Self-ordered CdSe quantum dots in ZnSe and (Zn, Mn)Se Matrices Assessed by transmission electron microscopy and photoluminescence spectroscopy

Möck, P.; Topuria, Teya; Browning, Nigel D.; Titova, Lyubov V.; Dobrowolska, M.; Lee, S.; Furdyna, J. K.

doi:10.1007/bf02665867

Cited by 19 publications

(20 citation statements)

References 27 publications

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“…Embedded within the barrier are 1.3 monolayers of CdSe. The lattice mismatch between the CdSe and the Zn 0.64 Be 0.3 Mn 0.06 Se induces a strain in the CdSe material, which is relaxed by the formation of isolated CdSe dots [10]. The full layer stack is given in Fig.…”

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confidence: 99%

Remanent Zero Field Spin Splitting of Self-Assembled Quantum Dots in a Paramagnetic Host

et al. 2006

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A key element in the emergence of a full spintronics technology is the development of voltage controlled spin filters to selectively inject carriers of desired spin into semiconductors. We previously demonstrated a prototype of such a device using a II-VI dilute-magnetic semiconductor quantum well which, however, still required an external magnetic field to generate the level splitting. Recent theory suggests that spin selection may be achievable in II-VI paramagnetic semiconductors without external magnetic field through local carrier mediated ferromagnetic interactions. We present the first experimental observation of such an effect using non-magnetic CdSe self-assembled quantum dots in a paramagnetic (Zn,Be,Mn)Se barrier.PACS numbers: 72.25. Dc, 85.75.Mm Nanomagnetics has over the past few years produced a series of fascinating and often unanticipated phenomena. To name a few, molecular magnets exhibit quantum tunnelling of the magnetization[1], magnetic atoms on a surface exhibit giant magnetic anisotropies [2], and magnetic domain walls are being harnessed as data carriers [3]. Here, we report on another remarkable phenomenon: self-assembled quantum dots, fabricated from II-VI dilute magnetic semiconductors (DMS) that macroscopically exhibit paramagnetism, possess a remanent magnetization at zero external field. This allows us to operate the dots as voltage controlled spin filters, capable of spin-selective carrier injection and detection in semiconductors. Such spin filter devices could provide a key element in the emergence of a full spintronics technology [4]. We present the first experimental observation of such a device using an approach based on the incorporation of non-magnetic CdSe self assembled quantum dots (SADs) in paramagnetic (Zn,Be,Mn)SeWe previously demonstrated a prototype of such a spin filter using a II-VI DMS-based resonant tunnelling diode [5]. However, while that device was tuned by a bias voltage, the spin filtering mechanism still required an external magnetic field. Moreover, ferromagnetic III-V semiconductors like (Ga,Mn)As are not suitable for resonant tunnelling devices due to the short mean free path of holes [6]. Recent theoretical works [7,8,9] have suggested that spin selection may be achievable in II-VI DMS without any external magnetic field by creating localized carriers that might mediate a local ferromagnetic interaction between nearby Mn atoms.Our sample is an MBE-grown all-II-VI resonant tunnelling diode (RTD) structure consisting of a single 9 nm thick semi-magnetic Zn 0.64 Be 0.3 Mn 0.06 Se tunnel barrier, sandwiched between gradient doped Zn 0.97 Be 0.03 Se injector and collector. Embedded within the barrier are 1.3 monolayers of CdSe. The lattice mismatch between the CdSe and the Zn 0.64 Be 0.3 Mn 0.06 Se induces a strain in the CdSe material, which is relaxed by the formation of isolated CdSe dots [10]. The full layer stack is given in Fig. 1. Standard optical lithography techniques were used to pattern the structure into 100 µm square pillars, and contacts wer...

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confidence: 99%

Remanent Zero Field Spin Splitting of Self-Assembled Quantum Dots in a Paramagnetic Host

et al. 2006

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“…Some three dimensional (3D) double period ± (-111) ordered agglomerates, Fig. 1b, were observed to be in the size range for quantum confinement to occur [3,6 ] and we consider these agglomerates to constitute a novel kind of self-assembled semiconductor QD. These QDs should have an enhanced confinement potential since atomic ordering leads typically to reduced band gaps [1,18].…”

Section: Methodsmentioning

confidence: 97%

“…488 nm light excitation, on the other hand, can be considered as resonant excitation below the ZnSe band gap, is typically orders of magnitude weaker than non-resonant excitation over the band gap, and selective of specific structures. [3,[5][6][7]. Some three dimensional (3D) double period ± (-111) ordered agglomerates, Fig.…”

Section: Methodsmentioning

confidence: 99%

“…In recent years, atomic ordering and phase separation has also been observed in several heteroepitaxial II-VI systems, e.g. (Cd,Zn)Se [2][3][4], (Cd,Mn,Zn)Se [3,[5][6][7], (Fe,Zn)Se [8], (Cd,Zn)Te [9][10][11], and Cd(Se,Te) [12]. Atomic ordering and phase separation in IV-VI systems has, to the best of our knowledge, only been reported once in epitaxial (Pb,Eu)Te [13].…”

Section: Introductionmentioning

confidence: 97%

“…Over recent years, there has, however, been an accumulation of experimental observations [3][4][5][6][7]16] that suggest that these assumptions are not always justified. In this paper we report on high resolution phase contrast TEM (HRTEM), selected area high energy transmission electron diffraction (SAED), and atomic resolution Z-contrast scanning TEM (Z-STEM) investigations on a nominal CdSe/(Mn 0.1 Zn 0.9 )Se multilayer QD structure and a nominal PbSe island (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Atomic Ordering in Self-assembled Epitaxial II-VI and IV-VI Compound Semiconductor Quantum Dot Systems

et al. 2002

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Transmission electron microcopy (TEM) in both the parallel illumination and scanning probe mode revealed atomically ordered entities within a 5 to 250 nm range in a IV-VI and a II-VI compound semiconductor quantum dot (QD) system. While the II-VI system was a nominal [001] CdSe/(Mn 0.1 Zn 0.9 )Se multilayer structure with the QDs embedded, the IV-VI system nominally consisted of [111] PbSe islands. The comparison of photoluminescence (PL) spectra from the CdSe/(Mn 0.1 Zn 0.9 )Se structure with those of a reference structure, that was grown to the same nominal specification under otherwise identical conditions except that no Mn was incorporated into the cladding layers, revealed for the former sample two peaks at approximately 2 and 2.1 eV. We tentatively attribute these two PL peaks to two groups of atomically ordered entities.

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CdSe/ZnSe heteroepitaxy: Aspects of growth and self organization of nanostructures

Mahapatra

Kießling

Margapoti

et al. 2007

Phys. Status Solidi (c)

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Formation and properties of quantum dots (QDs) and related nanostructures by conventional molecular beam epitaxy (MBE) and two other variants of the technique, have been systematically investigated. While MBE growth of CdSe on ZnSe at 300 °C results in the formation of rough CdSe quantum-well-like structures, by one of the variants, which combines epitaxial growth of a CdSe layer at 230 °C and subsequent in-situ annealing at 310-340 °C, tiny but distinct three-dimensional (3D) QDs are formed. We demonstrate that QD formation by this method, developed originally by Rabe et al. (J. Cryst. Growth 184/185, 248 (1998) [30]), essentially takes place during the annealing step, by a process of "controlled roughening" of the as-grown quasi-two-dimensional (2D) CdSe layer. In comparison to conventional MBE, this process results in reduction of the areal density of the self-organized QDs by up to two orders of magnitude, thus making them distinctly discernible. In the second variant technique, similar to that applied originally for the self-organization of CdTe/ZnTe quantum dots by Tinjod et al. (Appl. Phys. Lett. 82, 4340 (2003) [34], QD-formation takes place as a result of deposition of an amorphous group-VI layer onto a strained 2D CdSe layer at ~ 50 °C, and its subsequent re-desorption at temperatures of 280-320 °C. While deposition and desorption of amorphous Se leads to the formation of large isolated QDs, we show that use of amorphous Te results in the self-assembly and ordering of a rich variety of nanostructures. Luminescence, morphology, and composition of QDs and the underlying formation mechanism of the three processes are discussed in detail.

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Self-ordered CdSe quantum dots in ZnSe and (Zn, Mn)Se Matrices Assessed by transmission electron microscopy and photoluminescence spectroscopy

Cited by 19 publications

References 27 publications

Remanent Zero Field Spin Splitting of Self-Assembled Quantum Dots in a Paramagnetic Host

Remanent Zero Field Spin Splitting of Self-Assembled Quantum Dots in a Paramagnetic Host

Atomic Ordering in Self-assembled Epitaxial II-VI and IV-VI Compound Semiconductor Quantum Dot Systems

CdSe/ZnSe heteroepitaxy: Aspects of growth and self organization of nanostructures

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