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Tunable and ultracompact optical elements are highly important for the development of advanced nanophotonics. Such elements significantly expand the capabilities of photonic circuits and devices. Phase changing materials based on Ge‐Sb‐Te composition are very promising for tunable nanophotonic elements. This family of materials is excellent for the creation of tunable optical elements, since it has a non‐volatile reversible phase transition and exhibits a strong modulation of the dielectric permittivity in broad spectral range. In this work, fabrication of Ge‐Sb‐Te nanoparticles by laser ablation as well as strong and repeatable changing of their optical properties by fs‐laser irradiation are demonstrated. Beside the control of linear optical response, switchable second harmonic generation from Ge‐Sb‐Te nanoparticles over two orders of magnitude after the phase change is also demonstrated. [ABSTRACT FROM AUTHOR]

Experimental data on the rapid (≈4.4 nm s−1) axial growth rate of narrow (≈9 nm in radius) InAs nanowires (NWs) obtained by Au‐catalyzed molecular beam epitaxy on Si substrates at a low surface temperature of 270 °C are presented. These NWs exhibit pure wurtzite crystal structure and an unusually high ratio of the average NW length over the effective thickness of deposited InAs of about 60 despite the presence of parasitic InAs islands on the Si substrate. These trends are explained within a dedicated growth model. In the absence of In evaporation, In atoms either diffuse from the substrate to the NW tips or remain in the parasitic layer. This leads to a linear time dependence of the NW length and other unusual growth properties that are thought to have not previously been accessed. [ABSTRACT FROM AUTHOR]

X-band field-sweep electron spin echo and pulsed electron nuclear double resonance (ENDOR) spectroscopy were used to study n-type 15R SiC wafers grown under carbon (C)-rich conditions with the aim to verify the recently proposed concept that nitrogen (N) donors substitute both carbon (C) and silicon (Si) sites and may occupy nonequivalent positions at Si sites. It was found that besides the 14N ENDOR spectra of the C substituting quasicubic 'k1', 'k2', and 'k3' positions five doublet lines due to 14N nuclei at other lattice positions were observed in the ENDOR spectrum of highly compensated C-rich n-type 15R SiC. Three of them with the hyperfine interaction (HFI) constants 34.66, 32.20, and 29.77 MHz were attributed to the N donors substituting 'k1', 'k2', and 'k3' positions at Si sites. Two other additional ENDOR spectra were explained by the presence of the C antisite (CSi) defects in C-rich 15R SiC, which leads to the formation of CSiNC complexes with donor levels close to the conduction-band minimum and isotropic 14N HFI constants of 21.58 and 25.94 MHz. The energy levels of N donors have been evaluated by comparing the number of ENDOR spectra observed in C-rich 15R SiC with different degrees of compensation. [ABSTRACT FROM AUTHOR]