60keV Ar+-ion induced pattern formation on Si surface: Roles of sputter erosion and atomic redistribution (original) (raw)
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Nano- and micro-scale patterning of Si (100) under keV ion irradiation
Applied Surface Science, 2007
Evolution of Si (1 0 0) surface under 100 keVAr + ion irradiation at oblique incidence has been studied. The dynamics of surface erosion by ion beam is investigated using detailed analysis of atomic force microscopy (AFM) measurements. During an early stage of sputtering, formation of almost uniformly distributed nano-dots occurs on Si surface. However, the late stage morphology is characterized by self-organization of surface into a regular ripple pattern. Existing theories of ripple formation have been invoked to provide an insight into surface rippling. #
The evolution of a ripple pattern on Si(100) surfaces induced by 60 keV Ar + beam incident at 60°with the surface normal has been studied as a function of bombardment time using ex situ atomic force microscopy (AFM) in ambient condition. The ripple wavelength ͑l͒ and roughness amplitude ͑W͒ increase with bombardment time following a scaling law l ϰ t ␥ and W ϰ t  , where ␥ = 0.64± 0.08 to a crossover value 0.22± 0.07 and  = 0.76± 0.03 to a crossover at 0.27± 0.11. The ripple orientation and average wavelength observed in the early stage patterned morphology can be described by a linear continuum model. However, the scaling exponents for the power law variation of roughness amplitude and wavelength with bombardment time are not consistent with predictions of the linear model or the Kuramoto-Sivashinsky-equation-based nonlinear model.
Morphology change of the silicon surface induced by Ar$^+$ ion beam sputtering
2011
Two-level modeling for nanoscale pattern formation on silicon target by Ar$^+$ ion sputtering is presented. Phase diagram illustrating possible nanosize surface patterns is discussed. Scaling characteristics for the structure wavelength dependence versus incoming ion energy are defined. Growth and roughness exponents in different domains of the phase diagram are obtained.
Study of 1.5 keV Ar atoms beam induced ripple formation on Si surface by atomic force microscopy
Nuclear Instruments and …, 2006
The topography of Si(1 0 0) and Si(1 1 1) surfaces after irradiation with 1.5 keV Ar atoms beam incident at 45°with respect to the surface normal has been studied as a function of atom fluence using atomic force microscopy. The sputtered silicon (1 0 0) samples exhibit ripple pattern, with the average value of the ripple wavelength increasing from 15 nm to 19 nm as fluence increases from 1.7 · 10 17 atoms/ cm 2 to 5.1 · 10 17 atoms/cm 2 , though the height of ripples remains same i.e. 1.02 nm. On the other hand, in case of Si(1 1 1) samples, the average value of the ripple wavelength increases from 22 nm to 40 nm with fluence increasing from 1.7 · 10 17 atoms/cm 2 to 5.1 · 10 17 atoms/cm 2 . A close view of the surface morphologies of Si(1 0 0) and showed that the ripples on Si(1 1 1) surface are, more regular than Si(1 0 0). When the fluence is further increased, it is found that the wavelength of ripple tends to saturate and the height tends to decrease, as a result the surface becomes smooth at higher ($6.8 · 10 17 atoms/cm 2 ) fluence.
Unusual pattern formation on Si(100) due to low energy ion bombardment
Applied Surface Science, 2012
In this paper evolution of silicon surface topography, under low energy ion bombardment, is investigated at higher oblique incident angles in the range of 63⁰-83⁰. Si(100) substrates were exposed to 500 eV argon ions. Different surface morphology evolves with increasing angle of incidence. Parallel-mode ripples are observed up to 67⁰ which undergo a transition to perpendicular-mode ripples at 80⁰. However, this transition is not a sharp one but undergoes a series of unusual pattern formation at intermediate angles. Complete smoothening of silicon surface is observed at incident angles beyond 80⁰. The observed patterns are attributed to surface confined viscous flow and sputter erosion under ion bombardment.
2003
Using cross-section transmission electron microscopy ͑XTEM͒ we have studied the surface and subsurface structure of individual ripples having submicron scale wavelength and nanometer scale amplitude, generated by obliquely incident ͑50-120 keV͒ Ar ion bombardment of Si. The XTEM results reveal that the front slopes of ion-induced ripples have amorphous layers containing bubbles with sizes ranging from about 3 to 15 nm facing the ion beam direction. A thinner amorphous layer without bubbles, on the other hand, persists on the rear slope of ripples. We also observe an irregular interface between a-Si and c-Si, which is due to the direct impact amorphization mechanism prevalent near the end-of-range during heavy ion irradiation.
Morphology change of teh silicon surface by Ar+ ion beam sputtering
Two-level modeling for nanoscale pattern formation on silicon target by Ar + ion sputtering is presented. Phase diagram illustrating possible nanosize surface patterns is discussed. Scaling characteristics for the structure wavelength dependence versus incoming ion energy are defined. Growth and roughness exponents in different domains of the phase diagram are obtained.
Formation of ripple pattern on silicon surface by grazing incidence ion beam sputtering
2009
Off-normal low energy ion beam sputtering of solid surfaces often leads to morphological instabilities resulting in the spontaneous formation of ripple structures in nanometer length scales. In the case of Si surfaces at ambient temperature, ripple formation is found to take place normally at lower incident angles with the wave vector parallel to the ion beam direction. The absence of ripple pattern on Si surface at larger angles is due to the dominance of ion beam polishing effect. We have shown that a gentle chemical roughening of the starting surface morphology can initiate ripple pattern under grazing incidence ion beam sputtering, where the ripple wave vector is perpendicular to the ion beam direction. The characteristics of the perpendicular mode ripples are studied as a function of pristine surface roughness and ion fluence. The quality of the morphological structure is assessed from the analysis of ion induced topological defects.
Nanotechnology, 2002
We report on the production of nanoscale patterning on Si substrates by low-energy ion-beam sputtering. The surface morphology and structure of the irradiated surface were studied by atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM). Under ion irradiation at off-normal incidence angle (∼50 • ), AFM images show the formation of both nanoripple and sawtooth-like structures for sputtering times longer than 20 min. The latter feature coarsens appreciably after 60 min of sputtering, inducing a large increase in the surface roughness. This behaviour is attributed to the preferential direction determined on the substrate by the ion beam for this incidence angle, leading to shadowing effects among surface features in the sputtering process. Under irradiation at normal incidence, the formation of an hexagonal array of nanodots is induced for irradiation times longer than 2 min. The shape and crystallinity of the nanodots were determined by HRTEM. At this incidence angle, the surface roughness is very low and remains largely unchanged even after 16 h of sputtering. For the two angle conditions studied, the formation of the corresponding surface structures can be understood as the interplay between an instability due to the sputtering yield dependence on the local surface curvature and surface smoothing processes such as surface diffusion.