Effects of 1064 nm laser on the structural and optical properties of nanostructured TiO2 thin film

TiO₂ thin film has been widely used as photoelectrode in dye-sensitized solar cells. It can also be used in quantum dot synthesized solar cells. Study of its effects in different spectrum of light is important for its use in solar cells. We have reported effects of 1064 nm laser on the surface morphology, structural and optical properties of nanostructured TiO₂ thin film deposited on glass substrates using sol-gel spin coating technique. Q-Switched Nd:YAG pulsed laser at various power densities is used in this study. Surface morphology of the film is investigated using X-ray diffraction (XRD) and atomic force microscopy technique. The XRD pattern of as deposited TiO₂ thin film is amorphous and after laser exposure it became TiO₂ anatase structure. Atomic force microscopy of the crystalline TiO₂ thin film shows that the grain size increases by increasing laser power density. The calculations of the band gap are carried out from UV/Visible spectroscopy measurements with JASCO spectrometer. For laser power density of 25 MW/cm² there is an increase in the transmission and it decreases at the value of 38 MW/cm² and band gap decreases with increasing laser power density. Photoluminescence spectra of the crystalline TiO₂ thin film indicate two broad peaks in the range of 415 and 463 nm, one for band gap peak (415 nm) and other for oxygen defect during film deposition process.     

Structural,optical and electrical properties of laser irradiated Pb doped Ga–Se chalcogenide thin films

Using the Transverse Electrical Excitation at Atmospheric Pressure (TEA) nitrogen laser, we had irradiated the amorphous thin films of Ga₁₀Se₈₁Pb₉ chalcogenide glass and the results have been discussed in terms of the structural aspects of Ga₁₀Se₈₁Pb₉ glass. The observed changes are associated with the interaction of the incident photon and the lone-pairs electrons which affects the band gap. The X-ray structural characterization revealed the amorphous nature of as prepared films and polycrystalline nature of the laser irradiated films. The optical band gap of these thin films is measured by using the absorption spectra as a function of photon energy in the wavelength region 400–1200 nm. It is found that the optical band gap decreases while the absorption coefficient increases with increasing the irradiation time. The decrease in the optical band gap has been explained on the basis of change in nature of films, from amorphous to polycrystalline state, with the increase in exposure time. The dc conductivities and activation energies of these thin films are measured in temperature range 303–403 K. It has been found that the activation energy in Ga₁₀Se₈₁Pb₉ chalcogenide thin films decreases whereas the dc conductivity increases at each temperature by increasing the irradiation time.     

Structural and optical properties of amorphous hydrogenated silicon carbonitride films produced by PECVD

Amorphous hydrogenated silicon carbonitride thin films (a-Si:C:N:H), deposited by plasma enhanced chemical vapour deposition (PECVD) using hexamethyldisilazane (HMDSN) as monomer and Ar as feed gas, have been investigated for their structural and optical properties as a function of the deposition RF plasma power, in the range of 100-300 W. The films have been analysed by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), UV-vis-NIR spectrophotometry and atomic force microscopy (AFM). From the analysis of the FT-IR spectra it results that the films become more amorphous and inorganic as RF plasma power increases. The incorporation of oxygen in the deposited layers, mainly due to the atmospheric attack, has been evaluated by XPS and FT-IR spectroscopy. Reflectance/transmittance spectra, acquired in the range of 200-2500 nm, allow to descrive the film absorption edge for interband transitions. A relationship between the optical energy band gap, deduced from the absorption coefficient curve, and the deposition RF plasma power has been investigated. The reduction of the optical energy gap from 3.85 to 3.69 eV and the broadening of the optical absorption tail with RF plasma power increasing from 100 to 300 W are ascribed to the growth of structural disorder, while the increase of the refractive index, evaluated at 630 nm, is attributed to a slight densification of the film. The AFM analysis confirms the amorphous character of the films and shows how the deposited layers become rougher when RF plasma power increases. The wettability of the film has been studied and related to the chemical composition and to the morphology of the deposited layers.     

The effect of rf power on the growth of InN films by modified activated reactive evaporation

We report the effect of rf power on the structural, optical and electrical properties of InN films grown by modified activated reactive evaporation. In this technique, the substrates were kept on the cathode instead of ground electrode. The films grown at higher rf power shows preferential c-axis orientations for both silicon and glass substrates. The films prepared at 100 W show best structural, electrical and optical properties. The c-axis lattice constant was found to decrease with increase in rf power which can be attributed to reduction in excess nitrogen in the films. The band gap decreases with increase in rf power due to Moss-Burstein shift. The decrease in carrier concentration and optical band gap with increase in rf power can also be related to excess nitrogen in the film. The Raman spectra shows a red shift in the A₁(LO) and E₂ (high) mode from the reported value. The possible origin of the present large band gap is due to Moss-Burstein shift. The new film growth method opens opportunities for integrating novel substrate materials with group III nitride technologies.     

Effect of substrate temperature on structural, optical and electrical properties of pulsed laser ablated nanostructured indium oxide films

Nanocrystalline indium oxide (INO) films are deposited in a back ground oxygen pressure at 0.02 mbar on quartz substrates at different substrate temperatures (T_s) ranging from 300 to 573 K using pulsed laser deposition technique. The films are characterized using GIXRD, XPS, AFM and UV-visible spectroscopy to study the effect of substrate temperature on the structural and optical properties of films. The XRD patterns suggest that the films deposited at room temperature are amorphous in nature and the crystalline nature of the films increases with increase in substrate temperature. Films prepared at T_s ≥ 473 K are polycrystalline in nature (cubic phase). Crystalline grain size calculation based on Debye Scherrer formula indicates that the particle size enhances with the increase in substrate temperature. Lattice constant of the films are calculated from the XRD data. XPS studies suggest that all the INO films consist of both crystalline and amorphous phases. XPS results show an increase in oxygen content with increase in substrate temperature and reveals that the films deposited at higher substrate temperatures exhibit better stoichiometry. The thickness measurements using interferometric techniques show that the film thickness decreases with increase in substrate temperature. Analysis of the optical transmittance data of the films shows a blue shift in the values of optical band gap energy for the films compared to that of the bulk material owing to the quantum confinement effect due to the presence of quantum dots in the films. Refractive index and porosity of the films are also investigated. Room temperature DC electrical measurements shows that the INO films investigated are having relatively high electrical resistivity in the range of 0.80-1.90 Ωm. Low temperature electrical conductivity measurements in the temperature range of 50-300 K for the film deposited at 300 K give a linear Arrhenius plot suggesting thermally activated conduction. Surface morphology studies of the films using AFM reveal the formation of nanostructured indium oxide thin films.     

Effect of environment and heat treatment on the optical properties of RF-sputtered SnO2 thin films

Thin films of SnO₂ were deposited by RF-magnetron sputtering on quartz substrates at room temperature in an environment of Ar and O₂. The XRD pattern shows amorphous nature of the as-deposited films. The optical properties were studied using the reflectance and transmittance spectra. The estimated optical band gap (E_g) values increase from 4.15 to 4.3 eV as the Ar gas content decreases in the process gas environment. The refractive index exhibits an oscillatory behavior that is strongly dependent on the sputtering gas environment. The Urbach energy is found to decrease with increase in band gap. The band gap is found to decrease on annealing the film. The role of oxygen defects is explored in explaining the variation of optical parameters.     

Effect of Laser Fluence on the Structural and Optical Properties of Tantalum Oxide Films Ablated by Pulsed Laser

The influence of laser fluence on the properties of thin films of tantalum oxide is studied in this paper, varying the laser fluence from 5.7 to 8.3 J/cm². Thin films of tantalum oxide were deposited on glass substrates using pulsed-laser ablation technique. X-ray diffraction studies confirm the amorphous/nanocrystalline nature of all the films irrespective of the laser fluence. The Tauc plot analysis suggests that tantalum oxide is an indirect band gap material, whose band gap decreases with increase in laser fluence. The refractive index of the films is found to decrease with increase in laser fluence but the extinction coefficient of the films increases with increase in laser fluence. Fourier transform infrared studies suggest the use of tantalum oxide thin films as oxygen sensors. Micro-Raman analysis reveals the sensitiveness of Ta-O-Ta and Ta-O vibration modes to laser fluence. Among all the films, the film deposited at a laser fluence of 7 J/cm² is found to be superior in quality.     

Preparation and characterization of Al doped ZnO thin films by PLD

This paper describes the effect of doping on the composition, surface morphology and optical, structural and electrical properties of Al doped ZnO thin films by pulsed laser deposition. SEM analysis shows that the crystalline nature of the deposited films decreases with an increase of Al doping concentration from 1% to 6%. In the AFM analysis, the surface roughness of the deposited films increases by increasing the doping concentration of Al. Al doping strongly influences the optical properties of the ZnO thin films. Optical transmittance spectra show a very good transmittance in the visible region (450–700 nm). The calculated optical band gap was found to be in the range from 3.405 to 3.464 eV. Structural analysis confirms that the increases of Al concentration decrease the crystallinity of the ZnO films and the particle size decreases from 45.7±0.09 to 28.0±0.02 nm. In the Raman analysis, the active mode of Al(=1%) doped ZnO films were observed at 434.81 cm⁻¹. The shifts of the active mode (_E2)$\left(E_2\right)$ show the presence of tensile stress in the deposited films. The electrical properties of the deposited films showed that the values of the Hall mobility was in the range between 2.51 and 10.64 cm²/V s and the carrier concentration between 15.7 and 0.78×10¹⁷ and the resistivity values between 1.59 and 10.97 Ωcm, depending on the doping concentration.     

Highly conducting and transparent Ti-doped CdO films by pulsed laser deposition

Titanium-doped cadmium oxide thin films were deposited on quartz substrate by pulsed laser deposition technique. The effect of substrate temperature on structural, optical and electrical properties was studied. The films grown at high temperature show (2 0 0) preferred orientation, while films grown at low temperature have both (1 1 1) and (2 0 0) orientation. These films are highly transparent (63-79%) in visible region, and transmittance of the films depends on growth temperature. The band gap of the films varies from 2.70 eV to 2.84 eV for various temperatures. It is observed that resistivity increases with growth temperature after attaining minimum at 150 °C, while carrier concentration continuously decreases with temperature. The low resistivity, high transmittance and wide band gap titanium-doped CdO films could be an excellent candidate for future optoelectronic and photovoltaic applications.     

FDLC薄膜的化学结构对光学性能的影响

研究氟化类金刚石（FDLC）薄膜化学结构对光学性能的影响，用等离子体增强化学气相沉积（PECVD）法在玻璃基底上沉积氟化类金刚石（FDLC）薄膜，用俄歇能谱、傅里叶红外光谱(FTIR)、紫外 可见光分光光度计 (UV-VIS)对薄膜进行分析。分析结果表明：沉积薄膜是典型的类金刚石结构，薄膜中氟主要以C-F2键存在；随着沉积温度的提高，C-F2含量先增后减；随着F含量的增加，FDLC薄膜的sp3含量减少，sp2含量增加；光学带隙与sp2键含量密切相关，sp2含量越大，薄膜的光学带隙越小。     

Optical and hydrophobic properties of co-sputtered chromium and titanium oxynitride films

The chromium and titanium oxynitride films on glass substrate were deposited by using reactive RF magnetron sputtering in the present work. The structural and optical properties of the chromium and titanium oxynitride films as a function of power variations are investigated. The chromium oxynitride films are crystalline even at low power of Cr target (≥60 W) but the titanium oxynitride films are amorphous at low target power of Ti target (≤90 W) as observed from glancing incidence X-ray diffraction (GIXRD) patterns. The residual stress and strain of the chromium oxynitride films are calculated by sin² ψ method, as the average crystallite size decreases with the increase in sputtering power of the Cr target, higher stress and strain values are observed. The chromium oxynitride films changes from hydrophilic to hydrophobic with the increase of contact angle value from 86.4° to 94.1°, but the deposited titanium oxynitride films are hydrophilic as observed from contact angle measurements. The changes in surface energy were calculated using contact angle measurements to substantiate the hydrophobic properties of the films. UV-vis and NIR spectrophotometer were used to obtain the transmission and absorption spectra, and the later was used for determining band gap values of the films, respectively. The refractive index of chromium and titanium oxynitride films increases with film packing density due to formation of crystalline chromium and titanium oxynitride films with the gradual rise in deposition rate as a result of increase in target powers.     

Laser energy density, structure and properties of pulsed-laser deposited zinc oxide films

Zinc oxide thin films were deposited on soda lime glass substrates by pulsed laser deposition in an oxygen-reactive atmosphere at 20 Pa and a constant substrate temperature at 300 °C. A pulsed KrF excimer laser, operated at 248 nm with pulse duration 10 ns, was used to ablate the ceramic zinc oxide target. The structure, the optical and electrical properties of the as-deposited films were studied in dependence of the laser energy density in the 1.2-2.8 J/cm² range, with the aid of X-ray Diffraction, Atomic Force Microscope, Transmission Spectroscopy techniques, and the Van der Pauw method, respectively. The results indicated that the structural and optical properties of the zinc oxide films were improved by increasing the laser energy density of the ablating laser. The surface roughness of the zinc oxide film increased with the decrease of laser energy density and both the optical bang gap and the electrical resistivity of the film were significantly affected by the laser energy density.     

Structural and optical properties of YSZ thin films grown by PLD technique

We report on the structural and optical properties of yttria stabilized zirconia (YSZ) thin films grown by pulsed laser deposition (PLD) technique and in situ crystallized at different substrate temperatures (T_s = 400 °C, 500 °C and 600 °C). Yttria-stabilized zirconia target of ∼1 in. diameter (∼95% density) was fabricated by solid state reaction method for thin film deposition by PLD. The YSZ thin films were grown on an optically polished quartz substrates and the deposition time was 30 min for all the films. XRD analysis shows cubic crystalline phase of YSZ films with preferred orientation along 〈1 1 1〉. The surface roughness was determined by AFM for the films deposited at different substrate temperatures. The nano-sized surface roughness is found to increase with the increase of deposition temperatures. For the optical analysis, a UV-vis-NIR spectrophotometer was used and the optical band gap of ∼5.7 eV was calculated from transmittance curves.     

The thermoluminescence properties of CdS films under nitrogen atmosphere

Chemically deposited cadmium sulphide (CdS) films have been grown on glass at 60 °C and annealed at nitrogen atmosphere at different temperatures. The as-deposited film shows a mix phase of cubic and hexagonal. Once the film subjected to annealing the hexagonal phase becomes dominant and the crystal size increases due to these changes optical band gap energy decreases from 2.44 to 2.28 eV. The electrical conductivity increases depending on temperature and the film annealed at 423 K shows the highest conductivity. Thermoluminescence (TL) intensity of the films was measured after irradiating the films with ⁹⁰Sr/⁹⁰Y β-source and the trap depths were calculated after the TL curves deconvoluted by using the computer glow curve deconvolution (CGCD) method. It is observed that the as-deposited film has three different trap depths, at around 0.257, 0.372, and 0.752 eV corresponding to 383, 473, and 608 K, respectively.     

Structure and properties of zirconium oxide thin films prepared by filtered cathodic vacuum arc

Zirconium oxide (ZrO₂) thin films deposited at room temperature by the filtered cathodic vacuum arc (FCVA) technique are detailed in terms of the film structure, composition, morphology, and optical and mechanical properties, which are tailored by the oxygen (O₂) flow rate during deposition. The relationships between the film structure, composition, morphology, and properties are emphasized. With an increasing O₂ flow rate, the film evolves in structure from amorphous, through a pure monoclinic phase with varying preferential orientation, to amorphous again, accompanied by an increase in the O/Zr atomic ratio and a conversion of Zr ions from low oxidation states into Zr⁴⁺. Such a structural trend arises from the change in composition, and influences the film morphology and mechanical properties so that the amorphous films exhibit small clusters on the surface and smoother morphology as well as lower hardness compared with the polycrystalline films. The film composition rather than the density dominates the optical properties, where the transmittance and the optical band gap increase with increasing O/Zr values, while the refractive index and extinction coefficients behave conversely with the lowest refractive index (2.16 at 550 nm) approaching the bulk value (2.2) . PACS  68.55.Jk; 78.66.Nk; 68.37.Ps     

Electrical and structural properties of In-doped ZnO films deposited by RF superimposed DC magnetron sputtering system

Zinc-indium-oxide (ZIO) films were deposited on non-alkali glass substrates by RF superimposed DC magnetron sputtering with a ZIO (9.54 wt% In₂O₃ content) high-density, sintered target at room temperature. The electrical, structural and optical properties of the ZIO films deposited with different sputtering parameters were examined. The total power for RF superimposed DC magnetron sputtering was 80 W. The RF power ratio in the total sputtering power was changed from 0 to 100% in steps of 25%. The ZIO films deposited with a 100% RF discharge showed the lowest resistivity, 1.28×10⁻³ Ω cm, due to the higher carrier concentration. The ZIO film deposited at 50% RF power showed a relatively larger grain size and smaller FWHM. XPS suggested an increase in the level of In³⁺ substitution for Zn²⁺ in the ZnO lattice with increasing RF/(DC+RF) due to the low damage process. The average transmittance of all ZIO films in the visible light region was >80%. The increasing RF power portion of the total sputtering power led to a broadening of the optical band gap, which was attributed to the increase in carrier density according to Burstein-Moss shift theory.     

工作压强对硅掺杂辉光放电聚合物结构和性能的影响

采用辉光放电聚合技术,在不同工作压强条件下制备了掺硅的辉光放电聚合物(Si-GDP)薄膜.并采用傅里叶变换红外吸收光谱和X射线光电子能谱(XPS)对Si-GDP薄膜进行了表征,分析了压强变化对其内部结构及成分的影响.利用紫外—可见光谱对Si-GDP薄膜的光学带隙进行了分析.结果表明:Si-GDP薄膜中Si元素主要以Si—C,Si—H,Si—O,Si—CH₃的键合形式存在;随着工作压强的增大,薄膜中Si—C键相对含量先减小后增加;从Si-GDP薄膜的XPS分析可以发现,C—C与C C含 关键词： 硅掺杂辉光放电聚合物薄膜 工作压强 傅里叶变换红外吸收光谱 X射线光电子能谱     

Effects of laser irradiation on optical properties of a-Se100−x Te x thin films

The effect of laser irradiation on the optical properties of thermally evaporated Se_100?x Te _x (x=8, 12, 16) chalcogenide thin films has been studied. The result shows that the irradiation causes a shift in the optical gap. The results have been analyzed on the basis of laser irradiation-induced defects in the film. The width of the tail of localized state in the band gap has been evaluated using the Urbach edge method. As the irradiation time increases, the values of the optical energy gap for all compositions decrease, while tail energy width increases. It is also observed that the optical energy gap decreases with increasing Te content in the alloy. These changes are a consequence of an increment in disorder produced by laser irradiation in the amorphous structure of thin film.     

Laser radiation effects on optical and structural properties of nanostructure CdSe thin film

Cadmium selenide (CdSe) thin films were deposited on a glass substrate using the thermal evaporation method at room temperature. The changes in the optical properties (optical band gap and absorption coefficient) after irradiation by TEA N₂ laser at different energies were measured in the wavelength range 190–800 nm using a spectrophotometer. It was found that the optical band gap is decreased after irradiating the thin films. The samples were characterized using X-ray diffraction (XRD), and the grain size of the CdSe thin film was calculated from XRD data, which was found to be 41.47 nm as-deposited. It was also found that grain size increases with laser exposure. The samples were characterized using a scanning electron microscope and it was found that big clusters were formed after irradiation by TEA N₂ laser.     

Structure and optical properties of chemically synthesized titanium oxide deposited by evaporation technique

Titanium oxide inorganic ion exchange material was synthesized by hydrolysis with water and ammonia solution. Structural feature of the synthesized titanium oxide was analyzed using X-ray diffraction, X-ray fluorescence and infrared spectrometer technique. Tentative formula of titanium oxide was determined and written as TiO₂·0.58H₂O. Titanium oxide films were deposited on glass substrates by means of an electron beam evaporation technique at room temperature from bulk sample. The films were annealed at 250, 350, 450, and 550 °C temperatures. Transmittance, reflectance, optical energy gap, refractive index and extinction coefficient were investigated. The transmittance values of 85% in the visible region and 88% in the near infrared region have been obtained for titanium oxide film annealed at 550 °C. Kubelka-Munk function was used to evaluate the absorption coefficient which was used to determine the optical band gap. It was found that the optical band gap increases with increasing annealing temperature whereas the refractive index and extinction coefficient decreases.