水热—溶胶凝胶法制备PZT薄膜

采用水热—溶胶凝肢法制备了锆钛酸铅( PZT)压电陶瓷薄膜.首先利用水热法处理Si基板,使之生成SiO2/Si层,然后采用旋涂法在处理好的Si基板上涂覆摩尔比r(Zr:Ti)为52:48的PZT前驱体溶胶.研究了基板处理方式、退火温度以及涂胶层数对PZT薄膜结晶性能、表面形貌及厚度的影响.结果表明:水热处理Si基板对P...     

PT种子层对PZT薄膜结晶及压电性能的影响

采用溶胶-凝胶法(Sol-Gel)在Pt/Si衬底上制备了PbTiO3 (PT)薄膜和Pb (Zrx,Ti1-x)O3(PZT)薄膜,研究了退火温度以及PT种子层对PZT薄膜结晶及压电性能的影响。X射线衍射(XRD)结果表明,制备的PZT薄膜为纯钙钛矿结构的多晶薄膜,有PT种子层的PZT薄膜晶粒尺寸更大,(110)面取向度更高,结晶性能更好;原子力显微镜(AFM)结果表明,制备的薄膜表面形貌比较平整、均匀、无裂纹;压电力显微镜(PFM)结果表明,压电力显微镜(PFM)结果表明,有PT种子层时,PZT薄膜的平均压电系数d33为128～237 pm/V,无PT种子层时平均压电系数d33为21～29 pm/V。在升温速率为10 ℃/s的退火条件下保温10 min时,随着退火温度的升高,PZT薄膜晶粒尺寸增大,粗糙度增大,(110)面取向度升高,平均压电系数d33增大。PT种子层能够有效的改善PZT薄膜的结晶性能和压电性能。     

The influence of dielectric layers on the CW-Laser Annealing of polysilicon

Polysilicon films were deposited on the following four dielectric layers: 0.10 μm Si0₂, 0.10 μm Si₃N₄, 1.0 μm Si0₂ and a dual layer of 0.10 μm Si₃N₄ over 1.0 μm Si0₂. The films were doped with As or P and then annealed with a scanning CW-argon laser. The resulting sheet resistance at a given laser power depends upon both the dielectric material and its thickness. The threshold power, that causes complete melting of the polysilicon, is inversely proportional to the thermal resistance of the underlying dielectric layers. With certain laser parameters and substrate film combinations, excessive thermal stresses cause cracking of the polysilicon films. The laser annealing process is also influenced by the net optical reflectance of the polysilicon/ dielectric multilayer films.     

纳米尺度压电薄膜PZT的结构特征和性能

采用改进的溶胶-凝胶(Sol-Gel)方法在Pt/Ti/SiO2/Si基片上制备锆钛酸铅(PZT)纳米晶薄膜,研究了不同的热处理方式对PZT薄膜的晶粒结构、尺寸及电学性能的影响。X-射线衍射(XRD)分析表明:传统的热处理方式更有利于得到具有一定择优取向性的PZT薄膜。原子力显微镜(AFM)显示:快速热处理方式使PZT薄膜的晶粒具有自形晶结构,晶粒的排布更为有序,从而改善了薄膜的致密性。阻抗分析仪的测试结果表明:经快速热处理的薄膜,漏电流大约比传统热处理处理的薄膜的漏电流降低了20倍左右。     

高取向PZT厚膜的0-3复合法制备

采用 0 3复合法 ,在Pt/Ti/SiO2 /Si衬底上成功制备了单层厚度 0 .9μm ,总厚度 10 μm ,并且无裂纹的Pb(Zr0 .53,Ti0 .4 7)O3铁电薄膜。溶液中粉体的存在减小了加热时的体积收缩 ,降低了制备过程中膜内部产生的应力 ,从而使得单层厚度可达 0 .9μm ,防止了薄膜开裂。X射线衍射分析表明薄膜为单一钙钛矿相结构且结晶状态良好 ,采用已烧结的粉末时 ,薄膜呈〈110〉取向 ;扫描电子显微镜分析表明 ,薄膜表面无裂纹 ;介电性能测试结果显示 ,其相对介电常数可高达 115 0。为了研究粉末的状态和薄膜取向之间的关系 ,将未经烧结的未结晶的PZT粉末加入前驱溶液中 ,在相同的制备条件下 ,可得沿〈10 0〉晶向强烈取向的PZT薄膜     

Sol-Gel processing of Nb-doped Pb(Zr,Ti)O3 thin films for ferroelectric memory applications

The ferroelectric properties of Nb-doped PZT thin films prepared by a sol-gel method were evaluated relative to memory device application requirements. Within the range of 0 to 4 mol %, Nb-doping of PZT compositions near the morphotropic phase boundary region (i.e. PZT 53/47) enhanced overall ferroelectric properties by reducing the te-tragonal distortion of the unit cell. A 4 mol % Nb-doped PZT 53/47 thin film (0.26 μm) had a coercivity of 8 V/ μm, a remanence ratio of 0.54, a switchable polarization of 45 μC/cm², and a specific resistivity of 3 x 10⁹ Ω-cm. Nb-doping levels in excess of 5 mol had a detrimental effect on the resulting thin film ferroelectric properties. X-ray diffraction (XRD) analysis of highly doped films showed development of a significant PbO phase accompanied by diffraction line broadening of the perovskite phase. As such, it was postulated that the creation of excessive lead vacancies in the PNZT lattice resulted in PbO accumulation at the grain boundaries which impeded grain growth, and hence, adversely affected ferroelectric switching performance. The fatigue performance of the sol-gel derived thin film capacitor system was a function of switching voltage. At switching fields sufficient to saturate the polarization, the endurance of the thin film capacitor was greater than 10⁹ cycles. Cycling with lower fields reduced endurance values, but in all cases, the switchable polarization decreased linearly with the logarithm of cycles. Nb-doping did not have a significant effect on the fatigue performance.     

Neutralization of electrically active aluminum in recrystallized silicon-on-sapphire films

We report the effect of steam oxidation at 875° C on the electrical resistivity, crystalline quality (measured by ion channeling), and Al concentration (measured by secondary ion mass spectrometry) in 0.25 μm thick, Si-implanted and recrystallized, Si-on-sapphire films. After a deep Si implantation (180 keV, 1.4×l0¹⁵ Si/cm²) at room temperature, and solid-phase epitaxial regrowth from the non-amorphized, 0.03 μm thick surface region, the initially undoped SOS films become doped p-type, and their resistivity decreases from (1−5)xl0¹⁴ ficm to 0.5 Ωcm. The doping is due to electrically active Al, released from the A1₂O₃ by the Si implantation, and present in the recrystallized films at a concentration of ≃2×l0¹⁶ Al/cm³ . After a 75 min steam oxidation at 875 °C, which consumes 0.06 Μm of Si, the resistivity of the recrystallized films increases to over 40 Ωcm, but the Al concentration is unchanged. The oxidation also uncovers higher quality material below the non-recrystallized surface layer. A semi-quantitative model is proposed to explain the electrical data, based on the diffusion of oxygen from the Si/SiO₂ interface into the SOS film during oxidation, and the formation of Al-O-Si neutral complexes. Data on the stability of the high-resistivity films against high-temperature annealing or re-amorphization and annealing is given.     

Si-YBaCuO intermixing and reactive patterning technique

A novel Si-YBaCuO intermixing technique has been developed for patterning YBaCuO superconducting thin films on both insulating oxide substrates (MgO) and semiconductor substrates (Si). The electrical, structural, and interfacial properties of the Si-YBaCuO intermixed system have been studied using resistivity, x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy and Auger depth profiling measurements. The study showed that the reaction of Si with YBaCuO and formation of silicon oxides during a high temperature process destroyed superconductivity of the film and created an insulating film. On a MgO substrate, the patterning process was carried out by first patterning a silicon layer using photolithography or laser-direct-writing, followed by the deposition of YBaCuO film and annealing. For a silicon substrate, thin metal layers of Ag and Au were patterned as a buffer mask which defines the YBaCuO structures fabricated thereafter. Micron-sized (2-10 Μm) superconducting structures with zero resistance temperature above 77 K have been demonstrated. This technique has been used to fabricate current controlled HTS switches and interconnects.     

Material and electrical properties of electroless Ag-W thin film

Thin Ag-W films were prepared on Si (100) substrate and on metal (Ag and Co) seed layers by electroless technology for ULSI applications. The thin film electrical and physical parameters were studied as a function of the film composition. The thin film composition depends on the electroless bath formula. The role of the tungsten in silver matrix was studied via measurements of the film microhardness and thermal stability as function of the composition. The Ag-W films, thicker than 200 nm, exhibited a specific electrical resistivity of about 2μΩ* and a reflectivity larger than 90%. These films have not corroded in air at temperatures up to 200°C (thermal stable). Therefore, we assume that silvertungsten films can be used for applications where reliable conducting thin films is required, such as packaging and interconnects for microelectronics.     

MgO缓冲层对Si衬底上制备Fe3Si薄膜性能的影响

采用磁控溅射方法和热加工工艺在n型Si衬底上溅射不同厚度的MgO层并制备Fe-Si薄膜层,退火后形成Fe3Si/MgO/Si多层膜结构.利用MgO缓冲层对退火时Si衬底扩散原子进行屏蔽,并分析MgO层对Fe3Si薄膜结构和电学性质的影响.通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和四探针测试仪对Fe3Si薄膜的晶体结构、表面形貌、断面形貌和电阻率进行表征与分析.研究结果表明:当MgO层厚度为20 nm时生成Fe0.9Si0.1薄膜,当厚度为50,100,150和200 nm时都生成了Fe3Si薄膜,生成的Fe3Si和Fe0.9Si0.1薄膜以(110)和(211)取向为主.随MgO缓冲层厚度增加,Si衬底扩散原子对Fe3Si薄膜的影响减小,Fe3 Si薄膜的晶格常数逐渐减小,晶粒大小趋向均匀,平均电阻率呈现先增大后减小趋势.研究结果为后续基于Fe3 Si薄膜的器件设计与制备提供了参考.     

Low Fatigue in Epitaxial Pb(Zr<Subscript>0.2</Subscript>Ti<Subscript>0.8</Subscript>)O<Subscript>3</Subscript> on Si Substrates with LaNiO<Subscript>3</Subscript> Electrodes by RF Sputtering

Epitaxial PZT (001) thin films with a LaNiO₃ bottom electrode were deposited by radio-frequency (RF) sputtering onto Si(001) single-crystal substrates with SrTiO₃/TiN buffer layers. Pb(Zr_0.2Ti_0.8)O₃ (PZT) samples were shown to consist of a single perovskite phase and to have an (001) orientation. The orientation relationship was determined to be PZT(001)[110]∥LaNiO₃(001)[110]∥SrTiO₃ (001)[110]∥TiN(001)[110]∥Si(001)[110]. Atomic force microscope (AFM) measurements showed the PZT films to have smooth surfaces with a roughness of 1.15 nm. The microstructure of the multilayer was studied using transmission electron microscopy (TEM). Electrical measurements were conducted using both Pt and LaNiO₃ as top electrodes. The measured remanent polarization P _r and coercive field E _c of the PZT thin film with Pt top electrodes were 23 μC/cm² and 75 kV/cm, and were 25 μC/cm² and 60 kV/cm for the PZT film with LaNiO₃ top electrodes. No obvious fatigue after 10¹⁰ switching cycles indicated good electrical endurance of the PZT films using LaNiO₃ electrodes, compared with the PZT film with Pt top electrodes showing a significant polarization loss after 10⁸ cycles. These PZT films with LaNiO₃ electrodes could be potential recording media for probe-based high-density data storage.     

Optimization of Pb(Zr0.53,Ti0.47)O3 films for micropower generation using integrated cantilevers

Lead zirconate titanate, Pb(Zr_0.53,Ti_0.47)O₃ or PZT, thin films and integrated cantilevers have been fabricated for energy harvesting applications. The PZT films were deposited on PECVD SiO₂/Si substrates with a sol-gel derived ZrO₂ buffer layer. It is found that lead content in the starting solution and ramp rate during film crystallization are critical to achieving large-grained films on the ZrO₂ surface. The electrical properties of the PZT films were measured using metal-ferroelectric-metal and inter-digital electrode structures, and revealed substantial improvement in film properties by controlling the process conditions. Functional cantilevers are demonstrated using the optimized films with output of 1.4 V peak-to-peak at 1 kHz and 2.5 g.     

硅基铁电薄膜的电性能研究

以 Sol- Gel方法制备了有 Pb Ti O3 (PT)过渡层的硅基 Pb(Zr0 .53 Ti0 .47) O3 (PZT)铁电薄膜 ,底电极分别为低阻硅和硅衬底上溅射的金属钛铂。测试了铁电薄膜的电性能 ,比较了两种衬底电极对铁电薄膜性能的影响及各自的优势     

Annealing effects in the Ag/Al-(100) InP system: Al redistribution and film recrystallization

Annealing effects on contact metallurgy were examined in the Ag/Al-(100) InP system. Metal film configuration and annealing conditions were those that resulted in Schottky contacts with superior electrical characteristics. Metallurgical changes were observed with transmission electron microscopy combined with selected area diffraction (SAD) and x-ray diffraction. A1 was redistributed from the metal-semiconductor interface throughout the Ag overlayer upon annealing. Subsequent cooling resulted in the precipitation of Ag₂Al. During annealing the metal film underwent surface energy driven recrystallization (SEDR) with the predominant orientation observed in large recrystallized grains being: Ag(111)‖InP(100) and, to within 9° of rotation, Ag(110)‖InP(001). It is proposed that the thin Al interlayer and formation of Ag₂A1 early in the annealing cycle modifies the interaction between the metal film and InP substrate which results in contact metallurgy substantially different than that observed for either pure Ag or Al films on (100) InP.     

Microstructure and domain configurations in ferroelectric PbTiO3 and Pb(Zr,Ti)O3 thin fims

Ferroelectric domain configurations in PbTiO₃ and Pb(Zr_xT_1−x)O₃ (PZT, x = 0.3 or 0.5) thin films have been studied by transmission electron microscopy. The PbTiOg and PZT thin films have been deposited by the ionized cluster beam technique and radio frequency sputtering, respectively. The grain size in these thin films is typically less than 0.5 μm. Lamellar 90°-domain features have been observed in both PbTiO₃ and PZT (30/70) samples. The domain walls correspond to the {011} twin boundaries. La-doping and Ca-modification are shown to affect the microstructure of the PZT films. No clear domain feature occurs in the PZT thin film that has composition near the morphotropic phase boundary. The effects of grain sizes are briefly discussed.     

Comparison of the agglomeration behavior of Ag(Al) films and Ag(Au) films

It is essential to suppress agglomeration of Ag films caused by thermal treatment for their successful application as new metallization materials. Co-sputtered Ag(Al) and Ag(Au) films were investigated, with regard to their change in morphology and electrical resistivity after vacuum annealing. As a result, agglomeration of the Ag(Al) film (Al: 4.3 at.%) was not recognized even after annealing at 600 °C. However, void formation followed by de-wetting was observed for the Ag(Au) film after annealing, similar to that for a pure Ag film. The morphological change was accompanied by an increase in the resistivity of the Ag(Au) films with annealing temperature. On the other hand, the resistivity of the Ag(Al) films did not increase by annealing at temperatures from 400 to 600 °C. However, the film with the highest Al content, which was most resistive to agglomeration, had too high resistivity for use as a metallization material. By analysis of the Auger depth profile, the presence of very thin oxide layers at the surface of the film and at the interface with the substrate was confirmed for Ag(Al) films after annealing. This was considered to be the reason for the large difference in agglomeration behavior between the Ag(Au) and Ag(Al) films.     

Buckling and Delamination of Ti/Cu/Si Thin Film During Annealing

In this paper, the formation of buckling and delamination of sandwiched stacking of Ti/Cu/Si thin film are investigated. The crystallization structures, the composition of the Cu/Ti thin films, and the surface morphology are measured during annealing. The results show that the solid-phase reaction between Cu and Ti occurs at the interface. Buckling is initiated in the thin film annealed at 600°C. The volume expansion promotes the buckling and further produces microcracks. With increasing volume expansion, there are cavities formed in the middle layer when the annealing temperature is up to 700°C. Finally, thin film is delaminated from the substrate.     

硅基PZT铁电薄膜的制备与性能研究

用溶胶-凝胶（Sol-Gel）方法制备了硅基Pb(Zr0.53Ti0.47)O3(PZT)铁电薄膜。分析了PZT铁电薄膜的表面形貌、晶化程度、界面状态等性质。基于上述分析结果提出并实现了低温退火处理制备有PT过渡层的PZT铁电薄膜的工艺流程。测试了低温制备的PZT铁电薄膜的C-V、漏电等电性能,发现在Sol-Gel法制备PZT铁电薄膜的工艺中加入PT过渡层,有助于提高PZT薄膜的品质。     

PZT/NFO/LSMO多层磁电外延薄膜微观结构研究

用脉冲激光沉积法在(110)取向的SrTiO3(STO)单晶衬底上制备了Pb(Zr0.52Ti0.48)O3/NiFe2O4/La0.7Sr0.3MnO3(PZT/NFO/LSMO)磁电复合外延薄膜,并用X射线衍射和透射电镜技术研究了外延薄膜的物相和显微结构。原子力显微镜结果表明PZT、NFO和LSMO薄膜表面均平整,晶粒尺寸分布均匀,表面粗糙度分别为1.8,1.7和0.2 nm。X射线衍射、选区电子衍射和高分辨透射电子显微镜(HRTEM)测试结果均证明各层薄膜沿(110)STO衬底外延生长,其外延关系为(110)PZT//(110)NFO//(110)LSMO//(110)STO和[001]PZT//[001]NFO//[001]LSMO//[001]STO。HRTEM结果显示,NFO/LSMO界面和LSMO/STO界面平整外延性好,无缺陷,而PZT/NFO界面较粗糙;NFO薄膜表面呈锯齿状,锯齿状面为立方NFO的能量最低{111}面,而PZT薄膜表面呈岛状,进一步的显微结构分析认为PZT薄膜为层状-岛状生长模式。     

Intense Terahertz Radiation from InAs Thin Films

Terahertz (THz) radiation from InAs thin films grown by molecular-beam epitaxy on closely lattice-matched p-type GaSb (100) substrates and lattice-mismatched semi-insulating GaAs (100) substrates was investigated. The THz radiation intensity was measured from InAs films with thicknesses between 100 nm and 1.5 μm excited by a femtosecond laser pulse with a wavelength of approximately 780 nm. The radiation intensity increased as the InAs film thickness increased and it exceeded that from a bulk n-type InAs substrate with an electron concentration of 2.3 × 10¹⁶ cm⁻³ when the InAs film thickness was greater than about 500 nm. In addition, the THz intensity from a 1-μm-thick InAs film was greater than that from a bulk p-type InAs substrate. We ascribe this enhanced THz intensity to the wave reflected from the lower interface between the InAs film and the layer grown beneath it. We confirmed this by observing an increased pulse width due to constructive overlap of the reflected wave. The results demonstrate that InAs thin films are promising materials for THz emitting devices.