Chemical Tuning of the Electronic Properties of Nanostructured Semiconductor Films Formed through Surfactant Templating of Zintl Cluster

Abstract

Inorganic/organic coassembly provides a powerful route to the formation of periodic, nanostructured materials. In this work, the surfactant cetyltriethylammonium bromide is used as an organic structure directing agent, and the inorganic phase is formed from the condensation of metal cations with reduced main group clusters know as Zintl clusters. These anionic clusters are formed by alloying alkali metals with various main group elements. The chalcogenide-based Zintl clusters used here have an affinity for gold and other transition metals and will thus nucleate the formation of films on metal surfaces. Interface nucleated inorganic/organic co-organization results in thin films with the periodicity of a liquid crystal phase, but with a cross-linking inorganic network surrounding the surfactant domains. In this work, we investigate the extent to which the band structure of these films can be tuned by altering the elemental composition of the inorganic framework of these periodic nanocomposites. For the semiconducting films investigated here, the band gap and valence and conduction band energies of the inorganic network can be independently tuned by 1−2 eV by varying different elemental components. All trends in the data can be qualitatively understood by considering the orbital contribution to the band structure, in analogy to chalcogenide glass semiconductors. A variety of applications are anticipated for nanostructured semiconducting films for which band properties can be independently tuned across a broad range and films can be synthesized using low cost solution phase methods.