(011̄0) α-quartz surface: a LEED, XANES and ELS study

• Published in: Surface science 1992-08, Vol.274 (3), p.317-328
• Main Authors: Bart, F., Gautier, M., Duraud, J.P., Henriot, M.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Solid surfaces and solid-solid interfaces; Surface structure and topography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(92)90837-V

We studied the structure of the (011̄0) α-quartz surface after different treatments (900°C vacuum or air heating and ion bombardment). The long-range order was investigated by low-energy electron diffraction (LEED), the mean-range order by X-ray absorption spectroscopy at the oxygen K edge (XANES) and the electronic structure of the surface band gap by low-energy electron loss spectroscopy (ELS). The (1 × 1) structure is obtained only after a slight chemical etching in HF. A 900°C air-annealed sample exhibits a (3 × 1) or (1 × 3) LEED pattern associated with reconstructed surface regions, which structure is either related to the bulk α → β transition phase occurring at 573°C, or to a new SiO 2 phase present only at the surface (tridymite). Finally, a 900°C heating in vacuum provides a glassy surface, also containing oxygen vacancies. These three structures lead to different surface electronic properties: the reconstructed surface presents a larger surface band gap than the (1 × 1) (9.5 instead of 8.6 eV). The disordered surface shows an 8.8 eV wide surface band gap, containing two electronic levels associated with surface oxygen vacancies.