Nanosphere lithography: Size-tunable silver nanoparticle and surface cluster arrays

Nanosphere lithography (NSL) is an inexpensive, inherently parallel, high-t hroughput, and materials-general nanofabrication technique capable of produ cing well-ordered 2D periodic particle arrays of nanoparticles. This paper focuses on the synthesis of size-tunable silver nanoparticle arrays by nano sphere lithography and their structural characterization by atomic force mi croscopy (AFM). The in-plane diameter, a, of Ag nanoparticles was tuned fro m 21 to 126 nm by systematic variation of the nanosphere diameter, D. Simil arly, the out-of-plane height, b, was tuned from 4 to 47 nm by varying the mass thickness, d(m), of the Ag overlayer. Experimental measurements of a, b, and interparticle spacing di, of many individual nanoparticles as a func tion of D and d(m) were carried out using AFM. These studies show (i) b = d (m), (ii) d(ip) accurately corresponds to predictions based on the nanosphe re mask geometry, (iii) a, after correction for AFM tip convolution, is gov erned only by the mask geometry and the standard deviation, sigma(D), of th e nanosphere diameter, and (iv) line-of-sight deposition is strictly operat ive. Furthermore, we have established that nanosphere lithography can fabri cate nanoparticles that contain only ca. 4 x 10(4) atoms and are in the siz e range of a surface-confined cluster.