Preparation of stepped tungsten single crystal surfaces

Abstract

Tungsten single crystal surfaces orientated at a small angle with respect to a low‐indexed plane can show a terraced structure characterized by flat terraces of the low‐indexed plane with monatomic steps at equal distances. Stepped surfaces can play an essential role in surface processes (adsorption, catalysis). A method is described how stepped tungsten single crystal surfaces can be prepared with an accuracy of better than 15′ in orientation, an overall flatness of better than 1/10 of a wavelength of the Na‐D line, a surface roughness of smaller than 0.05 μm, and without destruction detectable by LEED.

Surface terraces in pure tungsten formed by high temperature oxidation

“…The orientation of the facets tends to be the nearest low-index plane. Therefore, to obtain multi-atomic steps, a well-controlled initial surface orientation is required with little angular deviation from the desired terrace orientation [9,11]. Surprisingly, after heat treatment of polycrystalline tungsten at 1500 °C in a vacuum furnace at pressures of an order of 10 -5 mbar, we observed the emergence of large surface terraces.…”

“…In addition, as a prototypical bcc material, tungsten has been extensively used to study surface morphology and evolution [8][9][10][11]. In particular, surface terraces and steps are widely investigated since surface defects like steps, ledges, kinks, vacancies and individual adatoms are strong adsorption sites [9,12].…”

“…In addition, as a prototypical bcc material, tungsten has been extensively used to study surface morphology and evolution [8][9][10][11]. In particular, surface terraces and steps are widely investigated since surface defects like steps, ledges, kinks, vacancies and individual adatoms are strong adsorption sites [9,12]. Clean and atomically smooth terraces aligned to a perfect crystal orientation can be readily prepared on the surface of tungsten by high temperature annealing (1500 °C) under ultrahigh vacuum conditions (1.3×10 −10 mbar) [9,11].…”

“…In particular, surface terraces and steps are widely investigated since surface defects like steps, ledges, kinks, vacancies and individual adatoms are strong adsorption sites [9,12]. Clean and atomically smooth terraces aligned to a perfect crystal orientation can be readily prepared on the surface of tungsten by high temperature annealing (1500 °C) under ultrahigh vacuum conditions (1.3×10 −10 mbar) [9,11]. The steps separating these terraces are normally one atomic layer high, and as such termed mono-atomic steps.…”