RESUMO
The elastic modulus of multilayer graphene is found to be more robust to damage created by high-energy α-particle irradiation as compared to monolayer graphene. Theoretical analysis indicates that irradiation of multilayer graphene generates interlayer links that potentially increase the stiffness of the multilayer by passivating local defects.
RESUMO
Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) have been used to study compositional modulation in In(x)Ga(1-x) N layers grown with compositions close to miscibility gap. The samples (0.34 < x < 0.8) were deposited by molecular beam epitaxy using either a 200 nm thick AlN or GaN buffer layer grown on a sapphire substrate. Periodic compositional modulation leads to extra electron diffraction spots and satellite reflections in XRD in the theta-2theta coupled geometry. The ordering period delta measured along c-axis was about delta = 45 A for x = 0.5 and delta = 66 A for x = 0.78 for samples grown on AlN buffer layer. TEM and XRD determinations of delta were in good agreement. Compositional modulation was not observed for the sample with x = 0.34 grown on a GaN buffer layer. Larger values of delta were observed for layers with higher In content and for those having larger mismatch with the underlying AlN buffer layer. The possibility that the roughness of the AlN growth surface promotes strong In segregation on particular crystallographic planes leading to compositional modulation is considered.
