Ternary CdS_xSe_1-x Deposited on Ag(111) by ECALE:  Synthesis and Characterization

Abstract

Morphology and electronic properties of CdS, CdSe, and the ternary compounds of formula CdSxSe1-x deposited on Ag(111) by ECALE have been characterized as a function of the composition. The number of the attainable x values is limited by the necessity of using well-defined CdS/CdSe deposition sequences. However, the quantitative analysis carried out by XPS and electrochemical stripping experiments indicates that the ECALE method has a good control on composition. The AFM images together with the electrochemical characterization indicate both two-dimensional and three-dimensional growth contributions.The photospectra recorded at CdS film electrodes in liquid junction with an alkaline (poly)sulfide electrolyte show good efficiency of photoconversion and band gap typical of the single crystal. Lower photoconversion efficiency and the presence of subband gap response are observed for CdSe; a possible reason is some crystalline disorder due to lower control of the layer-by-layer deposition in the case of Se. The dependence of band gap on composition of ternary CdSxSe1-x ECALE films is monotonic and in agreement with literature data reported for bulk materials. IntroductionThe interest in the electrochemical deposition of group II-VI compounds, in particular cadmium chalcogenides, stems from its ability to produce good quality materials with a relatively simple, soft procedure, operating at low temperature. Literature reports include preparation of layers of different thickness on various substrates, for potential applications going from solar energy conversion 1-3 to optoelectronics. 4,5 Recently, the electrochemical atomic layer epitaxy (ECALE) method has been proposed by Stickney and co-workers 6,7 for the deposition of well ordered group II-VI compounds. In the ECALE procedure, a binary compound is obtained by alternating the layerby-layer underpotential deposition of the metallic and nonmetallic elements. 6,7 The approach, initially developed for polycrystalline as well as for single-crystal gold substrates, was extended by our group to Ag(111) substrate. 8,9 One major advantage of ECALE method consists of the possibility of optimizing separately the different steps of the alternate electrodeposition by adjusting the solution and potential parameters.The deposition of ternary group II-VI compounds offers the possibility of tuning the band gap to meet specific

Underpotential deposition of selenium and antimony on gold

“…The crucial point in material electrodeposition is to control the dimensions, the stoichiometric ratio, and the crystallinity of the deposited structures. The electrochemical atomic layer epitaxy (EC-ALE) technique developed by Stickney [13] was proved to be a valid approach to control these parameters for the deposition of chalcogenide compounds on metallic substrates [14][15][16][17][18][19]. This method is based on the alternate underpotential deposition of atomic layers of the elements that form the compound, in a cycle that can be repeated as many times as desired.…”

Fabrication of CdSe/CdTe Quantum Dots Co-Sensitized TiO2Nanorods by Electrochemical Atomic Layer Deposition Method

“…The under potential deposited Se was stripped in the positive scan of the first cycle so that the surface limited deposition peak of Se can also be observed in the second scan and it is almost the same shape as that in the first scan, the phenomenon of which was also reported by M. Foresti. 34 The peak located at −0.85 V (C2) gets stronger in the second scan indicating more intense bulk Se deposition thus the peak can be ascribed to bulk deposition. Figure 1c displays the cycle voltammogram curve of the TiO 2 NRs array film electrode in a Te precursor solution.…”

Investigations on the Electrochemical Atomic Layer Growth of Bi2Se3 and the Surface Limited Deposition of Bismuth at the Silver Electrode

“…E-ALD exploits Surface-Limited Reactions (SLRs), such as Underpotential Deposition (UPD), thus achieving the layer-by-layer growth of various compound semiconductors [8,9,10,11,12,13,14,15,16,17]. The Nernst equation predicts the redox potential necessary to reduce metal ion A onto a substrate of the same element A.…”