EXOELECTRON EMISSION FROM UNEXCITED METALLIC GLASSES FE40NI38MO4B18 DURING HEAT-TREATMENT

In order to elucidate a mechanism for exoelectron emission from metall ic glasses during heat treatment, metallic glasses Fe40Ni38Mo4B18, whi ch have a 140 K lower crystallization temperature than the metallic gl asses Fe78B13Si9 reported previously, were heated up to 723 K with a c onstant heating rate of 0.5 K/s under ultrahigh vacuum condition. Alth ough specimens were not excited by ionizing radiations, mechanical tre atment, or chemical processes prior to measurements, exoelectrons have been detected for the first heating cycle. However, in the subsequent heating cycles, the counting rate does not exceed the background leve l. These results agree well with our previous report about metallic gl asses Fe78B13Si9, but it is recently found that from the present glass es exoelectrons are emitted from the lower temperature region, and the total number of emitted exoelectrons is larger than that from the pre vious glasses. An atomic force microscopy (AFM) study reveals many cry stallites formed on the surface of the heated specimen, and the spatia l density of crystallites on the surface is much higher than that of p revious glasses. Both results of exoelectron measurements and AFM obse rvations show that the number of emitted exoelectrons increases with i ncreasing the number of crystallites on the surface. This result impli es that exoelectrons are emitted associated with the crystallites form ation process on the surface.