Self-assembled two-dimensional distribution of nanoparticles with high-current Cu- implantation into insulators

High-current and low-energy implantation has been carried out with negative ions, alleviating specimen charging. Negative Cu ions of 60 keV were implanted into silica glasses over a wide dose-rate range up to 260 mu A/cm(2) with a total dose at 3.0x10(16) ions/cm(2). Cross-sectional TEM was conducted to quantitatively evaluate the microstructures. At high dose rates, spherical Cu nanocrystals were created near the projected range of Cu ions. The nanoparticle morphology showed significant variations with the dose rate. Depth profile of the Cu atoms became narrower and shallower with increasing the dose rate. A surface sputtering process was concurrently promoted with the dose rate. At an optimum dose rate, a magnificent in-plane arrangement of nanocrystals occurred. A critical balance between the in-beam nanocrystal growth and the surface recession attained the self-assembled two-dimensional distribution. (C) 1999 Elsevier Science B.V. All rights reserved.