Photo-irradiation effects on the surface morphology of poly(p-phenylene vinylene) films

In this work, we have studied the surface morphology of photo-irradiated poly(p-phenylene vinylene) (PPV) thin films by using atomic force microscopy (AFM). We have analyzed the first-order statistical parameters, the height distribution and the distance between selected peaks. The second-order statistical analysis was introduced calculating the auto-covariance function to determine the correlation length between heights. We have observed that the photo-irradiation process produces a surface topology more homogeneous and isotropic such as a normal surface. In addition, the polymer surface irradiation can be used as a new methodology to obtain materials optically modified.     

Interchain interactions effects on emission efficiency of poly(p-phenylene vinylene) films

In attempts to obtain poly(p-phenylene vinylene) (PPV) molecules without intermacromolecular aggregation two strategies were employed: the addition of a strong electrolyte, lithium chloride, to the solution of the precursor, or/and the preparation of solid solutions from co-dissolved precursor and poly(vinyl alcohol) (PVA). The effects on the thermal conversion process of PPV were studied. Complete isolation of the PPV chains was not attained, but a significant degree of chain separation was achieved, as demonstrated by spectroscopic data. The main observations were that strong intermacromolecular forces operate during the PPV elimination step, resulting in simultaneous aggregation with the formation of the final chains. The relative emission efficiency increases up to 115% for PPV and PPV:PVA films when 0.7% and 1.4% of LiCl, respectively, are added and lower conversion temperature (100 °C) procedure is employed. In the case of total annealing procedure (230 °C) the emission efficiency increases 65% for PPV:PVA film with 0.7% of LiCl. For PPV:LiCl films, this parameter decreases substantially (∼11%) when the salt concentration increases above 10%.     

Thermal conductivity of stretched and annealed poly (p-phenylene sulfide) films

The temperature variation of the thermal conductivities of as-prepared, mechanically stretched, as-prepared and then annealed PPS samples are presented. Unusually high thermal conductivity values are observed as compared to other polymeric materials. In agreement with the X-ray diffraction observations, the thermal conductivity of the oriented film is higher than that of the as-prepared or annealed films. The differences observed after stretching are comparable to those previously reported for polyethylene and polyacetylene films for the same draw ratios. These unusually high thermal conductivity values justify the use of PPS in devices where efficient heat dissipation, associated with electrical insulation, is required.     

The effects of xenon ion irradiation on the photoluminesce behavior of poly(p-cresolformaldeyde)/diazonaphtoquinone thin films

In the present paper, we investigate the origin of photoluminescence (PL) and the changes in the optical properties: refractive index and absorption coefficient, in poly(p-cresolformaldeyde) and diazonaphtoquinone thin films irradiated with Xe ions. Films 400 nm thick have been irradiated with 800 keV Xe²⁺ ions in a fluence range from 10¹³ to 6 × 10¹⁵ Xe cm⁻². The structural modifications were followed by the techniques of nuclear reaction analysis, elastic recoil detection analysis, Rutherford backscattering, Fourier transform infrared and Raman spectroscopies. The PL behavior was characterised with 488 nm excitation wavelength. The pristine films show emission with maxima of the main bands located at 635, 720 and 830 nm. For fluences up to 10¹⁴ Xe cm⁻², the photoluminescence intensity increases with the irradiation fluence. The chain mobility lowering, characterized by the crosslinked structure, explains this behavior in organic systems. Other possible contribution for increasing of PL intensity, at these fluences, is the presence of oxygen trapped in the polymer chains by the dangling bonds. At intermediate and higher fluences, the photoluminescence starts to decrease. At fluences higher than 10¹⁴ Xe cm⁻², irreversible changes of the organic structure occur and they are characterized by large losses of oxygen and hydrogen, transforming the material into amorphous carbon films. The loss of photoluminescent behavior is associated with the light absorption characteristics of the amorphous carbon structure. This conclusion is supported by the observed increase of the refractive indexes and absorption coefficients, obtained in the infrared region, as well as by the Raman results. Also, the effect of irradiation modifying the refractive index in the infrared region suggests the application of these films as waveguide in this region of wavelength.     

稀释磁性半导体Zn1—xFexSe薄膜的光学特性

用真空蒸镀法制备了稀释磁性半导体Zn_(1-x)Fe_xSe多晶薄膜,用X射线衍射和电子扫描电镜测定了薄膜结构和成份.其光吸收数据表明:光学能隙E_g随着Fe~(2+)成分x增加而线性减小,用线性回归法拟合得其关系.E_g=2.722-2.2x(eV).     

Characterization of the hole transport and electrical properties in poly(9,9-dioctylfluorene)

A systematic study of the hole transport and electrical properties in blue-emitting polymers as poly(9,9-dioctylfluorene) (PFO) has been performed. We show that the temperature dependent and thickness dependent current density versus voltage characteristics of PFO hole-only devices can be accurately described using our recently introduced improved mobility model based on both the Arrhenius temperature dependence and non-Arrhenius temperature dependence. Within the improved model, the mobility depends on three important physical quantities: temperature, carrier density, and electric field. For the polymer studied, we find the width of the density of states σ=0.115 eV and the lattice constant a=1.2 nm. Furthermore, we show that the boundary carrier density has an important effect on the current density versus voltage characteristics. Too large or too small values of the boundary carrier density lead to incorrect current density versus voltage characteristics. The numerically calculated carrier density is a decreasing function of distance from the interface. The numerically calculated electric field is an increasing function of distance. Both the maximum of carrier density and minimum of electric field appear near the interface.     

A variable electron beam and its irradiation effect on optical and electrical properties of CdS thin films

A low energy electron accelerator has been constructed and tested. The electron beam can operate in low energy mode (100 eV to 10 keV) having a beam diameter of 8–10 mm. Thin films of CdS having thickness of 100 nm deposited on ITO-coated glass substrate by thermal evaporation method have been irradiated by electron beam in the above instrument. The I–V characteristic is found to be nonlinear before electron irradiation and linear after electron irradiation. The TEP measurement confirms the n-type nature of the material. The TEP and I–V measurements also confirm the modification of ITO/CdS interface with electron irradiation.      

Effect of laser treatment on the optical properties of poly(methyl methacrylate) thin films

In this work, the effect of laser pulse treatment on the optical properties of poly(methyl methacrylate) (PMMA) films has been studied experimentally. The second harmonic of a pulsed Nd:YAG laser at 532 nm and 6 ns pulse width with 10 Hz repetition rate was used to modify the surface of red-BS-dye-doped PMMA films. Samples were ablated with 50 and 100 laser pulses. Optical reflectance and transmittance spectra were obtained in the range of 200–2000 nm. The optical properties of the films were influenced by the pulse number significantly. The oscillator and dispersion energies of the films were determined using the Wemple-Didomenico model. The optical band gap energy was extracted using the Tauc method. Results show that the optical parameters of the films were changed significantly after laser treatment.     

The influence of UV-irradiation and support type on surface properties of poly(methyl methacrylate) thin films

Thin poly(methyl methacrylate) (PMMA) films were prepared by a solution casting on different supports (glass and aluminium plates with different gloss). UV-irradiation (λ = 254 nm) was used for polymer modification. Surface properties of PMMA were studied by contact angle measurements, attenuated total reflection infrared spectroscopy and optical microscopy. It was found that support type has no influence on surface properties of virgin PMMA, however, the changes in these properties were observed during UV modification of polymer film. The most efficient photochemical reactions appeared in sample placed on the rough Al, whereas the smallest effect was observed in polymer on the glass.     

EDTA辅助水热合成FeS2/NiSe2复合纳米晶及其薄膜光电性质

以EDTA为螯合剂,加入MX2结构化合物NiSe_2作为晶种,水热合成了FeS_2 纳米晶 .x射线衍射分析结果表明产物为单一相黄铁矿型FeS_2 (pyrite) ,平均粒径约 4 0— 5 0nm .丝网印刷成膜且高温退火后FeS_2 薄膜光学直接带隙变宽 .随晶种量的增加 ,吸收边在紫外—可见光谱区红移、方块电阻升高、霍尔迁移率上升和载流子浓度下降 ,实现了n型掺杂 .并且对FeS_2 的形成机理进行了讨论     

Thickness effect on the structural and optical constants of stibnite thin films prepared by sulfidation annealing of antimony films

This paper deals with some physical properties of antimony sulphide Sb₂S₃ thin films obtained by an annealing process in sulphur vapors at 300 °C of Sb thermal evaporated thin films deposited on glass substrate. The crystal structure and surface morphology were investigated by both XRD and AFM techniques. This structural study shows that Sb₂S₃ thin films were well crystallized in orthorhombic structure and some parameters such as the lattice parameter, crystallite size, microstrain and degree of preferred orientation have been reported and correlated with the effect of crystallite size. On the other hand, the refractive index and the extinction coefficient were discussed in terms of the Forouhi–Bloomer model. The optical band gap was found to range from 1.75 to 2.23 eV. Finally, the analysis of the optical parameters extracted from the Urbach–Martienssen and Forouhi–Bloomer models lead to some explanations of the correlations between the structural properties in terms of the crystallite size and optical ones.     

Fe,Co共掺杂ZnO薄膜结构及发光特性研究

采用溶胶凝胶法在玻璃衬底上制备了Fe,Co共掺Zn0.9FexCo0.1-xO(x=0,0.03,0.05,0.07)系列薄膜.通过扫描电镜(SEM)、X射线衍射(XRD)、X射线光电子谱(XPS)和光致发光(PL)谱对薄膜样品的表面形貌、晶体结构、成分和光学性能进行了研究.XRD结果表明所有ZnO薄膜样品都呈六方纤锌矿结构,在样品中没有观察到与Fe和Co相关的团簇,氧化物及其他杂相的衍射峰,表明共掺杂改善了Fe或Co在ZnO的分散性.XPS测试结果揭示样品中Co离子的价态为+2价;Fe离子的价态为+2价和+3价共存,但Fe相对浓度的增大导致Fe3+含量增加.所有样品的室温光致发光谱(PL)均观察到紫外发光峰和蓝光双峰,其中Fe,Co共掺ZnO薄膜的紫外发光峰较本征ZnO出现蓝移,蓝光双峰峰位没有变化,但发光强度有所减弱;而掺杂ZnO薄膜的绿光发光峰几乎消失.最后,结合微结构和成分分析对薄膜样品的发光机理进行了讨论.     

Interface effects on the nonlinear optical properties of thin films

The optical nonlinearity of low-dimension structures is studied in the self-effect case at a wavelength of 630 nm in a range of light intensities below 0.1 W/cm² by waveguide methods. Common tendencies in relationships between intensity of light and optical properties of multilayer structures and semiconductor-doped glass films are detected. It is shown that the state of interfaces determines the character of optical nonlinearity.     

EDTA辅助水热合成FeS2/NiSe2复合纳米晶及其薄膜光电性质

以EDTA为螯合剂，加入MX2结构化合物NiSe₂作为晶种，水热合成了FeS₂纳米晶. x射线衍射分析结果表明产物为单一相黄铁矿型FeS₂（pyrite）,平均粒径约40—50nm.丝网印刷成膜且高温退火后FeS₂薄膜光学直接带隙变宽.随晶种量的增加，吸收边在紫外—可见光谱区红移、方块电阻升高、霍尔迁移率上升和载流子浓度下降，实现了n型掺杂.并且对FeS₂的形成机理进行了讨论. 关键词： 2纳米晶')" href="#">FeS₂纳米晶 水热 诱导结晶 直接禁带宽度      

Influence of thickness and annealing on linear and nonlinear optical properties of manganese (III) chloride tetraphenyl porphine (MnTPPCl) organic thin films

Thin films of manganese (III) chloride 5,10,15,20-tetraphenyl-21H,23H-porphine (MnTPPCl) with different film thickness were deposited by an evaporation technique. Some optical constants were calculated for these films at a thickness of 110, 220 and 330 nm and annealing temperature of 373 and 437 K. IR spectrum demonstrating that the thermal evaporation method is a good one to acquire undissociated and stoichiometric MnTPPCl films. Our perceptions demonstrate that the mechanism of the optical absorption obeys with the indirect transition. It was found that the energy gap, E_g, affected by the film thickness and annealing. Dispersion of the refractive index is described using single oscillator model. Dispersion parameters are calculated as a function of the film thickness and annealing temperature. In addition, the third-order nonlinear susceptibility, χ⁽³⁾, and the nonlinear refractive index, n₂, were calculated.     

Optical band gap and optical constants in a-Se80Te20−xPbx thin films

The optical constants (absorption coefficient, refractive index, extention coefficient, real and imaginary part of dielectric constant) have been studied for a-Se₈₀Te_20−xPb_x (where x = 0, 2, 6, 10) thin films as a function of photon energy in the wave length range (500–1000 nm). It has been found that the optical band gap increases while the refractive index and the extinction coefficient (k) decreases on incorporation of lead in Se–Te system. The value of absorption coefficient (α) and the extinction coefficient (k) increases, while the value of refractive index (n) decreases with incident photon energy. The results are interpreted in terms of the change in concentration of localized states due to the shift in fermi level.     

Influence of Al concentration on electrical, structural and optical properties of Al-As codoped p-ZnO thin films

We report the influence of Al concentration on electrical, structural, optical and morphological properties of Al-As codoped p-ZnO thin films using RF magnetron sputtering. Al-As codoped p-ZnO films with different Al concentrations were fabricated using As back diffusion from the GaAs substrate and sputtering Al₂O₃ mixed ZnO targets (1, 2 and 4 at%). The grown films were investigated by Hall effect measurement, X-ray diffraction (XRD), electron probe microanalysis (EPMA), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and atomic force microscopy (AFM) to study the electrical, structural, optical and morphological properties of the films. From the XRD, it was observed that both full-width at half-maximum (FWHM) and c-axis lattice constant have similar trends with respect to Al concentration. Hall measurements showed that the hole concentration increases as the Al concentration increases from 10¹⁵ to 10²⁰ cm⁻³. The increase in hole concentration upon codoping was supported by the red shift in the near-band-edge (NBE) emission observed from room temperature PL spectra. The proposed p-type mechanism due to As_Zn-2V_Zn complex was confirmed by low temperature PL and XPS analysis. The low FWHM, resistivity and peak-to-valley roughness observed by XRD, Hall measurement and AFM, respectively, suggest that 1 at% Al-doped ZnO:As film is the best codoped film.     

Effect of Cr implantation on structural and optical properties of AlN thin films

Molecular beam epitaxy (MBE) grown AlN thin layer on sapphire substrates have been implanted with Cr⁺ ions for various dose from 10¹³ to 10¹⁵ cm⁻². The analyses were carried out by an X-ray diffractometer (XRD), Raman spectroscopy, a spectrophotometer and spectroscopic ellipsometry (SE) for structural and optical analyses. E₂(high) and A₁(LO) Raman modes of AlN layer have been observed and analyzed. The behavior of Raman shift and the variation in intensity and in peak width of Raman modes as a function of ions flux are explained on the basis of chromium substituting aluminum atom and implantation-induced lattice damage. Both Raman and X-ray analyses reveal that the incorporation of chromium atoms increases in the host lattice with the increasing of Cr ions fluence. The band gap energy was determined by using transmission spectra. It was found that the band gap energy decreases as the ion dose increases. The band gap of the unimplanted AlN is 6.02 eV and it decreases down to 5.92 eV for the Cr⁺-implanted AlN with a ion dose of 1×10¹⁵ cm⁻². Optical properties such as optical constants of the samples were examined by using a spectroscopic ellipsometer. It was observed that the refractive index (n) decreases with the increasing of ion dose.     

Effects of post-thermal treatments on morphological and optical properties of NiO/Ni(OH)2 thin films synthesized by solution growth

Room temperature deposition of PVP capped nanostructured NiO/Ni(OH)₂ thin film, the morphological and optical characterizations by solution growth technique are reported. The nanostructured thin films which were deposited on optical glass substrates were annealed at different temperatures and then subjected to structural, morphological and optical characterizations. X-ray diffraction measurements of the films revealed that higher temperatures during the thermal treatment enhanced the crystallinity of the thin films. The SEM surface micrographs show non-interconnected uniformly deposited fibre-like structures with approximate lengths between 400 and 1200 nm. The optical band gap energy roughly decreased from about 2.7 eV to about 2.2 eV with thermal treatment. The absorbance of the thin films annealed at 300 and 400 °C was as high as 90% in the visible region of the electromagnetic spectrum. These materials could be useful in solar thermal conversion processes.     

Structural, optical and magnetic properties of (ZnO)1−x(MnO2)x thin films deposited at room temperature

The structural, magnetic and optical properties of (ZnO)_1−x(MnO₂)_x (with x = 0.03 and 0.05) thin films deposited by pulsed laser deposition (PLD) were studied. The pellets used as target, sintered at different temperatures ranging from 500 °C to 900 °C, were prepared by conventional solid state method using ZnO and MnO₂ powders. The observation of non-monotonic shift in peak position of most preferred (1 0 1) ZnO diffraction plane in XRD spectra of pellets confirmed the substitution of Mn ions in ZnO lattice of the sintered targets. The as-deposited thin film samples are found to be polycrystalline with the preferred orientation mostly along (1 1 0) diffraction plane. The UV-vis spectroscopy of the thin films revealed that the energy band gap exhibit blue shift with increasing Mn content which could be attributed to Burstein-Moss shift caused by Mn doping of the ZnO. The deposited thin films exhibit room temperature ferromagnetism having effective magnetic moment per Mn atom in the range of 0.9-1.4μ_B for both compositions.