  We study the quantum nature of current through plasma-probe junction from the
viewpoint of the metal probe. The intrinsic material properties of the metal
and their influence on the nature of the observed current are theoretically
worked out. The novel idea is that the plasma-sheath at the plasma-probe
junction is treated as a potential barrier, and in analogy with the current
conduction through a metal-metal junction, the current through the
plasma-sheath is treated as a quantum barrier penetration problem. Essentially,
we obtain an expression for the electron-current as a function of the bias
voltage in its full range, thereby unlocking the intricate dependency of the
current on the material properties of the probe.
