No abstract

In this letter, the authors demonstrate large size m-plane GaN substrates grown by ammonothermal method. These substrates have excellent structural quality. The concentration of threading dislocation density is below 5×104 cm−2 and the full width at half maximum for the symmetrical and asymmetrical peaks equals 16 and 19 arc sec, respectively. Also good optical quality, the energy gap-related transition is clearly observed at room temperature in photoluminescence and contactless electroreflectance spectra. GaN epilayers deposited on these substrates exhibit intrinsic narrow exciton lines which are very sensitive to the optical selection rules typical for hexagonal symmetry, proving truly nonpolar character of the material.

We have examined the influence of flake-substrate effects that affect one and few layers of MoS 2 in terms of their electrical and optical properties. In the measurements, we used SiO 2 /Si substrates with etched cavities and aluminum electrodes. Suspended areas are easily identifiable both on images depicting the topography and on the surface potential maps measured with the Kelvin probe force microscopy. Compared to the SiO 2 /Si supported material, surface potential decrease is observable at the membrane. The surface potential value of the flakes located on the electrodes is the lowest. PL measurements prove that single MoS 2 monolayer was obtained. Suspended regions are also correlated with maps obtained as a result of Raman spectroscopy.

Articles you may be interested inContactless electroreflectance and theoretical studies of band gap and spin-orbit splitting in InP1−xBix dilute bismide with x ≤ 0.034 Appl. Phys. Lett. 105, 222104 (2014); 10.1063/1.4903179 Contactless electroreflectance of In As ∕ In 0.53 Ga 0.23 Al 0.24 As quantum dashes grown on InP substrate: Analysis of the wetting layer transition