Surface patterning of high density polyethylene by oblique argon ion irradiation

Abstract

Oblique ion beam induced spontaneous patterning opens up a simple and inexpensive route to fabricate useful nanoscale textured materials that have important implications in biosensors, optoelectronic devices, templates for liquid crystal orientation, etc. In this regard, the evolution of patterns over high density polyethylene surfaces induced by 100 keV Ar+ irradiation at off normal incidences of 30°, 40°, and 50° with a fluence of 5 × 1016 Ar+ cm−2 has been investigated. Structural modifications have been analyzed using high resolution X-ray diffraction. An increase in crystallite size and a decrease in parameters such as dislocation density (δ), microstrain (ϵ), and distortion (g) have been observed after oblique Ar+ irradiation with an increase in the angle of incidence from 30° to 40°. Atomic force microscopy analysis revealed that the wavelength of ripplelike patterns decreases from 3.19 μm to 2.51 μm, while its amplitude increases from 77.4 nm to 101 nm with an increase in the angle of incidence from 30° to 40°. Similarly, with an increase of oblique incidence to 40°, the root mean square (Rq) and average surface roughness (Rav) have been found to increase. These results are accredited to the curvature dependent sputtering and smoothing processes at oblique incidences. The possible correlation between ion beam sputtering induced patterning and the structural modification in the matrix has been established and discussed.