Optimization of CdTe nanofilm formation by electrochemical atomic layer epitaxy (EC-ALE)

Abstract

This paper concerns optimization studies of the growth of cadmium telluride, an important II-VI compound semiconductor, using electrochemical atomic layer epitaxy (EC-ALE). The importance of the potentials used to deposit atomic layers of Cd and Te, as well as the potential used to strip excess Te, were investigated. These potentials were used in a cycle, an EC-ALE cycle, to form deposits one atomic layer at a time, using a sequence of surface limited reactions. The optimal potentials for the CdTe EC-ALE cycle included Cd deposition at ) 0.65 V, Te deposition at ) 0.35 V and bulk Te stripping at ) 0.70 V. The deposits obtained were stoichiometric, with a Te/ Cd atomic ratio of 1.01 from electron probe microanalysis (EPMA). Electrochemical quartz crystal microbalance (EQCM) studies of the optimal condition indicated that about a third of the deposited Cd was oxidatively stripped at the potential used to deposit Te. Glancing angle X-ray diffraction studies showed a (111) preferred orientation for the deposit, while room temperature near infrared absorption measurements indicated a direct band gap of 1.5 eV.

Recent Prospects in the Inline Monitoring of Nanocomposites and Nanocoatings by Optical Technologies

“…Ellipsometry has been performed in situ for fixed deposition processes, at the laboratory scale, for example of CdTe on Au by electrochemical deposition [106]. Again, an effective medium approximation is used to calculate the dielectric function.…”

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

“…The author's group and others have worked extensively on the growth of compound semiconductor nanofilms, and more recently on the growth of metal nanofilms using electrochemical atomic layer deposition [3,[33][34][35][36][37][38][39][40][41][42][43][44][45]. Electrochemical ALD makes use of underpotential deposition (UPD) [46][47][48][49], a phenomenon where an atomic layer of one element deposits on a second, at a potential prior to that needed to form bulk deposits.…”

“…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.…”

Formation of Metal-Semiconductor Core-shell Nanoparticles Using Electrochemical Atomic Layer Deposition

“…These techniques have been successfully used by a number of research groups to deposit binary semiconductor nanofilms (19)(20)(21), semiconductor heterojunctions (22), superlattices (20,(23)(24)(25)(26), and, more recently, metal nanofilms (27,28).…”