Spectroscopic ellipsometric characterization of organic films obtained via organic vapor phase deposition

Thin films of Tris(8-hydroxyquinoline)-aluminum(III) (Alq3) and N,N′-Di-[(1-naphthyl)-N,N′-diphenyl]-(1,1′-biphenyl)-4,4′-diamine (α-NPD ) were deposited on large-area silicon substrates by means of the recently developed organic vapor phase deposition (OVPD) method. Variable-angle spectroscopic ellipsometry was used to measure the optical constants of OVPD Alq3 and α-NPD layers in the 0.8–5 eV energy range. The absorption onset which defines the lower limit of the optical band gap was found to be at ∼2.65 eV and ∼2.9 eV for Alq3 and α-NPD , respectively. Additionally, the thicknesses of the layers as well as the thickness profiles of the organic thin films were determined along the 8′′ diameter of the wafers. The thickness analysis revealed large-area uniform deposition of the films.