Mn²⁺-Doped CdSe/CdS Core/Multishell Colloidal Quantum Wells Enabling Tunable Carrier–Dopant Exchange Interactions

Abstract

In this work, we report the manifestations of carrier-dopant exchange interactions in colloidal Mn(2+)-doped CdSe/CdS core/multishell quantum wells. The carrier-magnetic ion exchange interaction effects are tunable through wave function engineering. In our quantum well heterostructures, manganese was incorporated by growing a Cd0.985Mn0.015S monolayer shell on undoped CdSe nanoplatelets using the colloidal atomic layer deposition technique. Unlike previously synthesized Mn(2+)-doped colloidal nanostructures, the location of the Mn ions was controlled with atomic layer precision in our heterostructures. This is realized by controlling the spatial overlap between the carrier wave functions with the manganese ions by adjusting the location, composition, and number of the CdSe, Cd1-xMnxS, and CdS layers. The photoluminescence quantum yield of our magnetic heterostructures was found to be as high as 20% at room temperature with a narrow photoluminescence bandwidth of ∼22 nm. Our colloidal quantum wells, which exhibit magneto-optical properties analogous to those of epitaxially grown quantum wells, offer new opportunities for solution-processed spin-based semiconductor devices.

Time-resolved photoluminescence study of CdSe/CdMnS/CdS core/multi-shell nanoplatelets

“…[1][2][3][4][5][6][7][8] These are quasi twodimensional structures grown using relatively inexpensive solution-based synthesis methods, which have a significant cost advantage when compared to molecular beam epitaxy (MBE) and chemical vapor deposition (CVD) growth techniques. In addition, nanoplatelets also offer the following advantages: (a) a tunable emission spectrum, which is narrower than that of colloidal quantum dots (cQDs) 7,9 and (b) an enhanced absorption cross-section. 10 Our previous study of CdSe/CdMnS/CdS core/multi-shell nanoplatelets has shown that the interband emission acquires a net circular polarization of r þ (left circular polarization, LCP) in the presence of an externally applied magnetic field.…”

“…10 Our previous study of CdSe/CdMnS/CdS core/multi-shell nanoplatelets has shown that the interband emission acquires a net circular polarization of r þ (left circular polarization, LCP) in the presence of an externally applied magnetic field. 7 This has been attributed to the exchange interaction between the carrier spins and those of the Mn ions. 11 In contrast, the non-magnetic (CdSe/CdS) core/multi-shell structures exhibit r -(right circular polarization, RCP) net circular polarization when an external magnetic field is applied.…”

“…11 In contrast, the non-magnetic (CdSe/CdS) core/multi-shell structures exhibit r -(right circular polarization, RCP) net circular polarization when an external magnetic field is applied. 7 The photoluminescence (PL) spectrum is asymmetric and contains two distinct spectral features. This asymmetry has been previously observed in CdSe/CdZnS and CdSe/CdS nanoplatelets.…”

“…In these samples, one monolayer is approximately 0.3 nm thick, and the lateral core dimensions are 55 6 6 nm  10 6 2 nm; the values for these dimensions were obtained using TEM. 7 Further details regarding these samples have been described by Delikanli et al where the magnetic (nonmagnetic) sample corresponds to sample 1 (3). 7 The PL measurements were carried out by placing the samples in a variable-temperature, optical magnet cryostat.…”

“…7 Further details regarding these samples have been described by Delikanli et al where the magnetic (nonmagnetic) sample corresponds to sample 1 (3). 7 The PL measurements were carried out by placing the samples in a variable-temperature, optical magnet cryostat. The magnetic field was applied along the direction perpendicular to the sample substrate, hereby referred to as the z-axis.…”