No abstract

Graphene's novel electrical, optical, and mechanical properties are affected both by substrate interaction and processing steps required to fabricate contacts and devices. Annealing is used to clean graphene devices, but this can lead to doping and defect changes and strain effects. There is often disagreement about which of these effects are occurring and which result in observed changes in Raman spectra. The effects of vacuum annealing on mechanically exfoliated pristine, suspended, and attached thin and thick few-layer graphene on SiO 2 /Si are investigated here using scanning electron microscopy (SEM), Raman spectroscopy, and atomic force microscopy (AFM). Before annealing, Raman shows that the differences in 2D and G band positions and the appearance of a disorder-induced D band of all regions were mainly because of compressive or tensile structural deformations emerging through mechanical exfoliation instead of charge doping. Annealing at low temperature is sufficient to eliminate most of the defects. However, compressive strain is induced in the sheet by annealing at high temperature, and for thin regions increased substrate conformation leads to the apparent disappearance of the sheets. The intensity ratio of the 2D and G bands also reduces with induced compressive strain, and thus should not be used to detect doping.

Abstract—The fabrication processes of different nano- structures by electron beam lithography (EBL) and plasma dry etching are shown. The periodic circle and square patterns with different sizes were defined in the resist by EBL and then formed in the substrates by plasma etching. The holes were created with a diameter ranging from 1um to 5um and an etch depth from around 500nm to 1um. The quality and the size of fabricated patterns and their dependence on the etching time were investigated using top-down and cross-sectional scanning electron microscopy (SEM). It was found that the structures are well-resolved in the patterns with high levels of quality and good size uniformity. The results show that the depth of the structures does not depend on their size or geometry but rather on the etch time.  Keywords: EBL,plasma etching,nano-structures.