Electrodeposition of Nanostructured Materials by Farzad Nasirpouri

Author:Farzad Nasirpouri
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Electrolyte

title

Critical time at current peak

(s)

Mean diameter of nuclei (nm) (±standard deviation)

N

(1/cm−2)

Simple sulphate

3.8

318 (±59)

1.56 × 1010

Simple sulphate with chloride

1.14

217 (±30)

2.56 × 1010

Watt bath low pH

0.44

135 (±38)

1.51 × 1011

Reproduced from [75] with permission from Elsevier

As is evident from the data collected in Table 4.2, size of nuclei decreases with the addition of nickel content, chloride ions and also with the reduction of pH. Consequently, number of nuclei increases per surface area. However, an important feature of data acquired by SEM is the change of size distribution of nickel granules electrodeposited from different solution. As is seen for the Ni electrodeposits obtained from a dilute solution, the mechanism of nucleation and growth is instantaneous. But with addition of chloride ions and more nickel content, the size distribution is widened, until it seems not to obey the instantaneous mechanism and will be discussed thereafter.

These effects not reported before for the mechanism of the electrodeposition of nickel on n-type silicon reveal markedly different nucleation and growth of nickel on semiconductor substrates. We interpret those effects in some respect by the change of basic mechanism of electrodeposition of nickel already understood on the other substrates such as vitreous carbon and paraffin impregnated graphite electrodes previously studied [81, 82]. The surface characteristics of those substrates could be compared with n-type silicon in terms of relatively weak interaction energy between ad-atoms and substrates. Electrodeposition of nickel from sulfate and chloride solutions proceeds simultaneously with the hydrogen discharge reaction, based on the proposed reactions:

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