Influence of UV irradiation on optical properties of thermally evaporated 4,4'-(1E, 1'E)-2,2'-(2-aminopyrimidine-4, 6-diyl)bis(ethene-2,1-diyl)bis(N,N- dimethylaniline) thin films

• Published in: Journal of physics. D, Applied physics Applied physics, 2010-11, Vol.43 (45), p.455407-455407
• Main Authors: El-Mallah, H M, El-Ghamaz, N A, Waly, M A
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Dielectric constant; Dispersions; Energy gap; Evaporation; Exact sciences and technology; Growth from solid phases (including multiphase diffusion and recrystallization); Heating; Materials science; Methods of crystal growth; physics of crystal growth; Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Optical transition; Oscillators; Physical radiation effects, radiation damage; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Thin films; Ultraviolet, visible, and infrared radiation effects (including laser radiation)
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/43/45/455407

4,4′-(1 E , 1′ E )-2,2′-(2-aminopyrimidine-4,6-diyl)bis(ethene-2,1-diyl)bis( N , N -dimethylaniline), APBSD, was synthesized by fusing 2-amino-4,6-dimethylpyrimidine with p- N , N -dimethylaminobenzaldehyde. Thin films of APBSD were prepared by the thermal evaporation technique in a vacuum of 10 −5  mbar on quartz substrates. X-ray diffraction patterns showed the amorphous nature of the thin films. Differential scanning calorimetry measurements showed no evidence of any crystallization process during heating of APBSD. Optical measurements of the as-deposited APBSD thin films showed normal dispersion of the refractive index n at λ > 800 nm and anomalous dispersion at λ < 800 nm. The results of absorption index k showed many absorption peaks in the UV region in addition to a shoulder at λ around 560 nm. The values of the lattice dielectric constant ε L , the high-frequency dielectric constant ε ∞ , the dispersion energy E d and the oscillator energy E o were determined. The values of n and k were found to decrease with increasing UV-irradiation time. Absorption index patterns showed peak splitting and small changes in its position depending on the UV-irradiation time. The optical energy gap was estimated and the optical transitions were found to be indirect allowed transitions. The values of the fundamental energy gap slightly decrease, while the onset energy gap slightly increases with increasing UV-irradiation time.