Quantum Dot Acceptors in Two-Dimensional Epitaxially Fused PbSe Quantum Dot Superlattices

Abstract

Oriented attachment of colloidal quantum dots allows the growth of two-dimensional crystals by design, which could have striking electronic properties upon progress on manipulating their conductivity. Here, we explore the origin of doping in square and epitaxially fused PbSe quantum dot superlattices with low temperature scanning tunneling microscope and spectroscopy. Probing the density of states of numerous individual quantum dots reveals an electronic coupling between the hole ground states of the quantum dots. Moreover, a small amount of quantum dots shows a reproducible deep level in the band gap, which is not caused by structural defects in the 2 connections but arises from unpassivated sites at the {111} facets. Based on semiconductor statistics, these distinct defective quantum dots, randomly distributed in the superlattice, trap electrons, releasing a concentration of free holes, which is intimately related to the interdot electronic coupling. They act as acceptor quantum dots in the host quantum dot lattice, mimicking the role of dopant atoms in a semiconductor crystal.

Recent Progress on Nanomaterial‐Facilitated Electrochemical Strategies for Cancer Diagnosis

“…Quantum dots can exhibit many optical and physical properties that are different from those of macroscopic matter. [ 88–90 ] Therefore, they possess broad application potential in the construction of electrochemical cancer biosensors. Farzi et al.…”

“…Quantum dots can exhibit many optical and physical properties that are different from those of macroscopic matter. [88][89][90] Therefore, they possess broad application potential in the construction of electrochemical cancer biosensors. Farzi et al used semiconductor polymer quantum dots (PS-COOH-co-PFBT Pdots) as the biosensor interface to realize the sensitive detection of the cancer marker MUC1.…”

Application of Scanning Tunneling Microscopy and Spectroscopy in the Studies of Colloidal Quantum Qots

“…As shown in Figure 20(a), recently Notot et al [61] . peeled the lead oleate ligand from the PbSe QD {100} facets to realize the epitaxial connection of QDs, forming a p‐type‐doped superlattice with a square geometry, where the unbound facets are still passivated with oleate ligands.…”

“…This groundbreaking study provided an intuitive understanding of the internal single-electron energy level structure of semiconductor nanocrystals and the electron-electron and electron-phonon interaction, sparking a surge of interest in STM research on colloidal nanocrystals. [50][51][52][53][54][55][56][57][58] Since then, researchers have used STM to explore properties of colloidal QDs, mainly focusing on the effects of size and shape regulation of colloidal QDs on their properties, [49,58,59] the coupling between dots in colloidal QDs arrays, [34,35,60,61] the surface properties of colloidal QDs [62][63][64] and heterostructures. [58,65] These results have greatly deepened the understanding of the photoelectric properties of colloidal QDs, and rapidly promoted the applications of colloidal QDs in optoelectronic devices, biological detection, medical imaging, and other fields.…”

Simulations of nonradiative processes in semiconductor nanocrystals

“…In addition to core-shell QDs, dimers and superlattices of NCs and NC heterostructures are being developed and studied theoretically. 91,[188][189][190][191][192] These materials offer the potential for significant engineering and control of both electronic and phononic properties, enabling the realization of new phenomena. Thus far, we have described our framework for computing the electronic/vibronic properties of confined semiconductor NCs of experimentally relevant sizes.…”