Atomic Force Microscopy and Micro-Raman Imaging of Mixed Langmuir−Blodgett Films of Ytterbium Bisphthalocyanine and Stearic Acid

Abstract

The degree of mixing and surface coverage in Langmuir−Blodgett (LB) films of ytterbium bisphthalocyanine (YbPc2) mixed with stearic acid (SA) has been probed using atomic force microscopy (AFM) and micro-Raman imaging. The morphologies extracted for LB films at the nanometer (AFM) and micrometer (micro-Raman) scales are consistently in good agreement. The results show that a 5-layer mixed LB film with 75/25% YbPc2/SA (relative content by weight) displays smaller and more homogeneous distribution of aggregates compared with a 5-layer mixed film of 25/75% YbPc2/SA. Raman microscopy of neat LB films of ytterbium bisphthalocyanine (YbPc2) and mixed YbPc2/stearic acid LB films deposited on glass and silver islands is reported. Resonance Raman scattering (RRS), surface-enhanced resonance Raman scattering (SERRS), and surface-enhanced Raman scattering (SERS) were obtained using laser lines at 633 and 780 nm. The enhanced (SERRS) and unenhanced (RRS) resonance Herzberg−Teller spectra of neat YbPc2 LB films and mi...