FORMATION THRESHOLD AND STRUCTURAL EVOLUTION OF MOLYBDENUM NANOCRYSTALS WITH SPUTTERING PRESSURE

The evolution of the size and shape of molybdenum nanocrystals fabricated by sputtering in a thermal gradient has been studied as a function of the argon gas pressure, p. For 4 < p < 100 mTorr, continuous Mo films are deposited. At p = 150 mTorr, isolated and well-faceted Mo nanocrystals of two sizes (20 and 5 nm average size) are formed. For 200 less-than-or-equal-to p less-than-or-equal-to 400 mTorr, the particle size decreases with increasing pressure and is about 7 nm at 400 mTorr. On increasing p further, larger particles start to form and at p = 700 mTorr, particle agglomerates are observed. Possible mechanisms leading to these results are suggested.