Thermal Plasma-Induced Surface Modifications Correlated With the Field Emission Properties of Copper

The present work deals with the Argon (Ar) Thermal plasma-induced surface modification of Cu and its correlation with the electrical and field emission (FE) properties. Polycrystalline Cu targets were treated with Ar thermal plasma under atmospheric pressure at different treatment times ranging from 5 min to 30 min. XRD patterns revealed the absence of new phase in treated samples. However, significant variation in peak intensities and shifting is observed, which is explained on the basis of thermal plasma ions induced defect generation and annihilation processes. The electrical conductivity of processed Cu targets measured by four-probe method ranges from 1.9 MS/m to 70 MS/m and is well correlated with the crystallite size variation. Surface modification induced work function alternations investigated by employing Scanning Kelvin Probe (SKP) technique are in the range of 4.69 eV 4.97 eV. The irradiated morphology explored by optical and scanning electron microscopy analyses revealed the formation of localized melt pools, grains, hillocks, spheroids, and sputtered patches, which are explainable on the basis of Coulomb's explosion, thermal spike model, plasma-induced sputtering, and re-deposition. FE properties of thermal plasma-treated Cu are measured in diode configuration by measuring I-V characteristics of target under ultra-high vacuum condition. The improved FE parameters such as turn-on field (Eo), field enhancement factor (beta), and maximum current density (Jmax) come out to be in the range of 3-7.5 V/mu m, 1715-3223, and 284-872 nA/cm2, respectively and their correlation with plasma-induced surface structural, morphological and work function modifications is discussed.