Radiation damage in molybdenum monocrystals during ionic irradiation

Variations in grating period and microhardness were studied in molybdenum monocrystals irradiated by helium ions (50 keV) along the directions (111), (100) and (110). The grating period proved to decrease in all the cases. These variations increased at greater distances from the surface inside the radiation-damaged layer to attain maximum values at approximately 1 μm; in this case, the total depth of the radiation-damaged layer amounted to several dozen microns. Annealing at 180 deg C resulted in a greater effect of period decrease for all the three directions. Measurements of microhardness showed a considerable increase (by 30-40%) of sample hardness, which decreased with increase in depth. The presence of helium was recorded by mass spectrometry only near the sample surface. On scourino. a 1.5 μm layer, the helium liberation rate from the sample was close to that of the installation background