Nanoassembly control and optical absorption in CdTe-ZnO nanocomposite thin films

The spatial distribution of CdTe nanoparticles within a ZnO thin-film matrix was manipulated using a dual-source, sequential radio-frequency (RF)-sputter deposition technique to produce nanocomposite materials with tuned spectral absorption characteristics. The relative substrate exposure time to each sputtering source was used to control the semiconductor phase connectivity, both within the film plane and along the film growth direction, to influence the degree of photocarrier confinement and the resulting optical transition energies exhibited by the CdTe phase. Significant changes (up to ΔE ≈ 0.3 eV) in the absorption onset energy for the CdTe nanoparticle ensemble were produced through modification in the extended structure of the semiconductor phase. Raman spectroscopy, cross-sectional transmission electron microscopy, and x-ray diffraction were used to confirm the phase identity of the CdTe and ZnO and to characterize the nanostructures produced in these composite films. Isochronal annealing for 5 mi...