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 mu m 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 cm(2) V-1 s(-1) and the current on/off ratio can reach about 2 x 10(5).