Figure 3.

TEM in situ fabrication of graphene nanoconstriction. (a) Current–voltage (I–V) traces of graphene nanoconstriction during fabrication using electron beam sculpting. Black, red, blue, and green curves are I–V curves after four subsequent sculpting steps to reduce the constriction width, and vertical arrows indicate the associated conductance drops. Orange arrows on the black trace indicate direction of the voltage sweep. (Inset) Low bias I–V curves measured after each sculpting step. (b) Conductance vs time plot of graphene constriction between the end of the last sculpting step (w = 5 nm) and spontaneous breaking of the constriction (w = 0 nm) under voltage bias, where the contact resistance has been subtracted. Inset shows conductance vs time over the last 8 s. (c–h) TEM images for the same GNCs after each subsequent sculpting step from a width of (w = 280 nm) to fully broken (w = 0 nm). Note that (g) and (h) were taken at a slightly different focal point to enhance the contrast of the very thin GNCs.