Local field emission of electrons from an individual boron nanowire at nanometer electrode separation

The field electron emission properties of an individual β-rhombohedral boron nanowire (β-r BNW) with electrode separation at nanoscale have been studied by ultrahigh vacuum four-probe scanning tunneling microscope (STM) system. A reproducible and stable emission current can be obtained. The maximal emission current density of individual boron nanowire is about 5 × 10⁴ A/cm² at a low bias voltage (80 V). An obvious deviation from the Fowler-Nordheim (FN) theory appears, when the electrode separation reduced below 120 nm. This deviation is tentatively assumed to due to the invalidation of free electron cloud approximation in FN theory.