In-beam growth and rearrangement of nanoparticles in insulators induced byhigh-current negative copper ions

In fabricating metal nanoparticles in insulators, high-current negative ion s have been shown to cause efficient and spontaneous growth of nanospheres. The in-beam growth is inevitably subjected to rearrangement of implanted a toms, departing from initially deposited positions. For high-current techni ques for insulators, we discuss important experimental factors and explore possible mechanisms of the in-beam growth and atomic rearrangement of nanop articles, Experimental data of interest are for negative Cu ion implantatio n at 60 keV into insulators, amorphous(a-), crystalline (c-) SiO2 and a spi nel oxide, MgAl2O4. Dose rates ranged up to 260 mu A/cm(2), with a total do se of 3.0 x 10(16) ions/cm(2). Nanoparticle morphology and surface morpholo gy by AFM were significantly dependent not only on dose rate but also on th e boundary conditions. With increasing close ratel the in-beam growth of na noparticles became pronounced and the atomic profile shifted toward the sur face. Since beam heating, especially in vacuum, is of concern, thermal anal ysis was carried out with a one-dimensional simulation code. Candidate mech anisms are depth-oriented gradients of deposited nuclear/electronic energy, chemical/elastic potentials and thermal effects. The relevant mechanisms a re explored among these candidates. (C) 2000 Elsevier Science Ltd, All righ ts reserved.