TAILIEUCHUNG - Báo cáo hóa học: " Self-organized chains of nanodots induced by an off-normal incident beam"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Self-organized chains of nanodots induced by an off-normal incident beam | Lee et al. Nanoscale Research Letters 2011 6 432 http content 6 1 432 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Self-organized chains of nanodots induced by an off-normal incident beam Seungjun Lee1 Lumin Wang2 and Wei Lu1 Abstract We propose a model to show that under off-normal bombardment of an incident ion beam a solid surface may spontaneously form nanoscale dots lining up into chains perpendicular to the incident beam direction. These dots demonstrate a highly ordered hexagonal pattern. We attribute the self-organization behavior to surface instability under concurrent surface kinetics and to a shadow effect that causes the self-alignment of dots. The fundamental mechanism may be applicable to diverse systems suggesting an effective approach for nanofabrication. Introduction Self-organized nanostructures have wide applications from functional materials to advanced electronic and optical devices 1 2 . Recent experiments demonstrated ion beam sputtering as a promising approach to generate various self-organized nanostructure patterns over a large area 3-8 . In this process surface materials on the target are sputtered away by incoming ions and the interplay between sputter-induced roughening and surface smoothening produces patterns such as ripples and dots. The feature size and morphology of these patterns are affected by parameters such as the incident ion beam flux the beam energy and the material of the substrate. Among them the incident angle of the ion beam is an important factor to select the formation of different patterns. Normal bombardment produces hexagonally ordered dots 7 while off-normal bombardment produces ripples 4 . However by rotating a sample simultaneously during off-normal sputtering ordered dots can be obtained 3 . It was generally believed that sample rotation is necessary during off-normal bombardment to produce isotropic sputtering so that a pattern of dots can form. Recently

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