The formation of self-organized flower-like structures of copper hydroxide hydrate on copper foils was studied in mixed electrolytes of water and amides. The morphology of crystals deposited on copper foil changed with the formamide (FA) concentration. For mixed electrolytes of 6:4 and 5:5 of H2O:FA v/v, flower-like crystals consisting of nanosheets were deposited on the copper surface within a week. When immersed in 8:2 H2O:FA v/v, nanosheets were formed mainly on the copper surface. For the most concentrated solution of 3:7 H2O:FA v/v in this experiment, rectangular crystals were deposited without morphological control, forming rock-like structures. XRD patterns revealed crystals composed of Cu(OH)2·H2O. UV-Vis absorption spectra of FA solutions suggest that complexes of [Cu(HCONH2)4−x(H2O)x]2+, x=0～3, are formed in mixed electrolytes of water and FA according to the solution composition. Acetamide(AA) and N,N-dimethylformamide(DMF) were also examined. Flower-like structures were observed in AA aqueous solution, although the structures required 3 weeks to form. No change of copper foil surface morphology was observed in mixed electrolytes of water and DMF with copper foils during 3 weeks. These deposition rates of flower-like structures correspond to the concentrations of eluted Cu2+ ions in solutions in the following order: FA>AA>DMF.
By immersion of Si into a solution containing metal-salt and HF, fine metal particles are deposited onto the Si surface by electroless displacement reaction. The density of the deposited metal particles on the surface varies widely according to the metal-salt and Si pretreatment. The Pt particle density depends particularly strongly on the Si pretreatment. This study assessed the Pt electroless displacement deposition process. Single-crystalline n-Si(100) wafers were pretreated using the following three methods: immersion in a mixture of HF, HNO3, CH3COOH, and H2O(3:5:3:22 in volume)(CP4A), ordinary RCA method, and oxidization of the Si surface by immersion in HNO3 after RCA(RCA+HNO3). The electroless displacement deposition of Pt particles onto the Si surface proceeds by immersion of Si wafers into a H2PtCl6 solution containing HF for 5-900 s. On the Si surface pretreated using the CP4A method, Pt particles were deposited in the progressive mode. For the RCA method, Pt particles were deposited in two-stage progressive mode, which is separated at 180 s. For pretreatment of RCA+HNO3, Pt particles deposited in two-stage progressive mode were separated at 120 s. These two-stage progressive modes result from the local anodic reaction, which dissolved the Si surface in electroless displacement deposition solution. However, irrespective of the pretreatment method, Pt particles were deposited on the order of 109 cm−2 particle density by deposition for 900 s.