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Over 95% of large-scale length uniformity in template-assisted electrodeposited nanowires by subzero-temperature electrodeposition.

Shin S, Kong BH, Kim BS, Kim KM, Cho HK, Cho HH - Nanoscale Res Lett (2011)

Bottom Line: Even with highly disordered commercial porous anodic aluminum oxide template and conventional potentiostatic electrodeposition, length uniformity over 95% can be achieved when the deposition temperature is lowered down to -2.4°C.Decreased diffusion coefficient and ion concentration gradient due to the lowered deposition temperature effectively reduces ion diffusion rate, thereby favors uniform nanowire growth.Moreover, by varying the deposition temperature, we show that also the pore nucleation and the crystallinity can be controlled.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, Yonsei University, Seoul, 120-749, Korea. hhcho@yonsei.ac.kr.

ABSTRACT
In this work, we report highly uniform growth of template-assisted electrodeposited copper nanowires on a large area by lowering the deposition temperature down to subzero centigrade. Even with highly disordered commercial porous anodic aluminum oxide template and conventional potentiostatic electrodeposition, length uniformity over 95% can be achieved when the deposition temperature is lowered down to -2.4°C. Decreased diffusion coefficient and ion concentration gradient due to the lowered deposition temperature effectively reduces ion diffusion rate, thereby favors uniform nanowire growth. Moreover, by varying the deposition temperature, we show that also the pore nucleation and the crystallinity can be controlled.

No MeSH data available.


Transient electrodeposition current density curves of the Cu nanowires under varying temperature. (a) Full scale transient curves. Inset shows nanowire growth rate as a function of deposition temperature; (b) transient curves normalized by current and time maxima at the initial stage of the electrodeposition. Theoretical values for instantaneous and progressive nucleation models are also presented [31]. Dashed curve indicate instantaneous nucleation whereas dotted curve indicate progressive nucleation. im and tm denote current maximum and its corresponding time.
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Figure 2: Transient electrodeposition current density curves of the Cu nanowires under varying temperature. (a) Full scale transient curves. Inset shows nanowire growth rate as a function of deposition temperature; (b) transient curves normalized by current and time maxima at the initial stage of the electrodeposition. Theoretical values for instantaneous and progressive nucleation models are also presented [31]. Dashed curve indicate instantaneous nucleation whereas dotted curve indicate progressive nucleation. im and tm denote current maximum and its corresponding time.

Mentions: Figure 2a shows electrodeposition current density transient curves for the Cu nanowires at various deposition temperatures. Briefly mentioning the electrodeposition stages are: (1) charging of electric double layer and subsequent development of diffusion layer at the vicinity of the surface of the working electrode which leads to an instantaneous rise and drop of the initial current density; (2) growth of nanowires inside the template where the current density remains steady; (3) overgrowth of the nanowires after reaching the pore end which leads to gradual increase of the current density due to the increase of the electrodepositing area. The nanowire growth rate can be derived from the time taken at the stage 2 which is presented in the inset. Inside the long and narrow pore channels, diffusion is the rate-determining process in electrochemical reactions [25]. The diffusion rate can be determined by the Fick's first law of diffusion where it is expressed as j = -DΔC where j is the diffusion rate, D is the diffusion coefficient, and C is the local concentration. As the temperature is decreased, the diffusion coefficient of the Cu cations is also decreased since it follows the Arrhenius plot [26,27]. Moreover, not only the diffusion coefficient is decreased but also the thickness of the diffusion layer is elongated as the deposition temperature is decreased [28,29] since the nanoscale pore channels having aspect ratio up to 300:1 show a diffusion limited transport behavior [25]. In other words, concentration gradient at the diffusion layer is decreased. From the Fick's first law of diffusion, these two factors lead to the decrease of the mass transport rate. Therefore, by changing the deposition temperature, the nanowire growth rate can be significantly varied. At 60.5°C, it takes about 80 s to reach and fill the pore and the growth rate of the Cu nanowires is estimated as 745 nm/s whereas the growth rate is decreased down to about 45 nm/s at -2.4°C which is more than 16-fold decrease.


Over 95% of large-scale length uniformity in template-assisted electrodeposited nanowires by subzero-temperature electrodeposition.

Shin S, Kong BH, Kim BS, Kim KM, Cho HK, Cho HH - Nanoscale Res Lett (2011)

Transient electrodeposition current density curves of the Cu nanowires under varying temperature. (a) Full scale transient curves. Inset shows nanowire growth rate as a function of deposition temperature; (b) transient curves normalized by current and time maxima at the initial stage of the electrodeposition. Theoretical values for instantaneous and progressive nucleation models are also presented [31]. Dashed curve indicate instantaneous nucleation whereas dotted curve indicate progressive nucleation. im and tm denote current maximum and its corresponding time.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 2: Transient electrodeposition current density curves of the Cu nanowires under varying temperature. (a) Full scale transient curves. Inset shows nanowire growth rate as a function of deposition temperature; (b) transient curves normalized by current and time maxima at the initial stage of the electrodeposition. Theoretical values for instantaneous and progressive nucleation models are also presented [31]. Dashed curve indicate instantaneous nucleation whereas dotted curve indicate progressive nucleation. im and tm denote current maximum and its corresponding time.
Mentions: Figure 2a shows electrodeposition current density transient curves for the Cu nanowires at various deposition temperatures. Briefly mentioning the electrodeposition stages are: (1) charging of electric double layer and subsequent development of diffusion layer at the vicinity of the surface of the working electrode which leads to an instantaneous rise and drop of the initial current density; (2) growth of nanowires inside the template where the current density remains steady; (3) overgrowth of the nanowires after reaching the pore end which leads to gradual increase of the current density due to the increase of the electrodepositing area. The nanowire growth rate can be derived from the time taken at the stage 2 which is presented in the inset. Inside the long and narrow pore channels, diffusion is the rate-determining process in electrochemical reactions [25]. The diffusion rate can be determined by the Fick's first law of diffusion where it is expressed as j = -DΔC where j is the diffusion rate, D is the diffusion coefficient, and C is the local concentration. As the temperature is decreased, the diffusion coefficient of the Cu cations is also decreased since it follows the Arrhenius plot [26,27]. Moreover, not only the diffusion coefficient is decreased but also the thickness of the diffusion layer is elongated as the deposition temperature is decreased [28,29] since the nanoscale pore channels having aspect ratio up to 300:1 show a diffusion limited transport behavior [25]. In other words, concentration gradient at the diffusion layer is decreased. From the Fick's first law of diffusion, these two factors lead to the decrease of the mass transport rate. Therefore, by changing the deposition temperature, the nanowire growth rate can be significantly varied. At 60.5°C, it takes about 80 s to reach and fill the pore and the growth rate of the Cu nanowires is estimated as 745 nm/s whereas the growth rate is decreased down to about 45 nm/s at -2.4°C which is more than 16-fold decrease.

Bottom Line: Even with highly disordered commercial porous anodic aluminum oxide template and conventional potentiostatic electrodeposition, length uniformity over 95% can be achieved when the deposition temperature is lowered down to -2.4°C.Decreased diffusion coefficient and ion concentration gradient due to the lowered deposition temperature effectively reduces ion diffusion rate, thereby favors uniform nanowire growth.Moreover, by varying the deposition temperature, we show that also the pore nucleation and the crystallinity can be controlled.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, Yonsei University, Seoul, 120-749, Korea. hhcho@yonsei.ac.kr.

ABSTRACT
In this work, we report highly uniform growth of template-assisted electrodeposited copper nanowires on a large area by lowering the deposition temperature down to subzero centigrade. Even with highly disordered commercial porous anodic aluminum oxide template and conventional potentiostatic electrodeposition, length uniformity over 95% can be achieved when the deposition temperature is lowered down to -2.4°C. Decreased diffusion coefficient and ion concentration gradient due to the lowered deposition temperature effectively reduces ion diffusion rate, thereby favors uniform nanowire growth. Moreover, by varying the deposition temperature, we show that also the pore nucleation and the crystallinity can be controlled.

No MeSH data available.