Investigation of the Electron Energy Spectrum in a Three Dimensional Regimented Tetragonal Quantum Dot Superlattice

2001 ◽  
Vol 677 ◽  
Author(s):  
Olga L. Lazarenkova ◽  
Alexander A. Balandin

ABSTRACTWe analyze the electron energy spectrum in three-dimensional regimented arrays of semiconductor quantum dots. The coupling among quantum dots results in formation of three- dimensional electron mini-bands. Changing the size of quantum dots, inter-dot distance, barrier height and regimentation, one can control the electronic band structure of this quantum dot superlattice, which can also be referred to as quantum dot crystal due to its structure and energy spectrum that resemble those of a real crystal. Results of computer simulations carried out for a tetragonal InAs/GaAs quantum dot superlattice show that the electron density of states, effective mass tensor and other properties are different from those of bulk and conventional quantum well superlattices.

2015 ◽  
Vol 90 (6) ◽  
pp. 065801 ◽  
Author(s):  
R Nedzinskas ◽  
V Karpus ◽  
B Čechavičius ◽  
J Kavaliauskas ◽  
G Valušis

2019 ◽  
Author(s):  
Cecilia Gentle ◽  
Yuanheng Wang ◽  
Tyler N. Haddock ◽  
Conner P. Dykstra ◽  
Renske M. van der Veen

<p>This work shows that ZnTe/CdSe core/shell quantum dots synthesized by standard literature procedures in actuality have an alloyed Cd<sup>­</sup><sub>x</sub>Zn<sub>1-x</sub>Te core. We employ X-ray absorption spectroscopy (XAS) at all four <i>K</i>-shell ionization edges (Zn, Te, Cd, Se) and perform a global fitting analysis in order to extract the first-shell bond distances. We combine our XAS results with transmission electron microscopy (TEM) sizing and elemental analyses, which allows us to propose models of the internal particle structure. Our multimodal characterization approach confirms <b>(1) </b>the presence of Cd-Te bonds, <b>(2) </b>cation<b> </b>alloying in the particle core (and the absence of anion alloying), and <b>(3) </b>a patchy pure-phase CdSe shell. We synthesize particles of different shell thicknesses and performed synthetic control studies that allowed us to discard a ZnTe/CdTe/CdSe core/shell/shell structure and confirm the alloyed core/shell structure. Our structural analysis is extended with electronic band structure calculations and UV/vis absorption spectroscopy, demonstrating that the alloyed Cd<sup>­</sup><sub>x</sub>Zn<sub>1-x</sub>Te/CdSe core/shell quantum dots exhibit a direct band gap, different from the predicted type-II band alignment of the intended ZnTe/CdSe core/shell quantum dots. This study highlights the challenges with synthesizing II-VI quantum dot heterostructures and the power of XAS for understanding the internal structure of heterogenous nanoparticles.</p>


2019 ◽  
Author(s):  
Cecilia Gentle ◽  
Yuanheng Wang ◽  
Tyler N. Haddock ◽  
Conner P. Dykstra ◽  
Renske M. van der Veen

<p>This work shows that ZnTe/CdSe core/shell quantum dots synthesized by standard literature procedures in actuality have an alloyed Cd<sup>­</sup><sub>x</sub>Zn<sub>1-x</sub>Te core. We employ X-ray absorption spectroscopy (XAS) at all four <i>K</i>-shell ionization edges (Zn, Te, Cd, Se) and perform a global fitting analysis in order to extract the first-shell bond distances. We combine our XAS results with transmission electron microscopy (TEM) sizing and elemental analyses, which allows us to propose models of the internal particle structure. Our multimodal characterization approach confirms <b>(1) </b>the presence of Cd-Te bonds, <b>(2) </b>cation<b> </b>alloying in the particle core (and the absence of anion alloying), and <b>(3) </b>a patchy pure-phase CdSe shell. We synthesize particles of different shell thicknesses and performed synthetic control studies that allowed us to discard a ZnTe/CdTe/CdSe core/shell/shell structure and confirm the alloyed core/shell structure. Our structural analysis is extended with electronic band structure calculations and UV/vis absorption spectroscopy, demonstrating that the alloyed Cd<sup>­</sup><sub>x</sub>Zn<sub>1-x</sub>Te/CdSe core/shell quantum dots exhibit a direct band gap, different from the predicted type-II band alignment of the intended ZnTe/CdSe core/shell quantum dots. This study highlights the challenges with synthesizing II-VI quantum dot heterostructures and the power of XAS for understanding the internal structure of heterogenous nanoparticles.</p>


2015 ◽  
Vol 586 ◽  
pp. 012006
Author(s):  
A A Karmanov ◽  
I A Pronin ◽  
N D Yakushova ◽  
S E Igoshina ◽  
I A Averin

2014 ◽  
Vol 44 (2) ◽  
pp. 90-95
Author(s):  
I. F. Selyanin ◽  
V. B. Deev ◽  
A. I. Kutsenko ◽  
A. A. Kutsenko ◽  
O. G. Prikhod’ko

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