沉积法制备纳米TiO_2薄膜

利用TiO2胶体在石英玻璃表面沉积制备TiO2薄膜,用分光光度计测量TiO2薄膜的吸光度,研究沉积时间、TiO2胶体浓度、镀膜次数对TiO2薄膜的沉积吸附过程和等效膜厚的影响,讨论纳米TiO2沉积吸附的类型。结果表明,最大等效膜厚随着TiO2胶体浓度的增大而增加;最佳镀膜次数与TiO2胶体浓度无关,随着沉积时间的延长而减少;用气体吸附的B.E.T.和Langmuir吸附理论分析的纳米TiO2在石英玻璃上的沉积过程与实验结果相符。     

溅射工艺对BST薄膜取向行为的影响

采用射频磁控溅射法在Si(100)衬底上沉积了Ba0.65Sr0.35TiO3薄膜.借助XRD、AFM和SEM研究了衬底温度、退火温度、溅射气压等不同的溅射参数对Ba0.65Sr0.35TiO3薄膜的晶化行为和显微结构的影响.在室温下沉积并未经退火处理的Ba0.65Sr0.35TiO3 薄膜是无定形态,在较高温度下沉积的薄膜晶化相对较好;随着在氧气气氛中退火温度的升高,X射线衍射峰的半峰宽变窄,衍射峰强度增强;在0.37～1.2Pa气压下沉积的Ba0.65Sr0.35TiO3薄膜有(110)和(200)主衍射峰,且其强度随溅射气压的增加而增强;当溅射气压继续升到3.9Pa,(110)和(200)衍射峰明显增强,说明Ba0.65Sr0.35TiO3 薄膜具有(110) (200)择优取向.AFM和SEM结果显示薄膜晶粒细小均匀、结构致密、表面平整,且无裂纹、无孔洞.分析结果显示优化工艺参数制备的Ba0.65Sr0.35TiO3 薄膜是用以制备非致冷红外探测器的优质材料.     

柱状晶形貌TiO2膜厚对FTO/TiO2镀膜玻璃光催化活性影响

采用溶胶凝胶法,在FTO(SnO2:F)低辐射镀膜玻璃衬底上制备了柱状晶体结构的TiO2薄膜,获得双层结构FTO/TiO2镀膜玻璃样品.研究了TiO2薄膜厚度对FTO/TiO2镀膜玻璃样品的光催化活性、低辐射性能以及透光性能的影响.结果表明,FTO/TiO2镀膜玻璃样品光催化活性随着TiO2薄膜厚度的增加先升高后下降,在TiO2薄膜厚度为300 nm时光催化活性最佳;低辐射性能随着TiO2薄膜厚度的增加而下降,但TiO2薄膜厚度为300 nm时仍然具备一定的低辐射性能;透光性能与TiO2薄膜膜厚的关系不大,可见光透射比保持在72%左右;表面平均粗糙度约为1 nm,表面光滑,不易沾染油污灰尘.该镀膜玻璃在保证低辐射建筑节能和透光的前提下,兼具光催化自清洁功能,具有很好的应用前景.     

沉积时间对磁控反应溅射制备TiO2薄膜性能的影响

应用直流磁控反应溅射法,在玻璃基体上制备了具有光催化活性的TiO2薄膜.TiO2薄膜的厚度随沉积时间的增加而均匀增长.基体温度则在溅射的最初1h很快上升到110℃,溅射7h基体温度不超过130℃.溅射2h得到的是非晶态TiO2薄膜,而溅射3～7h制备的薄膜为锐钛矿型结构.非晶态和小晶粒TiO2薄膜的紫外一可见透射光谱谱带边沿与结晶较好的TiO2薄膜相比有明显的蓝移,薄膜的透射率随沉积时间的增加而下降.钛以四价钛的形式存在于TiO2薄膜中.TiO2薄膜的光催化活性随沉积时间争薄膜厚度的增加而有较大提高.     

TiO2/SiO2复合薄膜的晶化特征和结构转变研究

对TiO2／SiO2复合薄膜的晶化特征进行了分析，研究表明，随着TiO2含量的增加，其晶化温度降低，而由锐钛矿相完全转变为金红石相的速度减慢．SiO2的析晶温度也随着TiO2含量的增加而降低，即TiO2具有诱导SiO2析晶的作用．锐钛矿晶粒尺寸的增加幅度随着TiO2含量的降低和热处理温度的升高而增大．其晶粒尺寸的大小与热处理时间的平方根成正比．认为由于TiO2含量的不同，造成薄膜中由锐钛矿相完全转变成金红石相的速度差异主要来自于薄膜中应力的作用．     

透明氧化物半导体薄膜的制备技术及理论基础

为了进一步提高透明氧化物半导体薄膜制备水平,提高半导体薄膜的利用率,现以磁控溅射法应用为例,介绍了磁控溅射的具体应用,从衬底清洗、衬底反溅、溅射镀膜三个方面入手,分析了透明氧化物半导体薄膜制备的实验过程.结果表明,磁控溅射法具有非常高的可靠性和可行性,不仅增加了气体的离化率和溅射率,还保证了薄膜表面的平整性和光滑性,为进一步提高沉积镀膜的规模和透明氧化物半导体薄膜制备水平打下坚实的基础.     

溶胶-凝胶法制备TiO2薄膜光催化特性实验研究

采用溶胶-凝胶实验方法,研究了TiO2薄膜厚度、退火温度及退火时间对薄膜晶相结构、表面形貌和光催化性能的影响。结果表明,TiO2薄膜光催化活性随着薄膜厚度的增加而增加,当薄膜厚度为3层时,光催化活性达到最大,层数超过3层时,薄膜的光催化活性随薄膜厚度的增加反而降低;当退火温度为550℃时,TiO2薄膜中出现金红石相,质量分数为25.4%,此时的光催化效率最高;随着退火时间的延长,TiO2晶粒尺寸逐渐变大,光催化活性逐渐减弱。     

氧分压对RF磁控溅射ZrO2薄膜生长特性的影响

采用反应射频(RF)磁控溅射法在n型(100)单晶S基片上沉积了ZrO2膜,研究了氧分压与ZrO：薄膜的表面粗糙度和沉积速率、SiO2中间界层的厚度以及ZrO2薄膜的折射率之间关系。结果表明：随着氧分压增高,薄膜的沉积速率降低,表面粗糙度线性地增加;在低的氧分压情况下,Si基片表面的本征SiO2层的厚度增加幅度较小,在高的氧分压情况下,Si基片表面的本征SiO2层的厚度有较大幅度地增加;在O2／Ar混和气氛下,溅射沉积的ZrO2薄膜的折射率受氧分压的影响不显著,而在纯氧气气氛环境下,ZrO2薄膜的折射率明显偏低,薄膜的致密性变差。     

多晶Al2O3薄膜的制备及工艺研究

高能氩离子束溅射金属铝靶,沉积在SiO2基片上的非晶薄膜是Al和Al2O3的混合物.非晶薄膜在空气中800～1000℃退火后将完全氧化并晶化而成γ-Al2O3、oc-Al2O3.对溅射镀膜的工艺条件也进行了探索.     

纳米TiO2薄膜光催化剂的制备及性能研究

以钛酸四丁酯作为前驱体,用溶胶一凝胶法,在玻璃载体上煅烧制备了纳米TiO2薄膜光催化剂,利用扫描电子显微镜（SEM）、X射线衍射（XRD）等表征技术研究了TiO2薄膜的形貌和特性,其光催化性能用4支20W紫外石英杀菌灯照射TiO2薄膜分解亚甲基兰染料溶液表征,结果表明,该催化剂具有锐钛班红石混合晶相和纳米花状结构,纳米TiO2薄膜的光催化能力随着镀膜层数的增加而增加。     

Study of electrical and microstructure properties of high dielectric hafnium oxide thin film for MOS devices

Hafnium oxide (HfO₂) has emerged as the most promising highkdielectric for MOS devices. As-deposited sputtered HfO₂ thin films have large number of defects resulting in increased oxide charge and leakage current. In this paper the effect of sputtering voltage, bias sputtering and post deposition thermal annealing is investigated. The I–V and C–V characteristics of the dielectric film are studied employing Al–HfO₂–Si MOS capacitor structure. It is found that oxide charge increases with increasing sputtering voltage. Thermal annealing in oxygen reduces the interface/oxide charges and leakage current. It is shown that applying substrate bias during film deposition leakage current is further reduced by an order of magnitude. The microstructure of thin film is examined by AFM. The reduction in surface roughness with bias sputtering is shown. The experimental results are presented and discussed for device application.     

Defect passivation by O2 plasma treatment on high-k dielectric HfO2 films at room temperature

Oxygen plasma treatment process was used to passivate the non-stoichiometric HfO₂ films deposited by magnetron sputtering. After optimal oxygen plasma treatment, the gate leakage of HfO₂ films would be reduced and dielectric breakdown voltage would be improved to 30 percentage. XPS spectrum was used to analysis the non-stoichiometric HfO₂ films after oxygen plasma treatment which demonstrate a higher concentration of incorporated oxygen atoms at the surface in comparison to the bulk HfO₂. This simple method can maintain high-k dielectric deposition process at room temperature by sputtering. It would be useful for fabrication thin film transistor on polymer based substrate in the future.     

直接感光法制备钛酸锶钡图形化薄膜及其性能研究

采用改进的化学修饰的溶胶-凝胶工艺, 以聚乙烯吡咯烷酮(PVP)为薄膜开裂抑制剂, 以乙酰丙酮为化学修饰剂, 利用乙酰丙酮可以与金属盐形成的配位螯合物的特性, 制备了具有紫外光感光特性的钛酸锶钡(Ba_0.8Sr_0.2TiO₃)前驱溶胶及其凝胶薄膜; 结合直接感光法, 首先制备图形化凝胶薄膜, 再通过后续热处理, 在Pt/TiO₂/SiO₂/Si衬底上最终得到了具有钙钛矿结构的钛酸锶钡图形化薄膜, 其图形厚度约为793nm, 相对介电常数约为600, 介电损耗约为0.03.     

Dielectric property and electrical conduction mechanism of ZrO2–TiO2 composite thin films

ZrO₂–TiO₂ composite films were fabricated by radio frequency magnetron sputtering and post annealing in O₂. It was found the films remained amorphous below the annealing temperature of 500 °C. The as-deposited ZrO₂–TiO₂ film has a high dielectric constant of 22, and which increases to 34 after annealing at 400 °C. At low electric field, the dominant conduction mechanisms are Schottky emission for both the as-deposited and the annealed thin films. At high electric field, the conduction mechanism changes to space-charge-limited current and then changes to Poole–Frenkel (PF) emission after annealing at 400 °C.     

Advantages of transparent conducting oxide thin films with controlled permittivity for thin film photovoltaic solar cells

Our recent investigations have identified a pathway to produce transparent conducting oxide (TCO) films that demonstrate higher infrared transparency. The technique involves controlling the dielectric permittivity of the TCO film such that the electrical properties are maintained, but the plasma frequency (ω_p) is shifted to longer wavelength. This has the effect of reducing free-carrier absorption in the visible and near-infrared spectral region, thus producing a TCO film with higher optical transmission. The technique has been demonstrated for sputtered films of indium tin oxide by adding small amounts of ZrO₂ to a ceramic sputtering target, and for SnO₂:F films deposited by chemical vapor deposition using a metalorganic Zr source.     

Negative ions in reactive magnetron sputtering

Negative ions are present in magnetron sputtering if electronegative elements are involved. The majority of the negative ions impinging on transparent conductive oxide (TCO) films during growth is O^? produced at the oxidised target surface while it is rather unimportant whether it is bulk oxide or a surface oxide formed in reactive sputtering. O^? bombards the film with energies equivalent to the target voltage and by far exceed 100 eV. It is hence apt to cause radiation damage in sensitive TCO films. This is shown by the lateral distribution of the highenergy O^? flux in planar magnetron sputtering that exhibits the same pattern imaging the erosion groove as the resistivity of TCO films. This lateral inhomogeneity strongly depends on the erosion groove depth. The emission of O^? further depends on the sputtered material, for TiO₂ deposition it is much less than for other TCO materials. The emission probability correlates to the secondary electron emission coefficient of the oxide.     

High dielectric tunability of Ba0.6Sr0.4TiO3 thin film deposited by radio-frequency magnetron sputtering

In microwave tunable devices, one of the major challenges encountered is the simultaneous minimization of the material's dielectric loss and maximization of dielectric tunability. In this work, Ba_0.6Sr_0.4TiO₃ thin film with the thickness of 300 nm was deposited on Pt/SiO₂/Si substrates using radio-frequency magnetron sputtering technique, and its dielectric properties were investigated. Due to the high temperature annealing process at substrate temperature of 600 °C, well-crystallized Ba_0.6Sr_0.4TiO₃ film was deposited. The dielectric constant and dielectric loss of the film at 100 kHz are 300 and 0.033, respectively. Due to the good crystallinity of the Ba_0.6Sr_0.4TiO₃ films deposited by radio-frequency magnetron sputtering, high dielectric tunability up to 38.3% is achieved at a low voltage of 4.5 V.     

Investigation of Pb-Mg-Nb-O pyrochlore thin films for tunable material

PMN thin films have been investigated as a feasible material for tunable microwave applications. PMN thin films were deposited by RF magnetron sputtering from Pb₆MgNb₆O₂₂ ceramic target on platinized Si substrates. The crystallinity, thickness, surface morphology, dielectric property, and voltage tunable properties of thin films were investigated by means of X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and an impedance analyzer. The influences of sputtering substrate temperature and post-annealing on the tunable dielectric properties of thin films were investigated. Increasing the sputtering substrate temperature and annealing temperature can significantly increase tunability; however, these relations had the limitation that overly annealing temperature degraded the tunability of the thin film. A tunability of 38% at 1100 kV/cm of dc bias field under 1 MHz was achieved for a sample sputtered at 550 °C and annealed at 700 °C.     

Effects of physical growth conditions on the structural and optical properties of sputtered grown thin HfO2 films

HfO₂ thin films were prepared by reactive DC magnetron sputtering technique on (100) p-Si substrate. The effects of O₂/Ar ratio, substrate temperature, sputtering power on the structural properties of HfO₂ grown films were studied by Spectroscopic Ellipsometer (SE), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrum, and X-ray photoelectron spectroscopy (XPS) depth profiling techniques. The results show that the formation of a SiO_x suboxide layer at the HfO₂/Si interface is unavoidable. The HfO₂ thickness and suboxide formation are highly affected by the growth parameters such as sputtering power, O₂/Ar gas ratio during sputtering, and substrate temperature. XRD spectra show that the deposited films have (111) monoclinic phase of HfO₂, which is also supported by FTIR spectra. XPS depth profiling spectra shows that highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO₂ to form HfO₂, leaving Si-Si bonds behind.     

Microstructure and electrical properties of Al2O3-ZrO2 composite films for gate dielectric applications

Al₂O₃-ZrO₂ composite films were fabricated on Si by ultrahigh vacuum electron-beam coevaporation. The crystallization temperature, surface morphology, structural characteristics and electrical properties of the annealed films are investigated. Our results indicate that the amorphous and mixed structure is maintained up to an annealing temperature of 900 °C, which is much higher than that of pure ZrO₂ film, and the interfacial oxide layer thickness does not increase after annealing at 900 °C. However, a portion of the Al₂O₃-ZrO₂ film becomes polycrystalline after 1000 °C annealing and interfacial broadening is observed. Possible explanations are given to explain our observations. A dielectric constant of 20.1 is calculated from the 900 °C-annealed ZrO₂-Al₂O₃ film based on high-frequency capacitance-voltage measurements. This dielectric characteristic shows an equivalent oxide thickness (EOT) as low as 1.94 nm. An extremely low leakage current density of ∼2×10⁻⁷ A/cm² at a gate voltage of 1 V and low interface state density are also observed in the dielectric film.