Molecular beam epitaxial growth of GaAs/GaNAsBi core–multishell nanowires

GaAs/GaNAsBi/GaAs core–multishell nanowires were grown using molecular beam epitaxy on Si(111) substrates. The formation of the 20 nm wide GaNAsBi shell with a regular hexagonal structure was observed. The shell is estimated to contain approximately 1.5% N and 2.6% Bi and has a compressive lattice mismatch of less than 0.2% with GaAs layers. The strain mediation by the introduction of both N and Bi suppresses the crystalline deformation, resulting in the clear formation of the GaNAsBi shell. Thus, we obtained room-temperature photoluminescence with the maximum position at approximately 1300 nm from the GaAs/GaNAsBi/GaAs core–multishell nanowires

Effects of growth temperature and thermal annealing on optical quality of GaNAs nanowires emitting in the near-infrared spectral range

We report on optimization of growth conditions of GaAs/GaNAs/GaAs core/shell/shell nanowire (NW) structures emitting at ~1 μm, aiming to increase their light emitting efficiency. A slight change in growth temperature is found to critically affect optical quality of the active GaNAs shell and is shown to result from suppressed formation of non-radiative recombination (NRR) centers under the optimum growth temperature. By employing the optically detected magnetic resonance spectroscopy, we identify gallium vacancies and gallium interstitials as being among the dominant NRR defects. The radiative efficiency of the NWs can be further improved by post-growth annealing at 680 °C, which removes the gallium interstitials.Funding agencies:  Swedish Energy AgencySwedish Energy Agency [P40119-1]; Swedish Research CouncilSwedish Research Council [2015-05532]; Swedish Foundation for International Cooperation in Research and Higher Education (STINT) [JA2014-5698]; Swedish Government Strategic Res</p

Molecular beam epitaxial growth of dilute nitride GaNAs and GaInNAs nanowires

We report the growth of dilute nitride GaNAs and GaInNAs core-multishell nanowires (NWs) using molecular beam epitaxy assisted by a plasma source. Using the self-catalyst vapor-liquid-solid growth mode, these NWs were grown on Si(111) and silicon on insulator substrates. The GaNAs and GaInNAs shells contain nitrogen up to 3%. Axial cross-sectional scanning transmission electron microscopy measurements and energy-dispersive x-ray spectrometry confirm the formation of the core-multishell NW structure. We obtained high-quality GaNAs NWs with nitrogen compositions up to 2%. On the other hand, GaNAs containing 3% nitrogen, and GaInNAs NWs, show distorted structures; moreover, the optical emissions seem to be related to defects. Further optimisations of the growth conditions will improve these properties, promising future applications in nanoscale optoelectronics.Funding Agencies|KAKENHI by the Japan Society for the Promotion of Science [16H05970]; Swedish Energy Agency [P40119-1]</p

Stimulation of Menthol Production in Mentha Piperita Cell Culture

Plant cell culture provides an alternative means for producing secondary metabolites. In this study, experiments were carried out to study the impact of several parameters, independently and in combination, on the stimulation of menthol production in the cell suspension culture of Mentha piperita. Callus was obtained from leaf segments of in vitro grown plantlets on Murashige and Skoog (MS) medium supplemented with 0.2 mg l−1of 2,4- dichlorophenoxy acetic acid to initiate cell suspension culture. This culture was maintained in half-strength MS medium supplemented with 0.2 mg l−1of 2,4-dichlorophenoxy acetic acid at 15 d interval and used for further studies. Precursor feeding alone, i.e., menthone, at 35 μM concentration showed slightly improved productivity. γ- Cyclodextrin alone at 60 μM concentration and in combination with menthone feeding at 35 μM increased menthol yield up to 92 and 110 mg l−1 in comparison to 77 mg l−1 of control culture. Synergistic potentiation effect of menthone feeding at 35 μM and γ-cyclodextrin at 60 μM treatment followed by in situ adsorption with RP- 8 also showed potential stimulation of menthol production in M. piperita cell culture. Fungal elicitor treatment showed enhanced production level up to 140.8 mg l−1 in comparison to that of control. Further studies were carried out with the establishment of Agrobacterium tumefaciens (Ach5) gall-mediated calli, and consequently, cell suspension culture and results showed the significant enhancement of menthol yield up to 278 mg l−1