Effect of thiourea during nickel electrodeposition from acidic sulfate solutions

Abstract

The effect of thiourea on the cathodic current efficiency (CE), deposit quality, crystallographic orientations, surface morphology, and polarization behavior of the cathode was investigated during nickel electrodeposition from acidic sulfate solutions for 2 hours at 60 °C. A slight decrease of 3 to 4 pct in the CE was observed, when the concentration of thiourea was increased from 2 to 40 mg dm Ϫ3 . The nickel deposit quality deteriorated significantly at higher thiourea concentrations; the surface morphology deteriorated and the contamination of the nickel deposits increased. The presence of thiourea affected the peak intensities of the crystal planes. Cyclic voltammetric studies on nickel deposition at 25 °C revealed depolarization behavior of the cathode at lower thiourea concentrations, Յ10 mg dm Ϫ3 ; however, a mixed behavior is observed at higher thiourea concentrations. These changes were also observed in the exchange current density (i 0 ) values.

Electrodeposition of Ni in Submicrometer Trenches

“…20 The characteristic reduction potential for such TU decomposition to sulfide ion has been attributed to a voltammetric wave near −0.7 V vs SCE. 17 A similar reduction wave is evident in Fig. 4 for the S-containing depolarizing additives with the wave peak approximately at −0.75 V for TU, −0.72 V for SPS, −0.71 V As the overpotential increases the depolarizing effects of the additives diminish; TU and SPS actually begin to inhibit the nickel deposition rate at potentials below −0.92 V. A similar potentialdependent transition in TU behavior from acceleration to inhibition was also recently reported.…”

“…As a point of departure the effects of prototypical cationic, anionic, and nonionic surfactants on the nickel deposition were examined. The survey is far from exhaustive, and the molecules examined were largely selected from prior reports of conventional Ni leveling [11][12][13][14][15][16][17][18][19][20][21][22][23] as well as Cu electroplating and superfilling. [23][24][25][26][27][28][29][30] Experimental Ni electrodeposition was studied using a variant of a Watts bath composed of 1 mol/L NiSO 4 ·6H 2 O, 0.2 mol/L NiCl 2 ·6H 2 O, and 0.5 mol/L H 3 BO 3 dissolved in 18 M⍀ cm deionized water.…”

“…The species examined were drawn from previous reports of additive-induced inhibition and/or acceleration in nickel [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] and copper [23][24][25][26][27][28][29][30] , Alfa Aesar͒, 3-mercapto-1-propane sulfonic acid, sodium salt ͓MPS, HS͑CH 2 ͒ 3 SO 3 − Na + , Raschig͔, bis͑3-sulfopropyl͒ disulfide, sodium salt ͓SPS, Na 2 + ͓SO 3 − ͑CH 2 ͒ 3 S͔ 2 , Raschig͔, and 3-N,N-dimethylaminodithiocarbamoyl-1-propane sulfonic acid, sodium salt ͓DPS, Na + SO 3 − ͑CH 2 ͒ 3 SCSN͑CH 3 ͒ 2 , Raschig͔ were investigated as potential accelerating or depolarizing additives. For the survey, the concentrations of the suppressors were fixed at 100 mol/L with the exception of PEI that exhibited similar inhibition at much lower concentrations.…”

The evaluation of nickel deposit obtained via Watts electrolyte at ambient temperature

“…This typical morphological appearance of nickel deposition was also reported by various researchers. [13][14][15][16][17][18] Although these researchers employed varied techniques and parameters, they arrived at the same morphological patterns.…”

“…Mohanty et al 17 stated that the nickel deposition with dominant plane (111) produced more condensed nickel layer compared to other planes. Chao-qun et al 27 also reported the deposition of the (111) plane in their work.…”