Quantum Confinement Effect of 2D Nanomaterials

Abstract

Quantum confinement is the spatial confinement of electron-hole pairs (excitons) in one or more dimensions within a material, and also electronic energy levels are discrete. It is due to the confinement of the electronic wave function to the physical dimensions of the particles. In this effect can be divided into three ways, 1D confinement (free carrier in a plane), quantum wells; 2D confinement (carriers are free to move down), quantum wire; and 3D confinement (carriers are confined in all directions), which are discussed in detail. In addition the formation mechanism of exciton and quantum confinement behavior of strong, moderate, and weak confinement have been discussed below.

Recent Advances in Two-Dimensional Quantum Dots and Their Applications

“…The emission color and wavelength of QDs corresponding to their sizes are shown in Figure 1a; it can be seen that with increasing size, the emission wavelength increases. QDs are mainly composed of groups II-VI, III-V, and IV-VI materials in which the electron-hole pairs (excitons) are spatially confined in three dimensions (i.e., zero degree of freedom) owing to quantum confinement effect (QCE) [5,6]. The zero-dimensional QDs structures of InP QDs are shown in Figure 1b and InP/ZnSe/ZnS core-shell QDs in Figure 1c [7].…”

Role of the amine and phosphine groups in oleylamine and trioctylphosphine in the synthesis of copper chalcogenide nanoparticles

“…Their size range is usually from 2 to about 100 nm which allows their band gap to be tuned hence the Plasmon Resonance shifts [3]. When the material size is physically changed to be in the similar magnitude as the Bohr radii, quantum confinement effects are observed [4,5] and the new electronic and optical properties [6,7] emerging at the scale length that can be controlled by tuning the density of their electronic states [8]. During the synthesis of nanocrystals, the capping molecule is usually employed to provide passivation and electronic stabilisation to the nanocrystals as they form [9,11].…”

Friction of magnetene, a non–van der Waals 2D material

“…2 (C to L, respectively) . All of the 2D flakes were selected to be 2 nm < t < 8 nm in thickness, which is thin enough to exhibit confinement effects ( 23 , 24 ) while being thick enough to avoid the frictional layer dependence that occurs within the one- to five-layer regime ( 13 ) as noted in fig. S7.…”

“…The five 2D materials measure <8 nm in thickness, which is the typical threshold where quantum well effects begin to become relevant as the thickness approaches the de Broglie wavelength ( 23 , 24 ). A typical feature of quantum wells is altered valence states of the materials due to electron waveform confinement and asymmetric surface bonding ( 23 , 33 ).…”

“…The five 2D materials measure <8 nm in thickness, which is the typical threshold where quantum well effects begin to become relevant as the thickness approaches the de Broglie wavelength ( 23 , 24 ). A typical feature of quantum wells is altered valence states of the materials due to electron waveform confinement and asymmetric surface bonding ( 23 , 33 ). Examining the changes to the chemical signature, we perform x-ray photoelectron spectroscopy (XPS) measurements of the 2D materials and their bulk counterparts, as shown in Fig.…”