PREPARATION OF AU SINGLE-CRYSTALS FOR STUDIES OF THE ECALE DEPOSITION OF CDTE

A sequence of questions concerning the preparation of atomically flat Au surfaces is addressed. In addition, the formation of a 1/2 monolayer Te adlayer on a Au(100) is discussed. The 1/2 coverage Au(100)-Te surface is desired as a first step in the electrodeposition of CdTe by the ECALE methodology. The use of oxidation/reduction cycles (ORCs) to clean the Au(100) surface is shown to be counter productive, if atomically Bat planes are also desired. Roughening results from the ORCs as the surface reconstructs at low potentials, then unreconstructs at high potentials. The reconstructed surface contains excess surface atoms, such that upon lifting of the reconstruction, monoatomically high Au islands are formed on the surface. It is also shown that treatment in a mM I- solution results in the Formation of ordered iodine adlattices on each of the low index planes. In addition, electrochemical annealing is facilitated, resulting in the removal of previously formed Au islands, and formation of large, atomically Bat terraces. Te can be deposited directly on these I coated surfaces, displacing the I and forming thin films of bulk Te. The excess, bulk, Te can then be removed either reductively or oxidatively, to form ordered atomic layers of Te with coverages near 1/2.