取向对PLD法制备BiFeO3薄膜性能的影响

以快速等离子烧结法(SPS)制备的BiFeO3块体为靶材,用激光脉冲沉积(PLD)法在不同衬底上制备了BiFeO3(100)/LaNiO3(100)/Si(100)、BiFeO3(111)/LaNiO3(111)/SrTiO3(111)、BiFeO3(110)/Pt/TiO2/SiO2/Si、BiFeO3(110)LaNiO3(110)/Pt/TiO2/SiO2/Si不同择优取向的薄膜,并对薄膜进行了XRD和SEM分析。X射线衍射结果表明,BiFeO3薄膜外延沉积在导电层衬底上,并且它们具有相同的高度取向。SEM分析表明,薄膜上的晶粒是柱状形态,表面光滑致密且颗粒分布非常均匀,晶粒的边界和尺寸也能被清晰地观察到。通过铁电铁磁性能研究,BiFeO3(111)择优取向性能最佳。SrTiO3衬底上(111)取向的BiFeO3薄膜铁电剩余极化值达到了30.3μC/cm2,漏电流为1.0×10-3 A/cm2,饱和磁化强度为20.0kA/m。     

Sol-gel方法制备BiFeO_3/Bi_4Ti_3O_(12)多层薄膜及其电性能

采用溶胶-凝胶方法在FTO/glass底电极上制备了BiFeO3/Bi4Ti3O12和Bi4Ti3O12/BiFeO3多层薄膜。研究了室温下薄膜的结构,铁电性质和介电性质,并将其与纯的BiFeO3薄膜的性质进行了比较。从薄膜的XRD模式中可以观察到共存的BiFeO3相和Bi4Ti3O12相。通过电滞回线测量可以看出,相对于纯的BiFeO3薄膜,BiFeO3/Bi4Ti3O12和Bi4Ti3O12/BiFeO3多层薄膜能够承受更高的测试电场而获得充分极化,从而表现出较强的铁电性,在450kV/cm测试电场下,薄膜的剩余极化强度分别为37μC/cm2和23μC/cm2。     

Fe3+/Bi3+对纯相BiFeO3薄膜的影响及生长机理研究

以Bi(NO3)3·5H2O,Fe(NO3)3·9H2O为原料,柠檬酸为螯合剂,用液相自组装法,在ITO玻璃基片上制备了纯相BiFeO3薄膜.研究了前驱液中Fe3+/Bi3+摩尔比对BiFeO3薄膜的影响.利用XRD,EDS,XPS,FE-SEM和FT-IR等测试手段对BiFeO3薄膜进行了表征.结果表明,由于柠檬酸对...     

pH值对液相自组装法制备纯相BiFeO3薄膜的影响

采用液相自组装法,Bi(NO3)3·5H2O,Fe(NO3)3· 9H2O为原料,柠稼酸为螯合剂,以OTS单分子层为模板,在ITO玻璃基片上成功制备了BiFeO3晶态薄膜.研究了前驱液pH值对BiFeO3薄膜的影响.利用XRD,EDS和SEM等测试手段对在不同pH值下沉积的BiFeO3薄膜进行了表征.结果表明,由于Bi...     

PLD法制备BiFeO3薄膜及其性能研究

采用快速等离子烧结法(SPS)制得纯相BiFeO3靶材,利用脉冲激光沉积(PLD)法将其沉积在Si(100)衬底上,制得BiFeO3薄膜。通过调节各种工艺参数,在沉积温度650℃,氧压2Pa,靶基距5cm,脉冲激光频率7Hz、激光能量350mJ条件下获得了高择优取向、高结晶度的BiFeO3薄膜。在此工艺条件下,又制备了不同厚度的BiFeO3薄膜。用XRD、SEM等手段对薄膜相和形貌进行了表征。结果表明,制备的薄膜有较高的形貌质量,薄膜的铁电、铁磁性能呈现出与厚度的强相关性;其中300nm厚的薄膜质量最好。     

退火工艺对液相自组装法制备BiFeO3薄膜的影响

以Bi(NO3)3·5H2O,Fe(NO3)3·9H2O和柠檬酸为主要原料,采用液相自组装法,以OTS单分子层为模板,在ITO玻璃基片上成功制备了BiFeO3晶态薄膜.研究了退火温度以及保温时间对BiFeO3薄膜的影响.利用DSC/TG对铁酸铋前驱物结晶行为进行了表征,利用XRD和FE-SEM等测试手段对不同退火工艺下...     

La对BiFeO3薄膜的替代效应

用溶胶-凝胶方法在LaNiO3底电极上制备了纯的和10%A位La替代的BiFeO3薄膜.研究了室温下薄膜的介电与铁电性质和漏电流性质.铁电性研究表明,通过La替代,薄膜的铁电性得到显著增强,剩余极化强度由1.67 μC/cm2增加到2.20 μC/cm2.介电性质研究表明,在整个测试频率范围内,La替代的薄膜的介电性得到了增强.低频下的介电损耗增加而高频的介电损耗减少.而漏电流特性测试表明,La替代有效的限制了BiFeO3薄膜的漏电流.     

LaNiO3底电极上的BiFeO3薄膜的铁电性能

用溶胶一凝胶方法在LaNiO3底电极上制备了500℃退火的BiFeO3薄膜.研究了室温下薄膜的结构,介电与铁电性质和漏电流性质.XRD研究表明薄膜呈R3m结构,没有观察到不纯相.铁电性研究表明,薄膜具有大的剩余极化强度,在600 kV/cm的测试电场下,薄膜的剩余极化强度为20uC/cm2,矫顽场为440 kV/cm.介电性质研究表明,在整个测试频率范围内,薄膜具有小的介电损耗.而漏电流特性测试表明,通过工艺的改进,有效的限制了BiFeO3薄膜的漏电流.     

掺镧BiFeO3薄膜的制备及光伏特性研究

采用溶胶–凝胶法,用乙二醇甲醚作溶剂溶解Bi(NO3)3、Fe(NO3)3和La(NO3)3制备前体溶液,通过化学溶液沉积法在FTO导电玻璃基板上合成La3+掺杂的BiFeO3(BFO)薄膜,并研究了La3+掺杂对BiFeO3的能带及其光伏性能的影响。BiFeO3薄膜呈多晶钙钛矿结构,且随着La3+掺杂量的增加,BiFeO3的晶格常数依次递减。掺杂10%La3+的BiFeO3的能隙比未掺杂时稍有减小,为2.71 eV,随着La3+掺杂量的增加,BiFeO3的能隙增加到2.76 eV。采用改良法制备的La3+的掺杂量为10%的BiFeO3薄膜的最大开路电压为0.4 V,具有良好的光伏性能。     

β-FeSi2/Si异质结的制备及性质研究

采用直流磁控溅射和真空退火方法制备β-FeSi2/Si异质结,首先在n型Si(100)衬底上沉积Fe膜,经真空退火形成β-FeSi2/Si异质结,Fe膜厚度约238nm,退火后形成的β-FeSi2薄膜厚度约为720nm。利用XRD、SEM和红外光谱仪分别研究了β-FeSi2薄膜的晶体结构、表面形貌和光学性质。霍尔效应结果表明,制备的β-FeSi2薄膜为n型导电,载流子浓度为9.51×1015cm-3,电子迁移率为380cm2/(V.s)。     

Ferroelectric behavior in bismuth ferrite thin films of different thickness

The ferroelectric behavior of BiFeO(3) thin films is modified by changing the film thicknesses, where the BiFeO(3) thin films with different thicknesses were grown on SrRuO(3)/Pt/TiO(2)/SiO(2)/Si(100) substrates by radio frequency sputtering. The mixture of (110) and (111) orientations is induced for all BiFeO(3) thin films regardless of their thicknesses, together with the columnar structure and the dense microstructure. Their dielectric behavior is almost independent of the film thickness where all thin films have a low dielectric loss. A giant remanent polarization of 2P(r) ≈ 156.6-188.8 μC/cm(2) is induced for the BiFeO(3) thin films in the thickness range of 190-600 nm. As a result, it is an effective way to improve the ferroelectric behavior of the BiFeO(3) thin film by tailoring the film thickness.     

Nanoscale control of exchange bias with BiFeO3 thin films

We demonstrate a direct correlation between the domain structure of multiferroic BiFeO3 thin films and exchange bias of Co 0.9Fe 0.1/BiFeO3 heterostructures. Two distinct types of interactions - an enhancement of the coercive field ( exchange enhancement) and an enhancement of the coercive field combined with large shifts of the hysteresis loop ( exchange bias) - have been observed in these heterostructures, which depend directly on the type and crystallography of the nanoscale ( approximately 2 nm) domain walls in the BiFeO3 film. We show that the magnitude of the exchange bias interaction scales with the length of 109 degrees ferroelectric domain walls in the BiFeO 3 thin films which have been probed via piezoresponse force microscopy and X-ray magnetic circular dichroism.     

Structural and electrical characteristics of chemical solution derived (Bi3.2La0.4Nd0.4)Ti3O12 thin films

(Bi_3.2La_0.4Nd_0.4)Ti₃O₁₂ (BLNT) thin films were prepared on Pt/Ti/SiO₂/Si substrates by using chemical solution deposition technique, and the effects of annealing temperatures in the range of 550-750 °C on structure and electrical properties of the thin films were investigated. X-ray diffraction analysis shows that the thin films have a bismuth-layered perovskite structure with preferred (117) orientation. The surface morphology observation by field-emission scanning electron microscopy confirms that films are dense and smooth with uniformly distributed grains. The grain size of the thin films increases with increasing annealing temperature; meanwhile, the structural distortion of the thin films also increases. It was demonstrated that the thin films show good electrical properties. The dielectric constant and dielectric loss are 191 and 0.028, respectively, at 10 kHz for the thin film annealed at 600 °C, and the 2Pr value of the thin film annealed at 700 °C is 20.5 μC/cm² at an electric field of 500 kV/cm.     

Influences of oxygen pressure on optical properties and interband electronic transitions in multiferroic bismuth ferrite nanocrystalline films grown by pulsed laser deposition

Bismuth ferrite (BiFeO(3)) nanocrystalline films with the crystalline size of 27-40 nm have been grown on c-sapphire substrates under various oxygen pressures of 1 × 10(-4) to 1 Pa by pulsed laser deposition. The X-ray diffraction spectra show that the films are polycrystalline and present the pure rhombohedral phase. It was found that the Raman-active phonon mode E(TO1) shifts towards a higher energy side from 74 to 76 cm(-1) with increasing oxygen pressure, indicating a larger tensile stress in the films deposited at higher oxygen pressure. The X-ray photoelectron spectroscopy analysis suggests that the concentrations of both Fe(2+) ions and oxygen vacancies in the BiFeO(3) films increase with decreasing oxygen pressure. Moreover, the dielectric functions in the photon energy range of 0.47-6.5 eV have been extracted by fitting the transmittance spectra with the Tauc-Lorentz dispersion model. From the transmittance spectra, the fundamental absorption edge is observed to present a redshift trend with increasing the temperature from 8 to 300 K. Note that the optical band gap (E(g)) decreases with increasing the temperature due to the electron-phonon interactions associated with the interatomic distance in the BiFeO(3) films. However, the E(g) decreases from 2.88 to 2.78 eV with decreasing oxygen pressure at 8 K, which can be attributed to the increment of oxygen vacancies leading to the formation of some impurity states between the valence and conduction band. It can be concluded that the oxygen pressure during the film fabrication has the significant effects on microstructure, optical properties, and electronic band structure modification of the BiFeO(3) films.     

Fatigue-less relaxor ferroelectric thin films with high energy storage density via defect engineer

Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free 0.7Sr0.7Bi0.2TiO3-0.3BiFeO3-x％Mn(x=0,0.5,1.5,2,3)thin films via sol-gel method.Mn ions of divalent valence combine with oxygen vacancies,forming defect complex,which results in marked decline in leakage current and obvious enhancement in breakdown strength.A high energy storage density～47.6 J cm-3 and good efficiency～65.68％are simultaneously achieved in 2％Mn doped 0.7Sr0.7Bi0.2TiO3-0.3BiFeO3 thin film capacitor.Moreover,the 2％Mn-doped thin film exhibits excellent thermal stability in wide operating temperature range(35-115℃)and strong fatigue endurance behaviors after 108 cycles.The above results demonstrate that 2％Mn-doped 0.7Sr0.7Bi0.2TiO3-0.3BiFeO3 thin film capacitor with superior energy storage performances is a potential candidate for electrostatic energy storage.     

多层模型计算椭偏法测量的SiO2/Si超薄膜厚度

采用不同的光学模型对厚度为6 nm,密度为2.2 g/cm3的理想SiO2薄膜理论曲线进行了拟合,得到了薄膜厚度的计算结果随所采取的薄膜密度变化的规律:选用更大的薄膜密度值进行拟合计算会得到更小的厚度结果,其趋势近似线性.参考GIXRR方法测量得到的薄膜物理结构的结果,给出了优化的拟合计算模型(薄膜密度为2.4 g/cm3、表面粗糙度为0.4 nm、界面粗糙度为0.3 nm),对于热氧化法制备的厚度小于10 nm的SiO2超薄膜,使用此模型进行拟合计算,可以得到比常规模型更为准确的厚度结果.采用优化的模型拟合了期望厚度为2,4,6,8,10 nm的SiO2超薄膜的SE实验曲线,得到的厚度结果分别为2.61,4.07,6.02,7.41,9.43 nm,与传统模型计算结果相比,分别降低了13.8%,10.3%,8.1%,7.3%和6.6%.     

Ce3+掺杂钛酸钡纳米管薄膜的制备与性能

以阳极氧化制备的TiO_2纳米管薄膜为模版,通过水热法制备了Ba_(1-x)Ce_xTiO_3(0≤x≤0.08)纳米管薄膜,研究了Ba_(1-x)Ce_xTiO_3的结构、表面形貌及其电性能。采用X射线衍射仪表征其晶体结构,采用扫描电子显微镜和透射电子显微镜观察其表面及断口形貌,采用宽频介电阻抗谱仪测试其介电性能。结果表明,在较为温和的条件下用水热法成功制备出立方相结构的Ba_(1-x)Ce_xTiO_3纳米管薄膜,纳米管孔径在80~95nm之间;将制备的Ba_(1-x)Ce_xTiO_3经退火后生成多晶的Ba1-xCexTiO3纳米管薄膜,且样品的管外径尺寸在90~100nm之间,管壁的厚度为25~30nm,介电常数在1kHz下最高可达472,介电损耗为0.41。     

硅基板上Fe掺杂TiO2氧敏薄膜的制备、结构与性能研究

采用溶胶-凝胶法,以Ti(OC₄H₉)₄为前驱体,用提拉法在硅基板上制备了掺Fe的TiO₂氧敏薄膜,对薄膜物相结构进行了X射线衍射(XRD)测定,利用扫描电镜(SEM)对薄膜微结构进行了观察.结果表明:在硅基板上生长的TiO₂薄膜中锐钛矿相为均匀小晶粒分布结构,金红石相以大尺度团聚结构形貌出现.Fe离子的掺杂对硅基板上制备的TiO₂薄膜中金红石相的形成有很大的影响.Fe的掺入降低了金红石相的形成温度约100℃,Fe掺量在6mol% 时,形成金红石相的量达到最大,即析晶能力最强.薄膜中形成晶相的晶格常数在<6mol%的低Fe范围内,随较小的Fe离子取代较大的Ti离子,锐钛矿相和金红石相的晶格常数都随之减小;在>6mol%的高Fe掺量范围内,随Fe掺量的增加,体系缺陷过量增加,晶格结构畸变严重,伴随着畸变能的释放,金红石相的晶格常数c轴逐渐增长,n轴略有下降(或基本不变). TiO₂氧敏薄膜的氧敏性能受金红石相含量和氧空位浓度控制.当Fe离子掺杂浓度为6mol% 时,金红石相及相应氧空位达到最大值,TiO₂氧敏薄膜的氧敏性能也达到最大值,比刚形成金红石相的薄膜的氧敏性能增加近19倍.     

不同电极形式对掺镧钛酸铅铁电薄膜的介电性能的影响

采用射频磁控溅射技术在Si(100) 基底和Pt/Ti/SiO2/Si(100)基底上生长了掺镧钛酸铅[(Pb0.9,La0.1)TiO3, PLT10]铁电薄膜.用X射线衍射技术(XRD)研究了PLT10薄膜结晶性能.使用光刻工艺在Si(100) 基底的PLT10薄膜上制备了叉指电极,测试了PLT10薄膜的介电性能.在室温下,测试频率为1kHz时,PLT10薄膜的介电常数为386.而采用相同工艺条件制备的具有平行电极结构的PLT10薄膜, 其介电常数为365.但利用叉指电极测试的PLT10薄膜的介电常数和介电损耗随频率的下降比利用平行电极测试的PLT10薄膜的快些.这是因为叉指电极结构引入了更多的界面态影响的缘故.     

多层模型计算椭偏法测量的SiO2／Si超薄膜厚度

采用不同的光学模型对厚度为6nm,密度为2．2g/cm2。的理想Si02薄膜理论曲线进行了拟合,得到了薄膜厚度的计算结果随所采取的薄膜密度变化的规律：选用更大的薄膜密度值进行拟合计算会得到更小的厚度结果,其趋势近似线性．参考GIXRR方法测量得到的薄膜物理结构的结果,给出了优化的拟合计算模型（薄膜密度为2．4g／cm3、表面粗糙度为0．4nin、界面粗糙度为0．3nin）,对于热氧化法制备的厚度小于10nrn的SiO2超薄膜,使用此模型进行拟合计算,可以得到比常规模型更为准确的厚度结果．采用优化的模型拟合了期望厚度为2,4,6,8,10nrn的si02超薄膜的SE实验曲线,得到的厚度结果分别为2．61,4．07,6．02,7．41,9．43nm,与传统模型计算结果相比,分别降低了13．8％,10．3％,8．1％,7．3％和6．6％．