Cleaning Procedures of Molybdenum (110) Surface

An atomically clean surface of molybdenum (110) has been produced by the successive treatments of chemical reaction and high temperature heating. Carbon contamination is removed from the surface by heating the crystal to 14001500°C in 10-610-7 Torr of oxygen. The crystal is then cleaned by flashing to the same temperature in ultrahigh vacuum. The high-temperature heating for a long time for removal of oxide causes segregation of carbon to the surface. Therefore, it is necessary to heat the crystal to a high temperature in 10-4Torr of hydrogen in order to remove all adsorbed oxygen. The surface obtained is observed by LEED and Auger electron spectroscopy (AES) at a pressure of 10-10 Torr. After the cleaning procedures mentioned above, the LEED pattern expected from the bulk structure is obtained and the Auger peak heights of carbon and oxygen are extremely reduced. The LEED pattern expected from the bulk structure is also observed on the surface with small amounts of carbon and oxygen, that is, the surface which is not atomically clean. The results reported here show that the observation of the surface by LEED is unreliable as characterization of atomically clean surface of molybdenum, but AES with LEED observation seems to be much reliable technique for the purpose.