Nucleation and Growth of Cu₂O: Role of Potential, Electrolyte pH, and Substrate

Abstract

The nucleation and growth mechanism of functional oxides have a direct bearing on the structural and electronic properties of the deposit. We study the effect of electrolyte pH and deposition potential on the nucleation and growth of Cu2O on polycrystalline metal oxide (FTO) & metal (Au) substrates. Modelling of the recorded current-time transients indicates that both instantaneous and progressive nucleation occur with growth limited by diffusion or lattice incorporation of electro-active species or both. The preferred orientation of Cu2O shows strong dependence on electrolyte pH. The films are (100) oriented on both substrates at pH 9 except at high applied potential on FTO where the orientation changes to (111). Interestingly, irrelevant of electrolyte pH, the grain size of Cu2O decreases with potential on FTO whereas it increases on Au substrates. We attribute this to a difference in the number of active nucleation sites between the two substrates. The nucleation and growth at pH 12 is observed to be dependent both on diffusion and lattice incorporation of electro-active species. Additionally, the films are primarily (111) oriented on both the substrates, which is correlated to the availability of OH– ions.

Electrodeposition of Phase–Pure n–Type Cu2O: Role of Electrode Reactions and Local pH

“…29,30 Previous studies have commonly utilized temperatures of 55 °C and 60 °C for Cu 2 O deposition. 17,[31][32][33] Considering this, we selected a deposition temperature of 55 °C for our study. 2b, indicate the formation of copper at longer deposition time (according to JCPDS Card No.…”

“…Such behavior has been noted earlier by Hills et al and others and suggests that the system is undergoing an electrochemical nucleation process. 31,38,39 The important point to note is that the cathodic current in the voltammogram will saturate at a particular value, irrespective of whether it is under Cu 2+ diffusion control or kinetic control of the formation of Cu 2 O. Based on Fig.…”

“…The processes occurring during this induction period, namely, the double layer charging and the E step of the EC reaction scheme in this system, contribute to the current. 31,43,44 Nucleation of Cu 2 O i.e. the C step of the EC reaction scheme has not yet been initiated.…”

Formation of an extended defect cluster in cuprous oxide

“…Cuprous oxide is one such TMO semiconductor, whose widespread adoption in applications such as solar photovoltaics, photoelectrochemical cells and so on has been limited by defects [13,[19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Non-stoichiometry in cuprous oxide occurs due to the facile and irrepressible formation of two shallow acceptor defects, copper vacancies (V ′ Cu ) and copper split vacancies (V ′ Cu split) [33,34].…”