We use mechanical exfolation of bulk single crystal or chemical vapor deposition to produce atomically thin materials. These high quality materials form the critical foundation for our research. 1) Mechanical exfoliation is a simple yet powerful to produce various two-dimensional (2D) materials from bulk single crystal. It also provides a flexible method to combine different 2D material to form van der Waals heterostructures, through which we can design materials with atomic resolution. 2) Chemical vapor depostion (CVD) provides a way to produce high quality 2D materials over large scale which greatly facilitate our research. More importantly it potential leads to real applications.