On the possibility of using low-energy electron stimulated desorption of ions as a surface probe: Analysis of Au substrates

• Low-energy electron stimulated desorption (ESD) has been used for surface analysis.
• The efficiency of two methods of Au cleaning has been characterized by ESD.
• The masses of residual contaminants were determined.
• UV/O3 cleaning technique seems to be more efficient than the H2SO4 procedure.
• ESD can be considered as a highly sensitive surface analysis technique.

We explore the possibility of using low-energy (0–50 eV) electron stimulated desorption (ESD) of ions, analyzed by time-of-flight (TOF) mass spectrometry, as a surface analysis technique. As a first step, we measure the mass spectra from ions emanating from gold substrates prepared for molecular self-assembly by two different methods: cleaning with sulfochromic acid (CrO3/H2SO4) and exposure to UV/O3. Modifications of the yields of desorbed anions and cations as functions of incident electron energy provide information on the presence and the chemical nature of contaminants present on the Au surface, either before or after cleaning. Upon cleaning, the decrease in intensity of the yield functions of certain desorbed anions and cations associated with organic molecules confirms that both techniques are efficient in removing organic contaminants. On the other hand, other ESD signals increase or only appear by either cleaning procedure. This finding demonstrates how these cleaning techniques can contaminate Au surfaces with species, such as acid residues and nitrogenized organic molecules. Such observations have never been reported before with other methods of surface analysis. The present results strongly suggest that ESD of ions should be considered as a potential sensitive tool to complement surface analysis by other well-established methods.

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