Electron Microscopic Studies of CuS Nanocrystals Formed in Langmuir-Blodgett Films

摘要

The morphology and structure of CuS crystals formed during sulfidation of copper behenate films obtained by the Langmuir-Blodgett (LB) method have been studied using high resolution electron microscopy. The average size of these crystals is about 3 nm and increases by a factor of approximately 2.2 after annealing at a temperature of 150℃ or above. Analysis of interplanar distances has shown that in the range of annealing temperatures of 150-200℃, CuS nanocrystals have a P6_3/mmc hexagonal crystal lattice with parameters a = 0.38 nm and c = 1.64 nm. At annealing temperatures of 250℃ or above, the Cu_2S crystalline phase begins to form, in addition to CuS nanocrystals. The proportion of this phase increases with increasing annealing temperature. Cu_2S nanocrystals have a hexagonal crystal lattice type with the P6_3/mmc spatial group and unit cell parameters a = 0.39 nm and c = 0.68 nm. Quantitative evaluation of copper and sulfur in individual CuS and Cu_2S nanocrystals was performed by local analysis of characteristic X-ray spectra.