Integrated Wafer Scale Growth of Single Crystal Metal Films and High Quality Graphene.

Oliver J Burton,Fabien C-P Massabuau,Andrew J Pollard,Vlad-Petru Veigang-Radulescu,Barry Brennan,Stephan Hofmann

doi:10.1021/acsnano.0c05685

Abstract

We report on an approach to bring together single crystal metal catalyst preparation and graphene growth in a combined process flow using a standard cold-wall chemical vapor deposition (CVD) reactor. We employ a sandwich arrangement between a commercial polycrystalline Cu foil and c-plane sapphire wafer and show that close-spaced vacuum sublimation across the confined gap can result in an epitaxial, single-crystal Cu(111) film at high growth rate. The arrangement is scalable (we demonstrate 2″ wafer scale) and suppresses reactor contamination with Cu. While starting with an impure Cu foil, the freshly prepared Cu film is of high purity as measured by time-of-flight secondary ion mass spectrometry. We seamlessly connect the initial metallization with subsequent graphene growth via the introduction of hydrogen and gaseous carbon precursors, thereby eliminating contamination due to substrate transfer and common lengthy catalyst pretreatments. We show that the sandwich approach also enables for a Cu surface with nanometer scale roughness during graphene growth and thus results in high quality graphene similar to previously demonstrated Cu enclosure approaches. We systematically explore the parameter space and discuss the opportunities, including subsequent dry transfer, generality, and versatility of our approach particularly regarding the cost-efficient preparation of different single crystal film orientations and expansion to other material systems.

Highlights

We report on an approach to bring together single crystal metal catalyst preparation and graphene growth in a combined process flow using a standard cold-wall chemical vapor deposition (CVD) reactor
The critical process times, tdep and tgrowth, are ≤60 min, giving a total process time from input of sapphire to retrieval of graphene on single crystal Cu of less than 3.5 h. This reflects our motivation for efficient high-throughput processing, with time scales that already proved economic for current commercial graphene CVD based on poly crystalline Cu foils
We have demonstrated the wafer scale production of single crystal Cu(111) on c-plane sapphire using a close-spaced sublimation (CSS)-type deposition, allowing for versatile, fast, and high quality film deposition inside commercially available CVD equipment used for 2D materials

Summary

Introduction

We report on an approach to bring together single crystal metal catalyst preparation and graphene growth in a combined process flow using a standard cold-wall chemical vapor deposition (CVD) reactor. The arrangement is scalable (we demonstrate 2′′ wafer scale) and suppresses reactor contamination with Cu. While starting with an impure Cu foil, the freshly prepared Cu film is of high purity as measured by time-of-flight secondary ion mass spectrometry. The CSS-like metallization shows innate advantages similar to prior literature on CSS of polycrystalline CdTe thin films, namely, simplicity, low source material wastage, and fast deposition rates.[29−31] We systematically explore the parameter space of our integrated CVD process and discuss the opportunities, including subsequent dry transfer, and the generality of our approach

Methods

Results

Conclusion