ANISOTROPIC SPIN TRANSPORT IN ORIENTED LITHIUM PHTHALOCYANINE THIN-FILMS

Thin films of monolithium phthalocyanine (PcLi) were prepared by vacuum deposition on various substrates: cleaved mica, quartz glass, and drawn sheets of poly(tetrafluoroethylene). The highly anisotropic spin transport in these films was studied by electron spin resonance (ESR) as a function of film preparation (thickness and substrate temperature), orientation, and temperature. Transmission electron microscopy confirms the existence of enhanced orientation which can be controlled by adjusting the substrate temperature T-s during: film deposition. For low substrate temperatures. homogeneous films with no azimuthal orientation are formed. Above 400 K. epitaxial growth on mica leads to rectangular wedge-shaped crystals. Raising the temperature T-s does not improve the orientation but creates a more discontinuous coverage of the substrate and reduces the electronic relaxation times T-1 and T-2, as monitored by ESR. When increasing the film thicknesses, a steady change towards the bulk properties is demonstrated by the decreasing ESR linewidth.