CdTe electrodeposition on InP(100) via electrochemical atomic layer epitaxy (EC-ALE): Studies using UHV-EC
The II-VI compound semiconductor CdTe was electrodeposited on InP(100) surfaces using electrochemical atomic layer epitaxy (EC-ALE). CdTe was deposited on a Te-modified InP( 100) surface using this atomic layer by atomic layer methodology. The deposit started with formation of an atomic layer of Te on the InP(100) surface, as Cd was observed not to form an underpotential deposition (UPD) layer on InP( 100), although it was found to UPD on Te atomic layers. On the In-terminated 'clean' InP( 100) surface, Te was deposited at -0.80 V from a 0.1 mM solution of TeO2, resulting in formation of a Te atomic layer and some small amount of bulk Te. The excess bulk Te was then removed by reduction in blank solution at -0.90 V, leaving a Te atomic layer. Given the presences of the Te atomic layer, it was then possible to form an atomic layer of Cd by UPD at -0.58 V to complete the formation of a CdTe monolayer by EC-ALE. That cycle was then repeated to demonstrate the applicability of the cycle to the formation of CdTe nanofilms. Auger spectra recorded after the first three cycles of CdTe deposition on InP( 100) were consistent with the layer-by-layer CdTe growth. It is interesting to note that Cd did not form a UPD deposit on the In-terminated InP(100) surface and only formed Cd clusters at an overpotential. This issue is probably related to the inability of the Cd and In to form a stable surface compound.