Center for Functional Nanomaterials Seminar

The low density of electronic states found in carbon nanotubes and graphene near its’ Dirac point allows for modulation of the Fermi level of these materials in a manner unachievable by conventional metals. Recently, this Fermi level tuning was exploited in a novel device architecture, the carbon nanotube enabled vertical field effect transistor (CN-VFET), which demonstrated state-of-the-art current densities at low operating voltages from comparatively low mobility organic semiconductors without the use of lithographic patterning. Unlike in conventional thin film transistors, transconductance arises from a gate field modulation of the contact barrier at the organic semiconductor/nanotube interface. A continuous graphene electrode offers a means to disentangle the underlying mechanisms of Schottky barrier height and width modulation in these devices. Further, facile patterning of the graphene electrode to allow gate field penetration dramatically improves device performance, achieving on/off ratios and output current densities exceeding 106 and 200mA/cm2, respectively, at drain voltages below 5V. Here I will discuss these first graphene-enabled VFETs as well as the unique role that nanostructured, low density of states materials can play in a range of electronic devices.