Compact plasma source for removal of hydrocarbons for surface analysis

A low-energy, constricted-a node Anders-type plasma source was built and tested for the chemical removal of adventitious carbon on surfaces. Oxygen plasma, generated in the source, extends to the sample surface through an aperture in the anode. This plasma reacts with surface hydrocarbons and removes them in less than a minute without influencing the intrinsic surface stoichiometry of nonoxidizing samples such as minerals, glasses, and metal oxides. Adventitious carbon removal is critical for accurate binding energy determination and quantitative measurements in XPS and AES, particularly in multicomponent materials. We measure the plasma to be composed primarily of O(+) and O(2)(+), with minor H(+), H(2)(+), and O(++) components. Ion energy distributions were measured for O(+) and O(++) and show all emitted ions have energies less than 50 eV, confirming chemical desorption as the primary removal mechanism. The plasma source, easily built 'in house', is compact and can be mounted on a 2.75-in flange for in situ specimen cleaning prior to surface analysis. Copyright (c) 2009 John Wiley & Sons, Ltd.