Probing defectivity beneath the hydrocarbon blanket in 2D hBN using TEM-EELS

TL;DR

This study demonstrates the use of TEM-EELS to analyze atomic-scale defects in 2D hBN beneath hydrocarbon contamination, enabling defect characterization despite surface contamination and allowing systematic studies of defect engineering effects.

Contribution

The paper introduces a TEM-EELS based method to probe beneath hydrocarbon layers in 2D hBN, revealing defect structures and effects of ion irradiation treatments.

Findings

Spectral signatures indicate boron-oxygen bonding related to defectiveness.

Technique allows assessment of contamination and structural integrity.

Different ion doses produce distinguishable defect signatures.

Abstract

The controlled creation and manipulation of defects in 2D materials has become increasingly popular as a means to design and tune new material functionalities. However, defect characterization by direct atomic imaging is often severely limited by surface contamination due to a blanket of hydrocarbons. Thus, analysis techniques are needed that can characterize atomic scale defects despite the contamination. In this work we use electron energy loss spectroscopy to probe beneath the hydrocarbon blanket, characterizing defect structures in 2D hexagonal boron nitride (hBN) based on fine structure in the boron K-edge. Since this technique is performed in a transmission electron microscope, imaging can also be used to assess contamination levels and other factors such as tears in the fragile 2D sheets, which can affect the spectroscopic analysis. Furthermore, by locally probing individual areas, multiple regions on the same specimen that have undergone different defect engineering treatments can be investigated for systematic studies at increased throughput. For 2D hBN samples irradiated with different ions for a range doses, we find spectral signatures indicative of boron-oxygen bonding that can be used as a measure of sample defectiveness depending on the ion beam treatment.