CoNiP electroless deposition process for fabricating ferromagnetic nanodot arrays

An electroless deposition process for fabricating CoNiP nanodot arrays (less than 50 nm in height) with high magnetic coercivities was investigated. To fabricate such nanostructures, we improved the crystallinity of the CoNiP deposits in the initial deposition stage by applying an fcc-Cu(1 1 1) underlayer with low lattice mismatch to hcp-Co(0 0 0 2), and an autocatalytic electroless deposition process at the Cu surface was carried out by using dual reducing agents, H2PO2− and N2H4. CoNiP films demonstrated high perpendicular magnetic coercivities in the initial deposition stage since the highly crystalline hcp(0 0 0 2) CoNiP layers were grown parallel to the Cu underlayers. Nanopatterned substrates were formed by UV-nanoimprint lithography. CoNiP was electroless deposited on the nanopatterned substrates. As a result, CoNiP was deposited selectively from the bottom of the nanopores with few defects in a large area. Perpendicular coercivities higher than 3000 Oe were obtained for nanodots even with heights of 50 nm. Thus, an electroless deposition process that can be used to form nanostructures with high crystallinities in the initial stage without any anomalous deposition was demonstrated.

► Electroless CoNiP film with high perpendicular coercivity of 3 kOe with 20 nm thick was developed.
► Addition of N2H4 enables CoNiP to directly deposit onto Cu(1 1 1) to control crystal orientation.
► Formation of nanodot array of electroless CoNiP with 150 nm diameter and 300 nm pitch was achieved.