Indium Intercalation Through Epitaxial Graphene

Undergraduate #72
Discipline: Nanoscience
Subcategory: Materials Science

Ana De La Fuente Duran - Pennsylvania State University
Co-Author(s): Natalie C. Briggs, The Pennsylvania State University, University Park, PA; Brian M. Bersch, The Pennsylvania University, University Park, PA; Dr. Joshua A Robinson, The Pennsylvania University, University Park, PA

Nitride materials/Group III-V materials, such as indium nitride (InN) have proven to be important materials in the field of electronics and have been used as vital components in light emitting diodes, ultra-high frequency transistors, and sensing technologies1. However, the synthesis and properties of low-dimensional InN have not been extensively researched. Investigating the two-dimensional (2D) form of this material could prove to be highly interesting due to the fact that the quantum confinement in a 2D layer of InN may lead to both an increased band gap and enhanced electronic properties, making it all the more valuable as a technological material2. Here we present a method to intercalate indium atoms through graphene, resulting in a layer of encapsulated indium atoms that may subsequently be exposed to ammonia-rich atmospheres at high temperatures to form InN. The investigation of the intercalation of indium metal through epitaxial graphene and the subsequent nitridation process is important in order to achieve the ultimate goal of forming 2D InN. To realize intercalation, small amounts of indium powder are placed in a quartz boat under face-down samples of epitaxial graphene (EG) and heated to 400-800°C in a tube furnace at 300 Torr, under an Argon flow of 50 sccm. The nitridation step is completed by placing an indium intercalated sample in a quartz boat and heating it to 600-800°C in a tube furnace at 300 Torr under an Argon flow of 100 sccm and an ammonia flow of 100 sccm. X-ray Photoelectron Spectroscopy (XPS) confirms the presence of indium metal in all samples, and transmission electron microscopy shows 2-5 atomic layers of indium beneath graphene layers. Post nitridation, preliminary Auger-electron spectroscopy and XPS data both suggest that nitrogen is present at the surface. Scanning Electron Microscopy (SEM) images of nitridated samples have shown differences in contrast across the sample and cracking in the graphene. Further observation of SEM images indicates that the graphene is tearing and peeling back from the sample surface. However, the aforementioned signs of graphene damage have only been observed after a sample has been nitridated, and the graphene appears to stay intact throughout the intercalation process. This clear difference in the resulting samples after exposure to ammonia may be an indication of the formation of InN beneath the graphene layers. This is supported by both XPS and Auger spectroscopy data. Future work will involve further investigating the nitridation of indium intercalated samples through cross-sectional transmission electron microscopy and the properties of the resulting materials. Citations: 1. Crawford, M. H. et al. Solid-State Lighting: Toward Smart and Ultraefficient Materials, Devices, Lamps, and Systems. Photonics Sci. Found. Technol. Appl. 3, 1–56 (2015) 2. Balushi, Z. Y. Al et al. Graphene stabilization of two-dimensional gallium nitride. arXiv Prepr. arXiv1511.01871 (2015).

Funder Acknowledgement(s): Funding for this research project was provided by Northrop Grumman and EFRI REM.

Faculty Advisor: Dr. Joshua A. Robinson, jar403@psu.edu

Role: For this project, I did the vast majority of the intercalation and nitridation runs in the tube furnace. A lot of the Scanning Electron Microscopy of the resulting indium intercalated and nitridated samples was done by me as well. I also contributed to the interpretation of data, and the development of new experimental parameters to attempt.