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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 (β), and maximum current density (Jmax) come out to be in the range of 3–7.5 V/μm, 1715–3223, and 284–872 nA/cm2, respectively and their correlation with plasma‐induced surface structural, morphological and work function modifications is discussed. [ABSTRACT FROM AUTHOR]

The spatial confinement effect on the laser-induced plasma parameters and surface modifications of iron (Fe) has been investigated. The Fe plasma has been generated under ultrahigh vacuum (UHV) condition by employing Nd: YAG (532 nm, 6 ns) laser at different laser irradiances ranging from 3.3 to 10 GWcm $^{-2}$. Two important Fe plasma parameters, i.e., electron temperature ranging from 13 to 27 eV and electron number density ranging from $1.92\times 10^{15}$ cm $^{-3}$ to $4.60\times 10^{15}$ cm $^{-3}$ , are evaluated by employing Langmuir probe (LP) as diagnostic technique. The probe was placed at a distance of 1 cm from target. Both plasma parameters are found to be influenced by laser irradiances and spatial confinement. They increase with the increase in laser irradiances both in the presence and absence of metallic blockers. However, it is revealed that the values of both plasma parameters are slightly higher in the presence of blocker as compared to blocker-free case. The percentage increase in electron temperature varies from 10% to 15%, whereas percentage increase in electron density varies from 11% to 25%. These percentage increase in the values of Fe plasma parameters exceeds the limits of experimental errors (±2). Therefore, the role of spatial confinement via metallic blocker for the enhancement of plasma parameters is confirmed and is attributed to the reflection of shockwaves from the blocker. The surface modifications of laser irradiated Fe have been explored by scanning electron microscopy (SEM). Various features, such as ripples, ridges, and cones, have been observed on the surfaces of ablated Fe. More pronounced, organized, and fine structures are grown on the Fe surface in the presence of blocker at lower irradiances than the blocker-free case due to spatial confinement effect. The growth of ripples is attributed to Kelvin–Helmholtz instabilities. PACS: 61.80.Ba, 52.50. −b, 52.50.Jm, 52.50.Lp, 52.35.Tc, 35 52.38., 52.38.Dx. [ABSTRACT FROM AUTHOR]

The effect of laser fluence and nature of ambient environments on the sputtering yield, surface modifications, crater depth, UV-visible absorption spectra, chemical composition, and micro hardness of Zr has been investigated. Nd: YAG laser (532 nm, 10 Hz, 6 ns) at different fluences varying from 16 to 60.8 Jcm−2 was employed as an irradiation source. All measurements are performed under two ambient environments of Ar and O2 at a constant pressure of 10 Torr. Quartz crystal microbalance has been employed for the measurement of sputtering yield of laser irradiated Zr. It is revealed that sputtering yield increases monotonically with increasing fluence under both environments however, it is higher in Ar as compared to O2 environment. Scanning electron microscope (SEM) has been used to explore the surface morphology. SEM analysis exhibits the formation of cones, ridges, and cracks at the central ablated areas whereas, laser-induced periodic surface structures, periodic ridges and sharp cones are observed at inner boundaries in both environments of Ar and O2. Sharp spikes are observed in both environments, however, their height and distinctness are more pronounced in Ar as compared to O2. Cones are characteristic features in Ar, whereas, cavities and channels are dominant features in O2 environment at outer boundaries. The formation and growth of surface structures are dependent upon laser fluence and ambient gas nature. The depth profilometry has been used to measure the crater depth of irradiated Zr target by using an optical microscope. UV visible spectroscopy and energy-dispersive X-ray analyses reveal the oxide formation in the case of Zr irradiation in O2 environment. The Vicker Micro-hardness tester has been employed to measure the hardness. The higher observed values of sputtering yield, crater depth and hardness of laser ablated Zr in Ar as compared to O2 are well correlated with distinct surface structures. [ABSTRACT FROM AUTHOR]