Structural Pattern of Cinnamic Acid on Different Substrates Probed by Slow Positron Beam Technique

Cinnamic acid (phenyl acrylic acid) is an essential constituent of Cinnamon oil, and is well known for its medicinal values. The compound comprises of hydrogen bonded supra molecular structure due to strong hydrogen bonding between the carboxylic groups and other intermolecular hydrogen bonding as well. On the whole it forms a crystalline layered structure in solid state. In order to study its structural organization and orientation of the molecular functional groups it has been our astute interest if we could form thin layers of these molecules on suitable substrates. Thus, thin layer characteristics of cinnamic acid (CINN) on the two commonly used substrates namely: fused quartz plate and on silicon substrate has been attempted and they were subjected to Doppler broadening of positron annihilation radiation (DB) line shape analysis by slow positron beam on the range of 30 – 1200 eV energy to study the near surface properties. While CINN on quartz substrate showed a periodic pattern (the rippled nature) significant from the point of view of the layer structure, as compared to the pure solid state analysis, the results on the pure silicon substrate were not so regular, it is rather apparent that a strong substrate dependent property was noticed with the layer formation . The cause of this effect was also identified through coincidence DB analysis and another complementary technique XPS in corroboration and shall be presented.
The discussion on the organization of CINN on the quartz substrate as revealed from the DB will be presented.