In Situ STM Study of CdTe ECALE Bilayers on Gold

Abstract

Scanning tunneling microscopy (STM) has been used in situ to study the epitaxial growth of CdTe bilayers electrodeposited onto Au single-crystal surfaces. The films were produced by the alternate reductive underpotential deposition of Te and Cd by the electrochemical atomic layer epitaxy (ECALE) technique. The kinetics of electrocrystallization were found to be consistent with an instantaneous 2-D nucleation and growth model. Atomic resolution images of the corresponding first UPD structures of tellurium prior to Cd deposition in a CdSO4 solution have been obtained. Cd/Te bilayer structures formed by Cd UPD on Au(111)-(12×12)Te, Au(110)-c(2×8)Te, and Au(100)-(2×2)Te were Au(111)-(3×3)CdTe, Au(110)-(2×3)CdTe, and Au(100)-c(2×2)CdTe bilayers, respectively. To maintain stoichiometry, bilayer formation was accompanied where necessary (increasing in the order Au(111)-(3×3)CdTe < Au(110)-(2×3)CdTe < Au(100)-c(2×2)CdTe) by a significant rearrangement of the Te structure during bilayer growth. This process was found to take place without three-dimensional nucleation and resulted in the exposure of large Au(100) patches randomly distributed on the terraces, on which Cd was deposited. In striving for structural epitaxy on the gold substrates, structures exhibiting a compression of the bulk lattice planes were observed for cases where both excess and insufficient Te in the UPD layer was present to form the bilayer of ideal density. This observed inhomogeneity in the growth of Au(100)-c(2×2)CdTe was consistent with a Cd-induced structure in the Te stripping peak on Au(100) and a Coulometric excess of adsorbed Cd in the overall layer.

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

“…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.…”

Electrodeposition of CU2SE thin films by Electrochemical Atomic Layer Epitaxy (EC-ALE).

“…Recently, the electrochemical analog of atomic-layer epitaxy (ALE) has been developed to form compound thin films [22][23][24][25][26][27][28] . ALE refers to a methodology developed in the mid 70s for the formation of compounds an atomic layer at a time, using surface limited reactions [29][30][31] .…”

Successive Ionic Layer Adsorption and Reaction (SILAR) and Related Sequential Solution‐Phase Deposition Techniques

“…CdTe fi lms have been grown epitaxially on Au. 154 The fi lms were produced by the alternate reductive underpotential deposition of Te and Cd. The epitaxial growth was confi rmed by STM.…”

“…The epitaxial growth was confi rmed by STM. 154 Lead nitrate complexed with EDTA and lead perchlorate and sodium sulphide have been used for PbS ECALE -deposition. 158,159 The fi lms were cubic and highly (200) oriented, and AFM images showed the same cubic structure.…”