Improved efficiency of the sputtering technique for pyrite surface and its effect on reduction of electron beam damage

Abstract

A quick and highly efficient method is described for the preparation of clean and well-characterised (100) pyrite surfaces on natural crystals based on a sputter/annealing procedure in an ultra-high vacuum (UHV) chamber. The improvement has been achieved by controlling the ingress of the key contaminants water and oxygen and restricting the annealing temperature to 560 K, which is below the SO 2 dissociation temperature. Low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS) data were used to study the surface. As well as improving the efficiency of the sputtering technique for this surface, a further major benefit is its high stability against electron beam damage as investigated by a quantitative LEED study.

Spectroscopic study of cystine adsorption on pyrite surface: From vacuum to solution conditions

“…After cleaning the surface of a pyrite sample [20], the measured Fe and S binding energies were determined to agree with those expected for a clean pyrite surface. We then studied the adsorption of L-cystine under ultra-high-vacuum conditions, mimicking anoxic conditions; in other words, oxygen and carbon were eliminated to prevent any contamination of the pyrite(100) surface.…”

Nitrogen adsorption and desorption at iron pyrite FeS2{100} surfaces

“…After insertion into UHV, the sample was cleaned by He + ion sputtering at nominally 200 eV (the kinetic energy was reduced from the normal 500 eV value by applying a positive voltage bias to the sample, as described in detail below) for typically 15 min and then annealing to 600 K for 10 min. 15,16 Two or three such treatments were sufficient to obtain an Auger electron spectrum free of contaminants. However, a prolonged anneal (typically 2 hours) at 600 K was necessary to obtain a sharp (1 Â 1) LEED pattern.…”

The challenge of generating iron-sulfur clusters

“…These observations clearly show that oxygen contaminants do not play any role for the production of clusters from pyrite. This is further supported by previous Auger electron and X-ray photoelectron spectroscopic studies of natural and sputtered pyrite (100) surfaces [29,30]. While the untreated crystal contains oxygen impurities it has been demonstrated that sputtering of the surface with He + ions with a kinetic energy of 200 eV completely removes this impurity.…”