Abstract
Reliable fabrication of multiscale metallic patterns with precise geometry and size at both the nanoscale and macroscale is of importance for various applications in electronic and optical devices. The existing fabrication processes, which usually involve film deposition in combination with electron-beam patterning, are either time-consuming or offer limited precision. Inspired by the kirigami, an ancient handicraft art of paper cutting, this work demonstrates an electron-beam patterning process for multiscale metallic structures with significantly enhanced efficiency and precision. Similar to the kirigami, in which the final pattern is defined by cutting its contour in a paper and then removing the unwanted parts, we define the target multiscale structures by first creating nanotrench contours in a metallic film via an electron-beam-based process and then selectively peeling the separated film outside the contours. Compared with the conventional approach, which requires the exposure of the whole pattern, much less exposure area is needed for nanotrench contours, thus enabling reduced exposure time and enhanced geometric precision due to the mitigated proximity effect. A theoretical model based on interface mechanics allows a clear understanding of the nanotrench-assisted selective debonding behaviour in the peeling process. By using this fabrication process, multiscale metallic structures with sub-10-nm up to submillimetre features can be reliably achieved, having potential applications for anti-counterfeiting and gap-plasmon-enhanced spectroscopy.
Highlights
Multiscale structures including both macroscale and nanoscale features are essential for various applications in nanoelectronic and nano-optical devices[1,2,3,4]
Theoretical calculations indicate that the electric field enhancement factor could be as high as 3 × 103 when the radius of curvature is decreased to 5 nm[22]
The approach is realized by selectively stripping an unwanted metallic film using predefined nanotrenches as the templates without involving any pattern transfer and resist removal steps
Summary
Multiscale structures including both macroscale and nanoscale features are essential for various applications in nanoelectronic and nano-optical devices[1,2,3,4]. The nanoscale features are usually used, based on the size effect, to improve the device performance or to interact more precisely with smaller objects such as molecules[5,6,7], while the macroscale features are used to exchange electrical, optical or mechanical signals with the macroscopic world[8,9]. 10-nm-scale features with 1-nm-scale precision are required to obtain satisfactory performance[26] These high-resolution and precision requirements inevitably involve focused electron-beam processes, namely, electron-beam lithography (EBL)[27,28]. While EBL processes have shown the flexibility and capability to fabricate structures down to 5 nm, they are intrinsically not ideal tools for fabricating multiscale structures[29]
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