Bi1.5-xCaxZnNb1.5O7陶瓷结构、介电性能与结晶化学特性

采用固相反应法制备Bi1.5-xCaxZnNb1.5O7(0≤x≤0.50,BCZN)陶瓷,研究Ca2+替代Bi3+对Bi1.5ZnNb1.5O7陶瓷烧结特性、显微结构、介电性能和结晶化学特性的影响.结果表明:替代量x≤0.25 mol时,样品为单一的α-BZN相.随着Ca2+替代量增加,样品最佳烧结温度从1000℃升高到1020℃;致密度从7.011 g/cm3减小到6.353 g/cm3;样品晶粒尺寸、晶格常数、电阻率均减小;结晶化学参数键价和,AV(O’)[Bi4]、AV(O’)[Bi3Zn]、AV(O’)[Bi2Zn2]和AV(O’)[Ca3Zn]均增大,且该行为与其晶格常数、介电性能变化相吻合.     

脉冲激光沉积ZrW2O8薄膜的制备和性能

采用脉冲激光沉积法在石英基片上沉积制备了ZrW2O8薄膜.用X射线衍射仪(XRD)、原子力显微镜(AFM)研究了不同衬底温度对薄膜结构组分、表面粗糙度和形貌的影响,用台阶仪和分光光度计测量薄膜的厚度和不同衬底温度下制备薄膜的透射曲线,用变温XRD分析了ZrW2O8薄膜的负热膨胀特性.实验结果表明:在衬底温度为室温、550℃和650℃下脉冲激光沉积的ZrW2O8薄膜均为非晶态,非晶膜在1200℃保温3min后淬火得到立方相ZrW2O8薄膜;随着衬底温度的升高,ZrW2O8薄膜的表面粗糙度明显降低;透光率均约为80%,在20～600℃温度区间内,脉冲激光沉积制备的ZrW2O8薄膜的负热膨胀系数为-11.378×10-6 K-1.     

脉冲激光沉积法制备β-BBO薄膜

采用脉冲激光沉积法、选取β-BBO陶瓷作为靶材在掺在Sr2 的α-BBO(001)衬底上进行了生长β-BBO薄膊膜的实验,生长出表面光滑、无色透明的薄膜.采用X射线粉末衍射(XRD)、高分辨X射线衍射仪(XRC)对薄膜进行了分析测试,结果表明,所制备的β-BBO薄膜择优取向为(00l)面,薄膜的双晶摇摆曲线半峰宽值FWHM为1000“左右,显示出β-BBO薄膜较好的结晶质量,其紫外吸收边同β-BBO单晶一样也为190 nm,但薄膜的透过率略有下降.采用调Q脉冲Nd:YAG激光器观察了β-BBO薄膜的倍频效应.     

不同衬底温度下生长的Bi1.5Zn1.0Nb1.5O7.0薄膜的XPS研究

采用固相反应法合成具有焦绿石立方结构的Bi1.5Zn1.0Nb1.5 O7(BZN)陶瓷靶材,采用脉冲激光沉积法在Pt/TiO2/SiO2/Si(100)基片制备立方BZN薄膜,衬底温度在500～ 700℃范围内变化.X射线衍射测量结果表明:当在500℃沉积BZN薄膜时,薄膜呈现出无定形态结构.随着衬底温度增加到550℃,薄膜开始晶化,并且显示出立方焦绿石结构.X射线光电子能谱也被用来研究BZN薄膜的结构状态和元素价态.测试得到的全谱表明:在BZN薄膜中,除了用于定标的C元素之外,只有Bi、Zn、Nb、O元素的特征峰,此外有Ti2p特征峰出现,可能来自底电极的TiO2缓冲层.各元素的窄谱扫描表明:Bi,Zn,Nb,O四种元素的化学价态分别是+3,+2,+5,-2.BZN薄膜在550℃结晶,随着衬底温度升高到600℃,金属阳离子的结合能的峰位向高能方向移动,然而O1s的特征峰位也向高能方向移动,这归因于薄膜中存在的氧空位.     

紫外激光脉冲沉积法制备高温超导（Bi,Pb）2Sr2CaCu2O8薄膜的研究

用紫外脉冲激光沉积技术在单晶衬底上制备高温超导(Bi,Pb)2Sr2CaCu2O8薄膜,系统研究了不同镀膜参数对薄膜结晶质量的影响,获得了优化的镀膜工艺。并在较低温沉积、高温退火,以及高温沉积两种工艺下均获得了具有c轴取向、无杂相及无挥发(分解)的(Bi,Pb)2Sr2CaCu2O8薄膜。相比于高温沉积,低温沉积、高温退火制备的薄膜结晶质量更好。     

AlN薄膜的KrF准分子脉冲激光沉积

研究了采用脉冲激光沉积(PLD)技术在Si(100)衬底上AlN薄膜的制备及其性质。结果表明,衬底温度从室温到800℃的范围内,所得到的AlN薄膜为(002)择优取向的纤锌矿结构。随着衬底温度的升高,AlN薄膜从纳米晶结构转为多晶结构,同时表面微粗糙度上升。AlN晶粒呈柱状生长机制。     

沉积时间对脉冲激光沉积法制备ZnO薄膜性能的影响

采用脉冲激光沉积技术(PLD)在氧气气氛中以高纯Zn为(99.999%)靶材,在单晶硅和石英衬底表面成功生长了ZnO薄膜.通过X射线衍射仪、表明轮廓仪、荧光光谱仪、紫外可见分光光度计对合成薄膜材料的晶体结构、厚度、光学性质等进行了研究,分析了ZnO薄膜的沉积时间对其性能的影响.结果表明,采用PLD法在室温下可以制备出(002)结晶取向和透过率高于75%的ZnO薄膜,但室温下沉积的ZnO薄膜的发射性能较差,沉积时间的延长不能改善薄膜的发光性能.     

自组装单层膜表面的Bi2Ti2O7薄膜制备与表征

以硝酸铋和钛酸四丁酯为原料,以三氯十八烷基硅烷(OTS)为模板,采用自组装单层膜(self-as-sembled monolayers,SAMs)技术,在玻璃基板上成功制备了Bi2Ti2O7晶态薄膜。借助X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)、X射线能谱(EDS)及原子力显微镜(AFM)等测试手段对Bi2Ti2O7薄膜进行了表征。结果表明,以OTS为模板利用自组装技术,经540℃煅烧2h可成功制得立方相Bi2Ti2O7晶态薄膜,且薄膜表面平整光滑,均匀致密。     

Bi2O3薄膜的制备及其电阻开关特性的研究

电阻式存储器由于具有众多的优点有望成为最有前景的下一代高速非挥发性存储器的选择之一.实验利用射频磁控溅射法在重掺硅上沉积了Bi2O3薄膜,并对该薄膜的结晶状态和Au/Bi2O3/n+Si/Al结构的电阻开关特性进行了研究.XRD分析结果表明,射频磁控溅射法沉积所得的Bi2O3薄膜结晶性能好,(201)取向明显.I-V曲线测试结果表明,Au/Bi2O3/n+Si/Al结构具有单极性电阻开关特性.通过对不同厚度Bi2O3薄膜的Au/Bi2O3/n+Si/Al结构I-V特性比较发现,随着薄膜厚度的增加,电阻开关的Forming、Set和Reset阈值电压均随之增加.对于Bi2O3薄膜厚度为31.2 nm的Au/Bi2O3/n+Si/Al结构,其Forming、Set和Reset阈值电压均低于4 V,符合存储器低电压工作的要求.     

脉冲激光沉积制备立方AlN薄膜的研究

采用脉冲激光沉积(PLD)方法,在SrTiO3(100)衬底上在650℃、10Pa N2条件下成功制备了立方结构的AlN薄膜.高能电子衍射(RHEED)及X射线衍射(XRD)分析表明立方AlN和SrTiO3的外延关系为AlN[100]∥SrTiO3[100]和AlN(200)∥SrTiO3(100).其AlN(200)衍射峰的摇摆曲线半高宽(FWHM)为0.44°,说明薄膜结晶性能良好.原子力显微镜(AFM)表明外延的立方AlN薄膜表面具有原子级平整度,其表面均方根粗糙度(RMS)为0.674nm.通过X光电子能谱(XPS)分析AlN薄膜表面成分,结果表明AlN薄膜表面没有被氧化.     

Structure and microwave dielectric properties of Bi1.5Zn1.0Nb1.5O7 thin films deposited on alumina substrates by pulsed laser deposition

Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films were deposited on polycrystalline alumina substrates by pulsed laser deposition at different substrate temperatures. The phase structure and surface morphology were characterized using X-ray diffractometer (XRD) and atomic force microscopy. Microwave dielectric properties were performed using split-post dielectric resonator method at spot frequencies of 10, 15 and 19 GHz, respectively. The XRD results indicate that the as-deposited Bi_1.5Zn_1.0Nb_1.5O₇ thin films deposited at 650 °C are amorphous in nature. The dielectric permittivity and loss tangent of the amorphous BZN thin films are 75.5 and 0.013 at 10 GHz, respectively. As the measure frequency increased to 19 GHz, the dielectric permittivity slightly decreases and loss tangent slightly increases. BZN thin films were crystallized after the post-annealing by a rapid thermal annealing in air for 30 min. The crystallized BZN thin films exhibit the excellent dielectric properties and frequency responses. The dielectric permittivity and loss tangent of the crystallized BZN thin films are 154 and 0.038 at 10 GHz, respectively.     

Large nonlinear optical response of a Bi1.5Zn1.0Nb1.5O7 thin film fabricated by pulsed laser deposition

The Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin film has been fabricated on MgO (001) substrate by pulsed laser deposition. The nonlinear optical properties of the BZN film were investigated using Z-scan technique at a wavelength of 532 nm with 25 ps pulse duration. The two-photon absorption coefficient and the nonlinear refractive index of the BZN film were obtained to be 4.2 × 10^− 6 cm/W and 1.6 × 10^− 10 cm²/W respectively, which are comparable with those of some representative nonlinear optical materials. The large and fast response optical nonlinearities indicated that the BZN film is a promising candidate for future photonics devices.     

Influences of post-annealing on structural and electrical properties of Bi1.5Zn1.0Nb1.5O7 thin films prepared by pulsed laser deposition

Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films were prepared on Pt/TiO₂/SiO₂/Si(100) substrates at 650 °C under an oxygen pressure of 10 Pa by using pulsed laser deposition process. The crystallinity, microstructure and electrical properties of BZN thin films were investigated to verify the influences of post-annealing thermal process on them. The X-ray diffractometer (XRD) results indicate that all Bi_1.5Zn_1.0Nb_1.5O₇ thin films without post-annealing process or with post-annealing in situ vacuum chamber and in oxygen ambient exhibit a cubic pyrochlore structure. The improved crystallinity of BZN thin films through post-annealing was confirmed by XRD and scanning electron microscope (SEM) analysis. Dielectric constant and loss tangent of the as-deposited BZN thin films are 160 and 0.002 at 10 kHz, respectively. After annealing, dielectric properties of thin films are significantly improved. Dielectric constant and loss tangent of the in situ annealed films are 181 and 0.0005 at 10 kHz, respectively. But the films post-annealed in O₂ oven show the largest dielectric constant of 202 and the lowest loss tangent of 0.0002, which may attribute to the increase in grain size and the elimination of oxygen vacancies. Compared with the as-deposited BZN thin films, the post-annealed films also show the larger dielectric tunability and the lower leakage current density.     

Thickness-ratio-dependent dielectric properties of Bi1.5Zn1.0Nb1.5O7/Ba0.5Sr0.5TiO3 bilayered thin films

Bi_1.5Zn_1.0Nb_1.5O₇ (BZN)/Ba_0.5Sr_0.5TiO₃ (BST) thin films were prepared on Pt/Ti-coated sapphire substrates by radio frequency magnetron sputtering. The specific relationship between the dielectric properties and the thickness ratio of the BZN thickness to the BST thickness was investigated. The presence of BZN films effectively reduced the dielectric loss of the thin films. The thickness-ratio-dependent dielectric constant and dielectric loss behaviors were in good accordance with the simulation results based on the series connection theory. The optimum thickness ratio was determined to be around 0.5, exhibiting a maximum commutation quality factor of about 16,000. The built-in electric field at the region near the BZN–BST interface may be responsible for the asymmetric characteristic of the electric-field-dependent dielectric properties of the BZN/BST thin films.     

Enhanced tunable dielectric properties of Ba0.5Sr0.5TiO3/Bi1.5Zn1.0Nb1.5O7 multilayer thin films by a sol-gel process

Ba_0.5Sr_0.5TiO₃(BST)/Bi_1.5Zn_1.0Nb_1.5O₇(BZN) multilayer thin films were prepared on Pt/Ti/SiO₂/Si substrates by a sol-gel method. The structures and morphologies of BST/BZN multilayer thin films were analyzed by X-ray diffraction (XRD) and field-emission scanning electron microscope. The XRD results showed that the perovskite BST and the cubic pyrochlore BZN phases can be observed in the multilayer thin films annealed at 700 °C and 750 °C. The surface of the multilayer thin films annealed at 750 °C was smooth and crack-free. The BST/BZN multilayer thin films annealed at 750 °C exhibited a medium dielectric constant of around 147, a low loss tangent of 0.0034, and a relative tunability of 12% measured with dc bias field of 580 kV/cm at 10 kHz.     

The effect of Bi1.5Zn0.5Nb0.5Ti1.5O7 cover layer on the dielectric and tunable properties of Ba0.6Sr0.4TiO3/Bi1.5Zn0.5Nb0.5Ti1.5O7 bilayered thin films

Bi_1.5Zn_0.5Nb_0.5Ti_1.5O₇ (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba_0.6Sr_0.4TiO₃ (BST) thin films on the Pt/Ti/SiO₂/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces.     

硅基氧化铱薄膜的脉冲激光沉积及其微观结构研究

采用脉冲激光沉积技术，在Si（100）基片上制备了高致密的氧化铱（IrO2）薄膜，研究了不同沉积温度对薄膜结构的影响。利用X射线衍射（XRD）、拉曼光谱、扫描电镜（SEM）和原子力显微镜（AFM）对制备的IrO2薄膜进行了表征。结果表明：在20Pa氧分压，250℃～500℃范围内，得到的薄膜为多晶的IrO2物相，其晶粒尺寸和粗糙度随着沉积温度的升高而增加；所得到的IrO2薄膜表面粗糙度低，厚度均匀，与基片结合良好。     

Ferroelectric and dielectric multilayer heterostructures based on KTa0.65Nb0.35O3 and Bi1.5-xZn0.92-yNb1.5O6.92-1.5x-y grown by pulsed laser deposition and chemical solution deposition for high frequency tunable devices

Epitaxial growth of Bi_1.5-xZn_0.92-yNb_1.5O_6.92-1.5x-y (BZN) thin films was achieved on (100)_pc LaAlO₃ substrate by pulsed laser deposition (PLD) and by chemical solution deposition based on Pechini process. Effect of bismuth and zinc deficiency on the BZN thin films obtained by PLD was discussed, in relation with the starting target composition. Dielectric permittivity and bandgap values were determined from electrical and spectroscopic ellipsometry measurements performed on randomly oriented films grown on Pt/Si substrate. BZN thin films obtained by PLD exhibit, at 100 kHz, a dielectric constant of ε_r = 203 and quite low dielectric losses of tanδ = 5 × 10^− 2. Epitaxial ferroelectric − dielectric KTa_0.65Nb_0.35O₃ (KTN) − Bi_1.5-xZn_0.92-yNb_1.5O_6.92-1.5x-y (KTN on BZN and BZN on KTN) bilayers were obtained by PLD on (100)_pc LaAlO₃ with the insertion of a suitable buffer layer of KNbO₃ in the case of KTN on BZN. Such multilayer heterostructures with an epitaxial growth control of each layer are promising candidates for potential integration in microwave devices.     

脉冲激光沉积有机薄膜

脉冲激光沉积(PLD)技术是一门新兴的薄膜制备技术,在无机薄膜的制备和研究方面取得了令人满意的成果,技术也比较成熟.但利用脉冲激光沉积技术制备和研究有机膜方面的工作开展较晚,工作也比较少,尚未形成一个比较系统的体系.因此开展有机薄膜的脉冲激光沉积研究将具有重要的意义.     

脉冲激光沉积ZnO薄膜的结构和光学特性研究

采用脉冲激光，在Si（001）衬底上生长ZnO薄膜，利用X射线衍射（XRD），原子力显微镜（AFM）和光致发光光谱（PL）等测试手段研究了不同衬底温度所生长的ZnO薄膜结构特征和光学性能。研究表明：衬底温度影响ZnO薄膜结构和光学性能。在500℃～600℃沉积范围内随着温度升高，ZnO薄膜结构和光学性能提高。