单源进液金属有机化学气相沉积法工作气压对YBCO薄膜制备的影响研究

基于金属有机化学气相沉积法(MOCVD),在沉积有Y2O3/YSZ/ CeO2( YYC)多层过渡层的Ni - W_at.5％金属基带上沉积YBa2Cu3O7-x(YBCO)超导薄膜.通过对单源进液系统的优化,使金属有机源连续稳定地输送到蒸发皿进行闪蒸.优化总气压并通入N2O气氛,以获得高质量的YBCO薄膜.在优化的温...     

直流磁控溅射YBCO非晶薄膜的卢瑟福背散射研究

利用直流磁控溅射(D.C.Magnetron Sputtering)法,选取总气压为80Pa,沉积时间为60min,溅射靶尺寸为φ80,在磁场强度、靶与基片之间的距离及Ar/O₂比等参数变化的情况下,制备了四组YBCO/Al₂O₃非晶薄膜样品。用MeV Li卢瑟福背散射(RBS)分析技术,测量了各块样品中Ba和Cu相对Y的含量和薄膜厚度随基片的横向分布。分析结果表明:在不同的沉积条件下,薄膜中各点的Ba和Cu相对浓度差别较大,薄膜厚度分布也 关键词：     

前驱液成分对TFA-MOD法制备YBa2Cu3O7-x薄膜超导性能的影响

采用三氟乙酸盐-金属有机沉积法(TFA-MOD)在铝酸镧单晶基体上制备了YBa₂Cu₃O_7-x (YBCO)超导薄膜.通过改变前驱液的成分,研究了金属元素的不同化学计量比对YBCO薄膜的结构和性能的影响.结果表明,按照钇盐Y(CH₃COO)₃与钡盐Ba(CH₃COO)₂的比例为Y ∶Ba=1 ∶1.5时所制备的YBCO薄膜的临界电流密度比严 关键词： 三氟乙酸盐-金属有机沉积 钇钡铜氧薄膜 前驱液成分 磁通钉扎     

用于MOCVD的金属有机Ba源的制备及性质研究北大核心CSCD

金属有机化学气相沉积法(MOCVD)能够在长的柔性金属基带上连续、快速、均匀沉积YBa2Cu3O7-δ(YBCO)薄膜,因而极具开发价值.MOCVD制备YBCO涂层导体的关键技术之一在于金属有机源(MO)的制备.国外化学试剂公司在以2,2,6,6-4甲基-3,5庚二酮(thd)为配体的MO源上技术较为成熟,并已实现商业化生产,但是价格昂贵,其中Ba(thd)2价格约为700元/g.另外,与Y(thd)3和Cu(thd)2相比,Ba(thd)2挥发性、稳定性差且制备困难.本文对金属有机Ba源的制备、稳定性及真空下的蒸发特性进行了研究.通过引入助配体四乙烯基戊胺,该Ba源的蒸发温度比纯的Ba(thd)2更低,稳定性更高,且成本仅为30元/g,对于降低YBCO高温超导带材的制备成本具有重要意义.采用该Ba源制备的300nm厚YBCO薄膜的Jc达到2.0MA/cm2(77K,0T),表明其具有很好的实用性.     

YBa2Cu3O7-δ/LaAlO3和Tl2Ba2CaCu2O8/LaAlO3高温超导薄膜内的应变对其微波表面电阻影响的研究

YBa2Cu3O7-δ/LaAlO3 (YBCO/LAO) 超导薄膜是通过热蒸发沉积方法制备的,实验中使用的Tl2Ba2CaCu2O8/LaAlO3 (TBCCO/LAO) 超导薄膜是通过直流磁控溅射方法制备的.通过分析两片超导薄膜的XRD谱计算出了两片超导薄膜内的应变,ΔCY=4.8483×10-3;ΔCT=8.5272×10-5,结果显示YBCO超导薄膜内的应变要大于TBCCO超导薄膜内的应变.另外,采用共面谐振技术研究这两片超导薄膜内的微波表面电阻随温度的变化,结果表明YBCO超导薄膜具有更大的微波表面电阻.分析和讨论了应变对超导薄膜微波表面电阻的影响.     

瞬态液相辅助的 YBa2Cu3O7-δ 超导薄膜快速成相及界面反应

高温超导涂层导体因其良好的强电强磁应用前景备受关注. 本文在无氟金属有机沉积(FF-MOD) 工艺中, 通过快速将低氧压气氛切换到高氧压(p O2 ) , 实现了 YBa2Cu3 O7 -δ (YBCO) 薄膜在 LaMnO3 (LMO)/IBADMgO/Y2 O3/Al2 O3/Hastelloy 衬底上的瞬态液相和高速外延生长. 研究了快速成相的氧分压和最高晶化温度的影响, 关注超导薄膜与种籽层之间的界面反应而产生的 BaMnO3 (BMO) 异质相, 对 BMO 的成核和生长机制进行了研究, 分析了 BMO 含量对 YBCO 薄膜织构与超导性能的影响. 结果表明低晶化温度、 低氧分压气氛能够有效抑制BMO 的形成, 而低含量 BMO、 强c 轴取向有利于获得高性能的 YBCO 薄膜.     

高温热处理气氛对低氟MOD法制备YBCO超导薄膜的影响研究

金属有机物沉积法(MOD)制备YBa2Cu3O7-x(YBCO)涂层导体是最具有商业前景的方法之一.本文使用环烷酸铜代替三氟乙酸铜,降低了前驱液中大约50%的氟含量.然后在带有缓冲层(Y2O3/YSZ/CeO2)的Ni-5at.%W基带上采用MOD法制备了YBCO薄膜并系统研究了高温热处理过程中气体流速和氧分压对YBC...     

YBa2Cu3O7-δ薄膜厚度在多层异质结构(Ag/Ba0.1Sr0.9TiO3/YBa2Cu3O7-δ/LaAlO3)中对Ba0.1Sr0.9TiO3介电性能的影响研究

铁电/超导(Ba, Sr)TiO3/YBa2Cu3O7-δ异质结在可调谐微波器件方面具有非常好的应用前景.我们采用1.2°斜切LaAlO3基片,以脉冲激光沉积法(PLD)制备出性能较好的Ba0.1Sr0.9TiO3/YBa2Cu3O7-δ (BST/YBCO)异质薄膜.并进一步研究了YBCO薄膜厚度对BST性能的影响.研究发现当YBCO薄膜厚度增加到180nm附近时,其生长模式由二维step-flow转变为三维岛状模式,严重损害了在YBCO上面生长的BST薄膜的介电性能.具体表现在:BST薄膜的介电常数和可调谐率明显降低,介电损耗和漏电流却大幅度上升.通过测量电容与温度的关系,以应力效应模型对这一实验现象作出解释,认为YBCO薄膜厚度超过临界值,生长模式的转变促使晶格失配应力在YBCO和BST薄膜中得到释放,这导致BST/YBCO界面粗糙,以及BST薄膜中产生了大量的位错和缺陷,BST薄膜的性能因而大为降低.此外,通过对完全相同条件生长的单层YBCO薄膜的表面形貌进行了AFM研究,测试结果进一步验证了YBCO薄膜厚度增加到180nm时,其表面变得异常粗糙,均方根粗糙度(RMS)从120nm厚度时的3nm增加到180nm厚度时的9nm.因此,我们提出:通过严格控制底层YBCO薄膜的厚度,进而控制它的生长模式,能够非常有效地提高BST薄膜的介电性能.     

脉冲激光沉积法制备(Cu,C)Ba2Ca3Cu4Oy 涂层导体

(Cu,C)Ba2Ca3Cu4Oy 是超导转变温度Tc 约为116 K 的无毒铜氧化物超导材料, 在迄今为止的超导材料中, 高压法制备的(Cu,C)Ba2Ca3Cu4Oy 多晶块材在液氮温区具有最高的不可逆场 Hirr ~ 15 T. 为了实现(Cu,C)Ba2Ca3Cu4Oy 超导材料的规模化制备, 本文利用脉冲激光沉积技术在 LaMnO3/MgO/Y2 O3/Al2 O3/Hastelloy 柔性金属基底上依次外延生长了 LaAlO3 帽子层和(Cu,C)Ba2Ca3Cu4Oy 超导薄膜. X 射线衍射实验结果表明(Cu,C)Ba2Ca3Cu4Oy 薄膜沿a 轴外延生长, 电学输运数据表明(Cu,C)Ba2Ca3Cu4Oy 薄膜的超导转变温度Tc onset 为115K, 零电阻温度Tc0 为52 K, 不可逆场为9 T@35 K. 本文首次报道了(Cu,C)Ba2Ca3Cu4Oy 在柔性金属缓冲层衬底的成功制备, 推动了(Cu,C)Ba2Ca3Cu4Oy 超导材料的实用化进程.     

微量Ni~(2+)掺杂MOD-YBCO薄膜性能的研究

采用无氟高分子辅助金属有机物沉积法(PA-MOD)在La Al O3(LAO)单晶衬底上制备了一系列YBa2Cu3-xNixO7-z(x=0、0.0005、0.001、0.0015、0.002)超导薄膜。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)及综合物性测量系统(PPMS)分别研究了微量Ni2+掺杂YBCO薄膜的晶体结构、表面形貌及超导性能。结果表明,微量Ni2+掺杂明显提高YBCO薄膜在外加磁场下的临界电流密度,说明微量Ni2+掺杂增强了YBCO薄膜的磁通钉扎性能。     

高气压反射式高能电子衍射仪监控脉冲激光外延氧化物薄膜

在超高真空分子束外延（MBE）生长技术中，反射式高能电子衍射仪（RHEED）能实时显示半导体和金属外延生长过程，给出薄膜表面结构和平整度的信息，成为MBE必备的原位表面分 析仪.为了研究氧化物薄膜如高温超导（YBa₂Cu₃O₇） 、铁电薄膜（Sr_1-xBa_x TiO₃）及它们的同质和异质外延结构的生长机理，获得高质量的符合各种应用 需要的氧化 物多层薄膜结构，在常规的制备氧化 关键词： 高温超导薄膜 RHEED     

插入二氧化铈薄膜提高MOD-YBa2Cu3O7-x厚膜超导性能的研究

YBa₂Cu₃O_7-x(YBCO)膜存在“厚度效应”: 随着厚度增加, YBCO薄膜的临界电流密度下降, 尤其是YBCO薄膜的厚度超过1 μm时, 它的临界电流密度急剧下降. 本文在YBCO薄膜之间引入极薄的二氧化铈(CeO₂)薄膜, 成功制备出结构为YBCO/YBCO/CeO₂/YBCO的超导厚膜. 所制备的厚度为2 μm的YBCO膜临界电流密度为1.36 MA/cm² (77 K, 自场), 其性能比相同厚度的纯YBCO膜有了较大幅度的提升. 研究表明CeO₂薄膜起到了传递织构、松弛应力的作用.     

Synthesis of free-standing Ga_2O_3 films for flexible devices by water etching of Sr_3Al_2O_6 sacrificial layers

Flexible electronic devices have attracted much attention due to their practical and commercial value. Integration of thin films with soft substrate is an effective way to fabricate flexible electronic devices. Ga_2O_3 thin films deposited directly on soft substrates would be amorphous mostly. However, the thickness of the thin film obtained by mechanical exfoliation method is difficult to control and the edge of the film is fragile and easy to be damaged. In this work, we fabricated free-standing Ga_2O_3 thin films using the water-soluble perovskite Sr_3Al_2O_6 as a sacrificial buffer layer. The obtained Ga_2O_3 thin films were polycrystalline. The thickness and dimension of the films were controllable. A flexible Ga_2O_3solar-blind UV photodetector was fabricated by transferring the free-standing Ga_2O_3 film on a flexible polyethylene terephthalate substrate. The results displayed that the photoelectric performances of the flexible Ga_2O_3 photodetector were not sensitive to bending of the device. The free-standing Ga_2O_3 thin films synthesized through the method described here can be transferred to any substrates or integrated with other thin films to fabricate electronic devices.     

氧分压对PLD制备ZnO薄膜结构和发光性质的影响

采用脉冲激光沉积(PLD)技术,在Si(100)衬底上制备出高度c轴取向的ZnO薄膜。通过X射线衍射(XRD)谱,扫描电镜(SEM)和室温光致发光(PL)光谱的测量,研究了生长气氛压强的改变对薄膜结构和光致发光的影响。实验结果表明,当氧压从10Pa升高到100Pa时ZnO(002)衍射峰的半峰全宽(FWHM)增大。可以认为这是由于较高的氧压下,到达衬底表面的离子动能减小。这样部分离子没有足够的能量迁移到生长较快的(002)面,c轴取向变差,导致(002)衍射峰的强度降低,半峰全宽增大。随着氧压增大,紫外发光强度增强。这可能是氧压变大,薄膜的化学配比升高,说明化学配比对UV发光的影响要大于薄膜微结构的影响。改变氧气压强对薄膜的表面形貌也有较大的影响。     

GROWTH MODE OF Cu-RICH PARTICLES ON LASER-ABLATED YBa2Cu3O7 THIN FILMS

The microstructure of the laser-ablated YBa₂Cu₃O₇ (YBCO) thin film deposited on heated (100) SrTiO₃ substrate was examined by transmission electron microscope. The par-ticles on the film mainly consist of CuO and few CuYO₂. Most of these non-superconducting particles nucleate on or near the surface of the film and protrude about 100-400 nm in height, A large amount of a-axis YBCO grains also exist in the film, which nucleate at the substrate surface and grow perpendicularly above the c-axis YBCO film. The YBCO thin film deposited under low oxygen pressure has very different microstructure compared with YBCO thin film deposited under high oxygen pressure.     

Effect of relative humidity on morphology of YBCO films prepared by CSD method

YBa₂Cu₃O_7−x (YBCO) films have been prepared on LaAlO₃ (1 0 0) substrates by chemical solution deposition using metal trifluoroacetates. The influence of relative humidity in coating circumstance on the morphology of YBCO films was examined by optical microscopy and atomic force microscopy. The crack-free YBCO film was obtained if the relative humidity in coating circumstance was lower than 30%. During the decomposition step, the influences of the water vapor partial pressure and the heating rate within the temperature range from 200 °C to 320 °C were discussed. A smooth YBCO pyrolzed film could be obtained if the suitable water vapor partial pressure and the suitable heating rate within the temperature range from 200 °C to 320 °C were chosen. Furthermore, the smooth crystallized films show a high critical current density of 3 MA/cm² at 77 K.     

Enhanced flux pinning in pulsed laser deposited Y Ba2Cu3O7−δ : BaTiO3 nanocomposite thin films

The effect of incorporation of BaTiO₃(BTO) nanoparticles on the flux pinning properties of pulsed laser deposited YBCO:BTO thin films was studied. Substantial increase in the critical current density (J_C) and the pinning force density (F_p) of the nanocomposite thin films was observed. At 77 K, and zero applied magnetic field, the value of J_C for YBCO and YBCO:BTO (2%) thin films were 2.93 MA/cm² and 6.43 MA/cm², respectively. At the same temperature and an applied magnetic field of 4 T, the value of J_C increases from 3.6×10⁴ A/cm² for YBCO thin film to 2.7×10⁵ A/cm² for YBCO:BTO (2%) nanocomposite thin film. The study of temperature and field dependence of of YBCO and YBCO:BTO thin films indicates similar type of pinning. The lattice mismatch between YBCO and BTO seems to introduce more defects resulting in the improvement of flux pinning properties.     

利用微带谐振技术研究MgB_2/Al_2O_3和YBa_2Cu_3O_(7-x)/LaAlO_3超导薄膜的微波性质(英文)

利用微带谐振技术研究了MgB2/A12O3和YBa2Cu3o7-X/LaAlO3(YBCO/LAO)超导薄膜的微波性质.一个颗粒尺寸模型被用来分析超导薄膜的穿透深度和表面电阻.结果表明,对于高质的YBCO/LAO,微波性质主要由颗粒决定.对于低质的MgB2/Al2O3,该薄膜的微波性质主要由颗粒边界决定.     

La,V共掺杂的Bi_4Ti_3O_(12)铁电薄膜的溶胶-凝胶法制备及性能测试

采用溶胶-凝胶(sol-gel)工艺在Pt/TiO2/SiO2/p-Si(100)衬底上制备出Bi4Ti3O12(BIT)和Bi3.25La0.75Ti2.97V0.03O12(BLTV)铁电薄膜,研究了La,V共掺杂对BIT薄膜的晶体结构和电学性能的影响.BIT薄膜为c轴择优取向,BLTV薄膜为随机取向,拉曼光谱分析表明V掺杂降低了TiO6(或VO6)八面体的对称性,也增强了Ti—O键(或V—O键)杂化.BLTV薄膜的剩余极化Pr为25.4μC/cm2,远大于BIT薄膜的9.2μC/cm2,表现出良好的铁电性能.疲劳、漏电流测试显示BLTV薄膜具有优良的抗疲劳特性和漏电流特性,表明La,V共掺杂能有效地降低薄膜中的氧空位.