An Effective Charge Neutralization Enabled by Graphene Overlayer in Ambient Pressure XPS Measurements of Insulators

Chueh Cheng Yang, Meng Hsuan Tsai, Zong Ren Yang, Yaw Wen Yang*, Yuan Chieh Tseng*, Chia Hsin Wang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Ambient pressure XPS is a powerful technique capable of performing measurements with samples kept at mbar pressure. The filled gas, also X-ray ionized, provides electrons to neutralize positive charges built up on insulating samples. However, this convenient neutralization scheme does not solve the charging problem completely. In this study, the effectiveness of how the electrons generated from conducting mechanical parts mounted in the immediate front of insulating samples neutralize positive charges on the samples during XPS measurements is tested. The mechanical parts range from fine gold mesh, holey carbon film to graphene monolayer, and measured insulating samples are polished sapphire and rough pellets of CaCO3 powder. All these mechanical add-ons reduce the charging to different degrees at the expense of sample signal. Amazingly, the graphene monolayer is found to effect perfect charge neutralization for both smooth sapphire and rough CaCO3 pellet, evidenced by realistic spectral profile and binding energy values. The finding that an untreated CaCO3 pellet is often terminated with Ca(OH)(HCO3) is consistent with earlier reports. It is speculated that a likely conformal covering with graphene on the sample with rough morphology holds the key to its superb performance in charge compensation.

Original languageEnglish
Article number2201926
JournalAdvanced Materials Interfaces
Volume10
Issue number4
DOIs
StatePublished - 3 Feb 2023

Keywords

  • ambient-pressure XPS
  • calcium carbonate
  • charge compensation
  • graphene
  • insulator materials
  • sapphire

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