Electrodeposition of quantum confined thin films and nanostructures by electrochemical atomic layer epitaxy (ecale)
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Semiconductors show quantization effects when their physical dimensions are less than the Bohr radius for an exciton in the material. Controlling the physical size of materials can be used to tune the material properties. The length scale at which these effects begin to occur range from 3 to 70 nm for typical semiconductors (groups IV, III-V, II-VI). In my research group, we have developed an analog of atomic layer epitaxy, the electrochemical atomic layer epitaxy (EC-ALE). In electrochemistry, surface limited reactions are generally referred to as under potential deposition. An atomic layer of one element can frequently be electrodeposited on a second at a potential under that needed to deposit the element on itself, and this process is referred to as under potential deposition (UPD). EC-ALE is the use of UPD for the surface limited reactions in an ALE cycle. This provides atomic level control in stoichiometry, thickness and facilitates 2-D growth of the material. This makes EC-ALE a good candidate to form thin films, superlattices, and nanowires, where the compound deposited is modulated on the nanometer scale. In the following chapters, I have reported my research in the electrodeposition of III-V compound semiconductor InAs, In2Se3, Cu2Se, PbSe, PbTe and PbSe / PbTe superlattice thin films by EC-ALE. Strong quantum confinement effects were observed in InAs, PbSe, and PbTe thin films formed by EC-ALE. PbSe / PbTe strain layered superlattice thin films with 2 nd order Bragg diffraction peaks and different periodicities is reported and the first attempt to form semiconductor nanowires by ECALE, using the template electrodeposition is also reported.