Natural variability in the surface roughness of combinatorial libraries of materials

Using a conventional method for the fabrication of solid-state combinatorial libraries, we have produced the binary libraries Fe_1−xCr_x and Mo_1−xSn_x (0 < x < 1) and found that their surface roughness is highly dependent on chemical composition. Roughness enhancements of up to 20-fold have been observed on the nanometer scale and were manifested in the boundaries between structurally dissimilar phases. It is anticipated that this is a common occurrence in thin-film libraries of metals and an obstacle in separating the influence of roughness and composition on the performance of library materials in biomaterial studies.