NANOSCALE CHARACTERIZATION OF GOLD COLLOID MONOLAYERS - A COMPARISON OF 4 TECHNIQUES

Atomic force microscopy (AFM), field emission scanning electron micros copy (FE-SEM), transmission electron microscopy (TEM), and near-held s canning optical microscopy (NSOM) have been used to characterize the n anostructure of Au colloid-based surfaces. Because these substrates ar e composed of particles whose dimensions are known prior to assembly, they are well-suited for a critical comparison of the capabilities and limitations of each nanoscale imaging technique, The three criteria f or this comparison, which are relevant to the field of nanoparticle as semblies in general, are (i) accuracy in establishing particle size, p article coverage, and interparticle spacing; (ii) accuracy in delineat ing surface topography; and (iii) ease of sample preparation, data acq uisition, and image analysis. For colloidal Au arrays, TEM gives the m ost reliable size and spacing information but exhibits the greatest co nstraints with regard to sample preparation; in contrast, AFM is widel y applicable but yields data that are the least straightforward to int erpret. For accurate information regarding nanometer-scale architectur e of particle-based surfaces, a combination of at least one scanning p robe method (AFM, NSOM) and one accelerated-electron method (TEM, FE-S EM) is required.