xia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(47):13181-13187
Herein we describe a protocol that generates Au icosahedra in high yields by simply mixing aqueous solutions of HAuCl4 and N‐vinyl pyrrolidone. Our mechanistic study reveals that water plays an important role in this synthesis: as a nucleophile, it attacks the gold–vinyl complex, leading to the production of an alcohol‐based AuI intermediate. This intermediate then undergoes a redox reaction in which AuI is reduced to Au0, leading to the formation of Au atoms and then Au icosahedra of about 18 nm in size at a yield of 94 %, together with a carboxylic acid in the final product. This new protocol has also been employed to prepare multiply twinned nanoparticles of Ag (15–20 nm in size), spherical aggregates (25–30 nm in size) of Pd nanoparticles, and very small nanoparticles of Pt (2 nm in size). Since no organic solvent, surfactant, or polymer stabilizer is needed for all these syntheses, this protocol may provide a simple, versatile, and environmentally benign route to noble‐metal nanoparticles having various compositions and morphologies. 相似文献