Preparation, structure and ferromagnetic properties of the nanocrystalline Ti1-xMnxO2 thin films grown by radio frequency magnetron co-sputtering

This paper reported that the Mn-doped TiO2 films were prepared by radio frequency （RF） magnetron cosputtering. X-ray diffraction measurements indicate that the samples are easy to form the futile structure, and the sizes of the crystal grains grow big and big as the Mn concentration increases. X-ray photoemlssion spectroscopy measurements and high resolution transmission electron microscope photographs confirm that the manganese ions have been effectively doped into the TiO2 crystal when the Mn concentration is lower than 21%. The magnetic property measurements show that the Ti1-xMnxO2 （x = 0.21） films are ferromagnetic at room temperature, and the saturation magnetization, coercivity, and saturation field are 16.0 emu/cm^3, 167.5 × 80 A/m and 3740 × 80 A/m at room temperature, respectively. The room-temperature ferromagnetism of the films can be attributed to the new futile Ti1-xMnxO2 structure formed by the substitution of Mn^4＋ for Ti^4＋ into the TiO2 crystal .lattice, and could be explained by O vacancy （Vo）-enhanced ferromagnetism model.     

O2流量对磁控溅射N掺杂TiO2薄膜成分及晶体结构的影响

利用直流脉冲磁控溅射方法在室温下通过改变O₂流量制备具有不同晶体结构的N掺杂TiO₂薄膜,利用台阶仪、X射线光电子能谱仪、X射线衍射仪、紫外-可见分光光度计等设备对薄膜沉积速率、化学成分、晶体结构、禁带宽度等进行分析.结果表明:所制备的薄膜元素配比约为TiO_1.68±0.06N_0.11±0.01,N为替位掺杂,所有样品退火前后均未形成Ti—N相结构,N掺杂TiO₂薄膜的沉积速率、晶体结构等主要依赖于O₂流量.在O₂流量为2 sccm时,N掺杂TiO₂薄膜沉积速率相对较高,薄膜为非晶态结构,但薄膜内含有锐钛矿(anatase)和金红石(rutile)相晶核,退火后薄膜呈anatase和rutile相混合结构,禁带宽度仅为2.86 eV.随着O₂流量的增加,薄膜沉积速率单调下降,退火后样品禁带宽度逐渐增加.当O₂流量为12 sccm时,薄膜为anatase相择优生长,退火后呈anatase相结构,禁带宽度为3.2 eV.综合本实验的分析结果,要在室温条件下制备晶态N掺杂TiO₂薄膜,需在高O₂流量(＞10 sccn)条件下制备. 关键词： 2薄膜')" href="#">N掺杂TiO₂薄膜 磁控溅射 化学配比 晶体结构     

Anneal temperature dependence of Si/SiO2 superlattices photoluminescence

Photoluminescence spectroscopy, Fourier transform infrared spectroscopy, X-ray reflectometry and high resolution electron microscopy have been used to interpret the photoluminescence properties of annealed (3/19 nm) Si/SiO₂ multilayers grown by reactive magnetron sputtering. The multilayers show an emission in the visible and near-infrared range after heat treatment from 900°C which tends to decrease from 1200°C. Three different origins for the photoluminescence activity have been found. An anneal temperature of 1200°C is necessary to optimise the silicon crystallisation within the silicon sublayers.     

Si/SiO2 multilayers: synthesis by reactive magnetron sputtering and photoluminescence emission

This paper relates a complete study of Si/SiO₂ multilayer (ML) structures. First, we suggest an original way of synthesis based on reactive magnetron sputtering of a pure silica target. The photoluminescence spectra of these MLs consist of two Gaussian bands in the visible-near infrared spectral region. The stronger one (I band) is fixed at about 780 nm and probably due to interface states. The weaker one (Q band) is tuneable with the Si sublayer thickness and originates from a radiative recombination within the nanosized Si layers. For this latter band the peak position is a function of the Si sublayer thickness and shows a discontinuity at 30 Å. This corresponds to an Si phase change. For thicknesses above 30 Å, the sublayers are composed of nanocrystalline silicon whereas below 30 Å the sublayers are made of amorphous silicon. We develop a model based on a quantum well to which we have added an interfacial region between Si and SiO₂. It is characterised by an interfacial potential of 0.3 eV. This model depicts the simultaneous behaviour of Q and I bands for an Si sublayer thickness below 30 Å.     

磁控溅射法合成纳米β-FeSi2/a-Si多层结构

β-FeSi₂作为一种环境友好的半导体材料，颗粒化及非晶化正在成为提高其应用性能和改善薄膜质量、膜基界面失配度的有效途径.利用射频磁控溅射法在单晶Si基体上沉积Fe/Si多层膜，合成纳米β-FeSi₂/Si多层结构.通过透射电子显微镜、高分辨电子显微术等分析手段，研究了多层结构和制备工艺之间的相互关系.研究结果表明，采用磁控溅射Fe/Si多层膜的方法，不需要退火就可以直接沉积得到β-FeSi₂相小颗粒.β-FeSi₂相 关键词： 2')" href="#">β-FeSi₂ 磁控溅射 透射电子显微镜 半导体薄膜     

Effect of RF power and sputtering pressure on the structural and optical properties of TiO2 thin films prepared by RF magnetron sputtering

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.     

Influence of Ti nanocrystallization on microstructure, interface bonding, surface energy and blood compatibility of surface TiO2 films

Recent progress in ultrafine-grained/nano-grained (UFG/NG) titanium permits a consideration for TiO₂ films deposited on nano-grained titanium for antithrombogenic application such as artificial valves and stents. For this paper, the microstructure, interface bonding, surface energy, and blood compatibility features of TiO₂ films deposited by direct current magnetron reactive sputtering technology on NG titanium and coarse-grained (CG) titanium were investigated. The results show that the nanocrystallization of titanium substrate has a significant influence on TiO₂ films. At the same deposition parameters, the content of rutile phase of TiO₂ film was increased from 47% (on the CG titanium substrate) to 72% (on the NG titanium substrate); the adhesion of TiO₂ film was improved from 5.8 N to 17 N; the surface energy was reduced from 6.37 dyn/cm to 3.01 dyn/cm; the clotting time was improved from 18 min to 28 min; the platelets accumulation and pseudopodium of adherent platelets on TiO₂ film on NG titanium were considerably reduced compared to that on CG titanium. The present results demonstrate the possibility of improving the blood compatibility of TiO₂ film through the approach of substrate nanocrystallization. Also it may provide an attractive idea to prepare stents with biological coatings of more outstanding blood compatibility and interface bonding.     

磁控溅射制备Y2O3-TiO2薄膜形貌的研究

室温下采用射频磁控溅射法,在硅衬底上制备了Y₂O₃-TiO₂氧化物复合薄膜.利用XRD(X-ray diffraction)和AFM( atomic force microscopy)分析观察了退火前后样品的物相、形貌等变化,讨论了致密薄膜的生长机理.实验发现,溅射功率越大,薄膜的平整度和致密度越好.对热处理前后样品的结晶结构和表面形貌的分析结果显示,在本实验参数范围内,随着溅射功率的增大,更多的Y₂O_{3关键词： 2}O₃-TiO₂薄膜')" href="#">Y₂O₃-TiO₂薄膜 表面形貌 原子力显微镜 磁控溅射     

The structure and photocatalytic activity of TiO2 thin films deposited by dc magnetron sputtering

This paper seeks to determine the optimal settings for the deposition parameters, for TiO₂ thin film, prepared on non-alkali glass substrates, by direct current (dc) sputtering, using a ceramic TiO₂ target in an argon gas environment. An orthogonal array, the signal-to-noise ratio and analysis of variance are used to analyze the effect of the deposition parameters. Using the Taguchi method for design of a robust experiment, the interactions between factors are also investigated. The main deposition parameters, such as dc power (W), sputtering pressure (Pa), substrate temperature (°C) and deposition time (min), were optimized, with reference to the structure and photocatalytic characteristics of TiO₂. The results of this study show that substrate temperature and deposition time have the most significant effect on photocatalytic performance. For the optimal combination of deposition parameters, the (1 1 0) and (2 0 0) peaks of the rutile structure and the (2 0 0) peak of the anatase structure were observed, at 2θ ∼ 27.4°, 39.2° and 48°, respectively. The experimental results illustrate that the Taguchi method allowed a suitable solution to the problem, with the minimum number of trials, compared to a full factorial design. The adhesion of the coatings was also measured and evaluated, via a scratch test. Superior wear behavior was observed, for the TiO₂ film, because of the increased strength of the interface of micro-blasted tools.     

Co离子注入TiO2薄膜的显微结构和磁性研究

利用直流磁控溅射技术在玻璃衬底上沉积了TiO₂薄膜,并对其进行了Co离子注入,最后在真空中500 ℃退火50 min,得到系列薄膜样品. 利用剥离-分散方法制备了薄膜的透射电镜样品,并用扫描电镜(SEM)、X射线能量散射谱(EDX)和高分辨透射电镜(HRTEM)对样品做了近似原位观察,研究了薄膜样品中不同Co离子注入深度的成分分布和显微结构. 结果表明,薄膜呈锐钛矿结构,Co元素主要分布在薄膜表层,Co离子的注入使TiO₂薄膜的晶粒被部分破坏,并形成CoO,而5 关键词： 2薄膜')" href="#">Co注入TiO₂薄膜 电镜原位观察 室温铁磁性     

Microstructures and magnetic properties of CoPt-TiO2 nanocomposite films prepared by annealing CoPt/TiO2 multilayers

CoPt-TiO₂ nanocomposite films were synthesized by rapid thermal annealing of CoPt/TiO₂ multilayers. The effects of annealing temperature, annealing time, Ag addition and TiO₂ volume fraction on the microstructures and magnetic properties of the CoPt-TiO₂ nanocomposite films were studied. Results showed that the ordering degree of CoPt and coercivity of CoPt-TiO₂ nanocomposites increased with annealing temperature. Increasing annealing time and Ag addition were able to increase the ordering degree and coercivity of CoPt. However, complete L1₀-ordering of CoPt at 550 °C annealing was not realized by increasing annealing time up to 30 min and Ag addition up to 30 vol.%. Increasing TiO₂ volume fraction at 700 °C annealing did not lead to the change of ordering of CoPt. However, the grain structure of the films changed slightly when TiO₂ volume fraction was larger than 56%. The coercivity of the film decreased slightly with the addition of TiO₂.     

ZrO2／SiO2多层膜中膜厚组合周期数及基底材料对残余应力的影响

ZrO₂／SiO₂多层膜由相同沉积条件下的电子束蒸发方法制备而成， 通过改变多层膜中高(ZrO₂)、低(SiO₂)折射率材料膜厚组合周期数的方法，研究了沉积 在熔石英和BK7玻璃 基底上多层膜中残余应力的变化. 用ZYGO光学干涉仪测量了基底镀膜前后曲率半径的变化， 并确定了薄膜中的残余应力. 结果发现，该多层膜中的残余应力为压应力，随着薄膜中膜厚 组合周期数的增加，压应力值逐渐减小. 而且在相同条件下，石英基底上所沉积多层膜中的 压应力值要小于BK7玻璃基底上所沉积多层膜中的压应力值. 用x射线衍射技术测量分析了膜 厚组合周期数不同的ZrO₂／SiO₂多层膜微结构，发现随着周期数增 加，多层膜的结晶程 度增强. 同时多层膜的微结构应变表现出了与所测应力不一致的变化趋势，这主要是由多层 膜中，膜层界面之间复杂的相互作用引起的. 关键词： 2／SiO₂多层膜')" href="#">ZrO₂／SiO₂多层膜 残余应力 膜厚组合周期数     

Characterization of TiO2 Nanoparticles in Langmuir-Blodgett Films

In this work we have synthesized TiO₂ nanoparticles, using either a sol–gel base catalysed process in the interior of CTAB reversed micelles (TiO₂ CTAB sol), or the neutralization of a TiO₂/H₂SO₄ solution in the interior of AOT reversed micelles. From the absorption and emission data of the TiO₂ nanoparticles it is possible to conclude that in the sol–gel route there remains alkoxide groups in the structure, originating transitions lower than the energy gap of TiO₂ semiconductor. These transitions disappear in the neutralization procedure, where the alkoxide groups are absent in the structure. We have assigned the observed indirect and direct optical transitions according to the anatase band structure. TiO₂ Langmuir-Blodgett (LB) films were prepared either by direct deposition of titanium isopropoxide or by deposition of the TiO₂ CTAB sol. These films showed photoluminescence, which was attributed to band-gap emission and to surface recombination of defect states.     

硼(氮、氟)掺杂对TiO2纳米颗粒光学性能的影响

利用X射线衍射谱、拉曼光谱和紫外-可见光吸收光谱研究了硼(氮、氟)掺杂对TiO₂纳米颗粒光学性能的影响.X射线衍射谱和拉曼光谱结果表明,掺硼(氮、氟)对TiO₂纳米颗粒的锐钛矿相晶体结构无明显影响,而其锐钛矿晶格出现畸变(c/a值增大),这被归因于掺杂原子对TiO₂纳米颗粒表面氧原子缺位沿晶格c轴方向的占据.另外,掺硼(氮、氟)TiO₂纳米颗粒吸收带红移与TiO相似文献   

Preparation and Characterization of Poly(Methyl Methacrylate) Coated TiO2 Nanoparticles

Titanium dioxide (TiO₂) nanoparticles were modified with poly(methyl methacrylate) (PMMA) to improve the dispersion stability of the nanoparticles in a dielectric medium and to reduce the density mismatch between TiO₂ and a dielectric medium for a microcapsule‐type electrophoretic display application. Nanoparticles were coated with PMMA by in situ dispersion polymerization. The PMMA‐coated TiO₂ nanoparticles were characterized by fourier transform‐infrared spectrometrey (FT‐IR), electrophoretic light scattering (ELS), and scanning electron microscopy (SEM). Density of PMMA‐coated TiO₂ nanoparticles was found to be dependent on the thickness of the PMMA coating on the nanoparticles. An increase of thermal stability of the PMMA layer and the contents of PMMA on the surface of the nanoparticles were measured via thermogravimetric analysis (TGA).     

Surface modification of PMMA/O-MMT composite microfibers by TiO2 coating

In the present work, poly(methyl methacrylate) (PMMA)/organically modified montmorillonite (O-MMT) composite microfibers were firstly prepared by emulsion polymerization combined with electrospinning, and then coated by nanosize titanium dioxide (TiO₂) using RF magnetron sputter technique. The modified surfaces of PMMA/O-MMT composite microfibers were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), UV-vis spectroscopy and drop shape analyzer. Finally, the photocatalytic properties of TiO₂ coated PMMA/O-MMT composite microfiber membranes were evaluated by degradation of methylene blue(MB) under UV illumination. The experimental results revealed that anatase-TiO₂ and rutile-TiO₂ nanoparticles were well spread and physically deposited on the surface of PMMA/O-MMT microfibers, and the wettability of the PMMA/O-MMT composite microfibers was improved after surface modification by sputter coating. Furthermore, the PMMA/O-MMT microfibers membrane coated with TiO₂ performed well in photocatalytic degradation of MB.     

反应溅射法制备TiO2薄膜

报道了用反应溅射法制备TiO₂薄膜的实验研究.详细研究了氧分压、基底温度和退火温度对成膜结构的影响.制备出了具有金红石和锐钛矿晶体结构的TiO₂薄膜.分析了金红石和锐钛矿晶体的形成条件,并对薄膜的表面形貌进行了测量. 关键词： 反应溅射 2薄膜')" href="#">TiO₂薄膜     

Cr掺杂锐钛矿型TiO2（001）薄膜中Cr原子的直接观测

Imaging the doping elements is critical for understanding the photocatalytic activity of doped TiO₂ thin film. But it is still a challenge to characterize the interactions between the dopants and the TiO₂ lattice at the atomic level. Here, we use high angle annular dark-field/annular bright-field scanning transmission electron microscope (HAADF/ABF-STEM) combined with electron energy loss spectroscopy (EELS) to directly image the individual Cr atoms doped in anatase TiO₂(001) thin film from [100] direction. The Cr dopants, which are clearly imaged through the atomic-resolution EELS mappings while can not be seen by HADDF/ABF-STEM, occupy both the substitutional sites of Ti atoms and the interstitial sites of TiO₂ matrix. Most of them preferentially locate at the substitutional sites of Ti atoms. These results provide the direct evidence for the doping structure of Cr-doped A-TiO₂ thin film at the atomic level and also prove the EELS mapping is an excellent technique for characterizing the doped materials.     

Quantum chemical calculations of the structural influence on electronic properties in TiO2 nanocrystals

ABSTRACT

Quantum chemical calculations for two TiO₂ nanoparticle cluster models (rutile–(TiO₂)_n with n = 20, and anatase–(TiO₂)_n with n = 92), selected to represent different nanoparticle size regimes, are used to elucidate structural influences on the electronic properties. Structural and electronic properties were obtained using a variety of computational methods and structure optimisation schemes, including a comparison of results for several different density functional theory functionals, as well as complementary Hartree–Fock and semi-empirical calculations. The results demonstrate a strong dependence of electronic properties, such as the optical band gap of importance for photoelectrochemical and photocatalytic applications, on the structure of the nanocrystal. From a methodological point of view, the calculations also provide useful information of broader significance about the viability of different computational schemes to efficiently obtain reliable computational results for intrinsically nanostructured materials.     

Cobalt-doped TiO2: a computational analysis of dopant placement and charge transfer direction on thin film anatase

ABSTRACT

Titanium dioxide (TiO₂) nanocrystals are promising materials for photo-electrochemical water splitting. This study focuses on how surface dopant placement can affect the electronic properties. TiO₂ anatase thin films are doped two ways: a cobalt ion replacing a surface titanium ion (surface ingrained) and a cobalt ion chemisorbed to two surface oxygen ions and two NH₃ ligands. Specifically, when studying the binding pattern, the cobalt ion dopant changes from an electron acceptor for the surface ingrained model to an electron donor for the chemisorbed model. The optical absorption peaks of the surface ingrained model are attributed to p→d transitions and are much stronger when compared to the d→d transitions for the chemisorbed model. It is the conclusion of this computational study that one can alter the cobalt dopant on the anatase thin film to focus a positive or negative charge at the surface by changing the surface dopant location.