Fabrication of ordered nanostructures on the Ge surface using electron-beam lithography and ion beam irradiation

Abstract

Ordered nanostructure fabrication was performed via a two-step process using electron-beam lithography and ion beam irradiation. In the first process, a well-focused electron-beam was used to fabricate ordered holes on an electron-beam resist-coated Ge wafer. In the second process, an ion beam was used to irradiate the entire surface to promote nanostructure growth through the migration of ion beam-induced interstitial atoms. The formation of nanostructures with a 26 nm thickness, 59 nm height, and an aspect ratio of 2.2 was achieved in 60 nm diameter holes with equal center-center distances. High aspect ratio nanostructures were formed via limited migration of interstitial atoms on the walls. An estimated 1.1% point defect was obtained by changing the volume of the nanostructures after irradiation, which contributed to the growth of the structures.

Omnidirectional and broadband photon harvesting in self-organized Ge columnar nanovoids

“…Therefore, this effect can create a nanostructured porous surface that have the potential to drastically enhance photon absorption exploiting the motheye index grading effect. The process would be highly reproducible without any loss of material, no ambient contamination, exploiting a CMOS compatible process like ion implantation [43][44][45][46][47][48]. The thickness of the fabricated porous layer increases with the ion fluence and in the second instance with ion energy.…”