EFFECT OF GRAVITY ON COPPER PHTHALOCYANINE THIN-FILMS .1. ENHANCED SMOOTHNESS AND LOCAL HOMOGENEITY OF COPPER PHTHALOCYANINE THIN-FILMS GROWN IN A MICROGRAVITY ENVIRONMENT

Closed-cell physical vapor transport (PVT) has been used for the first time to deposit epitaxially thin films of organic pigments. A series of experiments were conducted both in low earth orbit on the Space Shuttle Orbiter and in the laboratory as ground controls using the 3M-PVTOS (PVT of organic solids) apparatus. The experiments used PVT as a process to deposit oriented organic thin films of phthalocyanine and perylene compound derivatives on epitaxially active substrates sealed within demountable ampoules. In a series of three papers, of which this is the first, the complete characterization of the microscopic physical structure and macroscopic optical properties of the thin films produced using copper phthalocyanine as the organic source material is presented, and detailed comparisons are made between the microgravity-grown and unit-gravity (laboratory) grown samples. In this first paper of the series, the results of comparisons of the microgravity and unit gravity films using visual photography, bright field and differential interference contrast microscopy, scanning ellipsometry, visible reflection spectroscopy and direct interferometric phase contrast microscopy are presented. These techniques together imply that the space-grown films are radially more uniform and homogeneous, are an order of magnitude smoother over the submillimeter to submicron range as indicated by their lower relative surface areas, and possess effective optical refractive index vs. position profiles which are distinctly different from those of the laboratory-grown control films. In the next two papers of this series, reflection IR spectroscopy, X-ray diffraction and scanning electron microscopy are used to show further that the microgravity-grown films are more highly uniaxially oriented, significantly denser and essentially contain only crystalline domains which consist of a previously unknown polymorph now designated as M-CuPc. © 1990.