In situ spectroscopic ellipsometry monitoring of multilayer growth dynamics via molecular layer epitaxy

Real time monitoring of organic monolayer self-assembly by molecular layer epitaxy (MLE) processes was studied by in situ spectroscopic ellipsometry t echniques. For the MLE of imide-based organic heterostructures using chemis orption of 3,4,7,8-naphthalenetetracarboxylic dianhydride (NTCDA) and 1,6-d iamino-n-hexane (DAH) on prefunctionalized surfaces, in situ ellipsometry r eveals that the reaction kinetics can be best fitted to an S-shaped deposit ion curve with saturated coverage of about 20 min by the Langmuir-Hinshelwo od model, with a slow initial phase, followed by a faster second phase. The rate of deposition at each moment is proportional to the number of empty s ites multiplied by the number of occupied sites. Calculated deposition rate constants for every pulse are k(T) = 5.6 x 10(-5) s(-1) for first depositi on of NTCDA on a template (T-layer), decreasing to k(A) = 1.5 x 10(-5) s(-1 ) for NTCDA and to k(B) = 7.2 x 10(-6) s(-1) for DAH assembly pulses corres pondingly. A modified Rudzinski-Aharoni kinetic model for adsorption that c orrelates adsorption energy with valid numbers of reactive sites was used t o estimate an equilibrium surface absorption energy of 16 kcal for a NTCDA layer and 29 kcal for a DAH layer.