TBA-enabled spin-coating of a percolatively connected GO nanosieve for thru-hole epitaxy: tuning GO flake stacking and coverage to control GaN nucleation

TL;DR

This paper introduces a spin-coating method with TBA to create a uniform GO nanosieve on sapphire, enabling precise control of GaN nucleation and epitaxy through engineered coverage and stacking of 2D materials.

Contribution

The study demonstrates a scalable, lithography-free technique to tune GaN nucleation by controlling GO flake stacking and coverage with TBA, advancing 2D material masks for epitaxy.

Findings

TBA improves GO coverage uniformity and modulates GaN nucleation.

Three distinct GaN nucleation behaviors are achieved by controlling GO coverage.

TBA addition suppresses undesired nucleation modes and enhances thru-hole epitaxy regions.

Abstract

We report a spin-coating-based approach for forming a percolatively connected graphene oxide (GO) nanosieve on SiO$_2$-patterned sapphire substrates, where the addition of tetrabutylammonium (TBA) to the GO solution significantly improves the uniformity of flake coverage and modulates GaN nucleation behavior. Upon thermal annealing of GO, the resulting reduced graphene oxide (rGO) films exhibit spatially varying coverage, leading to three distinct GaN nucleation outcomes: (i) ELOG-like nucleation on exposed substrate regions, (ii) thru-hole epitaxy (THE)-like nucleation through appropriately thin areas, and (iii) complete nucleation suppression on thickly stacked zones. On spin-coated GO films without TBA, all three behaviors coexist, and undesired ELOG- and no-nucleation modes persist due to uneven coverage. Importantly, these issues cannot be resolved by simply adjusting GO flake concentration, as concentration tuning alone fails to eliminate the formation of locally bare and overly thick regions. In contrast, the addition of TBA results in a more uniform, moderately stacked rGO morphology that suppresses both ELOG- and no-nucleation modes while expanding THE-like nucleation regions. This reshaped nucleation landscape confines GaN growth to areas with engineered percolative transport. The approach offers a scalable, lithography-free route for controlling GaN epitaxy using solution-processable 2D material masks.