  We report the observation of field emission from InP nanocrystals epitaxially
grown on an array of p-Si nanotips. We prove that field emission can be
enhanced by covering the InP nanocrystals with graphene. The measurements are
performed inside a scanning electron microscope chamber with a nano-controlled
W-thread used as an anode. We analyze the field emission by Fowler-Nordheim
theory and find that the field enhancement factor increases monotonically with
the spacing between the anode and the cathode. We also show that InP/p-Si
junction has a rectifying behavior, while graphene on InP creates an ohmic
contact. Understanding the fundamentals of such nanojunctions is key for
applications in nanoelectronics.
