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Potential well

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


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Journal ArticleDOI
TL;DR: In this paper, an anisotropic stress relaxation was attributed to the anisotropy of the X-ray rocking curves and the surface stripes of ZnO epilayers.
Abstract: Nonpolar m-plane ZnO epilayers and 5-period ZnO/Zn1−xMgxO (x = 0.45) multiple quantum wells (QWs) have been grown successfully on a LiGaO2 (100) substrate by plasma-assisted molecular beam epitaxy. The epilayer and QWs samples show different anisotropy of the X-ray rocking curves (RCs) and the surface stripes. The former exhibits a low FWHM value of 126 arcsec of the X-ray (100) RC along [110]ZnO, and its surface is composed of fine stripes along [0001]ZnO. The QW sample, in contrast, exhibits a low RC FWHM (169 arcsec) along [0001]ZnO with surface stripes oriented along [110]ZnO. These phenomena are attributed to an anisotropic stress relaxation. Moreover, combining the X-ray and TEM characterization techniques, both samples show an extremely low density of threading dislocations of less than 1 × 108 cm−2, but a high density of basal stacking faults of 1 × 106 cm−1. The room temperature cathodoluminescence spectrum of the ZnO/Zn1−xMgxO QWs shows a strong emission peak with an apparent blue shift to 3.56 eV, indicating the positive quantum confinement effect and hence the absence of induced polarization fields.

6 citations

Journal ArticleDOI
TL;DR: In this article, the authors used density functional theory (DFT) to identify anomalous quantum confinement effect (AQCE) materials with van der Waals-bonding, where the electronic bandgap of the 3D realization of a material is lower than that of its 2D counterpart.
Abstract: Materials with van der Waals-bonding are known to exhibit quantum confinement effect, in which the electronic bandgap of the three-dimensional (3D) realization of a material is lower than that of its two-dimensional (2D) counterpart. However, the possibility of an anomalous quantum confinement effect (AQCE) exists, where the bandgap trend is reversed. In this work, we computationally identify materials for which such AQCE occurs. Using density functional theory (DFT), we compute ~1000 OptB88vdW (semi-local functional), ~50 HSE06 and ~50 PBE0 (hybrid functional) bandgaps for bulk and their corresponding monolayers in the JARVIS-DFT database. OptB88vdW identifies 65 AQCE materials, but the hybrid functionals only confirm such finding in 14 cases. Some of the AQCE systems identified through HSE06 and PBE0 are: hydroxides or oxide hydroxide compounds (AlOH2, Mg(OH)2, Mg2H2O3, Ni(OH)2, SrH2O3) as well as Sb-halogen-chalcogenide compounds (SbSBr, SbSeI) and alkali-chalcogenides (RbLiS and RbLiSe). A detailed electronic structure analysis, based on band-structure and projected density of states, shows AQCE is often characterized by lowering of the conduction band in the monolayer and corresponding changes in the pz electronic orbital contribution, with z being the non-periodic direction in the 2D case. We believe our computational results would spur the effort to validate the results experimentally and will have impact on bandgap engineering applications based on low-dimensional materials.

6 citations

Journal ArticleDOI
TL;DR: In this article, a single layer of Ge and Si 3 N 4 composite was deposited by rf-magnetron sputtering with substrate heating, and X-ray diffraction and Raman spectroscopy were used to investigate structural properties of the Ge QDs.

6 citations

Journal ArticleDOI
TL;DR: In this article, the effect of periodic twinning on photoluminescence of ZnSe nanowires was investigated and a 10-meV-blue-shift was attributed to quantum confinement effect.
Abstract: Bandgap engineering in a single material along the axial length of nanowires may be realized by arranging periodic twinning, whose twin plane is vertical to the axial length of nanowires. In this paper, we report the effect of twin on photoluminescence of ZnSe nanowires, which refers to the bandgap of it. The exciton-related emission peaks of transverse twinning ZnSe nanowires manifest a 10-meV-blue-shift in comparison with those of longitudinal twinning ZnSe nanowires. The blue-shift is attributed to quantum confinement effect, which is influenced severely by the proportion of wurtzite ZnSe layers in ZnSe nanowires.

6 citations

Journal ArticleDOI
TL;DR: In this paper, an excitation energy transfer in a bulk heterojunction based on freestanding silicon nanocrystals (Si-NCs) and conjugated polymers {poly(3-hexylthiophene) (P3HT), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV)} is demonstrated.
Abstract: An excitation energy transfer in a bulk heterojunction based on freestanding silicon nanocrystals (Si-NCs) and conjugated polymers {poly(3-hexylthiophene) (P3HT), poly[2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)} is demonstrated. The electrochemical etching process is employed for fabrication of freestanding and polymer soluble Si-NCs. Formation of a bulk heterojunction is confirmed by a difference in a work function of both polymers and an ionization potential of the NCs. An annealing step significantly influences the polymer chain conformation and electronic interaction between the polymer and the NC, which improves the exciton energy migration. The presence of the Si-NCs in polymers suppresses the relative intensity of vibronic peaks, resulting in a red-shift of the blend photoluminescence (PL) spectra. This phenomenon is attributed to a temperature-dependent migration process of singlet exciton and Dexter excitation energy transfer from the polymer to the NC. Compared to MEH-PPV polymer, a lamella-type stacking structure of the P3HT and an abridged PL spectra overlap with NCs decreases an excitation energy transfer rate. At the same time, an improvement in photocurrent generation is recorded when Si-NCs are embedded in P3HT polymer. After Dexter-like excitonic energy transfer, the PL emission of both blends is controlled through a quantum confinement effect and electron-hole recombination in Si-NCs.

6 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20234
202215
202164
202062
201940
201875