STRUCTURAL IMAGING OF LANTHANOIDE DIPHTHALOCYANINES BY TRANSMISSION ELECTRON-MICROSCOPY

Thin films of the lanthanoide diphthalocyanines LnPc(2) (Ln: Ho, Er) a re deposited onto NaCl (001) surfaces by thermal evaporation under hig h Vacuum conditions and analysed by HRTEM. Based on the obtained image s a model is describing growth and structure of these films. The thin films consist of columnar crystallites with lateral dimensions of 10 t o 100 nm mainly of the tetragonal phase with a two-molecular base made of the two isomeric forms of the LnPc(2) molecule. According to this model each (001) plane of the crystallites is made of exclusively one of the two mirror-symmetric LnPc(2) isomers. The type of isomer is alt ernating from plane to plane. Depending on the lowest plane the growth of the crystallites is preferably continued laterally in two mirror-s ymmetric direction sets, because of the interactions with the substrat e. Staggering angles of 36.9 degrees and 53.1 degrees, respectively, b etween the crystallites occur, as is well known from literature. Small pieces of orthorhombic structure and increased concentrations of latt ice defects arise in the regions between the tetragonal crystallites a nd at the grain boundaries.