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Impact of processing-induced structural defects on the electrical properties of a graphene monolayer has been investigated using scanning microwave microscopy (SMM). Graphene sheets grown on copper foil by chemical vapor deposition were transferred to a silicon wafer covered with a 300 nm thick thermal SiO2 layer and then patterned into a grating structure using the standard lithography technique. Raman spectroscopy and SMM were employed to monitor the defect generation and the induced surface impedance change on graphene. Correlation of the SMM image contrast shows that the etching-induced defects cause a decrease of the electrical conductivity and permittivity of the graphene monolayer. In addition, the SMM image contrast shows a frequency dependency: at higher frequencies, the permittivity of the graphene monolayer plays an important role, resulting in the SMM phase imaging contrast reversed from the low frequency measurements. Numerical simulations were performed, which are in very good agreement with the experimental results.

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This work presents a theoretical study of the structural and electronic properties of bilayered silicon films under in-plane biaxial strain/stress using density functional theory. Atomic structures of the two-dimensional silicon films are optimized by using both the local-density approximation and generalized gradient approximation. In the absence of strain/stress, five buckled hexagonal honeycomb structures of the bilayered silicon film have been obtained as local energy minima and their structural stability has been verified. These structures present a Dirac-cone shaped energy band diagram with zero energy band gaps. Applying tensile biaxial strain leads to a reduction of the buckling height. Atomically flat structures with zero bucking height have been observed when the AA-stacking structures are under a critical biaxial strain.Increase of the strain between 10.7% ~ 15.4% results in a band-gap opening with a maximum energy band gap opening of ~168.0 meV obtained when 14.3% strain is applied. Energy band diagram, electron transmission efficiency, and the charge transport property are calculated.

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