新型脉冲激光能量计用无铅(Na_(1-x)K_x)_(0.5)Bi_(0.5)TiO_3铁电薄膜的制备及其激光感生热电电压信号的研究

采用脉冲激光沉积(PLD)技术,分别在LaA lO3(LAO)、(La,Sr)(A l,Ta)O3(LAST)及SrTiO3(STO)三种不同的单晶衬底上制备了一系列无铅(Na1-xKx)0.5B i0.5TiO3(x=0.00,0.08,0.19,0.30,NKBT)铁电薄膜材料。利用X射线衍射(XRD)仪对薄膜结构进行了分析,结果表明在单晶平衬底上生长的薄膜都是单取向生长的外延膜,其中摇摆曲线的半高宽(FWHM)显示在(La,Sr)(A l,Ta)O3单晶衬底上生长的薄膜结晶质量最好。另外,在20°倾斜的(La,Sr)(A l,Ta)O3单晶衬底上生长的(Na1-xKx)0.5B i0.5TiO3铁电薄膜中还首次观察到了激光感生热电电压(LITV)信号。发现在能量为0.48mJ/pulse的紫外脉冲激光辐照下,其最大激光感生热电电压为31mV,完全满足了制作脉冲激光能量计探测元件的要求,有望开发出可集成的新型脉冲激光能量计。     

掺杂浓度及退火对Ta-ZnO透明导电薄膜表面形貌的影响

室温下采用射频磁控溅射法在硅衬底上制备了掺Ta-ZnO透明导电薄膜,并在不同温度下退火处理。利用原子力显微镜、X射线光电子能谱仪对薄膜进行了表征分析,对于不同掺杂比例的Ta-ZnO薄膜以及退火后的Ta-ZnO薄膜的表面形貌进行了研究。当掺杂比例为5%(质量分数)时,薄膜有最大平均颗粒尺寸94.46nm和最小表面粗糙度4.48nm。随着退火温度的升高,该薄膜表面粗糙度(RMS)先增加后减小,平均颗粒尺寸在94.46～118.05nm之间。     

高k材料Ta2O5结构与电学性质的研究

利用双离子束沉积设备在p-Si（100）衬底上制备了Ta2O5基MOS电容,研究了不同辅源能量0、100、200、300eV下薄膜生长机制、内部结构以及电学性质的差异。实验结果显示,在辅源能量200eV下制备的Ta2O5薄膜具有最小的表面粗糙度和优异的界面特性。由C-V/I-V特征曲线表明,辅源能量200eV下制备的Ta2O5基MOS电容具有最小的平带电压偏移量、氧化层电荷密度以及漏电流。研究表明合适的辅源能量可有效改善薄膜生长机制,使薄膜由类岛状沉积转化为层状生长,从而提高晶粒均匀性、薄膜平整度以及致密性,使薄膜具有较好的电学性质。     

TiO2--Ta2O5 composite thin films deposited by radio frequency ion-beam sputtering

TiO2--Ta2O5 composite films were prepared by a radio frequency ion-beam sputtering deposition process, and the refractive indices and extinction coefficients of the composite films were found to be between those of the TiO2 and Ta2O5 films. The structure of the as-deposited films was amorphous, and the surface roughness was approximately 0.1 nm. The residual stress of the composite films was less than that of pure TiO2 film. The structure of the composite films after annealing was amorphous, with low surface roughness and slightly increased residual stress. The film containing 6.3% TiO2 displayed better properties than either the pure TiO2 or the pure Ta2O5 film.     

Microstructural enhancement of high coercivity L1(0)-FePt films for next-generation magnetic recording media

The effects of substrate Ar-ion milling and Ta adhesion layer on the microstructural and magnetic properties of L1(0)-FePt films prepared on Si, SiO2, and glass substrates were investigated. It was discovered that the relatively large in-plane surface roughness of CrRu/MgO/FePt films deposited on Si substrates was due to the deformation of the CrRu layer when the composition was heated to 550 degrees C. More than an order of magnitude improvement for the in-plane surface roughness was achieved when substrate Ar-ion milling or Ta adhesion layer was incorporated into the process. While the Ta adhesion layer proved to be detrimental to the (200) growth of the CrRu layer, optimal FePt film properties with coercivity values larger than 2 Tesla and out-of-plane roughness less than 1 nm were achieved when only substrate Ar-ion milling was implemented.     

K（Ta,Nb）O3薄膜中钙钛矿相的形成机理研究

研究了工艺参数和衬底材料对Ｋ（Ｔａ，Ｎｂ）Ｏ３薄膜生长的影响，研究表明钙钛矿相由焦绿石中间相转变而成，热处理时低速升温同样可以获得纯钙钛矿相的Ｋ（Ｔａ，Ｎｂ）Ｏ３薄膜，分析了（１００）ＳｒＴｉＯ３，（１００）ＭｇＯ单晶衬底上钙钛矿相的形成机理，并解释了在硅单晶和石英玻璃衬底上纯钙钛矿结构的Ｋ（Ｔａ，Ｎｂ）Ｏ３薄膜不易形成的原因。     

五氧化二钽薄膜的I—V特性

采用直流脉冲反应磁控溅射方法制备了高介电常数五氧化二钽(Ta_2O_5)薄膜。利用Ta/Ta_2O_5/Ta的MIM电容结构分析了Ta_2O_5的电学性能,研究了上电极面积对I-V特性的影响、I-V曲线的对称性和零点偏移以及薄膜缺陷和基底粗糙度对MIM电学性能的影响。结果表明,随着上电极面积增大,电容的漏电流密度增大,击穿场强减小。氧化钽薄膜中缺陷的存在和粗糙度增大容易引起漏电流增大,击穿强度降低。当上电极直径为1mm时,MIM电容的性能最佳:击穿强度为2.22MV/cm,漏电流密度低于1×10~(-8)A/cm~2。     

Controlling the crystallinity and roughness of atomic layer deposited titanium dioxide films

The surface roughness of thin films is an important parameter related to the sticking behaviour of surfaces in the manufacturing of microelectomechanical systems (MEMS). In this work, TiO2 films made by atomic layer deposition (ALD) with the TiCl4-H2O process were characterized for their growth, roughness and crystallinity as function of deposition temperature (110-300 degrees C), film thickness (up to approximately 100 nm) and substrate (thermal SiO2, RCA-cleaned Si, Al2O3). TiO2 films got rougher with increasing film thickness and to some extent with increasing deposition temperature. The substrate drastically influenced the crystallization behaviour of the film: for films of about 20 nm thickness, on thermal SiO2 and RCA-cleaned Si, anatase TiO2 crystal diameter was about 40 nm, while on Al2O3 surface the diameter was about a micrometer. The roughness could be controlled from 0.2 nm up to several nanometers, which makes the TiO2 films candidates for adhesion engineering in MEMS.     

Ta2O5-Incorporated WO3 nanocomposite film for improved electrochromic performance in an acidic condition

We report electrochromic and electrochemical properties of a WO3-Ta2O5 nanocomposite electrode that was fabricated from co-sputtering. Transmission electron microscopy (TEM) images of the WO3-Ta20 nanocomposite electrode revealed that morphology of the WO3 film was changed by incorporation of Ta2O5 nanoparticles, and their chemical states were confirmed to be W6+ and Ta5+ oxides from X-ray photoelectron spectroscopy (XPS). The introduction of Ta2O5 to the WO3 film played a role in alleviating surface roughness increase during continuous potential cycling; whereas the surface roughness of the WO3 film was increased from ca. 3.0 nm to ca. 13.4 nm after 400 cycles, the roughness increase on the WO3-Ta2O5 was significantly reduced to 4.2 nm after 400 cycles, as investigated by atomic force microscopy (AFM). This improvement of the stability by adding Ta2O5 may be responsible for the enhanced electrochemical and optical properties over long-term cycling with the WO3-Ta2O5 nanocomposite electrode.     

紫外脉冲激光淀积法制备Pb(Ta0.05Zr0.48Ti0.47)O3薄膜的铁电性质

用紫外脉冲激光淀积方法在Pt／TiO2／SiO2／Si(001)衬底上制备了La1-xSrxCoO3／Pb(Ta0.05Zr0.48Ti0.47)O3(PTZT)／La1-xSrxCoO3异质结构薄膜。发现底电极La0.25Sr0.75CoO3可以诱导PTZT薄膜沿(001)方向取向生长。在500kHz和5V的工作电压下铁电电容器La0.25Sr0.75CoO3/PTZT／La0.25Sr0.75CoO3经过5×1010次反转之后,仍保持其初始电极化的96％。此异质结构横截面的扫描电镜照片表明界面上没有明显的因化学反应导致的第二相存在。     

Al2O3基陶瓷及玻璃基底制备Ta-N薄膜微结构与电学特性的比较研究

在N2、Ar气氛中,采用反应直流磁控溅射法在Al2O3基陶瓷及玻璃基底上制备了Ta-N薄膜,并对各样品的形貌结构、化学组分及电学特性进行了比较分析研究。结果表明,沉积于Al2O3陶瓷及玻璃基底的Ta-N薄膜分别呈团簇状生长与层状紧密堆积生长;Al2O3陶瓷基底沉积的Ta-N为单相薄膜,而玻璃基底上的Ta-N薄膜,随N2、Ar流量比增加,呈单相向多相共存转变;薄膜表面形貌和微结构与基底材料的原始形貌和微结构紧密相关,这说明基底材料对薄膜的形成有重要的影响;N2、Ar流量比相同时,玻璃基底上沉积的Ta-N薄膜电性能优于Al2O3基陶瓷基底上沉积的Ta-N薄膜。     

氧化铟薄膜制备及其特性研究

采用射频磁控溅射法在玻璃衬底上制备氧化铟薄膜,通过测试原子力显微镜、X射线衍射、X射线光电子谱、紫外可见分光光度计以及霍尔效应,研究了氧化铟薄膜的结构和光、电特性.实验发现,氧化铟薄膜表面粗糙度随着生长温度的升高而增大.X射线衍射结果表明薄膜为立方结构的多晶体,并且随着生长温度的升高,可以看到氧化铟薄膜的晶粒变大以及半高宽减小,这也说明结晶质量的改善.在可见光范围的透射率超过90%.同时,在氩气氛围下制备的薄膜迁移率最大,其电阻率、霍尔迁移率和电子浓度分别达到了0.31Ω.cm、9.69 cm2/(V.s)和1×1018cm-3.退火处理可以改善氩氧氛围下制备的薄膜的电学性能.     

Broadband NIR emission in sol-gel Er(3+)-activated SiO2-Ta2O5 glass ceramic planar and channel waveguides for optical application

An Er(3+)-doped SiO2:Ta2O5 optical channel waveguide and nanocomposite were prepared by the sol-gel route at a Si:Ta 50:50 molar ratio. Channels with an excellent surface profile were easily and quickly fabricated by focusing a femtosecond laser onto the surface of multilayered films deposited on SiO2/Si substrates. In parallel, the same sol used to prepare the film was annealed at 900, 1000, and 1100 degrees C for 2 h, to get the nanocomposite materials. A broadband NIR emission around 1538 nm, assigned to the 4I13/2 --> 4I15/2 transition of the Er3+ ions was observed in the nanocomposites of amorphous SiO2 containing dispersed Ta2O5 nanocrystals. The 4I13/2 lifetime and emission bandwidth depend on the annealing temperature. In conclusion, Er(3+)-doped SiO2:Ta2O5 channel waveguides and nanocomposites are promising materials for photonic applications.     

采用水基原子层沉积工艺在石墨烯上沉积Al2O3介质薄膜研究

采用水基原子层沉积(H2O-based ALD)方法在石墨烯上直接生长Al2O3介质薄膜,研究了Al2O3成核机理.原子力显微镜(AFM)对Al2O3薄膜微观形态分析表明,沉积温度决定着Al2O3在石墨烯表面的成核生长情况,物理吸附在石墨烯表面的水分子是Al2O3成核的关键,物理吸附水分子的均匀性直接影响Al2O3薄膜的均匀性.在适当的温度窗口(100～130℃),Al2O3可以均匀沉积在石墨烯上,AFM测得Al2O3薄膜表面均方根粗糙度(RMS)为0.26 nm,X射线光电子能谱(XPS)表面分析与元素深度剖析表明,120℃下在石墨烯表面沉积的Al2O3薄膜中O和Al元素的含量比约为1.5.拉曼光谱分析表明,采用H2O-based ALD工艺沉积栅介质薄膜不会降低石墨烯晶体质量.     

五氧化二钽薄膜的制备及其I-U特性

本文利用脉冲直流反应磁控溅射的方法制备了五氧化二钽 (Ta2 O5)薄膜 ,俄歇电子能谱仪测试了薄膜的成分含量 ,椭偏仪测试了Ta2 O5薄膜的厚度和折射率 ,XRD分析了薄膜的晶体结构 ,并且分别研究了氧气含量、基底温度等成膜工艺对薄膜的影响。研究结果表明薄膜的成分主要是由氧气含量决定的。利用金属 绝缘体 (介质膜 ) 金属 (MIM)结构初步对Ta2 O5薄膜进行了电学性能的测试 :皮安电流电压源测试了薄膜的I U特性 ,制备出的薄膜折射率在 2 1～ 2 2 ,MIM的I U特性曲线显示了较好的对称性和低的漏电流密度     

氧气-乙炔火焰法在Al2O3陶瓷上沉积金刚石薄膜

用氧气－乙炔火焰法在氧化铝陶瓷片上沉积出了金刚石薄膜，并观察了薄膜的形貌结构及其在基片上的分布规律。对基片进行了适当的预处理，可以提高金刚石薄膜在基片上的成核密度。认为氧化铝陶瓷片与沉积金刚石薄膜之间易形成过渡层，初步探讨了在氧化铝陶瓷片上沉积金刚石薄膜的机理。     

Al2O3 and TiO2 atomic layer deposition on copper for water corrosion resistance

Al(2)O(3) and TiO(2) atomic layer deposition (ALD) were employed to develop an ultrathin barrier film on copper to prevent water corrosion. The strategy was to utilize Al(2)O(3) ALD as a pinhole-free barrier and to protect the Al(2)O(3) ALD using TiO(2) ALD. An initial set of experiments was performed at 177 °C to establish that Al(2)O(3) ALD could nucleate on copper and produce a high-quality Al(2)O(3) film. In situ quartz crystal microbalance (QCM) measurements verified that Al(2)O(3) ALD nucleated and grew efficiently on copper-plated quartz crystals at 177 °C using trimethylaluminum (TMA) and water as the reactants. An electroplating technique also established that the Al(2)O(3) ALD films had a low defect density. A second set of experiments was performed for ALD at 120 °C to study the ability of ALD films to prevent copper corrosion. These experiments revealed that an Al(2)O(3) ALD film alone was insufficient to prevent copper corrosion because of the dissolution of the Al(2)O(3) film in water. Subsequently, TiO(2) ALD was explored on copper at 120 °C using TiCl(4) and water as the reactants. The resulting TiO(2) films also did not prevent the water corrosion of copper. Fortunately, Al(2)O(3) films with a TiO(2) capping layer were much more resilient to dissolution in water and prevented the water corrosion of copper. Optical microscopy images revealed that TiO(2) capping layers as thin as 200 ? on Al(2)O(3) adhesion layers could prevent copper corrosion in water at 90 °C for ~80 days. In contrast, the copper corroded almost immediately in water at 90 °C for Al(2)O(3) and ZnO films by themselves on copper. Ellipsometer measurements revealed that Al(2)O(3) films with a thickness of ~200 ? and ZnO films with a thickness of ~250 ? dissolved in water at 90 °C in ~10 days. In contrast, the ellipsometer measurements confirmed that the TiO(2) capping layers with thicknesses of ~200 ? on the Al(2)O(3) adhesion layers protected the copper for ~80 days in water at 90 °C. The TiO(2) ALD coatings were also hydrophilic and facilitated H(2)O wetting to copper wire mesh substrates.     

Radiation damage effects in far-ultraviolet filters, thin films, and substrates

Advances in vacuum ultraviolet thin-film filter technology have been made through the use of filter designs with multilayers of materials such as Al(2)O(3), BaF(2), CaF(2), HfO(2), LaF(3), MgF(2), and SiO(2). Our immediate application for these filters will be in an imaging system to be flown on a satellite where a 2 × 9 R(E) orbit will expose the instrument to approximately 250 krad of radiation. Because to our knowledge no previous studies have been made on the potential radiation damage of these materials in the thin-film format, we report on such an assessment here. Transmittances and reflectances of BaF(2), CaF(2), HfO(2), MgF(2), and SiO(2) thin films on MgF(2) substrates, Al(2)O(3) thin films on fused-silica substrates, uncoated fused silica and MgF(2), and four multilayer filters made from these materials were measured from 120 to 180 nm beforeand after irradiation by 250 krad from a (60)Co gamma radiation source. No radiation-induced losses in transmittance or reflectance occurred in this wavelength range. Additional postradiation measurements from 160 to 300 nm indicates 2-5% radiation-induced absorption near 260 nm in some of the samples with MgF(2) substrates. From these measurements we conclude that far-ultraviolet filters made from the materials tested should experience less than 5% change from exposure to up to 250 krad of high-energy radiation in space applications.     

Center wavelength shift dependence on substrate coefficient of thermal expansion for optical thin-film interference filters deposited by ion-beam sputtering

Single-layer films of Ta2O5 and multilayer thin-film filters of Ta2O5 and SiO2 were deposited by ion-beam-sputter deposition. Postdeposition annealing of the structures resulted in increased optical thickness of the films, resulting in an upward shift in the wavelength of the transmission-reflection spectra. Modeling of the single-layer films by means of the effective media approximation indicates an increase in the void fraction of the film after annealing. This increase is consistent with an observed decrease in refractive index and an increase in physical film thickness. The multilayer structures, deposited on substrates of varying coefficient of thermal expansion (CTE), were annealed at various temperatures, and the change in the center wavelength was measured. The measured change is dependent on the annealing temperature and the substrate CTE, indicating that the increase in the void fraction is caused in part by thermally induced stress during the annealing process. A simple model is proposed that relates the void fraction present in the films after annealing with the substrate CTE and the annealing temperature.     

以Al2O3为过渡层脉冲激光法制备PZT铁电薄膜

为实现PZT铁电薄膜与半导体衬底的直接集成引入Al2O3为过渡层，首先用真空电子束蒸发法在Si(100)，多昌金刚石（111）衬底上生长约20nm厚的Al2O3过渡层，接着在上述衬底上采用脉冲激光淀积（PLD）法淀积PZT薄膜，衬底温度为350-550℃。X光电子能谱（XPS）测试表明，在高真空下，电子束蒸发Al2O3固态源能获得化学配比接近蒸发源的Al2O3薄膜。X射线衍射（XRD）测试说明，不论衬底是硅还是多晶金刚石，当衬底温度为550℃时，PZT在Al2O3过渡层上呈现（222）取向的焦绿石相结构，当衬底是金刚石时，通过如下工艺：（1）较低温度（350℃）淀积；（2）空气氛围650℃快速退火5min，可以在Al2O3过渡层上获得高度（101）取向的钙钛矿结构的铁电相PZT薄膜，最后AFM测试显示，在硅衬底上，PZT薄膜的表面均方根粗糙度为9.78nm；而在多晶金刚石衬底上，PZT薄膜的表面均方根粗糙度为17.2nm。