In this work, the concept of plasma–metal junction (pm-junction) is presented, in addition to well established physics of pn-junction, metal–semiconductor junction, semiconductor–insulator junction, etc. We demonstrate experimentally the dependence of I-V characteristics on work function of the metal for a pm-junction. The experiment is done using tungsten (W) and stainless steel (SS) having different work functions (Φm) of 4.55 eV and 4.30 eV, respectively. The W and SS planar metal probes of identical geometry were exposed to plasma simultaneously, making two distinct pm-junctions. The plasma exposed is identical for both the metals, and therefore, the difference observed in the I-V characteristics of these two pm-junctions is attributed only to the difference in an energy-band diagram of these junctions, owing to respective work function. The proposed concept of the pm-junction may simplify the complex plasma–material interactions in all laboratory plasmas, including cold glow discharges to hot fusion plasmas.

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Plasma based technologies find wide technological applications. The theory for electrical properties of plasma is well established, for different systems including simple dc discharges to complex fusion machines, using fluid model and statistical model. However, there are still several areas that are unexplored and one of such topics is plasma-material interaction. In present investigation we propose the concept of energy band diagram for plasma-metal junction analogous to the energy band diagram of P-N junction. The I-V characteristics of P-N junction diode and Schottky barrier diode are explained using well established energy band theory. In this work the concept of energy-band diagram for plasma-metal junction has been introduced and concentrates on how the I-V characteristics of plasma-metal junction vary for metals with different work functions. Using the proposed energy band diagram, I-V characteristics of plasma-metal junction obtained numerically. The I-V characteristics obtained using this concept of energy-band diagram of plasma-metal junction is consistent with theory and therefore this concept may have wide impact on laboratory plasmas and may provide a new method for higher accuracy for experimental measurements.