Sequential Growth in Solution of NiFe Prussian Blue coordination network nanolayers on Si(100) surfaces

Abstract

Controlling the elaboration of Coordination Networks (CoNet) on surfaces at the nanoscale remains a challenge. One suitable technique is the Sequential Growth in Solution (SGS), which has the advantage to be simple, cheap and fast. We addressed two issues in this article: i) the controlled synthesis of ultra thin films of CoNet (thickness lower than 10 nm), and ii) the investigation of the influence of the precursors' concentration on the growth process. Si(100) was used because it is possible to prepare atomically flat Si–H surfaces, which is necessary for the growth of ultrathin films. We used, as a model system, the sequential reactions of K₄[Fe^II(CN)₆] and [Ni^II(H₂O)₆]Cl₂ that occur by the substitution of the water molecules in the coordination sphere of Ni^II by the nitrogen atoms of ferrocyanide. We demonstrated that the nature of the deposited film depends mainly on the relative concentration of the anchoring sites versus the precursors' solution. Attenuated Total Reflection Fourier Transformed Infra Red (ATR-FTIR), X-ray reflectivity, X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) were used to characterize the steps of the growth process.