Preparation of highly oriented thin film of nonlinear optical material by vacuum deposition

Highly (001)‐oriented thin films of 4‐(N,N‐dimethylamino)‐3‐acetamidonitrobenzene were prepared on a thermally oxidized silicon substrate using vapor deposition. The degree of (001) orientation depends considerably on the substrate temperature (T_s) and deposition rate (R), which determines the kinetic energy (E_k) of the molecules in a flux. Under the optimized experimental parameters of T_s=30 °C and R=600 nm/min, we fabricated the (001)‐oriented thin film showing the full width at half‐maximum of x‐ray rocking curve of 1.6°. Surface flatness was also improved as the deposition rate increased. It became clear that kinetic energy (E_k) of the molecules in an evaporating flux strongly promoted (001) preferred orientation as could be seen by observing the surface morphology and a cross‐sectional view of the samples at their initial stage of growth.