Lateral Templating for Guided Self‐Organization of Sputter Morphologies

Abstract

Methods for the fabrication of large areas of nanoscale features with controlled period and intraperiod organization are of interest because of the potential for high-throughput mass production of nanoscale devices. Due to their potential in this regard, much recent attention has been devoted to self-organization processes, [1][2][3][4][5] in which processing causes the spontaneous emergence of a nanoscale pattern. The short-range order can be quite high [2][3][4] but some envisaged applications require long-range order, which is destroyed by uncontrolled topological defects arising spontaneously from the self-organization process. A potentially successful hierarchical fabrication strategy is the fabrication of controlled features at a small, but lithographically tractable, length scale by methods such as conventional mask or optical-standing-wave lithography, in order to guide a self-organization process at the finest length scale. [6][7][8] Topographic patterning has been used for templating the local disorder in two-dimensional (2D) self-assembled monolayers [9] and for templating defect organization or elimination in three-dimensional (3D) colloidal crystallization.[10] Topography has also been used to manipulate semiconductor quantum-dot placement, composition, and strain, through its effect on stress, [11] surface energy, and mobility.[12]3D short-range ordering of grown-in quantum-dot short-period superlattices can result from multilayer growth; [1,4] nanoscale topographic templating of the first layer could dramatically accelerate the development of order and lead to true long-range order. Lithographically and focused ion beam (FIB)-patterned topographies have recently been used to template quantum-dot growth in linear chains, [8] periodic 2D lattices, [7] and in more complex configurations that are promising for novel nanoelectronic architectures, such as quantum cellular automata.[13] The finest features have been templated by serial writing with a FIB, a prohibitively expensive process for mass production that might be circumvented by using a hierarchical fabrication strategy. Here we report the influence of patterned boundaries on the primary material of complementary metal oxide semiconductor (CMOS) technology, i.e., a Si(001) substrate, in guiding self-organized topographic ripples spontaneously appearing during uniform irradiation with low energy Ar + ions. We show that the long-range order of the features can be greatly enhanced by this lateral-templating approach. The emerging pattern can be manipulated by changing the boundary spacing and misorientation with respect to the projected ion-beam direction. We develop a scalar figure of merit, a dimensionless topological defect density, to characterize the degree of order of the pattern. At small boundary separation, greatest order is observed when the separation is near an integer multiple of the spontaneously arising feature size. The defect density is exceedingly low up to a critical misorientation angle, beyond which topological defects develop i...

Multiple Bifurcation Types and the Linear Dynamics of Ion Sputtered Surfaces

“…Periodic self-organized patterns with wavelength as small as 7 nm [2] have stimulated interest in this method as a means of sublithographic nanofabrication [3]. The classical linear stability theory of Bradley and Harper (BH) [4] attributes the pattern to a competition between a destabilizing (roughening) effect in which the erosion rate is enhanced at regions of high concave curvature and the stabilizing (smoothening) effect of surface diffusion.…”

Creating sharp features by colliding shocks on uniformly irradiated surfaces

“…This erodes a surface at different rates depending on the slope of the surface, so intricate two-dimensional structures can emerge. Currently, focused ion beam bombardment is used to micromachine tall, steep features 5,6 , and to sculpt nanopore single-biomolecule detectors 7,8 , while uniform ion bombardment of a flat surface is used to create semiconductor quantum dots from the linear instabilities that are excited [9][10][11] . The utility of these techniques is, however, limited.…”

Molecular dynamics of single-particle impacts predicts phase diagrams for large scale pattern formation

“…On the one hand, observations of periodic patterns including highaspect ratio quantum dots 3 , with occasional long-range order 4 and characteristic spacing, as small as 7 nm (ref. 5), have stimulated interest in self-organized pattern formation as a means of sub-lithographic nanofabrication 6 . On the other hand, extended exposure to energetic particle irradiation can lead to the structural degradation of fission and fusion reactor components 7,8 .…”