Combining Azimuthal and Polar Angle Resolved Shadow Mask Deposition and Nanosphere Lithography to Uncover Unique Nano-Crystals

Abstract

In this article, we present a systematic investigation on a multistep nanosphere lithography technique to uncover its potential in fabricating a wide range of two- and three-dimensional nanostructures. A tilted (polar angle) electron beam shower on a nanosphere mask results in an angled shadow mask deposition. The shape of the shadow also depends on the azimuthal angle of the mask sitting on top of the substrate. We performed angled shadow mask depositions with systematic variation of these two angular parameters, giving rise to complex nanostructures (down to 50 nm), repeated over a large area without defect. In this article, nanosphere lithography with two- and four-fold azimuthal symmetry was studied at constant tilt angles followed by variations in tilt without azimuthal rotation of the substrate. Finally, both angular parameters were simultaneously varied. The structure of shadow crystals was explained using Matlab simulation. This work stretches the horizons of nanosphere lithography, opening up new scopes in plasmonic and magnonic research.

Stretching the Horizon of Nanosphere Lithography

“…One of the recent works on NSL finds a technique to pattern bridge networks between nanostructured arrays called nano-bridged NSL (NB-NSL) [31]. Further, step-wise formation of patterns using shadow mask deposition-based NSL is developed to precisely control the shape, size, gap between features, and overall symmetry of the complex 2D and 3D nanostructures [11,32] using the azimuthal and polar angle of the shadow mask as a control parameter. As further extension of this work angular acceleration of a continuously rotating substrate has been introduced as functional control to the vertically asymmetric unique 3D structure [32].…”

“…Further, step-wise formation of patterns using shadow mask deposition-based NSL is developed to precisely control the shape, size, gap between features, and overall symmetry of the complex 2D and 3D nanostructures [11,32] using the azimuthal and polar angle of the shadow mask as a control parameter. As further extension of this work angular acceleration of a continuously rotating substrate has been introduced as functional control to the vertically asymmetric unique 3D structure [32]. Darvill et al [10] described a scheme of etching-assisted NSL for structural symmetry breaking along the thickness.…”

Controlling Vertical Asymmetry of Nanocrystals Through Anisotropic Etching‐Assisted Nanosphere Lithography

“…Nanosphere lithography (NSL) [31][32][33][34][35][36] is a popular fabrication technique which depends on the self-assembly of nanoscale features to attain the periodic nanostructures. This technique has been studied extensively since the last decade due to certain advantages like simplicity of the process, cost, and time effectiveness, and easily industrializable.…”

“…and symmetries along their surfaces, and also possess asymmetrical characteristics along their thickness (3D structures). These accomplishments have been achieved by multistep shadow mask deposition, [33,37,38] as well as by precise control of colloidal nanosphere, and substrate morphology via ion-beam-irradiationbased dry-etching techniques. [39][40][41] All the processes are carried out within meticulously engineered nanofabrication conditions.…”

“…For instance, Darvill et al [ 41 ] described the formation of nanomushroom structures by means of etching process with a temperature gradient. Ganguly et al [ 33 ] showed that the azimuthal and polar angle of the deposition shower can be varied with respect to the substrate for shadow mask deposition either in steps or even continuously at a constant (or varying) angular velocity to create structures having different 3D shapes and special symmetry.…”