posted on 2015-07-08, 00:00authored byDaeGwi Kim, Shougo Tomita, Kazuma Ohshiro, Taichi Watanabe, Takenobu Sakai, I-Ya Chang, Kim Hyeon-Deuk
Semiconductor quantum dot (QD) superlattices,
which are periodically ordered three-dimensional (3D) array structures
of QDs, are expected to exhibit novel photo-optical properties arising
from the resonant interactions between adjacent QDs. Since the resonant
interactions such as long-range dipole–dipole Coulomb coupling
and short-range quantum resonance strongly depend on inter-QD nano
space, precise control of the nano space is essential for physical
understanding of the superlattice, which includes both of nano and
bulk scales. Here, we study the pure quantum resonance in the 3D CdTe
QD superlattice deposited by a layer-by-layer assembly of positively
charged polyelectrolytes and negatively charged CdTe QDs. From XRD
measurements, existence of the periodical ordering of QDs both in
the lamination and in-plane directions, that is, the formation of
the 3D periodic QD superlattice, was confirmed. The lowest excitation
energy decreases exponentially with decreasing the nano space between
the CdTe QD layers and also with decreasing the QD size, which is
apparently indicative of the quantum resonance between the QDs rather
than a dipole–dipole Coulomb coupling. The quantum resonance
was also computationally demonstrated and rationalized by the orbital
delocalization to neighboring CdTe QDs in the superlattice.