Potential well

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

Laser annealing of silicon nanocrystal films prepared by pulsed-laser deposition

Abstract: We studied the laser annealing effects on the structures and properties of silicon (Si) nanocrystal films fabricated by pulsed-laser deposition in inert argon gas. The as-deposited samples show large particles (i.e., droplets) with size ranging from ∼100 nm to several μm on a uniform background film. The strong photoluminescence (PL) was from the background film rather than from the crystalline droplets. The consistency of the PL and crystal size from the background film supports the quantum confinement effect theory. After KrF excimer laser annealing, nanoparticles (NPs) with sizes of 10–50 nm were formed in the as-deposited films. In the vicinity of the droplets, the NPs were aligned together to form incident-light-angle-dependent cylindrical ripples which were caused by the interference of the incident light and the surface-scattered waves. The threshold fluence of surface melting was also reduced due to the interference. The intensity enhancement and blueshift of PL, the correlation between the indirect transition in optical absorption, and the bonding information in infrared spectra, further reveal the oxidation and ablation during the laser annealing process.

Energy spectrum of a nonideal quantum well in an electric field

Abstract: The effect of an electric field on the energy spectrum of a quantum well with macroscopic fluctuations is studied. The Stark shift of the quasibound states in a quantum well and three field-dependent broadening mechanisms (field-induced homogeneous broadening and broadening due to well width and depth fluctuations) are calculated in a wide range of electric fields. As an example, the effect of an electric field on the energy spectrum of electrons in a 12-nm-wide GaAs/Al0.3Ga0.7As quantum well with 5% width and depth fluctuations is determined.

Self-Trapped Exciton and Large Stokes Shift in Pristine and Carbon-Coated Silicon Carbide Quantum Dots

Abstract: SiC quantum dots have potential applications in the fields of optoelectronics, biological imaging, etc. However, the theoretical studies of their optical spectra have been limited to the energy gap calculations, and the microscopic mechanism of the photoluminescence process has not been clearly understood. Here, we study the optical absorption and emission spectra for pristine and carbon-coated SiC quantum dots via time-dependent density functional tight-binding method. The results show that optical absorption spectra of pristine SiC quantum dots are generally governed by the quantum confinement effect, which however will break down for the carbon-coated SiC quantum dots. Large Stokes shift in the optical emission spectra for all quantum dots is found, which is attributed to the self-trapped exciton accompanying with stretched chemical bond. The location of self-trapped exciton and the type of stretched bond will be affected by the coated carbon shell, which can be utilized to tune the optical emission pr...

Bandgap shift by quantum confinement effect in 〈100〉 Si-nanowires derived from threshold-voltage shift of fabricated metal-oxide-semiconductor field effect transistors and theoretical calculations

Abstract: Si-nanowire (Si-NW) MOSFETs, the cross-sectional size (square root of the cross-sectional area of NWs) of which was changed from 18 to 4 nm, were fabricated and characterized. Both n- and p-channel MOSFETs have shown a nearly ideal subthreshold swing of 63 mV/decade. The threshold voltage of n-/p-channel MOSFETs has gradually increased/decreased with decreasing the cross-sectional size. The bandgap shift from bulk Si has been derived from the threshold-voltage shift. The bandgap of Si-NWs was calculated by a density functional theory, tight binding method, and effective mass approximation. The calculated bandgap shows good agreement with that derived from threshold voltage. The theoretical calculation indicates that the bandgap is dominated by the cross-sectional size (area) and is not very sensitive to the shape within the aspect-ratio range of 1.0-2.5.

Dielectric Mismatch at Finite Barrier Cubic Quantum Dots

Abstract: We study the exciton states in the cubic quantum dots with finite potential barrier at the presence of dielectric mismatch. The dependence of electron and hole ground states as well as exciton binding energy and oscillator strength are found as a function of quantum dot size and dielectric constant of quantum dot and surrounding matrix. The developed theoretical approach has been applied to analyze the peculiarities of exciton spectra in CdTe quantum dots embedded in a variety of dielectric matrices.