Fabrication of CdS thin films assisted by Langmuir deposition, self-assembly, and dip-pen nanolithography

Thin CdS films were fabricated by Langmuir deposition, self-assembly, and dip-pen nanolithography methods. Firstly, LB films of saturated arachidic acid and LS films of unsaturated 10,12-pentacosadiynoic acid were reacted with cadmium ions and exposed to H,S gas. Formation of CdS crystal was observed with Fourier transform infrared (FTIR) spectra and atomic force microscope (AFM). Secondly, mercaptohexadecanoic acid was self-assembled on Au substrate and was reacted with CdS colloidal particles. At pH=9.1, the density of CdS colloids immobilized on Au substrate was very high compared to one at pH=5.0. Finally, thin films of CdS were also prepared on silicon and Au substrates by cadmium chloride-coated AFM tip and successive exposure of H,S gas. Localized formation of CdS crystal was suggested with AFM and depth-profiling Auger electron microscopy (AES).