Fabrication and morphology of mixed copper tetra-tert-butyl phthalocyanine/arachidic acid Langmuir-Blodgett films

Deposition characteristics of mixed copper tetra-tert-butyl phthalocyanine (CuTTBPc) /arachidic acid Langmuir-Blodgett (LB) films on hydrophilic glass and hydrophobic silanized-glass substrates were investigated. Transfer ratios for the LB deposition were measured, and morphology of the LB films was analyzed by atomic force microscopy (AFM). With the addition of 20 or 50 mol% arachidic acid in a CuTTBPc monolayer, poor deposition quality was found for the continuous LB transfer on a glass substrate due to the return of the deposited layer to the air/water interface during down-stroke deposition. With a 1-h drying period at the end of up-stroke deposition, the extent of peeling of the films became less significant, and imperfect Y-type LB films may be prepared. However, by the same deposition approach, Y-type mixed CuTTBPc/arachidic acid LB films with good deposition quality could be fabricated on a silanized-glass substrate. Moreover, the AFM analysis demonstrated that the existence of 20 mol% arachidic acid caused aggregated in a CuTTBPc LB film to become smaller. This result suggests that arachidic acid not only promoted the LB transfer of a CuTTBPc layer, but also had a dispersion effect on the film. With a higher arachidic acid molar fraction of 0.5, aggregates in the mixed LB film became larger, which may be related to the accumulation characteristic of arachidic acid.