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911.
Malko AV Park YS Sampat S Galland C Vela J Chen Y Hollingsworth JA Klimov VI Htoon H 《Nano letters》2011,11(12):5213-5218
We report a systematic study of photoluminescence (PL) intensity and lifetime fluctuations in individual CdSe/CdS core/shell nanocrystal quantum dots (NQDs) as a function of shell thickness. We show that while at low pump intensities PL blinking in thin-shell (4-7 monolayers, MLs) NQDs can be described by random switching between two states of high (ON) and low (OFF) emissivities, it changes to the regime with a continuous distribution of ON intensity levels at high pump powers. A similar behavior is observed in samples with a medium shell thickness (10-12 MLs) without, however, the PL intensity ever switching to a complete "OFF" state and maintaining ca. 30% emissivity ("gray" state). Further, our data indicate that highly stable, blinking-free PL of thick-shell (15-19 MLs) NQDs ("giant" or g-NQDs) is characterized by nearly perfect Poisson statistics, corresponding to a narrow, shot-noise limited PL intensity distribution. Interestingly, in this case the PL lifetime shortens with increasing pump power and the PL decay may deviate from monoexponential. However, the PL intensity distribution remains shot-noise limited, indicating the absence of significant quantum yield fluctuations at a given pump power intensity during the experimental time window. 相似文献
912.
I. S. Vasil’evskii G. B. Galiev E. A. Klimov K. Požela J. Požela V. Jucienė A. Sužiedėlis N. Žurauskienė S. Keršulis V. Stankevič 《Semiconductors》2011,45(9):1169-1172
An increase in the electron mobility and drift velocity in high electric fields in quantum wells of selectively doped InAlAs/InGaAs/InAsAs
heterostructures is obtained experimentally via controlling the composition of semiconductors forming the interface. The electron
mobility at the interface in the In0.8Ga0.2As/In0.7Al0.3As metamorphic structure with a high molar fraction of In (0.7–0.8) is as high as 12.3 × 103 cm2 V−1 s−1 at room temperature. An increase in the electron mobility by a factor of 1.1–1.4 is attained upon the introduction of thin
(1–3 nm) InAs layers into a quantum well of selectively doped In0.53Ga0.47As/In0.52Al0.48As heterostructures. A maximal drift velocity attains 2.5 × 107 cm/s in electric fields of 2–5 kV/cm. The threshold field F
th for the intervalley Γ-L electron transfer (the Gunn effect) in the InGaAs quantum well is higher than in the bulk material by a factor of 2.5–3.
The effect of two- to threefold decrease in the threshold field F
th in the InGaAs quantum well is established upon increasing the molar fraction of In in the InAlAs barrier, as well as upon
the introduction of thin InAs inserts into the InGaAs quantum well. 相似文献
913.
R. A. Khabibullin I. S. Vasil’evskii G. B. Galiev E. A. Klimov D. S. Ponomarev R. A. Lunin V. A. Kulbachinskii 《Semiconductors》2011,45(10):1321-1326
Molecular-beam epitaxy is used for growing structures differing in doping technique and doping level and having a high two-dimensional-electron
concentration n
s in the quantum well. The effect of doping combining uniform and δ doping on the electron-transport properties of heterostructures
is investigated. A new type of structure with a two-sided silicon δ doping of GaAs transition layers located on the quantum-well
boundaries is proposed. The largest value of electron mobility μH = 1520 cm2/(V s) is obtained simultaneously with a high electron density n
s = 1.37 × 1013 cm−2 at 300 K with such a doping. It is associated with decreasing electron scattering by an ionized impurity, which is confirmed
by the carried out calculations. 相似文献
914.
V. V. Klimov I. K. Skirdina N. I. Selikova A. N. Bronnikov S. N. Loboda A. S. Shtonda 《Inorganic Materials》2008,44(5):527-529
We have studied the effect of bismuth oxide additions (2 wt %) on the electrical properties of thick lead zirconate titanate films. The results demonstrate that the addition of bismuth oxide to the starting mixture, followed by grinding in a high-energy vibratory mill, enables the sintering temperature to be lowered to 820–850°C. 相似文献
915.
Bhola N. Pal Istvan Robel Aditya Mohite Rawiwan Laocharoensuk Donald J. Werder Victor I. Klimov 《Advanced functional materials》2012,22(8):1741-1748
Chemically synthesized nanocrystal quantum dots (NQDs) are promising materials for applications in solution‐processable optoelectronic devices such as light emitting diodes, photodetectors, and solar cells. Here, we fabricate and study two types of p‐n junction photodiodes in which the photoactive p‐layer is made from PbS NQDs while the transparent n‐layer is fabricated from wide bandgap oxides (ZnO or TiO2). By using a p–n junction architecture we are able to significantly reduce the dark current compared to earlier Schottky junction devices without reducing external quantum efficiency (EQE), which reaches values of up to ~80%. The use of this device architecture also allows us to significantly reduce noise and obtain high detectivity (>1012 cm Hz1/2 W?1) extending to the near infrared past 1 μm. We observe that the spectral shape of the photoresponse exhibits a significant dependence on applied bias, and specifically, the EQE sharply increases around 500–600 nm at reverse biases greater than 1 V. We attribute this behavior to a “turn‐on” of an additional contribution to the photocurrent due to electrons excited to the conduction band from the occupied mid‐gap states. 相似文献
916.
K. A. Balygin M. S. Ippolitov A. I. Klimov V. A. Lebedev V. I. Manko E. A. Meleshko Yu. G. Sibiriak A. V. Akindinov V. I. Izucheev V. A. Arefiev A. S. Vodopyanov N. V. Gorbunov N. A. Kuzmin P. V. Nomokonov Yu. P. Petukhov I. A. Rufanov D. V. Budnikov O. V. Vikhlyantsev V. A. Demanov N. V. Zavyalov A. V. Kuryakin A. D. Tumkin S. V. Filchagin 《Instruments and Experimental Techniques》2018,61(5):639-644
It is shown that an increase in the area of photodetectors allows the PHOS electromagnetic calorimeter of the ALICE experiment to operate at room temperature with better spectrometric characteristics. The linearity of the calorimeter response has been investigated in the 1–110 GeV energy range using both Hamamatsu S8664-1010 avalanche photodiodes with a large area (10 × 10 mm2) and arrays of MPPC Hamamatsu S12572-015C silicon photomultipliers with a sensitive area of 6 × 6 mm2. The calorimeter based on avalanche photodiodes is linear in the energy range under investigation compared to a calorimeter composed of silicon-photomultiplier arrays. 相似文献
917.
Silicon - Carbon Fiber Reinforced Polymers (CFRPs) have been applied potentially for various application components owing to their lightweight and better mechanical properties. However, the... 相似文献