Optical characterization of organic material bromoindium phthalocyanine thin films grown by electron beam evaporation

This paper presents the optical properties of organic material bromoindium phthalocyanine (BrInPc) thin films grown by electron beam evaporation technique. The paper describes the optical characteristics of BrInPc thin films, which have been determined using spectrophotometric measurements of the absorbance, transmittance and reflectance at normal incident of light in the spectral range 300–1,100 nm. The optical band gap energy and type of the electronic transition have been determined by analysis of spectral behavior of absorption coefficient, which reveals the probability of both direct and indirect transitions. Other optical constants, such as refractive index, extinction coefficient, complex dielectric constant and optical conductivity of thin films have been evaluated. Moreover, the width of band tails of localized states (Urbach energy), steepness parameter and width of the defect states have been determined by studying the absorption coefficient spectra just below the fundamental absorption edge.     

Synthesis, morphology and optical properties of nanocomposite thin films based on polypyrrole-bromo-aluminium phthalocyanine

This paper is focused on the synthesis of nanocomposite Polypyrrole–Bromoaluminium phthalocyanine (PPy-BrAlPc). Morphology of prepared nano-compositethin films by electron beam evaporation technique have been well characterized by Field Emission-Scanning Electron Microscopy (FESEM). FESEM shows that the grain sizes are increased with increase in concentration of pyrrole. The optical properties of nanocomposite thin films have been investigated using a spectrophotometric measurement of absorbance in the wavelength range 300–800 nm. Absorption spectra of the films show B-band in the UV region followed by Q-band in the visible region. Moreover, the optical band gaps of the thin films are evaluated. It is found that the energy of the optical band gap increases as the concentration of Bromo-aluminium phthalocyanine increases.     

Morphology, structural and optical characterization of electron beam evaporated bromoaluminium phthalocyanine (BrAlPc) thin films

Bromoaluminium phthalocyanine (BrAlPc) thin films have been deposited onto pre-cleaned glass substrates by electron beam evaporation technique. Thin films have been characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and optical absorption (UV–Vis) spectra. XRD studies of BrAlPc thin film deposited at room temperature shows the indication of the α-phase. FESEM images have shown that the most of particles are spherical in shape with an average size about 26–34 nm. Using UV–Visible spectra over the wavelength range 300–800 nm, the optical band gap, absorption coefficient and extinction coefficient of BrAlPc thin films are evaluated. The optical absorption measurements of thin films show that the absorption mechanism is due to direct transition.     

Studies on phase transformation and molecular orientation in nanostructured zinc phthalocyanine thin films annealed at different temperatures

Studies on the electronic and optical properties of thin films of organometallic compounds such as phthalocyanine are very important for the development of devices based on these compounds. The nucleation and grain growth mechanism play an important role for the final electronic as well as optoelectronic properties of the organic and organometallic thin films. The present article deals with the change in the film morphology, grain orientation of nanocrystallites and optical properties of zinc phthalocyanines (ZnPc) thin films as a function of the post deposition annealing temperature. The effect of annealing temperature on the optical and structural property of vacuum evaporated ZnPc thin films deposited at room temperature (30 °C) on quartz glass and Si(100) substrates has been investigated. The thin films have been characterized by the UV-vis optical absorption spectra, X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy. From the studies of UV-vis absorption spectra and XRD data, a metastable α to β-phase transformation has been observed when the thin films were annealed at a temperature greater than about 250 °C. The FESEM images have shown the particlelike structure at room temperature and the structure became rodlike when the films were annealed at high temperatures. TEM image of ZnPc film dissolved in ethanol has shown spectacular rod-shaped crystallites. High resolution transmission electron microscopy image of a single nanorod has shown beautiful “honey-comb” like structure. Particle size and root mean square roughness were calculated from AFM images. The changes in band gap energy with increase in annealing temperature have been evaluated.     

Langmuir-Blodgett films of Cu(II)-tetrakis (3,3-dimethylbutoxycarbonyl) phthalocyanine: a spectrophotometric and TEM analysis of their structure and morphology

Langmuir-Blodgett (LB) films of copper(II)-tetrakis (3,3-dimethylbutoxycarbonyl) phthalocyanine [Cu(dmbc)Pc] have been prepared from toluene solutions; multilayers (up to 80 layers) were deposited onto hydrophobic quartz substrates. The refractive index n and extinction coefficient κ at normal incidence have been determined from both transmission and reflection measurements carried out in the 400–800 nm spectral range. The optical absorption spectrum as a function of the incident photon energy was also registered in order to determine the optical transition type in Cu(dmbc)Pc LB films by using a band model approach. Linearly polarised light absorbance measurements were performed at room temperature in the same spectral range. The average orientation of the phthalocyanine molecular rings in the LB film, with respect to the normal to the substrate and the dipping direction, has been evaluated. We have found that such orientation differs from that determined for LB films deposited from ethyl acetate solutions.

Structural and morphological analysis were also carried out by transmission electron microscopy techniques. Small ordered domains in a low range order matrix were observed by high resolution images. The structure of the material in the substrate plane has been determined by electron diffraction performed on single ordered domains.     

Characterization of optical, electrical and structural properties of silverphthalocyanine thin films

Silverphthalocyanine thin films are deposited on to glass substrates by thermal evaporation technique. Optical data have been obtained from both absorption and reflectivity spectra over the wavelength range 350–900 nm. The absorption coefficient α and extinction coefficient k are estimated from the spectrum. The mechanism of optical absorption follows the rule of direct transition. Using α and k, the refractive index and the dielectric constants are determined. Electrical conductivity studies are done at different substrate temperatures and using the Arrhenius plot the activation energy in the intrinsic region and impurity region is estimated. From the X-ray diffractograms of AgPc thin films subjected to heat treatments the variation of grain size is also studied. The scanning electron microscopy images are taken to study the surface morphology of the films. Silver phthalocyanine thin film is expected to find application in the fabrication of organic transistors and LED devices.     

(Pb,Ca)TiO3铁电薄膜光学性质的研究

用溶胶凝胶法在Ｓｉ（１００）衬底上制备了（Ｐｂ,Ｃａ）ＴｉＯ３铁电薄膜样品,测量了其在２．３￣５．０ｅＶ能量范围的鸫谱,并获得样品的膜厚和在该区间的光学常数谱,实验发现Ｐｂ离子被Ｃａ离子取代后,折射率向低能方向移动;同时随着Ｃａ含量的增加,（Ｐｂ１Ｃａ（ＴＩＯ３工能方向移动,表明Ｃａ离子取代Ｐｂ离子后,禁带宽度Ｅｇ减小,还了引起折射率峰移动和禁带宽度Ｅｇ减小的原因。     

Effects of post-deposition annealing on morphology and optical properties of electron beam evaporated Bromoaluminium phthalocyanine thin films

In this paper, effects of post-deposition annealing on morphology and optical properties of electron beam evaporated Bromoaluminium phthalocyanine thin films have been investigated. Surface morphology of the films have been characterized by field emission scanning electron microscopy (FESEM). The FESEM micrographs have shown densely packed nanoparticles and nanorod-like structures for the films annealed at different temperatures. Conditions leading to β-phase have been identified by monitoring post-deposition annealing using optical absorption spectroscopy (UV–Vis). The optical absorption measurements on the as-deposited and annealed films shows that the absorption mechanism is due to direct transition. Also, it is found that the optical band gap decreases with increase in annealing temperature.     

Chemical bath deposition and characterization of CdSe thin films for optoelectronic applications

Cadmium selenide (CdSe) thin films of high crystalline quality on glass substrate have been prepared by chemical bath deposition technique from an aqueous bath containing tetramine cadmium and sodium selenosulphate. Structural analysis using XRD shows that the film is single phase, crystallized in hexagonal structure with preferred growth in (111) direction. The energy band gap calculated from the absorption spectra of unannealed CdSe thin films shows an optical band gap of 1.8 eV and absorption coefficient near band edge (α)—0.58 × 10⁵ cm⁻¹. The conductivity of CdSe thin films is n-type.     

Influence of gamma radiation on the optical properties of ZnSe nanocrystalline thin films

The effect of gamma (γ) irradiation on the absorption spectra and the optical energy bandwidth of ZnSe nanocrystalline thin films have been studied. Thin films of different thicknesses from 20 to 120 nm were deposited by Inert gas condensation technique at constant temperature of 300 K and under pressure 2 × 10⁻³ Torr of Argon gas flow. The optical transmission (T) and optical reflection (R) in the wavelength range 190–2,500 nm of ZnSe nanocrystalline thin films were measure for unirradiated and irradiated films. The dependence of the absorption coefficient α on photon energy hν was determined for different γ-doses irradiated films. The ZnSe thin films show direct allowed interband transition by γ-doses. Both the absorption coefficient (α) and optical energy bandwidth were found to be γ-dose dependent. The optical energy band width has been decreased by irradiated of γ-doses. The E_gn values of irradiated thin films by 34.5 Gy of γ-doses were recovered to nearly their initial values after 100 days at 300 K.     

Structural and optical properties of thermally evaporated zinc phthalocyanine thin films

Thermally evaporated zinc phthalocyanine (ZnPc) films in the as deposited condition were identified to be as-amorphous. It undergoes structural transformation upon annealing up to 613 K. The optical properties and spectral behavior of as deposited and annealed thin films of ZnPc were studied using spectrophotometric measurements of the transmissivity and reflectivity at normal incidence of light in the wavelength range 200–2500 nm. The refractive index, n, and absorption index, k, were calculated and it was found that they are independent of film thickness in the thickness range 205–530 nm. Annealing at 613 K increases absorbance of films by 5–6 times in comparison with absorbance of as deposited ones and shifts peak positions of all bands towards low energy side of spectra except the peak position of N-band is shifted towards high energy side of spectra. The absorption spectra in the UV–VIS. region has been analyzed in terms of both molecular orbital and band theories. Indirect allowed transitions near the onset and fundamental absorption edges were observed. The energy at the onset was obtained and equals to 1.45 and 1.51 eV for as deposited and annealed films, respectively. The fundamental energy gap was obtained and equals to 2.94 and 2.88 eV for as deposited and annealed films, respectively. The absorption spectra shows four absorption bands. The oscillator strength, f, the electric dipole strength, q², the molar extinction coefficient, ζ_molar, were calculated for as deposited and annealed ZnPc thin films.     

Effects of annealing temperatures on optical and electrical properties of vacuum evaporated Ga15Se77In8 chalcogenide thin films

The optical constants (absorption coefficient, optical band gap, refractive index, extinction coefficient, real and imaginary parts of dielectric constants) of amorphous and thermally annealed thin films of Ga₁₅Se₇₇In₈ chalcogenide glasses with thickness 4000 Å have been investigated from absorption and reflection spectra as a function of photon energy in the wave length region 400-800 nm. Thin films of Ga₁₅Se₇₇In₈ chalcogenide glasses were thermally annealed for 2 h at three different annealing temperatures 333 K, 348 K and 363 K, which are in between the glass transition and crystallization temperature of Ga₁₅Se₇₇In₈ glasses. Analysis of the optical absorption data shows that the rule of non-direct transitions predominates. It was found that the optical band gap decreases with increasing annealing temperature. It has been observed that the value of absorption coefficient and extinction coefficient increases while the values of refractive index decrease with increasing annealing temperature. The decrease in optical band gap is explained on the basis of the change in nature of films, from amorphous to crystalline state. The dc conductivity of amorphous and thermally annealed thin films of Ga₁₅Se₇₇In₈ chalcogenide glasses is also reported for the temperature range 298-393 K. It has been observed that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. The dc conductivity was observed to increase with the corresponding decrease in activation energy on increasing annealing temperature in the present system. These results were analyzed in terms of the Davis-Mott model.     

The influence of molecular structure modification on the photoluminescence and optical absorption of thin copper phthalocyanine films in the near-IR range

We have studied the luminescence and optical absorption of thin films of copper phthalocyanine (CuPc) with a modified molecular structure of the peripheral fragments. The coefficient of absorption in the near-IR and visible range (absorption by defects) and the photoluminescence spectra exhibit correlated changes depending on the modification of the CuPc structure.     

Synthesis, characterization and optical properties of mono- and bis-chalcone

Mono- and bis-chalcone have been synthesized by the reaction of 3-acetyl-2,5-dimethylthiophene and N, N-di-methylbenzaldehyde/terephthalaldehyde in ethanolic NaOH in microwave oven. The structure of these compounds was established by elemental analysis, IR, ¹H NMR, ¹³ C NMR and GC-MS spectral analysis. Thin films with thickness of 100 nm of mono- and bis-chalcone were evaporated by thermal evaporation onto glass/Si wafer substrates under a vacuum of 10^− 6 Torr. The optical constants (absorption coefficient and optical band gap) of these films have been studied as a function of photon energy in the wavelength region 300-1100 nm. Analysis of the optical absorption data shows that the rule of non-direct transitions predominates. The optical band gaps for mono- and bis-chalcone are found to be 2.31 and 0.99 eV respectively. It has been found that the absorption coefficient changes with increasing photon energy. The peak values of the absorption coefficient are found to be at 370 nm for mono-chalcone and 460 nm for bis-chalcone thin films.     

Effect of pH on the properties of ZnS thin films grown by chemical bath deposition

Zinc sulphide thin films have been deposited on glass substrates using the chemical bath deposition technique. The depositions were carried out in the pH range of 10 to 11.5. Structure of these films was characterized by X-ray diffraction and scanning electron microscopy. Optical properties were studied by spectrophotometric measurements. Influence of the increased pH value on structural and optical properties is described and discussed in terms of transmission improvement in the visible range. Transmission spectra indicate a high transmission coefficient (70%). The direct band gap energy is found to be about 3.67 eV for the films prepared at pH equal to 11.5.     

The effects of Al doping on the optical constants of ZnO thin films prepared by spray pyrolysis method

Aluminum doped ZnO (AZO) thin films doped with different aluminum concentrations have been prepared by spray pyrolysis method onto glass substrates. The optical and structural properties of the films have been investigated by X-ray diffraction and optical characterization methods. The X-ray diffraction spectra showed that all of the thin films are of polycrystalline nature. The thin films have (002) as the preferred orientation. The optical band gaps of the films were calculated. The E _g values decrease with increasing Al doping concentration. The refractive index, the extinction coefficient, and the real and imaginary components of dielectric constant are calculated. The obtained results show that all optical parameters keep constant in the visible region, whereas in the ultraviolet region, doping concentration strongly affects the optical parameters of AZO thin films. Optical constants tend to decrease with increasing doping concentration.     

Comparative study of the properties of ZnO thin films deposited on poly propylene carbonate (PPC) and glass substrates

In this study, we report a comparative study of the structural, morphological, and optical properties of the deposited ZnO thin films on Poly Propylene Carbonate (PPC) and glass substrates by direct current (DC) sputtering technique. X-ray diffraction (XRD) spectra of the films on PPC and glass substrates show mainly the ZnO (002) diffraction peaks at 2θ = 34.1 and 34.3^o with full width at half maximum (FWHM) of 0.31 and 0.34^o, respectively. Scanning electron microscopy (SEM) images show that both ZnO thin films have smooth surface. Photoluminescence (PL) spectra show two peaks, the first intense peak was found in the UV region. The second weak peak was observed in the visible region. The transmission and absorption spectra of the ZnO thin films deposited on both substrates showed that the films have good transmission in the visible region and a good absorption in the UV region. The optical energy gap (E _g) values of the deposited ZnO thin films on PPC plastic and glass substrates were derived from absorption measurements and it found to be 3.38 and 3.40 eV, respectively.     

Optical and electrical characterization of r.f. sputtered ITO films developed as art protection coatings

Transparent and conductive tin-doped indium oxide (ITO) films have been prepared by r.f. plasma sputtering technique in Ar and Ar + O₂ gas mixture. The influence of the deposition conditions, film thickness, and substrate heating, as well as the post-annealing treatment on the optical and electrical properties of the ITO films has been investigated.The present study has extended the optical behaviour characterization of the ITO films in a wide UV-VIS-IR spectral region in addition to the comprehensive optical studies of this material at shorter wavelengths.The optical constants: refractive index (n), extinction (k) and absorption (α) coefficient, and the optical band gap (E_go) have been calculated for the ITO films in the spectral range between 350 and 2500 nm. A combination of several well-known theoretical models has been applied to describe precisely the complex optical behaviour of ITO films in separate spectral parts. In this approach, a good overlapping between the experimental and the simulated spectra in the whole investigated spectral region has been achieved.The deposition conditions and the optical and electrical properties of the ITO films have been optimized with respect to the requirements for their applications in art protection coatings.     

REVERSE OPTICAL CHANGE AND RECORDING CHARACTERISTICS OF LANGMUIR-BLODGETT FILMS OF PHTHALOCYANINE COMPOUNDS

报导了酞菁化合物的吸收光谱随中心金属离子的有机基团的替代而产生的变化，以及酞菁铜（ＴＮＰｃＣｕ）和酞菁锌（ＴｎＰＰｃＺｎ）的单分子薄膜的吸收光谱随温度的变化。发现酞菁铜薄膜在７４０ｎｍ波长的光吸收的滞后回旋现象以及酞菁锌的可逆光吸收变化。报导了利用上述现象的可擦重写的光存储特性。     

Optical study of poly(vinyl alcohol)/hydroxypropyl methylcellulose blends

The proposal in this study was to evaluate the optical properties of different biopolymers films. The materials used were poly(vinyl alcohol) (PVA) and hydroxypropyl methylcellulose (HPMC). PVA/HPMC blends were prepared by casting technique. Variations in the group coordination in the infrared region were followed. The effects of HPMC concentrations on the optical properties of the PVA films were studied by near infrared, ultraviolet/visible, transmittance, and reflectance in the spectral region 200–2500 nm. Absorption, transmittance, and reflectance spectra were used for the determination of the optical constants. The study has been also extended to include the changes in the optical parameters including the band tail width and band gap energies and extinction coefficient for the investigated films. The results indicate that the optical band gap was derived from Tauc’s extrapolation and decreases with the HPMC contents. The obtained optical parameters were found to be strongly affected by HPMC contents.