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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]

Pulse laser deposited thin films of TiN are irradiated by 1 MeV carbon (C+) ions beam for various doses ranging 0.4 to 2.8 × 1014 ions/cm2. Atomic force microscopy (AFM) analysis reveals the formation of hillocks like structures after ion irradiation. X-ray diffraction (XRD) investigations show that the film crystallinity increases for lower doses ranging from 0.4 to 1.2 × 1014 ions/cm2 and decreases for higher doses (2 to 2.8 × 1014 ions/cm2) of ions. No new bands are identified from Raman spectroscopy. However, a noticeable change in microhardness has been observed. The hillock densities as well as hardness are strongly dependent upon ion dose. [ABSTRACT FROM AUTHOR]