Potential well

About: Potential well is a research topic. Over the lifetime, 1430 publications have been published within this topic receiving 30812 citations.

Preparation and Characterization of PbS Quantum Dots Doped Ormocers

Abstract: A new method for the preparation of semiconductor PbS quantum dot-doped Ormocer (Organically Modified Ceramic) has been developed. The Ormocer matrix was prepared through the hydrolysis and condensation of alkoxysilane precursors (sol-gel process). Formation of PbS particles took place in the porous Ormocer through H2S gas reaction with a lead precursor incorporated at the solution stage. Control of the PbS dot size was achieved through the use of organically substituted trifunctional silanes. Particle formation and growth was studied under different experimental conditions (e.g. temperature and lead precursor concentrations) where nucleation and aggregation processes occurred. Determination of the average particle size was done by XRD. Transmission electron microscopy was also used to determine particle diameter as well as particle size distribution. Optical absorption spectra were measured at the UV-VIS wavelength range. Absorption edge blue shifts showed the quantum confinement effect in these materials. The non-hydrolyzed groups bonded to the silane prevented uncontrolled nucleation and aggregation during the particle formation and growth, i.e. at the solution stage by the homogeneous distribution of the Pb salts or at the xerogel state by the capping of the growing particles.

Energy band leveling modulation doped quantum well

Abstract: A superlattice structure comprising a host quantum well with a plurality of mini quantum wells formed therein is provided. The host quantum well has a confined energy state E2 which lies very near a lower band energy V1 of the host well, while each of the mini quantum wells has a single confined energy level E1 which lies below V1. Charge carriers are provided to the quantum well by doping material in the barrier layers to provide modulation doping of the quantum well. The mini quantum wells contain at least one monolayer of another material within their boundaries. The monolayer material is preferably electrically inactive and is a source of phonons which are generated for the purpose of charge carrier-phonon coupling in order to cause charge carrier pairing. In a preferred embodiment a transfer quantum well is formed between the barrier region of the host quantum well and the outermost mini quantum wells. The transfer quantum well has an energy state which couples to the E1 energy state of the mini quantum wells and serves to transfer charge to the mini quantum wells.

Local-field calculation of the optical diamagnetic response of a metallic quantum well.

Abstract: A theoretical study of the local field inside a metallic quantum well placed on top of a dielectric substrate is presented in the case where the optical diamagnetic response is the dominating one. Taking as a starting point a fundamental integral equation for the local field, the prevailing sand p-p p-polarized case it is demonstrated that the so-called slave approximation gives a result in complete agreement with the exact numerical calculation. In the slave approximation it is assumed that (i) the field-induced motion of the conduction electrons parallel to the plane of the film is independent of the local field across the quantum well and (ii) the motion of the particles across the well is driven by the background field plus the local field caused by the motion of the carriers along the quantum well. On the basis of the homogeneous part of the fundamental integral equation the self-sustaining oscillations in the local field, i.e., the local-field eigenmodes, are investigated. The basic theory for the local field is used to calculate the s- and p-polarized amplitude-reflection coefficients of the quantum well/substrate system, and it is shown that for thin quantum wells a macroscopic two-layer model carrying surface currents as well as surface charges at the vacuum/substrate interface can account for the optical-reflection properties once the surface currents and charges have been determined from microscopic considerations. Numerical calculations of the local field inside the quantum well, the local electric displacement field, the s-polarized energy-reflection coefficient, and the surface-wave dispersion relation are presented for superthin niobium films deposited on crystalline quartz. It is demonstrated that our theory is in excellent agreement with experimental results for the s-polarized reflectivity of the Nb/quartz system recently obtained by Alieva et al. [Phys. Lett. A 152, 89 (1991)].

Impact of the stacking fault and surface defects states of colloidal CdSe nanocrystals on the removal of reactive black 5

Abstract: The photodegradation of the reactive black 5 (RB5) with CdSe-MSA nanocrystals (NCs) synthesized by using mercaptosuccinic acid (MSA) was studied. The quantum confinement effect was confirmed via the blue shift of absorbance band and higher energy band gap values. Photoluminescence (PL) emissions were riddled with low energy bands arising from the recombination of trapped charge carriers. The surface stress of the nanocrystals from the ligand capped surface and the atomic position relaxation at the stacking fault interface was linked to an observed hexagonal distortion. The comparison of SO and LO modes was used to analyze the quality of NCs, defect and disorder on the NCs surface. Contact time and RB5 degradation with NCs were investigated to understand the adsorption-photocatalysis synergy. Statistical physics parameters were calculated to explain the dye adsorption on tested nanocrystals. CdSe-MSA showed remarkable UV-light photocatalytic activity with a dye degradation of 89% in 120 min.