RESUMO
The electronic properties of graphene depend critically on its lattice orientation and edge type. However, it is very difficult to identify them, and they are accessible only using sophisticated tools. In this paper, we show an easy and reliable way to reveal the lattice orientation and edge type of graphene and graphite flakes, i.e. multi-layered graphene. Nematic liquid crystals have the potential to align themselves into three symmetric and equivalent orientations on crystalline graphite. The director of macroscopic texture due to the elasticity indicates the lattice orientation of the top graphite layer. By analyzing the director orientation using a polarizing optical microscope, we were able to show the lattice orientation, chiral angle and edge type of graphene and graphite flakes on the macroscopic scale. As liquid crystals are soft and easily removable, our technique has little chance of influencing the following processes for graphene manipulation.
RESUMO
To acquire the uniform resist patterns in thermal nanoimprint lithography (TH-NIL), the major considerations include control of the resist, stamp and substrate resist under the imprint condition. Examples of these factors are management of the imprinting pressure, imprinting temperature and releasing temperature. Non-uniform patterns of thermal imprinted resist appear after TH-NIL according to the pattern size, substrate size and resist thickness. Particularly, the hole-shaped patterns with a diameter of 100 nm and a height of 100 nm on a 4 inch Si wafer after TH-NIL were deformed under tension to the maximum strain 70%. The experimental results showed that uniform nano-patterns can be acquired by minimizing the thermal mismatch while nanoimprinting through using a pair of Si stamp and Si substrate, thinning the resist thickness and separating the stamp at a relatively high temperature.