Deposition of Cobalt-Nickel Hybrid Electro-Electroless Deposited (HEED) Modulated Multilayers

Abstract

Hybrid electro-electroless deposition (HEED) is the unification of electroplating and electroless deposition in a single electrolyte for the reduction of separate and distinct metals/alloys. The novel combination has the capacity to create unique layered and alloyed deposits by having electroplating and electroless deposition each target a different metal ion within the electrolyte. Electroplating from a Co/Ni-P electrolyte has the capacity to produce Co(Ni-P) layers having over 60% Co atomically. Similarly, electroless Ni-P layers produced from the same electrolyte contain atomically at most 2% Co. Both the electroplating and electroless deposition processes can be tuned to allow greater, or lesser, Co alloying in each layer. The sequential deposition of electroplated Co(Ni-P) and electroless Ni-P within the single electrolyte is used herein to produce a compositionally modulated pentalayer deposit.The recent development of hybrid electro-electroless deposition (HEED) 1 has provided a means to produce several interesting multilayered deposits which were previously unavailable using a single bath. Broadly put, HEED is described as any single electrolyte in which one metal/alloy is the target of electroplating while another metal, or compositionally different alloy, is the target of electroless plating. Deposits formed using HEED typically contain at least one metallically pure, or nearly pure, layer, most often an alloy produced using electroless deposition, and one electroplated alloy layer, which may contain some, trace amounts, or in some cases none, of the electrolessly plated metal/alloy.Most notably, the advent of HEED allows for the possibility of depositing metal pairs with smaller differences in standard electrode potential (E • ) due to the use of two different deposition techniques within the same electrolyte. The deposition of modulated metal layers with similar E • is not possible from a single electroplating electrolyte, such as the works of Yahalom and O. Zadok 2 as well as Bird et al., 3 as each of the electroplated layers will be prone to substantial alloying. While restrictions exist as to the identity of the metal pairs, a single HEED electrolyte can, in some instances, produce layers of higher metal purity compared to those produced using modulated electroplating from a single electrolyte. The ability to produce layers of higher metallic purity often comes at a cost of non-metal inclusion in the deposit. Inclusion of the non-metal in the deposit is due to the presence of a reducing agent, and associated anodic reaction, required for the electrolessly deposited layer.It is therefore a requirement of HEED that at least one metal be a candidate for electroless deposition and that the presence of the second metal does not interfere with the electroless deposition process in which it is not involved. Nickel {Ni} is an often deposited metal for the purposes of corrosion resistance, wear resistance, and as a diffusion barrier among other applications. Electroless Ni is most often deposited as a phosp...

Developments in Co(Ni-P) Hybrid Electro-Electroless Deposited (HEED) Alloys and Composites

“…Hybrid electro-electroless deposition (HEED) is a process which combines electroplating and electroless deposition for the reduction of separate and distinct metal ions to produce alloys, composites, and compositionally modulated multi-layer films from a single electrolyte (1,2). Coatings produced using HEED have a wide array of applications that include corrosion resistance, wear resistance, puncture resistance, and magnetic coatings, among others.…”