Theoretical and experimental analysis of defined 2D-graded two-metal nanoparticle-build surfaces

The paper presents a theoretical as well as an experimental study of 2D-graded, two-metal nanocomposite structures built from nanoparticles (NPs). We derived a theoretical description of a planar surface (x,y) with defined NPs distribution; the linear, exponential and logarithm graded distributions are presented. The analytical model employees gradient functions of (i) nanoparticle volume surface density and (ii) volume chemical composition ratio; both mutually orthogonal across the (x,y) plane. Such graded surfaces, with variable d/d(x,y) properties, supported by an analytical model are appreciated in many applications, e.g. for tunable plasmonic absorption as studied in our case. The relevance of our approach was experimentally approved by preparation of 2D-linearly graded Ag-Cu nanocomposite; here the amount of nanoparticles, as well as chemical composition ratio, varies linearly along with the principal and minor diagonal, respectively. The nanocomposites were prepared by a two-step deposition of Ag and Cu NPs produced by a gas aggregation cluster source equipped by a movable mask.