Optical and structural characterization of thin films containing metallophthalocyanine chlorides (original) (raw)
The structural and optical investigation of thin films containing aluminum and gallium phthalocyanine chlorides is presented. The films were fabricated by Physical Vapor Deposition technique onto quartz substrates and annealed after fabrication in an ambient atmosphere for 24 h at the temperature equal to 150 C or 250 C. The experimental results and theoretical calculation of the Third Harmonic Generation process are reported. The third order nonlinear optical properties are expected and can be more or less accurately predicted due to the assembly of the molecules and theoretical calculations of the frequency-dependent dipole polarizabilities, third hyperpolarizabilities, third order susceptibilities, frontier and second frontier molecular orbitals. These parameters were used to understand the relationship of optical properties with the molecular structures. We found that the annealing process causes formation of nanostructures and the value of the third order optical susceptibility makes these materials interesting for future nonlinear optical applications.
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Applied Physics Letters, 1997
Second-harmonic generation from λ=1.06 μm fundamental light has been measured in both evaporated and spin-coated films of trinitro-substituted subphthalocyanines. Ordering of these noncentrosymmetric molecules with the dipole moment perpendicular to the film face has been achieved either by the deposition process (evaporated samples) or by corona poling (spin-coated samples). The second-order susceptibilities χ31(2)=2.36×10−9 esu (for vacuum evaporated samples) and χ31(2)=9.62×10−10–1.14×10−9 esu (for poled spin-coated samples) have been determined by comparison with an X-cut LiNbO3 crystal used as reference.
Gold(III) phthalocyanine chloride: Optical and structural characterization of thin films
In the present work, the investigation of gold(III) phthalocyanine chloride (AuClPc) which received very little attention before is progressed further using a range of optical spectroscopic techniques. Thin films of gold(III) phthalocyanine chloride were produced by organic molecular beam deposition deposition and their structure was investigated by UVevisible spectroscopy, polarization dependent Raman spec-troscopy and atomic force microscopy. Experimental observations were confirmed by theoretical analysis using quantum chemical calculations; the latter were used for the detailed assignment of different bands in IR spectra of the gold(III) phthalocyanine chloride. The orientation of gold(III) phthalocyanine chloride molecules relative to the substrate surface was studied in detail using techniques based on the polarization dependent Raman spectroscopy. It was shown that gold(III) phthalocyanine chloride films deposited on quartz substrates at 100 C exhibit a co-facial structure with the average tilt angles of Pc moieties of ~70 .
We present a study on the impact of phase transformation (α→ β) of tetra-tert-butylphthalocyanine (H 2 Pc) thin films on their third-order as well as fifth-order nonlinear optical (NLO) properties. The α-phase of H 2 Pc thin film is prepared by thermally evaporating the commercially available H 2 Pc powder on a glass substrate which is further annealed at 473 K to obtain the more stable β-phase. The structural modifications in H 2 Pc films have a distinct signature in UV−vis absorption spectra, powder X-ray diffraction, and Raman spectra which have been employed for identifying the transformation from α-phase to β-phase. The NLO characteristics which include nonlinear refractive indices such as n 2 and n 4 , as well as nonlinear absorption coefficient (β eff), were measured by using a single beam Z-scan technique. Using an ultrashort pulsed fiber laser at 1064 nm central wavelength in the Z-scan experiment, we obtained a smaller value of β eff in α-phase as compared to β-phase due to a smaller value of saturation intensity (I s) which, in turn, is a consequence of ground-state bleaching in thermally unstable amorphous state of the molecule. The impact of χ (5) nonlinearity in the Z-scan transmittance of α-phase was apparent, and interestingly, the optical phase changes due to χ (3) and χ (5) nonlinearities bear opposite sign. In addition, they alter their signs as the laser intensity increases. A dominant fifth-order NLO contribution is mainly a consequence of inherently large χ (5) for the films as well as two-photon-assisted nonlinear refraction as a result of excited state absorption.
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