Cyclotron resonance has been measured in far-infrared transmission of GaAs/Al x Ga 1−x As heterostructures with an etched trigonal lateral superlattice intended to mimic graphene with lattice constant of the order of 100 nm (about 1000 times larger than that of natural graphene). Nonlinear dependence of the resonance position on magnetic field was observed, as well as its splitting into several modes. Our explanation, based on a perturbative calculation, describes the observed phenomena as a weak effect of the lateral potential on the twodimensional electron gas. Using this approach, we found a correlation between parameters of the lateral patterning and the created effective potential and obtained thus insights into how the electronic miniband structure has been tuned. The miniband dispersion was calculated using a simplified model and allowed us to formulate four basic criteria that have to be satisfied to reach graphene-like physics in such systems.
Silicon vacancy (SiV) centers are optically active defects in diamond. The SiV centers, in contrast to nitrogen vacancy (NV) centers, possess narrow and efficient luminescence spectrum (centered at ≈738 nm) even at room temperature, which can be utilized for quantum photonics and sensing applications. However, most of light generated in diamond is trapped in the material due to the phenomenon of total internal reflection. In order to overcome this issue, we have prepared two-dimensional photonic crystal slabs from polycrystalline diamond thin layers with high density of SiV centers employing bottom-up growth on quartz templates. We have shown that the spectral overlap between the narrow light emission of the SiV centers and the leaky modes extracting the emission into almost vertical direction (where it can be easily detected) can be obtained by controlling the deposition time. More than 14-fold extraction enhancement of the SiV centers photoluminescence was achieved compared to an uncorrugated sample. Computer simulation confirmed that the extraction enhancement originates from the efficient light-matter interaction between light emitted from the SiV centers and the photonic crystal slab.
Nanocrystalline diamond (NCD) films were grown on gold/Al 2 O 3 substrate using microwave plasma-enhanced chemical vapor deposition (PECVD) process. The NCD morphology was controlled by the deposition time and it was investigated by scanning electron microscopy (SEM). Gas sensing properties of NCD surface conductivity to humid air, CO 2 , NH 3 , and COCl 2 gases were measured by impedance measurements at room and at high temperature (140 • C). The H-terminated NCD surface shows a significant response to oxidizing gas (humid air, COCl 2 ) in comparison to reducing gases (CO 2 , NH 3 ).
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