Preparation And Growth Mechanism Of PdNiP Amorphous Metallic Films

Pd₄₀Ni₄₀P₂₀, characterized by simple component and strong glass forming ability, is the prototype of metal-metalloid metallic glasses. After nearly three decades of its discovery, there are rare reports on amorphous Pd₄₀Ni₄₀P₂₀ films down to mesoscopic scale. Due to dimension and confinement effects, research works on amorphous Pd₄₀Ni₄₀P₂₀ films must own great theoretical and practical significance. The idea of this work is to prepare amorphous Pd₄₀Ni₄₀P₂₀ films and to investigate its growth mechanism. This endeavor would be the cornerstone for the following works on Pd₄₀Ni₄₀P₂₀ films.Amorphous Pd₄₀Ni₄₀P₂₀ films with thickness ranging from tens to hundreds of nanometers are prepared from aqueous solutions by electrochemical deposition. The reproduibility of this sophisticated Pd₄₀Ni₄₀P₂₀ electrodeposition technique is about 70%. Composition and performance of PdNiP films severely depend on the pH of electrolyte, rather than the concentration of reactants. The growth behavior of Pd₄₀Ni₄₀P₂₀ in the initial and middle stages is roughly sketched in this work. In the initial stage, Pd is reduced preferentially from the electrolyte, which leads to drastic hydrogen evolution reactions and PdP co-deposition. There are nanopores on film surface with short growth time, which would be the remnant of hydrogen bubbles. The electrodeposition process saturates, and the film content approaches the ideal composition during further deposition. The surface morphology of the middle stage is characterized by diffusive nodular structure. Basically, it is an electrochemical reaction controlled process, and can be regarded as Pd-induced PdNiP co-deposition together with hydrogen evolution.Surface kinetic roughening concerns on the scaling behavior of growing surface. In this work, kinetic roughening during Pd₄₀Ni₄₀P₂₀ electrodeposition is briefly introduced. Program named RoughnessMNG is used to calculate data for dynamic scaling from original AFM images. The results indicate intrinsic anomalous scaling behavior during deposition. This would be the first report on intrinsic anomalous scaling in amorphous or metallic alloys electrodeposition systems. The largeβ_loc value can be attributed to diffusional instability caused by large overpotenital and j/j_DL Further analysis shows that the scaling exponents in present work are similar to the simulation results of discrete models in KPZ universality class, such as the noised reduced Eden model and KK model. The growth behavior of Pd₄₀Ni₄₀P₂₀ can be treated as KPZ local growth process influenced by diffusional instability.