“…Interestingly, not all materials exhibit the formation of nanocones under He ion irradiation. Ti [19][20][21][22], beryllium [23], copper [24] and stainless steel [20,21] exhibited nanocones on their surfaces after irradiation, whereas tungsten (W) never exhibited cone structures formed on its surface [25][26][27][28][29]. It is suspected that the sputtering yield [30] and the shear modulus [31] of the materials may have a considerable influence on the evolution of the surface morphology, especially in cone development.…”