Surface morphology correlated with sputtering yield measurements of laser-ablated iron

Abstract

AbstractIron (Fe) targets are exposed to 100 pulses of Nd: YAG laser (532 nm, 6 ns, 10 Hz) at various fluences ranging from 4.8 to 38.5 J/cm2. In order to explore the effect of background environment, targets have been exposed under vacuum as well as under five different pressures ranging from 5 to 100 Torr of various background gases like Ar, Ne, O2, and air. The sputtering yield measurements and surface modifications of laser-ablated Fe are explored by quartz crystal microbalance (QCM) and scanning electron microscopy (SEM) analysis, respectively. QCM measurements reveal that the sputtering yield of Fe is strongly affected by laser fluence, pressure and nature of gas. By increasing laser fluence, the sputtering yield initially increases due to enhanced energy deposition and then saturates due to self-regulating regime. However, with increasing pressures of background gases, the sputtering yield of Fe initially increases and then decreases. Owing to thermal conductivity, ionization potential, and mass of background gas, the sputtering yield of Fe varies in accordance with the sequence vacuum >Ar>Ne>O2> air. The SEM analysis reveals the formation of several features like laser-induced periodic surface structures, cones, cavities, channels, multiple ablative craters, and dot-like structures. The difference in the periodicity, size, and shape of features is explained on the basis of confinement and shielding effects of plasma and various energy deposition mechanisms. The surface profilometry analysis reveals that the crater depth increases with increasing the laser fluence in inert environments, while in case of reactive environments, it tends to decrease initially and afterwards it increases. X-ray diffraction and energy-dispersive X-ray analyses confirm the oxide formation in case of Fe treatment in O2 and air; however, no additional phases are observed for Fe irradiation under inert environments.