EC-STM Studies of Te and CdTe Atomic Layer Formation from a Basic Te Solution

Abstract

The cyclic voltammetry of Te on Au is markedly affected by pH. This fact can be used to advantage when designing an electrodeposition cycle for CdTe. For instance, if a pH 2 Te solution is used, the underpotential deposition ͑UPD͒ potential for Te is 0.8 V positive of that for Cd. However, if a pH 9.2 Te deposition solution is used, the potential for Te UPD coincides with that for Cd, greatly simplifying the development of an electrochemical atomic layer epitaxy ͑EC-ALE͒ cycle. This report describes electrochemical scanning tunneling microscopy ͑EC-STM͒ studies of Te deposition on Au͑111͒ and Au͑100͒ from basic media. Several structures were observed on Au͑111͒: a (6 ϫ 6) tellurite adlayer which spontaneously adsorbed prior to Te formation, a 1/4 coverage (2 ϫ 2)-Te, and a 1/3 coverage (2 ϫ ͱ10)-Te. While on Au͑111͒, a 1/3 coverage (ͱ3 ϫ ͱ3)-Te with (13 ϫ 13) light domain walls, and two (3 ϫ 3)-Te structures, with coverages of 4/9 and 5/9, were observed. Results of the formation of the first CdTe compound monolayer using an EC-ALE cycle which includes Te deposition from a basic solution are also included.

Formation of PbTe nanofilms by electrochemical atomic layer deposition (ALD)

“…Previous studies showed that Te deposition is kinetically slow and dependent on the pH. The peaks for Te UPD and stripping tend to shift in a linear fashion to more negative potentials the more basic the solution [54]. Fig.…”

“…1 and 2) were used to determine an initial set of UPD potentials for the cycle. Both Te and Pb deposition have been extensively studied by this group and others [54,[66][67][68][69]. Previous studies showed that Te deposition is kinetically slow and dependent on the pH.…”

“…Numerous compounds that have been successfully formed by electrochemical ALD, include II-VI compounds such as CdTe [44,[50][51][52][53][54][55][56], CdS [35,57], ZnSe [58], ZnS [57] and CdS/HgS superlattices [59], IV-VI compounds such as PbS [60], PbSe [43] and superlattice of PbSe/PbTe [33], as well as III-V compounds such as GaAs [61,62], InAs [63,64], InSb [65] and superlattices of InAs/InSb [65]. This paper will focus on the optimization of an electrochemical ALD cycle used for the growth of PbTe nanofilms on Au on glass substrates.…”

Aqueous Electrodeposition of Ge Monolayers

“…UPD results from the free energy of surface compound or alloy formation, where the first atomic layer of an element is stabilized by bonding to the second element. The UPDs of both Te and Sb on Au in aqueous solution have been the subject of studies by our group and others. − However, little work has been done toward an atomic-level understanding of Ge electrodeposition in aqueous solution. Recently, the alternated deposition of Sb and Te has been reported with respect to the formation of phase-change materials by a group at IBM, Watson. , In the IBM work, single-crystalline Sb 2 Te 3 films were deposited onto Au and TiN by EC-ALD in aqueous solution.…”

Formation of CuIn(1-x)GaxSe2(CIGS) by Electrochemical Atomic Layer Deposition (ALD)

“…22, 26 The slow kinetics for Se can be seen in the pronounced irreversibility of the cyclic voltammogram in Figure 3.…”