Influences of Bath Chemistry and Plating Variables on Characteristics of Electroless Ni–P Films on Si Wafers from Alkaline Citrate Solutions

Abstract

Electroless nickel–phosphorus (Ni–P) films were produced on the surface of p-type monocrystalline silicon in the alkaline citrate solutions. The influences of bath chemistry and plating variables on the chemical composition, deposition rate, morphology, and thermal stability of electroless Ni–P films on silicon wafers were studied. The as-deposited Ni–P films were almost all medium- and high-P deposits. The concentrations of Ni2+ and citric ions influenced the deposition rate of the films but did not affect P content in the deposits. With increasing H2PO2− content, the P content and deposition rate were steadily increased. The pH and plating temperature had a significant effect on the chemical composition and the deposition rate of the films. The thermal stability of the medium-P film was better than that of the high-P deposit. At the same time, the proposed mechanism of Ni–P films on monocrystalline silicon substrates in the alkaline bath solution was discussed and addressed.

Origin of Electrocatalytic Activity in Amorphous Nickel–Metalloid Electrodeposits

“…The reason why we observe an increase in C and O in Table is probably because of the accumulation of oxide and hydroxide upon potentiodynamic polarization, confirmed by the rise in the oxide peak intensity and shift toward larger binding energy in XPS (Figure d), and entrapment of citrate particles, enabling Ni–citrate complexes . Before the XPS measurements, gradual ion etching was applied to eliminate all of the surface adsorbents.…”

“…The reason why we observe an increase in C and O in Table 3 is probably because of the accumulation of oxide and hydroxide upon potentiodynamic polarization, confirmed by the rise in the oxide peak intensity and shift toward larger binding energy in XPS (Figure 6d), and entrapment of citrate particles, enabling Ni−citrate complexes. 64 Before the XPS measurements, gradual ion etching was applied to eliminate all of the surface adsorbents. After hydrogen production, since the etching mainly etched away this newly formed oxide and hydroxide layer, the entrapped citrate and remaining oxide layer increased their relative atomic percent values within the samples.…”

Study of electrochemical deposition of Ni-Mo thin films from alkaline electrolytes

“…Although nickel possesses electrocatalytic properties, and due to these properties is often used in industry, the overvoltage of hydrogen evolution (HER) on the nickel electrode is quite high, causing an increase in the energy consumption during its use. Therefore, in order to reduce overvoltage, nickel is often doped with other elements such as Mo [11], Co [12], P [13], Cu [14], etc. Besides, the results of water electrolysis on titanium and molybdenum electrodes from neutral (NaCl) and alkaline (NaOH) electrolytes showed that addition of Mo(VI) ions into the electrolyte activated HER [15].…”