Metal-assisted exfoliation of few-layer black phosphorus with high yield

We introduce a metal-assisted exfoliation method to produce few-layer black phosphorus with the lateral size larger than 50 μm and the area 100 times larger than those exfoliated using the normal "scotch-tape" technique. Using a field effect transistor it was found the hole mobility is 68.6 cm2 V-1 s-1 and the current on/off ratio can reach about 2 × 105.