Optimization of CdTe nanofilm formation by electrochemical atomic layer epitaxy (EC-ALE)
. J Appl Electrochem 2006
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.