Electrodeposition of a PbTe/CdTe superlattice by electrochemical atomic layer deposition (E-ALD)

• First formation of a lattice matched superlattice using E-ALD.
• Development of cycle chemistry for the deposition of CdTe using ramped potentials.
• Observations of satellite peaks in XRD of PbTe/CdTe superlattice corresponding to 11 nm period.

A PbTe/CdTe superlattice was deposited using the electrochemical form of atomic layer deposition (E-ALD). The E-ALD program consisted of 15 periods of 5 cycles of CdTe and 15 cycles of PbTe, grown on a 15 cycle PbTe pre-layer formed on 200 nm of Au vapor deposited on glass. The cycle used for CdTe nanofilm formation involved ramped potentials, that is, the potentials used to deposit Cd and Te were incremented negatively for each of the first 20 cycles. After 20 cycle the potentials were held constant for all the remaining cycles, and resulted in a stoichiometric and homogeneous CdTe deposit, as shown by Electron Probe Microanalysis (EPMA). Peaks corresponding to the cubic phase of CdTe were observed in the XRD pattern of the CdTe, with the (1 1 1) dominant. Optical studies of the CdTe revealed a band gap of 1.5 eV. The PbTe/CdTe superlattice was formed using the period above fifteen times. Deposition potentials, current–time traces and elemental coverages are described. The superlattice was determined to be stoichiometric, as determined by EPMA. The superlattice X-ray diffraction pattern displayed satellite peaks on the (1 1 1) peak, as symmetric shoulders, indicating a period of 11 nm, rather than the anticipated 6 nm.