共查询到20条相似文献,搜索用时 31 毫秒
1.
Prabitha B. Nair V.B. Justinvictor Georgi P. Daniel K. Joy V. Ramakrishnan P.V. Thomas 《Applied Surface Science》2011,257(24):10869-10875
TiO2 thin films were deposited onto quartz substrates by RF magnetron sputtering. The samples deposited at various RF powers and sputtering pressures and post annealed at 873 K, were characterized using X-ray diffraction (XRD), micro Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-vis spectroscopy and photoluminescence (PL) spectroscopy. XRD spectrum indicates that the films are amorphous-like in nature. But micro-Raman analysis shows the presence of anatase phase in all the samples. At low sputtering pressure, increase in RF power favors the formation of rutile phase. Presence of oxygen defects, which can contribute to PL emission is evident in the XPS studies. Surface morphology is much affected by changes in sputtering pressure which is evident in the SEM images. A decrease in optical band gap from 3.65 to 3.58 eV is observed with increase in RF power whereas increase in sputtering pressure results in an increase in optical band gap from 3.58 to 3.75 eV. The blue shift of absorption edge in all the samples compared to that of solid anatase is attributed to quantum size effect. The very low value of extinction coefficient in the range 0.0544-0.1049 indicates the excellent optical quality of the samples. PL spectra of the films showed emissions in the UV and visible regions. 相似文献
2.
《Current Applied Physics》2014,14(3):421-427
Nb–TiO2 nanofibers and thin films were prepared using a sol–gel derived electrospinning and spin coating, respectively, by varying the Nb/Ti molar ratios from 0 to 0.59 to investigate the effect of Nb doping on morphology, crystal structure, and optical band gap energy of Nb–TiO2. XRD results indicated that Nb–TiO2 is composed of anatase and rutile phases as a function of Nb/Ti molar ratio. As the Nb/Ti molar ratio rose, the anatase to rutile phase transformation and the reduction in crystallite size occurred. The band gap energy of Nb–TiO2 was changed from 3.25 eV to 2.87 eV when the anatase phase was transformed to rutile phase with increasing the Nb doping. Experimental results indicated that the Nb doping was mainly attributed to the morphology, the crystal structure, the optical band gap energy of Nb–TiO2, and the photocatalytic degradation of methylene blue. 相似文献
3.
Effects of thermally induced anatase-to-rutile phase transition in MOCVD-grown TiO2 films on structural and optical properties 总被引:2,自引:0,他引:2
D.-J. Won C.-H. Wang H.-K. Jang D.-J. Choi 《Applied Physics A: Materials Science & Processing》2001,73(5):595-600
Titanium dioxide (TiO2) films with a thickness of 550 nm were deposited on quartz glass at 300 °C by metalorganic chemical vapor deposition. The
effects of post-annealing between 600 °C and 1000 °C were investigated on the structural and optical properties of the films.
X-ray diffraction patterns revealed that the anatase phase of as-grown TiO2 films began to be transformed into rutile at the annealing temperature of 900 °C. The TiO2 films were entirely changed to the rutile phase at 1000 °C. From scanning electron spectroscopy and atomic force microscopy
images, it was confirmed that the microstructure of as-deposited films changed from narrow columnar grains into wide columnar
ones. The surface composition of the TiO2 films, which was analyzed by X-ray photoelectron spectroscopy data, was nearly constant although the films were annealed
at different temperatures. When the annealing temperature increased, the transmittance of the films decreased, whereas the
refractive index and the extinction coefficient calculated by the envelope method increased at high temperature. The values
of optical band gap decreased from 3.5 eV to 3.25 eV at 900 °C. This abrupt decrease was consistent with the anatase-to-rutile
phase transition.
Received: 4 October 2000 / Accepted: 4 December 2000 / Published online: 23 May 2001 相似文献
4.
Faruque M. Hossain Leigh Sheppard Graeme E. Murch 《Journal of Physics and Chemistry of Solids》2008,69(7):1820-1828
The optical properties of rutile and anatase titanium dioxide (TiO2) are calculated from the imaginary part of the dielectric function using pseudopotential density functional method within its generalized gradient approximation (GGA) and a scissors approximation. The fundamental absorption edges calculated for the unit cell of both rutile and anatase are consistent with experimentally reported results of single crystal rutile and anatase TiO2 and with previous theoretical calculations. A significant optical anisotropy is observed in the anatase structure which holds promise for investigating the band gap modification with better visible-light response and provides a reliable foundation for addressing the effect of impurities on the fundamental absorption edge/band gap of anatase TiO2. Further calculations on the electronic structure and the optical properties of C-, N-, and S-doped anatase TiO2 are performed. The results are analyzed and discussed in terms of optical anisotropy and scissors approximations. 相似文献
5.
S. A. Nepijko D. N. Ievlev W. Schulze 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):115-117
The plasmon energy of Ag clusters produced on an amorphous
carbon substrate by gas-aggregation technique has been measured.
It has been determined from the plasmon peak position in the
light emission spectrum obtained during bombardment of Ag
clusters by low-energy electrons. For Ag cluster films with
maximum of the cluster size distribution at 30, 8 and 2.5 nm,
the plasmon energy comprised 3.76, 4.13 and 4.28 eV (the
wavelength was 330, 300 and 290 nm), respectively. The blue
shift of the plasmon energy is probably related to the effect of
confounding of collective and single-particle excitations. 相似文献
6.
G.K. Li 《Applied Surface Science》2006,253(2):425-431
Polycrystalline TiO2 films were fabricated using dc facing-target reactive sputtering at different sputtering pressures. The films deposited consist of pure anatase phase or a mixture of anatase and rutile and increasing rutile content to some extent deteriorates the crystallinity of the anatase. It was found that the plasma heating effect, which plays the role of substrate heating, is an important factor for the crystallinity of the films in the case of without substrate heating. The roughness of the films increases monotonically with the increase of the sputtering pressure, which can be ascribed to the decrease in the mobility of the impinging particles. UV-vis transmission measurements reveal that the pure anatase films have higher transmittance than those having mixed phases of anatase and rutile. The band gap value decreases from ∼3.35 to 3.29 eV owing to the increase in the fraction of rutile phase. 相似文献
7.
8.
采用射频和脉冲磁控共溅射法并结合快速光热退火法制备了含硅量子点的SiC_x薄膜.采用掠入射X射线衍射、喇曼光谱、紫外-可见-近红外分光光度计和透射电子显微镜对薄膜进行表征.研究了脉冲溅射功率对薄膜中硅量子点数量、尺寸、晶化率和薄膜光学带隙的影响.结果表明:当溅射功率从70 W增至100 W时,硅量子点数量增多,尺寸增至5.33nm,晶化率增至68.67%,而光学带隙则减至1.62eV;随着溅射功率进一步增至110 W时,硅量子点数量减少,尺寸减至5.12nm,晶化率降至55.13%,而光学带隙却增至2.23eV.在本实验条件下,最佳溅射功率为100 W. 相似文献
9.
C. Ravichandiran A. Sakthivelu R. Davidprabu S. Valanarasu A. Kathalingam V. Ganesh Mohd Shkir C. J. Sreelatha S. AlFaify 《Optical and Quantum Electronics》2018,50(7):281
The cuprous oxide (Cu2O) thin films were electrodeposited with different reaction temperatures. The structural, morphological, optical, photoluminescence and photo response properties of the deposited films were analyzed. XRD analysis reveals cubic crystal structure for the deposited films with polycrystalline nature. The film deposited at room temperature possess high crystallite size of 37 nm. The surface morphology shows that by increasing the deposition temperature pyramid shaped morphology changes. Laser Raman study confirms the peaks 109, 148, 219, 415 and 635 cm?1 conforms the Cu2O phase formation. The band gap of the films are 2.02, 2.10 and 2.27 eV for the RT, 40 and 50 °C, respectively. The photoluminescence spectral analysis contains an emission peak at 618 nm confirm the formation of Cu2O. The photo response study confirms the ohmic nature of the films. The film electrodeposited at room temperature showed good I–V curve at the illumination of 300 W cm?2. 相似文献
10.
Damian Wojcieszak Danuta Kaczmarek Jaroslaw Domaradzki Anna Lukowiak Wieslaw Strek 《Central European Journal of Physics》2013,11(2):239-244
In this work analysis of the structural and optical properties of TiO2 thin films doped with terbium has been described. Samples were prepared by a high energy reactive magnetron sputtering process under low pressure of oxygen plasma. X-ray diffraction results have shown that different TiO2 crystal forms have been produced, depending on the amount of Tb dopant. The undoped matrix had rutile structure with crystallites with a size of 8.7 nm, while incorporation of 0.4 at. % of Tb into the film during the sputtering process resulted in anatase structure with bigger crystallites (11.7 nm). Increasing the amount of terbium up to 2 at. % and 2.6 at. % gave rutile structure with crystallites with a size of 6.6 nm for both films. However, Raman spectroscopy has revealed that in the case of TiO2:(2 at. % Tb), except for the rutile form, the presence of fine-crystalline anatase was observed. Moreover, the lack of Raman peaks shift attests to the lack of stress in the titania lattice of all of the TiO2:Tb films. This fact indicates localization of Tb3+ ions on the surface of TiO2 nanocrystals. In the case of optical investigation, results have shown that doping with terbium has a significant influence on the properties of TiO2, but it does not decrease the high transparency of the matrix. The observed changes of the transmission characteristics were produced only due to modification of the TiO2:Tb structure. Photoluminescence measurements have shown that emission of light from TiO2:Tb films occurs when the amount of terbium is 2.6 at. %. Based on the obtained results a scheme of direct energy transfer from titanium dioxide matrix (with rutile structure) to Tb3+ ions has been proposed. 相似文献
11.
Chemical bath deposition of ZnS thin films from NH3/SC(NH2)2/ZnSO4 solutions has been studied. The effect of various process parameters on the growth and the film quality are presented. The influence on the growth rate of solution composition and the structural, optical properties of the ZnS thin films deposited by this method have been studied. The XRF analysis confirmed that volume of oxygen of the as-deposited film is very high. The XRD analysis of as-deposited films shows that the films are cubic ZnS structure. The XRD analysis of annealed films shows the annealed films are cubic ZnS and ZnO mixture structure. Those results confirmed that the as-deposited films have amorphous Zn(OH)2. SEM studies of the ZnS thin films grown on various growth phases show that ZnS film formed in the none-film phase is discontinuous. ZnS film formed in quasi-linear phase shows a compact and a granular structure with the grain size about 100 nm. There are adsorbed particles on films formed in the saturation phase. Transmission measurement shows that an optical transmittance is about 90% when the wavelength over 500 nm. The band gap (Eg) value of the deposited film is about 3.51 eV. 相似文献
12.
For photocatalytic thin film applications TiO2 is one of the most important materials. The most studied TiO2 crystal phase is anatase, though also rutile and brookite show good photoactivity. Usually anatase or a mixture of rutile and anatase is applied for powder or thin film catalysts. It has been claimed that amorphous films do not exhibit any or only a very low photocatalytic activity.We have deposited amorphous thin films by dc magnetron sputtering from sub-stoichiometric TiO2−x targets. The coatings are transparent and show a photocatalytic activity half of that of a thin layer of spin-coated reference photocatalyst powder. Annealing the thin films to yield anatase crystallization more than doubles their photocatalytic activity. At the same film thickness these thin films show the same activity as a commercially available photocatalytic coating.The dependence of the photocatalytic activity on deposition parameters like gas pressure and sputter power is discussed. A decrease in film density, as deduced from the refractive index and the microstructure, resulted in an increase in photocatalytic activity. Film thickness has a marked influence on the photocatalytic activity, showing a strong increase up to 300-400 nm, followed by a much shallower slope. 相似文献
13.
Titanium dioxide thin films have been prepared from tetrabutyl-orthotitanate solution and methanol as a solvent by sol-gel dip coating technique. TiO2 thin films prepared using a sol-gel process have been analyzed for different annealing temperatures. Structural properties in terms of crystal structure were investigated by Raman spectroscopy. The surface morphology and composition of the films were investigated by atomic force microscopy (AFM). The optical transmittance and reflectance spectra of TiO2 thin films deposited on silicon substrate were also determined. Spectroscopic ellipsometry study was used to determine the annealing temperature effect on the optical properties and the optical gap of the TiO2 thin films. The results show that the TiO2 thin films crystallize in anatase phase between 400 and 800 °C, and into the anatase-rutile phase at 1000 °C, and further into the rutile phase at 1200 °C. We have found that the films consist of titanium dioxide nano-crystals. The AFM surface morphology results indicate that the particle size increases from 5 to 41 nm by increasing the annealing temperature. The TiO2 thin films have high transparency in the visible range. For annealing temperatures between 1000 and 1400 °C, the transmittance of the films was reduced significantly in the wavelength range of 300-800 nm due to the change of crystallite phase and composition in the films. We have demonstrated as well the decrease of the optical band gap with the increase of the annealing temperature. 相似文献
14.
Surasing Chaiyakun Artorn Pokaipisit Pichet Limsuwan Boonlaer Ngotawornchai 《Applied Physics A: Materials Science & Processing》2009,95(2):579-587
Titanium dioxide thin films were deposited on three different unheated substrates by unbalanced magnetron sputtering. The
effects of the sputtering current and deposition time on the crystallization of TiO2 thin films were studied. The TiO2 thin films were deposited at three sputtering current values of 0.50, 0.75, and 1.00 A with different deposition times of 25,
35, and 45 min, respectively. The surface morphology of the films was investigated by atomic force microscopy (AFM). The structure
was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The film thickness was determined
by field emission scanning electron microscopy (FE-SEM), and the optical property was evaluated with spectroscopic ellipsometry.
The results show that polycrystalline anatase films were obtained at a low sputtering current value. The crystallinity of
the anatase phase increases as the sputtering current increases. Furthermore, nanostructured anatase phase TiO2 thin films were obtained for all deposition conditions. The grain size of TiO2 thin films was in the range 10–30 nm. In addition, the grain size increases as the sputtering current and deposition time
increase. 相似文献
15.
M. Schulze S. Gourley S. A. Brown A. Dunbar J. Partridge R. J. Blaikie 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):291-294
A range of percolating atomic cluster films, with
nanoscale overall dimensions, have been studied using a
combination of in situ and
ex situ electrical transport
measurements, together with field emission electron microscopy
and atomic force microscopy. Bismuth clusters with mean diameter
20 nm were deposited between electrical contacts defined by
electron beam lithography. The morphology of the films can be
understood within percolation theory, and the electrical
measurements show complex behaviour characteristic of both
percolation effects and modification of the cluster films by
current flow and by oxidation. 相似文献
16.
二氧化钛薄膜的制备及退火对其形貌、结构的影响 总被引:1,自引:0,他引:1
利用磁控溅射技术,在石英基片上沉积Ti膜,分别在400、600、700、900℃的大气中退火获得TiO2薄膜。采用这种制备方式获得的TiO2薄膜呈现不同的颜色,退火温度为400℃的样品为暗紫红色,600℃时为黑色,而在700℃和900℃时均为黄色。采用X射线衍射、扫描电子显微镜(SEM)以及Raman光谱等手段研究了退火温度对TiO2薄膜的结构和形貌的影响。结果表明:退火温度为400℃时,TiO2薄膜为锐钛矿相,温度升高至600℃时,几乎转变为金红石晶相,但仍存在微量锐钛矿相,温度升高至700℃以上,则完全转变为金红石晶相。由XRD衍射图可知退火温度为700℃和900℃时,薄膜的金红石相沿(101)晶面择优取向。 相似文献
17.
J.C. Pivin M.A. García H. Hofmeister A. Martucci M. Sendova Vassileva M. Nikolaeva O. Kaitasov J. Llopis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):251-260
Precipitation of silver clusters in silica is achieved by different methods: ion implantation, ion beam mixing of superimposed
layers and ion irradiation of films deposited by means of co-sputtering or sol-gel technique. Main features of the nanoparticles
depending on the preparation method are investigated by TEM. The optical extinction resonance of these clusters is analysed
in terms of sizes and interaction between the clusters on the basis of calculations. We found that resonances in sputtered
and gel films with low metal concentrations are well described by plasmon polaritons in isolated clusters and calculations
based on Mie theory allow the study of their growth under irradiation. This theory is not appropriate to describe the optical
response of silver clusters in silica implanted with Ag concentrations higher than 5 at.% or in ion beam mixed films, because
of the interaction between clusters. Using an effective medium model, it is demonstrated that the random dispersion of clusters
in implantation films causes fluctuations and, on average, an increase of the clusters polarization. On the contrary, the
particular arrangement of the clusters with a bimodal size distribution in ion beam mixed films induces a screening effect
between the clusters of largest size.
Received 10 January 2002 / Received in final form 26 April 2002 Published online 19 July 2002 相似文献
18.
Jianjun Tian Hongmei Deng Lin Sun Hui Kong Pingxiong Yang Junhao Chu 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(3):550-554
The influences of Co doping on the anatase-to-rutile transformation of TiO2 thin films have been investigated by Raman spectroscopy and X-ray diffraction. Raman spectra and XRD patterns for the samples of various Co concentrations present a clear evolution of TiO2 with different anatase-to-rutile ratios. The fraction of rutile phase increases gradually with increasing Co contents. When Co content exceeds 7 mol%, anatase phase is not detected in the samples. The results may be related to the oxygen vacancies, which are introduced by Co doping. According to the Adachi model, optical constant was extracted by spectroscopic ellipsometry. It is found that the refractive index n increases with increasing Co content from 2.29 to 2.4, and that the optical band gap decreases and varies with increment of Co content between 3.6 and 3.38 eV. This may be related to the changes in film density and band gap tailed due to the Co doping. 相似文献
19.
This work presents the annealing temperature effect on the properties of mercury (Hg)-doped titanium dioxide (TiO2). Thin films and polycrystalline powders have been prepared by sol-gel process. The structure, surface morphology and optical properties, as a function of the annealing temperature, have been studied by atomic force microscopy (AFM), Raman, reflectance and ellipsometric spectroscopies. In order to determine the transformation points, we have analyzed the xerogel-obtained powder by differential scanning calorimetry (DSC). Raman spectroscopy shows the crystalline anatase and rutile phases for the films annealed at 400 °C and 1000 °C respectively. The AFM surface morphology results indicate that the particle size increases from 14 to 57 nm by increasing the annealing temperature. The complex index and the optical band gap (Eg) of the films were determined by the spectroscopic ellipsometry analysis. We have found that the optical band gap decreases by increasing the annealing temperature. 相似文献