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1

Control of simultaneous effects of the temperature, indium composition and theimpact ionization process on the performance of the InN/InₓGa₁₋xN quantum dot solar cells

Afkir Noureddine, Feddi El Mustapha, Meziane Jaafar, Kouari Youssef, Zazoui Mimoun, Migalska-Zalas Anna

Opto-Electronics Review

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2019

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Vol. 27, No. 1

25--31

EN

The impact ionization in semiconductor materials is a process that produces multiple charge carrier pairs from a single excitation. This mechanism constitutes a possible road to increase the efficiency of the p-n and p-i-n solar cells junctions. Our study considers the structure of InN/InGaN quantum dot solar cell in the calculation. In this work, we study the effect of indium concentration and temperature on the coefficient of the material type parameter of the impact ionization process for a p(InGaN)-n(InGaN) and p(InGaN)-i(QDs-InN)-n(InGaN) solar cell. Next, we investigate the effect of perturbation such as temperature and indium composition on conventional solar cell’s (p(InGaN)-n(InGaN)) and solar cells of the third generation with quantum dot intermediate band IBSC (p(InGaN-i(QD-InN)-n(InGaN)) by analyzing their behaviour in terms of efficiency of energy conversion at the presence of the impact ionization process. Our numerical results show that the efficiency is strongly influenced by all of these parameters. It is also demonstrated that decreased with the increase of indium concentration and temperature which contributes to an overall improvement of the conversion efficiency.

2

Colloidal quantum dots conjugated with human serum albumin : interactions and bioimaging properties

Wojnarowska-Nowak R., Polit J., Zięba A., Stolyarchuk I. D., Nowak S., Romerowicz-Misielak M., Sheregii E. M.

Opto-Electronics Review

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2017

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Vol. 25, No. 2

137--147

EN

Quantum dots, due to their unique optical properties, constitute significant materials for many areas of nanotechnology and bionanotechnology. This work presents a review of researches dedicated to the interaction between quantum dots (QDs) with human serum albumin (HSA) and human cell culture as important for nanomedicine applications. The optical properties of bio-nanocomplexes formed by nanoparticles including colloidal QDs (e.g., CdTe, CdS, CdCoS) and albumin are displayed. The absorption spectra show that adding HSA to colloidal QDs leads to a gradual decrease of absorption and broadening of the exciton structure. The photoluminescence quenching results indicate that the quenching effect of QDs on HSA fluorescence depends on the size and temperature. The nature of quenching is rather static, resulting in forming QD-HSA complexes. The CdTe QD-HSA complexes show chemical stability in a PBS buffer. Furthermore, it is stable in cytoplasm and suitable for cell labeling, tracking, and other bioimaging applications.

3

Wszechstronność zastosowań kropek kwantowych

Geszke-Moritz M., Moritz M.

Przemysł Chemiczny

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2015

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T. 94, nr 11

1924-1931

PL

Kropki kwantowe ze względu na swoje wyjątkowe właściwości fizykochemiczne, a w szczególności optyczne, są wykorzystywane w wielu dziedzinach nauki oraz produkcji przedmiotów codziennego użytku. Zaprezentowano krótki opis zastosowań kropek kwantowych w naukach medycznych jako sond fluorescencyjnych oraz nośników substancji leczniczych. Przedstawiono także ich użyteczność podczas fluorymetrycznego wykrywania różnych związków chemicznych. Półprzewodnikowe właściwości kropek kwantowych sprawiają, że mogą one stanowić również elementy diod elektroluminescencyjnych, fotokatalizatorów lub ogniw słonecznych.

EN

A review, with 85 refs., of uses of quantum dots in medicine, anal. chem., photocatalysis, solar cells and light-emitting diodes.

4

Optymalizacja warunków otrzymywania kropek kwantowych metodą SILAR

Trenczek-Zając A., Łącz A., Ziąbka M., Radecka M.

Materiały Ceramiczne

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2014

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T. 66, nr 1

49--54

PL

W celu otrzymania kropek kwantowych PbS i CdS zastosowano metodę adsorpcji kolejnych warstw jonów i reakcji (SILAR) z wykorzystaniem roztworów siarczku(II) sodu, azotanu(V) ołowiu(II) i siarczanu(VI) kadmu na bazie wody destylowanej lub metanolu. Zastosowano stężenia z zakresu 0,001-0,1 M oraz liczbę cykli osadzania zmieniającą się w granicach 5-15. Obecność poszczególnych pierwiastków w otrzymanych strukturach potwierdzona została analizą widma EDS. Na podstawie wyników XRD stwierdzono, że zarówno PbS jak i CdS krystalizują w układzie regularnym. Analiza zdjęć otrzymanych metodą SEM pozwoliła na określenie zależności pomiędzy parametrami procesu SILAR, takimi jak stężenie roztworów prekursorów, liczba cykli osadzania i rodzaj rozpuszczalnika, a rozmiarem nanostruktur PbS i CdS. W przypadku obu siarczków, zastosowanie roztworów wodnych prekursorów o stężeniu nie przekraczającym 0,01 M stwarza warunki do krystalizacji pojedynczych kropek kwantowych, których rozmiar rośnie wraz ze wzrostem stężenia. Analogiczne zależności obserwowane są w przypadku zwiększania liczby cykli, bez względu na rodzaj rozpuszczalnika. Stosowanie roztworów wodnych o większym stężeniu (≥ 0,1 M) prowadzi do częściowej aglomeracji. Zmiana rozpuszczalnika na metanol pozwala na zmniejszenie rozmiaru nanostruktur.

EN

In order to deposit quantum dots of PbS and CdS successive ionic layer adsorption and reaction, SILAR route was employed. Water- and methanol-based solutions of sodium sulfide(II), lead(II) nitrate and cadmium sulfate were used. A concentration of solutions varied from 0.001-0.1 M and a number of cycles changed from 5-15. The EDS analysis confirmed the presence of sulphur and lead or cadmium in the obtained structures. Based on the XRD results it was found that both PbS and CdS crystallizeed in the cubic structure. SEM images allowed us to determine the relationship between size of deposited QDs and SILAR parameters such as the solution concentration, the number of cycles and the solvent type. In the case of both sulphides, deposition from the water-based solutions of concentrations up to 0.01 M creates the conditions suitable for crystallization of individual QDs. Along with the increase in the solution concentration the size of QDs increases. Similar effects are observed in case of the increase in the number of cycles regardless of the solvent type. The usage of more concentrated solutions (≥ 0.1 M) leads to partial agglomeration. Changing the solvent to methanol leads to smaller nanostructures.

5

Strain distributions in group IV and III-V semiconductor quantum dots

Wijewardena Gamalath K. A. I. L., Fernando M.A.I.P.

International Letters of Chemistry, Physics and Astronomy

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2013

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Vol. 2

36-48

EN

A theoretical model was developed using GreenˇŚs function with an anisotropic elastic tensor to study the strain distribution in and around three dimensional semiconductor pyramidal quantum dots formed from group IV and III-V material systems namely, Ge on Si, InAs on GaAs and InP on AlP. A larger positive strain in normal direction which tends to zero beyond 6nm was observed for all three types while the strains parallel to the substrate were negative. For all the three types of quantum dots hydrostatic strain and biaxial strain along x and z directions were not linear but described a curve with a maximum positive value near the base of the quantum dot. The hydrostatic strain in x-direction is mostly confined within the quantum dot and practically goes to zero outside the edges of the quantum dot. For all the three types, the maximum hydrostatic and biaxial strains occur in x-direction around �{1nm and around 2nm in z-direction. The negative strain in x-direction although realtively weak penetrate more deeper to the substrate than hydrostatic strain.The group IV substrate gave larger hydrostatic and biaxial strains than the group III-V semiconductor combinations and InAs /GaAs was the most stable. The results indicated that the movements of atoms due to the lattice mismatch were strong for group III-V.

6

Temperature dependence of the spontaneous emission mechanisms of localized-state heterosystem

Lee J. C.

Optica Applicata

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2011

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Vol. 41, nr 4

911--919

EN

The temperature dependent photoluminescence (PL) spectra measured from localized-state material system is presented. Two localized-state heterosystems, including InGaN/GaN multi-quantum well (MQW) and InAs/GaAs quantum dot (QD) samples were prepared. The samples were investigated both experimentally and theoretically. It has been found that the temperature dependence of the PL peak energies from both samples behaves differently. S-shaped and anti-S-shaped PL peak energies have been observed for MQW and QD samples, respectively. We present a model which takes into account all of the key factors for the localized-carrier dynamics. The model is applied to interpret the experimental data obtained from the two kinds of material systems. Detailed discussion concerning this model provides an explicit interpretation that it is the difference in the electronic structure of the two material systems that leads to the significantly different temperature dependence of their luminescence bands.

7

Influence of quantum dots shape approximation on size reconstructed from atomic force microscopy measurements

Piotrowski T., Sikorski S.

Opto-Electronics Review

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2009

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Vol. 17, No. 3

252-254

EN

In this work we discuss the influence of the atomic force microscopy (AFM) probe tip geometry and the object - quantum dot form on the quantum dots dimension in the growth plane reconstructed from the AFM measurements. It is shown that ignoring the geometry of the probe tip and the quantum dot leads to significant differences between dimensions obtained from the AFM measurements and the real dimensions. Inaccuracies in QD size determination of the nano-objects from AFM measurements are defined.

8

Transient effects in electron transport through quantum dots

Wiertel M., Parafiniuk P., Taranko R.

Optica Applicata

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2009

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Vol. 39, nr 4

959-965

EN

We investigate the transient electron transport through the quantum dot and double quantum dot systems coupled with the time-dependent barriers to infinitely large reservoirs of noninteracting electrons. Time-dependent currents and quantum dot occupancies are calculated using both nonequilibrium Green's functions formalism and the equation of motion method for appropriate correlation functions. We show that the sequence of ultrafast modulation of the tunneling amplitudes between the electron reservoirs and the quantum dots can induce quite different electron occupation of the quantum dot in comparison with the static case. We also find that the oscillations of the transient current following the sudden coupling of the electron reservoirs with the double quantum dot system have the same frequency as Rabi's oscillations of the double dot state vector.transient current.

9

Spin-polarized transport through two quantum dots: interference and Coulomb correlation effects

Trocha P., Barnaś J.

Materials Science Poland

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2008

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Vol. 26, No. 3

708--714

EN

Electronic transport through two single-level quantum dots attached in parallel to ferromagnetic leads has been analyzed theoretically. The intra-dot Coulomb correlation was taken into account, while the inter-dot hopping and Coulomb repulsion have been neglected. The dots, however, may interact via the external leads when the off-diagonal elements of the coupling matrix do not vanish. Conductance and tunnel magnetoresistance associated with the magnetization rotation from antiparallel to parallel configurations are calculated by the non-equilibrium Green function technique. The relevant Green functions are derived from the appropriate equation of motion in the Hartree–Fock approximation. We focus on the interference effects due to nonzero off-diagonal elements of the coupling matrix.

10

Phonon-assisted tunneling through a quantum dot coupled to magnetic leads

Rudziński W

Materials Science Poland

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2008

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Vol. 26, No. 4

879--883

EN

We study theoretically spin-polarized transport in double barrier tunneling junctions based on a single level quantum dot interacting with a local phonon mode. It is shown that the electron-phonon interaction gives rise to oscillations of the tunnel magnetoresistance (TMR). In asymmetrical junctions, the polaronic transport through the junction may lead to a significant suppression of the diode-like behavior. The case of negative effective charging energy is also analyzed numerically. It is shown in particular that for a mesoscopic diode an interplay between the single -electron cotunneling and the pair tunneling processes leads to inversion of TMR.

11

Influence of external magnetic field on transport properties of a quantum dot attached to non-collinearly polarized magnetic electrodes

Wawrzyniak M

Materials Science Poland

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2008

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Vol. 26, No. 4

1083--1090

EN

Transport properties of a single level quantum dot attached to non-collinearly polarized magnetic leads and under the influence of external magnetic field have been analyzed theoretically. Description of the considered system has been modeled by the Anderson Hamiltonian with the finite Coulomb repulsion parameter. The analysis has been performed using the equation of motion method for the non-equilibrium Green function within the Hartree-Fock approximation. Numerical illustration of the transport properties such as differential conductance, tunneling magnetoresistance and spin accumulation on the dot under influence of external magnetic field is presented and discussed.

12

Wavelength and polarization selective multi-band tunnelling quantum dot detectors

Perera A. G. U., Ariyawansa G., Apalkov V. M., Matsik S. G., Su X. H., Chakrabarti S., Bhattacharya P.

Opto-Electronics Review

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2007

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Vol. 15, No. 4

223-228

EN

The reduction of the dark current without reducing the photocurrent is a considerable challenge is developing far-infrared (FIR)/terahertz detectors. Since quantum dot (QD) based detectors inherently show low dark current, a QD-based structure is an appropriate choice for terahertz detectors. The work reported here discusses multi-band tunnelling quantum dot infrared photo detector (T-QDIP) structures designed for high temperature operation covering the range from mid- to far-infrared. These structures grown by molecular beam epitaxy consist of a QD (InGaAs or InAlAs) placed in a well (GaAs/AlGaAs) with a double-barrier system (AlGaAs/InGaAs/AlGaAs) adjacent to it. The photocurrent, which can be selectively collected by resonant tunnelling, is generated by a transition of carriers from the ground state in the QD to a state in the well coupled with a state in the double-barrier system. The double-barrier system blocks the majority of carriers contributing to the dark current. Several important properties of T-QDIP detectors such as the multi-colour (multi-band) nature of the photoresponse, the selectivity of the operating wavelength by the applied bias, and the polarization sensitivity of the response peaks, are also discussed.

13

Two-level quantum dot in the Aharonov-Bohm ring. Towards understanding "phase lapse"

Stefański P.

Materials Science Poland

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2007

|

Vol. 25, No. 4

1243--1249

EN

It is shown theoretically that indirect interaction between two quantum dot levels can generate an anomalous phase shift for a system of the dot placed in one of the arms of the Aharonov-Bohm ring. The interaction between levels arises from the non-conservation of the orbital quantum number during the hopping process of electrons between the levels and leads. Such an unusual "phase lapse" behavior is observed experimentally and still lacks of proper theoretical description.

14

Interference and Coulomb correlation effects in spin-polarized transport through coupled quantum dots

Trocha P., Barnaś J.

Materials Science Poland

|

2007

|

Vol. 25, No. 2

545--552

EN

Spin-dependent transport through two coupled single-level quantum dots attached to ferromagnetic leads with collinear (parallel and antiparallel) magnetizations is analyzed theoretically. The intra-dot Coulomb correlation is taken into account, whereas the inter-dot Coulomb repulsion is neglected. Transport characteristics, including conductance and tunnel magnetoresistance associated with the magnetization rotation from parallel to antiparallel configurations, are calculated by the noneqiulibrium Green function technique. The relevant Green functions are derived by the equation of motion method in the Hartree-Fock approximation. We have found a splitting of the Fano peak, induced by the intra-dot Coulomb interaction. Apart from this, the intra-dot electron correlations are shown to lead to an enhancement of the tunnel magnetoresistance effect.

15

Aharonov-Bohm interferometry with the T-shaped capacitively coupled quantum dots in the orbital Kondo regime

Krychowski D., Lipiński S.

Materials Science Poland

|

2007

|

Vol. 25, No. 2

435--439

EN

The magnetic field dependence of coherent transport through a pair of wires attached to two Aharonov-Bohm rings with embedded double dots is considered. The double dots are electrostatically coupled. The many-body problem is studied within the mean field slave boson approach and complementarily by the method of equation of motion in the limit of infinite intra and finite or infinite interdot Coulomb interactions.

16

Searching DNA decision trees using quantum dots detection

Mulawka J.J.

Prace Naukowe Politechniki Warszawskiej. Elektronika

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2006

|

z. 156

281-290

EN

Concept of self-assembly of DNA molecules may be utilized to implement different algorithms of computing. In particular, this methodology is useful in artificial intelligence because it operates on symbols. As has been shown by the author [7] DNA computing is suitable for searching the decision tree which is encoded by DNA molecules. Thus, the algorithms of artificial intelligence can be performed by this technique. In the contribution we demonstrate that by proper encoding and manipulating with DNA molecules it is possible to implement reasoning procedure by searching the decision tree. The method uses standard genetic engineering operations like hybridization, ligation, and purification. Quantum dot technique is applied to speed up detection of the final output eliminating the slow operation of electrophoresis. The approach presented is very simple and fast because the technique used allows an enormous number of molecules to be labeled, reduces instrument tie-up and improves analysis throughout the process.

17

Quantum structures for multiband photon detection

Perera A. G. U.

Opto-Electronics Review

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2006

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Vol. 14, No. 2

103-112

EN

The work describes multiband photon detectors based on semiconductor micro- and nano-structures. The devices considered include quantum dot, homojunction, and heterojunction structures. In the quantum dot structures, transitions are from one state to another, while free carrier absorption and internal photoemission play the dominant role in homo or heterojunction detectors. Quantum dots-in-a-well (DWELL) detectors can tailor the response wavelength by varying the size of the well. A tunnelling quantum dot infrared photodetector (T-QDIP) could operate at room temperature by blocking the dark current except in the case of resonance. Photoexcited carriers are selectively collected from InGaAs quantum dots by resonant tunnelling, while the dark current is blocked by AlGaAs/InGaAs tunnelling barriers placed in the structure. A two-colour infrared detector with photoresponse peaks at ~6 and ~17 µm at room temperature will be discussed. A homojunction or heterojunction interfacial workfunction internal photoemission (HIWIP or HEIWIP) infrared detector, formed by a doped emitter layer, and an intrinsic layer acting as the barrier followed by another highly doped contact layer, can detect near infrared (NIR) photons due to interband transitions and mid/far infrared (MIR/FIR) radiation due to intraband transitions. The threshold wavelength of the interband response depends on the band gap of the barrier material, and the MIR/FIR response due to intraband transitions can be tailored by adjusting the band offset between the emitter and the barrier. GaAs/AlGaAs will provide NIR and MIR/FIR dual band response, and with GaN/AlGaN structures the detection capability can be extended into the ultraviolet region. These detectors are useful in numerous applications such as environmental monitoring, medical diagnosis, battlefield-imaging, space astronomy applications, mine detection, and remote-sensing.

18

Resonant tunneling through a single level quantum dot attached to ferromagnetic leads with non-collinear magnetizations

Wawrzyniak M., Gmitra M., Barnaś J.

Materials Science Poland

|

2006

|

Vol. 24, No. 3

695--700

EN

Resonant tunnelling through a non-interacting single-level quantum dot attached to ferromagnetic leads is analysed theoretically. The magnetic moments of the leads are assumed to be non-collinear. Apart from this, an external magnetic field is applied to the system, which is non-collinear with the magnetizations. The magnetic moments of the leads and the external magnetic field are, however, in a common plane. Basic transport characteristics, including current-voltage curves, differential conductance, and tunnel magnetoresistance associated with magnetization rotation, are calculated using the non-equilibrium Green function technique. The dependence of transport characteristics on the bias voltage has been calculated numerically.

19

Calculation of the Fermi wavevector for thin films, quantum wires and quantum dots

Balcerzak T.

Materials Science Poland

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2006

|

Vol. 24, No. 3

719--724

EN

A comparison of the Fermi surface construction for thin films, quantum wires and quantum dots has been made in the framework of the free-electron model. The numerical results for the Fermi wavevector dependence upon the confined size of low-dimensional systems have been obtained for the model with some experimental parameters corresponding to the Cu structure.

20

Quantum Computing with Quantum Dots

Adamowski J., Bednarek S., Szafran B.

Schedae Informaticae

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2005

|

Vol. 14

95-111