Making Sense of Complex Carbon and Metal/Carbon Systems by Secondary Electron Hyperspectral Imaging.

Ivo Konvalina,Zuzana Pokorna,Cornelia Rodenburg,Maurizio Dapor,Martina Azzolini,Filip Mika,Kerry J Abrams,Antje Quade,Danielle Mehta,Stanislav Kratky,Nicola Stehling,Jan Schäfer,Kate Black,Stephan J Kyle

doi:10.1002/advs.201900719

Abstract

Carbon and carbon/metal systems with a multitude of functionalities are ubiquitous in new technologies but understanding on the nanoscale remains elusive due to their affinity for interaction with their environment and limitations in available characterization techniques. This paper introduces a spectroscopic technique and demonstrates its capacity to reveal chemical variations of carbon. The effectiveness of this approach is validated experimentally through spatially averaging spectroscopic techniques and using Monte Carlo modeling. Characteristic spectra shapes and peak positions for varying contributions of sp2‐like or sp3‐like bond types and amorphous hydrogenated carbon are reported under circumstances which might be observed on highly oriented pyrolytic graphite (HOPG) surfaces as a result of air or electron beam exposure. The spectral features identified above are then used to identify the different forms of carbon present within the metallic films deposited from reactive organometallic inks. While spectra for metals is obtained in dedicated surface science instrumentation, the complex relations between carbon and metal species is only revealed by secondary electron (SE) spectroscopy and SE hyperspectral imaging obtained in a state‐of‐the‐art scanning electron microscope (SEM). This work reveals the inhomogeneous incorporation of carbon on the nanoscale but also uncovers a link between local orientation of metallic components and carbon form.

Highlights

Films and nanomaterials made of complex carbon systems are key to many next-generation technologies[1,2,3] and scientists are keen to exploit their functionalities, for example in batteries and electrode surfaces.[4,5,6] Their versatility originates from the strong dependence of their physical properties on the ratio of sp2-graphite like bonds to sp3-diamondlike bonds.[7]
This white contrast is dynamic and differs from the appearance of the typical contamination seen in electron beam ion deposition (EBID)
Secondary electron hyperspectral imaging (SEHI) analysis of highly oriented pyrolytic graphite (HOPG) surfaces in LV-scanning electron microscope (SEM) revealed a two stage process in surface modification of HOPG through hydrogenation and charge induced deposition of amorphous carbon species (Secondary). This insight into carbonaceous film formation on carbon has elucidated on different carbon bond types and is reflected in the changing shape of secondary electron (SE) spectra which are confirmed by Monte Carlo (MC) modeling

Summary

Introduction

Films and nanomaterials made of complex carbon systems are key to many next-generation technologies[1,2,3] and scientists are keen to exploit their functionalities, for example in batteries and electrode surfaces.[4,5,6] Their versatility originates from the strong dependence of their physical properties on the ratio of sp2-graphite like bonds to sp3-diamondlike bonds.[7]. During the fabrication of carbon film based devices, electron irradiation is prevalently used for nanopatterning, nanostructure characterization and surface modification.[8] Compositional changes on the nanoscale on carbon surfaces are often difficult to elucidate, as available techniques can modify the surface of interest. Knowledge of these surfaces and their interaction

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Results

Conclusion