Electrodeposition Growth of Oriented ZnO Deposits in Ionic Liquid Media

Abstract

ZnO is a material of great interest for microelectronics because it offers a panel of attractive physical properties. It has been grown for decades as thin films from a wide variety of physical-chemical deposition techniques, most of them leading to films oriented with the polar direction perpendicular to the substrate. Here we report the electrodeposition of ZnO in ionic liquids (EMImTFSI (1-ethyl-3methylimidazolium bis(trifluoromethylsulfonyl)imide), BMPTFSI (1-Butyl-1-Methylpyrrolidinium bis(trifluoromethylsulfonyl)imide) or BMImTf (1-butyl-3-methylimidazolium trifluoromethanesulfonate)), together with the feasibility of manipulating the growth orientation of the ZnO deposits by adding the proper co-solvent to ionic liquid. We establish solvent dielectric constant as a key parameter to tailor the deposit growth direction. Moreover, via the use of Electrochemical Quartz Crystal Microbalance (EQCM) measurements, we determine the importance of the competition between Zn 2+ and O 2 reduction to properly trigger the transport phenomena leading to the growth of ZnO. This work provides insight which can be implemented to the growth of other binary and ternary oxides deposits in ionic liquid media, a field still poorly explored.

Electrochemical Reduction of Oxygen in Aprotic Ionic Liquids Containing Metal Cations: A Case Study on the Na–O2 system

“…[11] Aside from classical electrolytes based on cyclic and acyclic carbonates, ionic liquids (ILs) such as hydrophobic and aprotic N-butyl-N-methylpyrrolidiniumb is(trifluoromethanesulfonyl)imide (PYR14TFSI) have also been considered because of their potentially attractive physicochemical properties, [12][13][14] which make them suitable candidates for technological development based on green, safe, and sustainable chemistry. There are af ew reports about using the electrochemical reduction of O 2 in ILs containing metal cations( i.e., Zn 2 + , [20,21] Ni 2 + , [22] Ce 4 + [23] )t od eposit metal oxide films [Eqs. Several groups [16][17][18][19] have investigated this aspect and concluded that in ILs free of metal cations the generationofs uperoxides firstly and peroxides subsequently occur accordingly to Equations (1) and (2).…”

Potentiostatic Cu-Zn Alloying for Polymer Metallization Using Medium-Low Temperature Ionic Liquid Baths

“…In particular, many ionic liquids can dissolve more oxygen (O 2 ) and superoxide ion (O 2 − ) than water, 16,17 which probably result in ZnO formation (2Zn 2+ + O 2 + 4e = 2ZnO) rather than Zn deposition (Zn 2+ + 2e = Zn). [18][19][20] Formation of Cu-Zn intermetallic compounds.- Figure 3 summarizes the appearances and XRD patterns of the Cu-Zn layers obtained by alloying for 24 h at various potentials between +20 to +300 mV vs Zn 2+ /Zn 0 (i.e. Zn rod).…”

Electrodeposition of Semiconductors in Ionic Liquids

“…In recent years ZnO has attracted a great interest as promising material for several technological applications (e.g., solar cells, UV light-emitting diodes, catalysis, photocatalysis, field emission, piezoelectric, gas sensing, etc.). In 2009, Azaceta et al [26] [29]. The authors studied the influence of temperature, substrate, the nature of the ionic liquid, and electrochemical deposition conditions on the morphology and the crystal structure of electrochemically made ZnO film.…”

“…It was shown that the deposition potential and temperature influence significantly morphology and crystal structure of the deposit. Furthermore, it was reported that the film growth orientation can be manipulated by addition of different cosolvents into ILs as a solvent dielectric constant seems to be a key parameter to tailor the deposit growth direction [29].…”