Richard Anthony Hann

Electrical and structural studies on copper tetra-tert- butyl phthalocyanine Langmuir-Blodgett films

Abstract Copper and zinc derivatives of tetra- tert -butyl phthalocyanine (TBP) form monolayers on the water surface. Electron microscopy of a single monolayer of Cu-TBP supported on amorphous carbon indicates that the film consists of small ordered domains in an amorphous matrix. In-plane conduction is ohmic with a resistivity of approximately 10 4 Ωm and an activation energy of 0.19 eV. Preliminary measurements of conduction normal to the plane also indicate ohmic behaviour with a resistivity an order of magnitude higher.

Second harmonic generation in alternate non-linear Langmuir-Blodgett films☆

Second harmonic generation experiments are performed in alternate multilayers of two non-linear molecules, the hydrophobic chain being grafted onto the acceptor group of the first species A and onto the donor group of the second species B. Two families of non-linear molecules are studied: p-aminobenzoic acid derivatives and diazostilbene derivatives. High χ(2) values (around 5×10-10SI) and β values (around 10-37 SI) are obtained for the diazostilbenes. The variation in the second harmonic intensity with respect to the number N of active layers is interpreted in terms of the disorder appearing in the upper monolayer of the Langmuir-Blodgett film.

Formation of stable Langmuir-Blodgett multilayers from oxiran carboxylic acids

Abstract Long-chain carboxylic acids, having oxiran groups at various positions along the chain, were synthesized and tested for their capacity to form ordered monolayers and multilayers. The oxiran groups were included because of their potential for polymerization during electron beam lithography. The hydrophilic nature of both the carboxylic acid and the oxiran groups in the same molecule afforded some difficulties in film formation, but one of these compounds provided stable monolayers and multilayers. Initial investigations have revealed that these multilayers are sensitive to electron beam polymerization.

The structure of some Langmuir-Blodgett films. Part I. Substituted phthalocyanines

Abstract Electron diffraction and high-resolution electron microscopy has been used to investigate the structure of Langmuir-Blodgett films of tetra-t-butyl copper phthalocyanine and its lead analogue. Both films were shown to consist of islands of ordered structure embedded in disordered material. Electron diffraction and lattice imaging of the ordered regions showed that the copper derivative had the phthalocyanine molecular plane inclined normal to the substrate. It was inferred that the lead derivative had the phthalocyanine plane parallel to the substrate.

The structure of some Langmuir-Blodgett films: II. Aromatic polar molecules

Abstract Monolayer and multilayer Langmuir-Blodgett films of 9-butyl-anthryl propionic acid have been examined by electron microscopy and electron diffraction. The computer-modelled energy-minimized molecular configuration for a single molecule was different from that suggested by other workers, and this revised structure was used to model monolayer arrays. Good agreement between the experimental and modelled monolayer structures was obtained. For this compound, the aliphatic chain interactions were energetically more important than the aromatic piane interactions, and the two-dimensional monolayer structure was closer packed than the multilayer structure. The multilayer structure was similar to that of the bulk crystalline material.

Electron beam lithography with very thin, highly ordered films

Abstract Very thin, molecularly ordered films of suitable amphiphilic monomers have been prepared as Langmuir-Blodgett multilayers. The effect of electron beams on these films has been examined and shown to lead to either polymerization or degradation. Some theoretical considerations are presented on the effects of electron beams on very thin films of highly ordered substances and compared with experiments.