Metal sulfides semiconducting materials: case studies on cadmium sulfide/carbon nanotubes and iron disulfide

Abstract

In this work, we studied the synthesis and properties of metal sulfides. First, we analyzed the energy band alignment at the interface of CdS nanoparticles and metallic MWCNTs by photoelectron spectroscopy, and observed the formation of ohmic contact between the materials. Then, we studied the synthesis of iron pyrite (FeS2) films by Aerosol Assisted Chemical Vapor Deposition (AACVD) and sulfurization of spin-coated iron oxide (Fe2O3) films. AACVD processes were carried out in a reactor built during the realization of this work. The films deposited by AACVD presented opaque black color, poor adhesion to the substrate, mix composition of different iron sulfides and did not show continuous microstructure. Conversely, pyrite films produced by sulfurization presented dark golden specular color and good adhesion to the substrate. The films were sulfurized in a novel apparatus we named Russian Doll. We varied several sulfurization parameters obtaining several different resulting compositions. We determined an optimum route to obtain pure phase good quality films. We investigated the influence of the precursor Fe2O3 films in the microstructure of the sulfurized films and observed that oxide films with larger particles resulted in FeS2 films with larger particles as well. Additionally, we observed that oxide films with varying physical properties also influenced the optical properties of the FeS2 films. All pure phase pyrite films produced presented n-type conductivity. Lastly, we tested the use of our apparatus to produce MoS2 and SnS, which have interesting potential applications.