Nanomaterials @ Interfaces Research Group

Fabrication of monocrystalline semiconductor thin films using chemical solution deposition (CD) has far reaching fundamental and technological implications. We have recently reported on chemically deposited, epitaxial single-crystal PbS films on GaAs, and we report here for the first time on single-crystal PbSe films that were directly grown on the same substrates using CD. A gradual transition from weakly oriented domains to 〈1 1 1〉-oriented growth was obtained on both GaAs(1 1 1) and GaAs(1 0 0) substrates. We demonstrate orientation control in CD PbS (or PbSe) thin films by depositing an intermediate layer of PbSe (or PbS). When deposited on GaAs(1 0 0) substrates, CD PbSe films tend to grow along the 〈1 1 1〉 axis, while CD PbS films grow along the 〈1 1 0〉 axis. Intermediate thin films of 〈1 1 0〉 PbS induced the 〈1 1 0〉 orientation in overgrown PbSe films. Similarly, intermediate films of 〈1 1 1〉 PbSe were used for obtaining 〈1 1 1〉- oriented PbS films. In both cases, films were grown in orientations that could not be otherwise obtained. Cross-sectional transmission electron microscopy (TEM) and selected area electron diffraction (ED) were used for studying the epitaxial relationship between the film and the underlying intermediate layer. Superimposed atomic position maps were constructed in order to illustrate the orientation relationships obtained.