| 摘要: | 本研究在焦磷酸鹽鍍液中，分別以傳統之平板電鍍法(planar electrodeposition, PE)製備銅-鋅薄膜(thin films, TFs);以即時影像監控之微陽極導引法(micro anode-guided electroplating, MAGE)之局部電鍍法(localized electrodeposition, LE)，製備銅-鋅合金微柱 (micropillars, MPs)。首先分別在平板電鍍法(PE)與局部電鍍法(LE)中，藉由解析產物在表面形貌、化學成分、晶體結構、機械性質、和抗腐蝕性能上與其實驗參數之關聯性。隨後，比較平板電鍍(PE)所得薄膜(TFs)與微電鍍(LE)所得微柱(MPs)在電化學 液中陰極極化曲線(cathodic polarization curve, CPC)和電化學阻抗頻譜(electrochemical impedance spectroscopy, EIS)的行為，有助於理解其反應過程之機制與差異。
在[Zn2+]/[Cu2+]比值為8/1的鍍液中，陰極極化曲線掃描分別解釋一般平板電鍍和微電鍍的電沉積機制，電化學交流阻抗驗證了電沉積機制，薄膜的鋅含量分布較廣(13.3~57.9 at.%)且有不同的銅鋅合金相(α、β和β′相)，而微柱鋅含量較低(3.3~8.1 at.%)且只有單一銅鋅合金α相。微柱α相的硬度大於薄膜(1.7~3.0 GPa > 1.0~1.5 GPa)。經COMSOL 5.2軟體模擬得知薄膜和微柱的電場分佈與電力線密度明顯的不同。薄膜抗腐蝕優於微柱。
改變鍍液中銅離子濃度實驗中，藉由陰極極化曲線觀察微陽極導引局部電鍍的電化學還原機制。在特定的電位下進行電化學交流阻抗分析可以解析電鍍的機制。微柱的鋅含量從8.05 at.% (α 相)增加到54.60 at.% (β和β′相)。微柱由不同尺寸的奈米晶粒組成;含40.51 at.% Zn (β相)的微柱表現出最大硬度(5.30 GPa)和最高楊氏模數(113.64 GPa);電場模擬顯示，隨著鍍液中[Zn2+]/[Cu2+]比值的增加，集中在微柱頂端的最高場強僅略有增加(從152.2增加到152.5 kV/m)。
當[Zn2+]/[Cu2+]比值為64/1的鍍液中實驗改變電鍍電位，初始間距為30 μm微柱會有不同的結晶晶相(α、β和β + β′)，其中鋅含量範圍為37.12~68.94 at.%;然後使用數據來描述電場強度對晶相、成分、生長速率和微柱直徑的相關性。
;Cu–Zn alloys consisting of thin films (TFs) were prepared through ordinary planar electrodeposition (PE), and those of micropillars (MPs) were fabricated through localized electrodeposition (LE). Energy-dispersive spectroscopy and X-ray diffractometry analyses indicated that the TFs contained a wider range of Zn content (13.3–57.9 at.%) with different crystal phases (α-, β-, and β′-phases) than that in MPs (i.e., Zn content ranging from 3.3 to 8.1 at.%, confined to only α-phase). The results of the nano-indentation test indicate that the hardness of the α-phases in MPs was greater (1.7–3.0 GPa) than that in TFs (1.0–1.5 GPa). Simulations using the commercial software COMSOL 5.2 revealed that the distribution of the electric field in PE and LE was distinct. Through potentiodynamic cathodic polarization, we distinguished between the mechanisms of the PE and LE processes. Electrochemical impedance spectroscopy results confirm these mechanisms. The corrosion resistance in 3.5 wt% NaCl is lower for the MPs than for the TFs.
Cu–Zn alloy micropillars were fabricated using microanode-guided electroplating (MAGE) at a constant potntical under an initial inter-electrode gap of 30 μm in pyrophosphate baths. Energy-dispersive spectroscopy and X-ray diffractometry analysis revealed that the micropillar alloys exhibit an increase in the Zn content from 8.05 at.% (in α phase) to 54.60 at.% (in β, and β′ phases) with an increase in the ratio of [Zn2+]/[Cu2+] in the bath from 8/1 to 128/1. Transmission electron microscopy revealed that the Cu–Zn alloy micropillars were composed of nano-grains with different sizes depending on the bath employed. Nano-indentation test indicated that the micropillar containing 40.51 at.% Zn (in presence of β-phase) exhibits the maximum hardness (at 5.30 GPa) and highest Young′s modulus (at 113.64 GPa). Simulation of the electric field using the commercial software COMSOL 5.2 revealed that the highest field strength centralized at the cylindrical top displayed only a slight increase (from 152.2 to 152.5 kV/m) with an increase in the ratio of [Zn2+]/[Cu2+] in the bath. Potentiodynamic cathodic polarization is useful for understanding the mechanism of microanode-guided electroplating.
This process was carried out via micro-anode-guided electroplating in a pyrophosphate bath at a constant negative potential in the range -1.85 to -2.05 V. Thus, at an initial gap of 40 μm, the process afforded micropillars with a single α-brass crystal phase and at.% Zn contents in the range 17.20–32.01%. A reduction in the initial gap to 30 μm resulted in varied micropillar crystal phases (α, β, and β+ β′) with at.% Zn contents in the range 37.12–68.94. The simulation commercial software COMSOL 5.2 was employed to correlate the asymmetric distribution of the electric field to the experimental parameters and pillar characteristics. The resultant data was then used to delineate the dependence of the field strength on the crystal phase, composition, growth rate, and micropillar diameters. Finally, a potentiodynamic cathodic polarization study was employed to elucidate the mechanism for the fabrication of the Cu-Zn alloy micropillars via potentiostatic LECD. |
