Spectroscopic study of poly(3-alkylthiophenes) electrochemically synthesized in different conditions

In this work, poly(3-alkylthiophenes) films were synthesized electrochemically in acetonitrile with LiClO₄ or Et₄NBF₄ at 5 or 18 °C. The films were deposited on platinum plates, and the polymer as-prepared was referred to as-oxidized. The as-reduced polymer was obtained by subjecting the as-oxidized product to ?1.70 V for 1 min. These various products were characterized by cyclic voltammetry, reflectance UV–Vis and Raman spectroscopy, and the results were used to estimate the ionization potential (I _P), electron affinity (E.A.) and energy gap (E _g) parameters. This study was possible because the Raman spectra demonstrated three structures (aromatic, radical cation and dication segments) which formed the P3MT and P3OT polymer chains.     

Microstructural properties of electrochemically synthesized ZnSe thin films

In this study, we report the electrosynthesis of zinc selenide (ZnSe) thin films on indium-doped tin oxide-coated glass substrates. The deposited ZnSe thin films have been characterized for structural (X-ray diffraction), surface morphological (scanning electron microscopy), compositional (energy dispersive analysis by X-rays), photo luminescence property, and optical absorption analysis. Formation of cubic structure with preferential orientation along the (111) plane was confirmed from structural analysis. In addition, the influence of the deposition potential on the microstructural properties of ZnSe is plausibly explained. The optical properties of ZnSe thin films are estimated using the transmission spectrum in the range of 400–1200 nm. The optical band gap energy of ZnSe thin films was found to be in the range between 2.52 and 2.61 eV. Photoluminescence spectra were observed at blue shifted band edge peak. The morphological studies depict that the spherical and cuboid shaped grains are distributed evenly over the entire surface of the film. The sizes of the grains are found to be in the range between 150 and 200 nm. The ZnSe thin film stoichiometric composition was observed at optimized deposition condition.     

Structural, electrical and optical properties of Ga-doped ZnO films on cyclo-olefin polymer substrates

Ga-doped ZnO (GZO) films with a thickness of 100 nm were prepared on cyclo-olefin polymer (COP) and glass substrates at various temperatures below 100 °C by ion plating with direct-current arc discharge. The dependences of the characteristics of GZO films on the substrate temperature Ts were investigated. All the polycrystalline GZO films, which exhibited a high average visible transmittance of greater than 86%, were crystallized with a wurtzite structure oriented along the c-axis. The lowest resistivities of the GZO films were 5.3 × 10^− 4 Ωcm on the glass substrate and 5.9 × 10^− 4 Ωcm on the COP substrate.     

Side radical influence on the nonlinear optical properties and thermal stability of poled polymer films

Films of polyetherketone doped with the chromophores Disperse Red 1 (DR1) and Disperse Red 13 (DR13) were prepared by spin-coating method. By the in situ Second-harmonic Generation (SHG) signal intensity measurement, the optimal poling temperatures were obtained. For the investigated polyetherketone polymer doped with DR1 (DR1/PEK-c) and polyetherketone polymer doped with DR13 (DR13/PEK-c) films, the optimal poling temperatures were 150°C and 140°C, respectively. Under the optimal poling conditions, the high second-order nonlinear optical coefficient ₃₃ ⁽²⁾ = 11.02 pm/V has been obtained for the DR1/PEK-c; and for DR13/PEK-c at the same conditions the coefficient is 17.9 pm/V. The SHG signal intensity DR1/PEK-c could maintain more than 80% of its initial value when the temperature was under 100°C, and the SHG signal intensity of the DR13/PEK-c could maintain more than 80% of its initial value when the temperature was under 135°C.     

The optical and electrical properties of copper indium di-selenide thin films

Thin films of copper indium di-selenide (CIS) with a wide range of compositions near stoichiometry have been formed on glass substrates in vacuum by the stacked elemental layer (SEL) deposition technique. The compositional and optical properties of the films have been measured by proton-induced X-ray emission (PIXE) and spectrophotometry (photon wavelength range of 300–2500 nm), respectively. Electrical conductivity (σ), charge-carrier concentration (n), and Hall mobility (μ_H) were measured at temperatures ranging from 143 to 400 K. It was found that more indium-rich films have higher energy gaps than less indium-rich ones while more Cu-rich films have lower energy gaps than less Cu-rich films. The sub-bandgap absorption of photons is minimum in the samples having Cu/In ≈ 1 and it again decreases, as Cu/In ratio becomes less than 0.60. Indium-rich films show n-type conductivities while near-stoichiometric and copper-rich films have p-type conductivities. At 300 K σ, n and μ_H of the films vary from 2.15 × 10⁻³ to 1.60 × 10⁻¹ (Ω cm)⁻¹, 2.28 × 10¹⁵ to 5.74 × 10¹⁷ cm⁻³ and 1.74 to 5.88 cm² (V s)⁻¹, respectively, and are dependent on the composition of the films. All the films were found to be non-degenerate. The ionization energies for acceptors and donors vary between 12 and 24, and 3 and 8 meV, respectively, and they are correlated well with the Cu/In ratios. The crystallites of the films were found to be partially depleted in charge carriers.     

非平衡磁控溅射沉积Ta-N薄膜的结构与电学性能研究

采用直流反应非平衡磁控溅射技术在单晶Si(100)和玻璃表面沉积氮化钽(Ta-N)薄膜,分别测试了薄膜的结构、成分、电阻率和吸收光谱,研究了氮氩流量比(N2∶Ar)变化对Ta-N薄膜的结构和电学性能的影响.研究结果表明随N2∶Ar增加,依次生成六方结构的γ-Ta2N、面心立方结构(fcc)的δ-TaNx、体心四方结构(bct)的TaNx;N2∶Ar在0.2～0.8的范围内,Ta-N薄膜中只存在着fcc δ-TaNx;当N2∶Ar＞1之后,Ta-N薄膜中fcc δ-TaNx和bct TaNx共存.Ta-N薄膜电阻率随N2∶Ar流量比增加持续增加,当N2∶Ar为1.2时,薄膜变为绝缘体,光学禁带宽度为1.51eV.     

The influence of deposition rate on the electrical properties of thin tellurium films

The Hall mobility μ and the carrier concentration p of thin evaporated tellerium films 130 Å thick were investigated as a function of the deposition rate. We found that both these parameters increase as the deposition rate increases. These results are compared with results published in the literature for thicker films of evaporated tellurium.     

Influence of texture on optical and electrical properties of diamond films

The optical and electrical properties of variously textured diamond films have been investigated in this paper. SEM and Raman spectrum indicated that the films produced were of high quality with either (0 0 1) or (1 1 1) orientation. A four-layer model was used to fit the measured spectroscopic ellipsometry data. The results indicated that the properties of (0 0 1)-oriented diamond films were superior to those of (1 1 1)-oriented one. The refractive index and extinction coefficient of (0 0 1)-oriented diamond film in the infrared region of 2500-12500 nm was measured as 2.391 and of the order of 10⁻⁵, respectively and that for (1 1 1)-oriented one was 2.375 and of the order of 10⁻⁴, respectively. The dark current of the (0 0 1)-oriented diamond film was measured as 33.7 nA for an applied electric field of 100 kV cm⁻¹, its resistivity being about 2.33×10¹⁰ Ω cm. Current passing through the (0 0 1)-oriented diamond film during testing did not change significantly.     

Structural,optical and electrical properties of solvothermally synthesized PbTe nanodisks

The present study investigates the properties of mechanically compacted pellets of nanosized lead telluride powders synthesized by using ethylene glycol as solvent and PVP as surfactant. XRD analysis indicates the formation of PbTe nanocrystals which exhibit both cubic and orthorhombic phases. Morphological study reveals that the prepared PbTe nanocrystals have disk-like shape. Electrical analysis reveals that the electrical conductivity of PbTe nanocrystals can be enhanced by the formation of nanodisks. Optical absorption and PL results show a large blue-shift which implies that the prepared PbTe nanodisks show strong quantum confinement effect. The possible formation mechanism of the PbTe nanodisks was also discussed.     

The influence of deposition parameters on the optical properties and growth of ZnS films

A vacuum automatic ellipsometer was used to observe and reveal the effect of the rate of deposition on the structural irregularities of ZnS films during growth.The high accuracy and sensitivity of this instrument were exploited for measuring the refractive index of ZnS films prepared at various rates of deposition and substrate temperatures.     

The electrical and optical properties of BiSiO2 cermet films

The electrical and optical properties of BiSiO₂ cermet films were studied. Using the temperature dependence of the resistivity of the cermet films and the dependence of the amount of oxidation of the fine bismuth particles on the volume percentage of bismuth, the three-dimensional percolation threshold composition was determined to be approximately 18 vol. % Bi.     

The influence of deposition temperature on the crystalline and electrical properties of thin silver films

Silver films were evaporated onto glass substrate under ultrahigh vacuum conditions and investigated using X-ray diffraction analysis and electrical measurements. The influence of the deposition temperature on the crystallite size, the surface roughness and the electrical properties was studied by analysing the width, intensity and fine structure of the diffraction peaks and the film resistivity.     

The influence of deposition parameters on the optical and electrical properties of r.f.-sputter- deposited indium tin oxide films

The fabrication and characterization of indium tin oxide thin films prepared by r.f. sputter deposition from a target of composition 90mol.% In₂O₃-10mol.%SnO₂ are described. The properties were found to depend on the rate of deposition, the post-deposition heat treatment and the composition of the sputtering gas. Using the optimum combination of these parameters, films with a resistivity of 1.36 x 10^-4 Ω cm were produced. Films with a thickness of less than 1000 Å had a visible transmittance of greater than 80% for wavelengths in the range 450–1500 nm (being greater than 90% above 550 nm).     

The influence of epitaxial strain on magnetic and electrical properties of BiFeO3 thin films

Strained epitaxial BiFeO₃ films deposited on (001) SrTiO₃ substrates by metal organic chemical vapor deposition were studied by optical second harmonic generation (SHG) and SQUID magnetometry. The observed SHG intensity vs temperature dependencies indicate that for less strained films (σ < 0.6 GPa) a strong interplay between the ferroelectric and magnetic subsystems exists, while for the films with larger σ-values strain-induced destruction of the magnetic cycloidal ordering takes place.     

Determination of optical and electrical properties of ZnSe thin films

A thin film of zinc selenide (ZnSe) was deposited onto a clean glass substrate using a vacuum evaporation technique. This thin film was characterized through X-ray diffraction, which indicated that the film was polycrystalline in nature. Absorption and transmission spectra of this thin film were recorded using a spectrophotometer. The energy band gap, refractive index and extinction coefficient were determined using these spectra. It was found that the energy band gap of ZnSe film was 2.55 eV. It was also observed that the refractive index and extinction coefficient of the film decreased with the increase of wavelength. The conductivity of this thin film was determined by current–voltage measurement using an electrometer over the temperature range from room temperature to 413 K. It was observed that conductivity increased with increase in temperature. This is explained on the basis of structural changes occurring due to the change in grain size and the increase in carrier density.     

Investigation of optical and electrical properties of ZnO thin films

Zinc oxide (ZnO) thin films were deposited on Si substrates using various working pressures by magnetron sputter. The resistivity of the deposited ZnO films decreases with working pressure, and the resistivity of 4.3 × 10⁻³ Ω cm can be obtained without post annealing. According to the optical transmittance measurements, the optical transmittance above 90% in the wavelength longer than 430 nm and about 80% in the wavelength of 380 nm can be found. Using time-resolved photoluminescence measurement, the carrier lifetime increases with working pressure due to the reduction of nonradiative recombination rate. The reduction of nonradiative recombination rate is originated from the decrease of oxygen vacancies in the ZnO films deposited at a higher working pressure. This result is verified by the photoluminescence measurements. Besides, by increasing the working pressure, the absorption coefficient was decreased and the associated optical energy gap of ZnO thin films was increased.     

The electrical and optical properties of indium zinc tin oxide thin films with different Sn/Zn ratio

Indium zinc tin oxide (IZTO) thin films with two different chemical compositions, i.e. IZTO15 and IZTO25, where In content was fixed at 60 at.% and Sn content was 15 and 25 at.%, respectively, were deposited onto alkaline-free glass substrate at temperature from 37 °C to 600 °C. The deposition process was carried out in argon using an RF magnetron sputter. After deposition, the films were annealed in argon atmosphere at 450 °C for 30 min. The effect of substrate temperature and annealing treatment was investigated, and the minimum resistivity value of 3.44 × 10^− 4Ω.cm was obtained from the film deposited at 400 °C using IZTO25 target followed by rapid thermal annealing at 450 °C for 30 min. The average optical transmittance was kept fairly high over 80%. It was proven that both substrate temperature and thermal annealing were important parameters in lowering the electrical resistivity without deteriorating optical properties.     

Structural,optical and electrical properties of CdZnS thin films

The thin films of Cd_1-x Zn _x S (x?=?0, 0.2, 0.4, 0.6, 0.8 and 1) have been prepared by the vacuum evaporation method using a mechanically alloyed mixture of CdS and ZnS. The structural, optical and electrical properties have been investigated through the X-ray diffractometer, spectrophotometer and Keithley electrometer. The X-ray diffraction patterns of these films show that films are polycrystalline in nature having preferential orientation along the (002) plane. In the absorption spectra of these films, absorption edge shifts towards lower wavelength with the increase of Zn concentration. The energy band gap has been determined using these spectra. It is found that the energy band gap increases with increasing Zn concentration. The electrical conductivity of so prepared thin films has been determined using a I–V characteristic curve for these films. The result indicates that the electrical conductivity decreases with increasing Zn content and increases with temperature. An effort has also been made to obtain activation energy of these films which increases with increasing Zn concentration in CdS.     

Nonlinear optical properties of several siloxane polymer Langmuir-Blodgett films

The Langmuir-Blodgett film formation and the nonlinear optical properties of three polysiloxane polymer materials have been investigated. All three compounds could be built-up as Z-type layers on a variety of substrates. Experiments on the linear electrooptic (Pockels') effect revealed a second-order nonlinear susceptibility χ⁽²⁾ (−ω; ω, 0) of 10.6 pmV⁻¹ for one of the materials; the order of magnitude of this result was confirmed using second-harmonic generation. For multilayer films the second-harmonic intensity was found to increase with the thickness of the LB structure. However, a linear dependence upon film thickness was evident, rather than the expected quadratic variation.