Increasing the Diversity and Understanding of Semiconductor Nanoplatelets by Colloidal Atomic Layer Deposition

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/pssr.202000282.

Enhanced Optical Gain from Photoactivated Colloidal Quantum Wells

“…The Bohr radius of bulk CdSe is 5.6 nm, which is much greater that the thickness of 4 ML (1.22 nm) and 6 ML (1.82 nm) CdSe NPL. [15,25] Therefore, the exciton sphere experiences significant compression in one direction, and the transition energies of the heavy-hole-exciton and light-hole-exciton are significantly influenced by quantum confinement arising from the thickness.…”

“…[13] Thanks to colloidal atomic layer deposition (c-ALD), core/shell structures and thickness control can be achieved at an unprecedentedly precise level. [14][15][16] Therefore, c-ALD provides a valuable approach to systematically study the properties of CQWs by varying the thickness while maintaining the lateral size and atomic flatness unchanged. Meanwhile, via manipulation of the landscape of the confinement potential, the Auger process can be effectively mitigated.…”

Phonons in Core–Shell CdSe/CdS Nanoplatelets Studied by Vibrational Spectroscopies

“…Among nanocrystals of various morphologies, created by methods of colloidal chemistry, anisotropic NCs, in particular nanoplatelets, are of special interest. They belong to a new class of so-called two-dimensional (2D) nanocrystals and represent planar semiconductor structures with lateral dimensions of the order of tens of nm and thicknesses from several monolayers (MLs) (of the order of 1 nm) , to 1 monolayer (so-called extended nanosheets). , This geometry providing strong spatial confinement of charge carriers in one direction, along with high uniformity of the NPL thickness ensured by the specific features of the formation method, leads to polarized ultrafast and narrow-band exciton PL with a high quantum yield ,, and anisotropic absorption of light in 2D nanocrystals. The extremely small thickness of NPLs leads, among other things, to a drastic change in the phonon spectrum of the nanostructure, which is quantized in one direction and remains quasi-continuous in the other two.…”

Near-Infrared-Emitting CdxHg1–xSe-Based Core/Shell Nanoplatelets

“…Cadmium layers terminate both basal sides of the NPLs, and therefore, the thickness of the NPLs is represented as n monolayers (MLs) of CdX, containing n and n + 1 layers of chalcogen (X) and Cd atoms, respectively. ZB CdSe NPLs with thicknesses of 2–8 ML have already been obtained in a direct colloidal synthesis that allows for tuning of their optical properties in the visible spectral range. − The colloidal atomic layer deposition method was successfully employed to increase the thickness of NPLs up to 13 ML, but the thus-obtained NPLs exhibited no photoluminescence (PL). , In turn, the synthesis of CdS, CdTe, HgSe, and HgTe NPLs enabled the widening of the spectral range of NPLs, but, as in the case of CdSe, they exhibited limited tunability in their optoelectronic properties due to the integer number of MLs within the NPL thickness. To achieve widely tunable excitonic properties, NPLs made of homogeneous CdSe x S 1– x alloys were successfully synthesized. , In addition, doping of CdSe NPLs with Cu, Ag, or Hg gives the possibility to change their optical properties considerably. − …”

“…11−14 The colloidal atomic layer deposition method was successfully employed to increase the thickness of NPLs up to 13 ML, but the thusobtained NPLs exhibited no photoluminescence (PL). 15,16 In turn, the synthesis of CdS, 17 CdTe, 18 HgSe, and HgTe 19 NPLs enabled the widening of the spectral range of NPLs, but, as in the case of CdSe, they exhibited limited tunability in their optoelectronic properties due to the integer number of MLs within the NPL thickness. To achieve widely tunable excitonic properties, NPLs made of homogeneous CdSe x S 1−x alloys were successfully synthesized.…”