Electric field effect in ultrathin black phosphorus

Black phosphorus exhibits a layered structure similar to graphene, allowing mechanical exfoliation of ultrathin single crystals. Here, we demonstrate few-layer black phosphorus field effect devices on Si/SiO2 and measure charge carrier mobility in a four-probe configuration as well as drain current modulation in a two-point configuration. We find room-temperature mobilities of up to 300 cm(2)/Vs and drain current modulation of over 10(3). At low temperatures, the on-off ratio exceeds 10(5), and the device exhibits both electron and hole conduction. Using atomic force microscopy, we observe significant surface roughening of thin black phosphorus crystals over the course of 1 h after exfoliation. (C) 2014 AIP Publishing LLC.