Surface preparation and patterning by nano imprint lithography for the selective area growth of GaAs nanowires on Si(111)

TL;DR

This study improves the vertical yield of GaAs nanowires on Si(111) by surface treatments and advanced patterning techniques, enabling high-quality growth with scalable methods like nano imprint lithography.

Contribution

It demonstrates that substrate surface preparation and a novel NIL-IPT process significantly enhance nanowire growth and patterning scalability.

Findings

Boiling in ultrapure water increases NW vertical yield to 80%.

NIL-IPT achieves sub-50 nm holes with growth quality comparable to EBL.

Surface roughness reduction correlates with improved NW growth.

Abstract

The selective area growth of Ga-assisted GaAs nanowires (NWs) with a high vertical yield on Si(111) substrates is still challenging. Here, we explore different surface preparations and their impact on NW growth by molecular beam epitaxy. We show that boiling the substrate in ultrapure water leads to a significant improvement in the vertical yield of NWs (realizing 80%) grown on substrates patterned by electron-beam lithography (EBL). Tentatively, we attribute this improvement to a reduction in atomic roughness of the substrate in the mask opening. On this basis, we transfer our growth results to substrates processed by a technique that enables the efficient patterning of large arrays, nano imprint lithography (NIL). In order to obtain hole sizes below 50 nm, we combine the conventional NIL process with an indirect pattern transfer (NIL-IPT) technique. Thereby, we achieve smaller hole sizes than previously reported for conventional NIL and growth results that are comparable to those achieved on EBL patterned substrates.