Temperature range for fiber-form nanostructure growth on molybdenum surfaces due to helium plasma irradiation

Nanostructure formation on molybdenum surfaces due to helium plasma exposure is investigated, with a focus on determining the temperature band for the growth of fiber-form nanostructures. Precise temperature measurements can be obtained using thin thermocouples inserted into sheet specimens. The temperature range for nanostructure growth was determined to be 800 ∼ 1050 K under incident helium ion energies of 50 ∼ 100 eV and an ion flux of 2×10²¹ m^-2 ·s^-1. Surface morphologies near the upper and lower boundary temperatures differ from those of a standard fiber-form nanostructure. In a standard case, nano-fibers of molybdenum were found to have diameters of approximately 50 nm, whereas those of tungsten are half of the molybdenum fibers. (author)