溅射法快速沉积YBCO超导薄膜的研究北大核心CSCD

溅射法制备高温超导YBa2Cu3O7-δ(YBCO)薄膜材料目前存在的主要问题是沉积速率慢,制备效率低,大面积薄膜均匀性差.本文中,设计了多工位盒型靶直流溅射镀膜系统,提高了YBCO薄膜沉积速率和制备效率,一次工艺流程可沉积六片产品,总薄膜沉积速率最高可到250nm/h.基片自转与公转相结合,提高了薄膜的面内均匀性,同时研究了公转速度与自转速度的关系以及它们对薄膜生长的关系,发现只有在基片公转速度合适的情况下才能生长出性能好的薄膜.LaAlO3(LAO)单晶基片上YBCO薄膜临界电流密度超过2.8MA/cm2(77K,500nm,0T),薄膜微波表面电阻Rs(10GHz,77K)﹤0.2mΩ,1.8英寸内薄膜面内厚度起伏小于3%,双面薄膜一致性好,能够满足微波器件应用的要求.     

钛酸锶衬底表面改性对YBCO高温超导薄膜性能的影响北大核心CSCD

YBa_2Cu_3O_(7-x)(YBCO)高温超导材料在高温高场中具有比较高的临界电流密度,因此具有较好的应用前景.通过研究YBCO高温超导薄膜,以提高它的载流能力和超导性能是市场应用的迫切需要.文中所研究的钛酸锶(SrTiO_3)衬底,作为一种钙钛矿结构,不仅具有良好的化学和热稳定性,而且与YBCO高温超导薄膜具有较小的晶格失配度.通过酸腐蚀法和无酸腐蚀处理钛酸锶SrTiO_3(100)(STO)衬底,运用原子力显微镜观察了两种衬底处理方法对钛酸锶衬底表面结构的影响.并在其上用三氟乙酸盐金属有机沉积法(TFA-MOD)制备出临界密度达到约2.50~3.00 MA/cm^2的YBCO高温超导薄膜.通过四引线法表征YBCO高温超导薄膜的Tc达到了均约93K.通过扫描电子显微镜(SEM)分析了衬底处理技术的不同对其表层生长的YBCO高温超导薄膜形貌的影响.通过X射线衍射仪(XRD)固定方位角法表征了不同的衬底处理技术对薄膜内的残余应力的影响.     

钛酸锶衬底表面改性对YBCO高温超导薄膜性能的影响

YBa_2Cu_3O_(7-x)(YBCO)高温超导材料在高温高场中具有比较高的临界电流密度,因此具有较好的应用前景.通过研究YBCO高温超导薄膜,以提高它的载流能力和超导性能是市场应用的迫切需要.文中所研究的钛酸锶(SrTiO_3)衬底,作为一种钙钛矿结构,不仅具有良好的化学和热稳定性,而且与YBCO高温超导薄膜具有较小的晶格失配度.通过酸腐蚀法和无酸腐蚀处理钛酸锶SrTiO_3(100)(STO)衬底,运用原子力显微镜观察了两种衬底处理方法对钛酸锶衬底表面结构的影响.并在其上用三氟乙酸盐金属有机沉积法(TFA-MOD)制备出临界密度达到约2.50~3.00 MA/cm~2的YBCO高温超导薄膜.通过四引线法表征YBCO高温超导薄膜的Tc达到了均约93K.通过扫描电子显微镜(SEM)分析了衬底处理技术的不同对其表层生长的YBCO高温超导薄膜形貌的影响.通过X射线衍射仪(XRD)固定方位角法表征了不同的衬底处理技术对薄膜内的残余应力的影响.     

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：     

对靶溅射技术制备的La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3薄膜中Tc的降低

本文用对靶溅射技术制备了La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3薄膜.与YBCO单层薄膜相比,由于超导/铁磁系统中的磁性邻近效应,三层薄膜表现出较低的超导转变温度.薄膜的R～T测量曲线显示出超磁阻(CMR)效应和超导转变,预示着超导和铁磁特性共存于LCMO/YBCO/LCMO三文治结构.     

MgO单晶基片上YBCO高温超导薄膜的制备

在2英寸MgO(001)单晶基片上,采用直流溅射法,通过基片高温退火,成功制备了性能优越的YBa2C3O7-δ(YBCO)双面超导薄膜,能够满足超导滤波器的设计要求。X射线衍射(XRD)分析表明经过退火的基片上生长的YBCO薄膜与基片有单一的外延取向关系;用原子力显微镜(AFM)和高能电子衍射(RHEED)分析高温退火对基片表面状况的改变。结果表明制备的YBCO薄膜具有很好的超导电性,薄膜临界电流密度Jc(77K,0T)≈2.5×106A/cm2,微波表面电阻Rs(10GHz,77K)≈0.16mΩ。     

100ns高温超导延迟线

介绍了所设计的100ns高温超导延迟线。采用的基片直径为2英寸的铝酸镧,双面溅射高温超导YBCO薄膜,制备了实际的电路,通过级联的方式,获得了长延时的结果。实测结果显示:在65K下,此高温超导延迟线在1.5~6.5GHz的频率范围内,延时100ns以上,插入损耗小于7.6dB,驻波比优于1.5。良好的驻波性能(反射波损耗)使得这种延迟线能够与其它组件级联起来而不会使系统的性能降低。     

快速前处理TFA-MOD制备YBCO超导薄膜的研究

三氟乙酸盐金属有机物沉积(TFA-MOD)方法是制备YBa2Cu3O7(YBCO)超导薄膜最有应用前景的方法之一。采用快速前处理TFA-MOD的方法在LaAlO3单晶基片上生长YBCO薄膜并与常规的TFA-MOD方法进行对比研究。XRD分析表明用快速前处理TFA-MOD方法制备的YBCO薄膜的c轴取向一致性,没有常规的TFA-MOD制备的YBCO薄膜好。SEM的分析表明快速前处理TFA-MOD制备的YBCO超导薄膜表面有孔洞和YBCO(103)取向生长的晶粒,常规方法制备的YBCO薄膜表面比较光滑,孔洞较少。虽然较常规方法制备的薄膜的临界电流密度(JC)低,但超导电性能分析表明,快速前处理方法制备的YBCO薄膜JC达到1mA/cm2以上,且前处理时间大幅缩短,对于提高YBCO薄膜制备的效率非常有效。     

YBa2 Cu3 O7-δ/SrNb0.01 Ti0.99 O3 p-n结的制备及其特性

采用脉冲激光沉积技术,在n型SrNb0.01Ti0.99O3(SNTO)单晶基片上生长p型YBa2Cu3O7-δ(YBCO)薄膜,制备出YBCO/SNTO p-n结.YBCO薄膜是高度c轴织构的超导薄膜,且具有良好的超导电性.YBCO/SNTO p-n结具有较好的整流特性和很好的温度与磁场稳定性.     

PLD法制备PZT-YBCO结构的铁电薄膜的研究

本文利用脉冲准分子激光在LaAlO3单晶基片上淀积了YBCO和Zr/Ti为94/6的PZT铁电薄膜,并通过高频溅射将Pt蒸镀在PZT薄膜上作为上电极;用X射线衍射表征了该多层膜的晶相结构,测量了PZT的铁电性能和介电特性,讨论了PZT/YBCO薄膜的制备工艺,以及工艺条件对晶相结构和薄膜性能的影响.     

低能离子对高温超导YBa_2Cu_3O_(7-δ)薄膜的表面改性和机理

低能氩离子束轰击并后退火处理的离子束表面改性,会影响高温超导薄膜的表面结构和超导特性,但是其中的深刻微观机理不清楚.本文通过连续改变离子束轰击时间,系统研究了离子束表面改性对于超导膜结构和临界电流密度的影响.通过扫描电子显微镜、X射线衍射、J_(c-scanning)测试表征样品的结构特性和超导特性,并得出内应变、氧空位缺陷等参量.研究表明,经过表面改性的钇钡铜氧(YBa_2Cu_3O_(7-δ),YBCO)薄膜,随轰击时间增加表面形貌会变得更加均匀致密,a轴晶粒消失,并且临界电流密度有了显著的提高.由化学键收缩配对模型分析得出,临界电流密度的提高与薄膜内应变增大和引发的局部YBCO结构中Cu—O键收缩有关.     

Simulation of boron nitride sputtering process and its comparisonwith experimental data

In the paper, TRIM and TRIDYN simulation codes were used to simulate the sputtering processes of boron nitride (BN) films during bombardment of ions. The TRIM and TRIDYN codes are applicable to the simulation of sputtering processes of different target materials with amorphous and polycrystalline structure. The results of the simulations are compared with experimental data. The sputtering experiments of polycrystalline hexagonal BN (h-BN) and cubic BN (c-BN) films were performed in a Commonwealth Scientific Corporation (CSC) 38-cm ion beam source device. The comparison of calculated and experimental results indicated that a) the experimental sputtering yields of h-BN and c-BN films bombarded with Ar⁺ ions versus the angle of incidence are in reasonable agreement with the calculated results; b) the sputtering yields of h-BN and c-BN bombarded with Ar⁺ are nearly of the same values versus the angle of incidence-preferential sputtering of h-BN was not found; c) the calculated sputtering. Yields of BN as a function of Ar⁺ ion energy are very sensitive to values of the surface binding energy (SEE); and d) surface binding energy between 2 and 3 eV for BN appears to be reasonable for the simulation of sputtering process of h-BN and c-BN films     

PREPARATION OF a-AXIS ORIENTED YBa2Cu3Ox THIN FILMS

The a-axis oriented YBa₂Cu₃O_x(YBCO) thin films could be grown on (100) SrTiO₃(STO) substrates with STO buffer layers by dc and rf magnetron sputtering either by low-ering the deposition temperature, or by using a self-template technique. For the latter, the resistivity of the thin film at 290K along the substrate [001] direction is about four times larger than that in the [010] direction. The zero resistance temperatures T_c0 are 89 K in both directions. So high quality a-axis oriented YBCO thin films can be prepared by the self-template technique. Also the T_c0 increase monotonously with the reduction of the thickness of the YBCO seed layer.     

HREM study of the YBCO/MgO interface on an atomic scale

The film-substrate interface of c oriented YBCO thin films grown by sputtering or laser ablation on (001) MgO substrate has been investigated with high-resolution electron microscopy. The first atomic plane of the YBCO lattice is a CuO chain layer. Two interface configurations occur: (1) the YBCO lattice and the MgO lattice continue up to the interface (this configuration is occasionally associated with some periodic strain in the MgO lattice; (2) the YBCO lattice and the MgO lattice are separated by an (almost) amorphous layer with a thickness of the order of two atomic layers. This amorphous layer is found to lead to the absence of strain. In some cases the surface roughness coincided with misoriented grains but most of the steps in the MgO substrate were accommodated by steps in the YBCO of one or more complete unit cells in height and some lattice bending in the YBCO film.     

Relation between surface structures and sputtering ratios of copper single crystals

Polished (100) Cu crystals have been bombarded at target temperatures of 204 K, 294 K and 456 K by 10 and 20 keV Ne⁺ ions up to a total dose of 1.7 × 10¹⁹ ions/cm². The plane of incidence was chosen to be a {100} plane perpendicular to the surface. Measurements have been performed for incident angles between 36° and 44° with respect to the surface normal. In this angular interval the sputtering ratio and the surface structure have been studied by weightloss and replica electron microscope techniques respectively. At target temperatures of 204 K and 294 K an anomaly was observed in the curve of the sputtering ratio versus angle of incidence. A small peak appears where the curve slopes towards the 〈110〉 minimum. The position and height of the peak is a function of target temperature and ion energy.

This sputtering submaximum is accompanied by the formation of {100} orientated furrows perpendicular to the ion beam. The nucleation of this relief is tentatively discussed in terms of local deviations from perfection of the surface, which might be due to a singularity in the production of focusing collisions influencing the damage structure. The growth of the furrows and the submaximum in the sputtering ratio are discussed in terms of the angle between the ion beam and the characteristic {110} side of the furrows.

These sputtering and faceting phenomena have not been observed at 20 keV Ar⁺ ion bombardment nor generally under bombardment at a target temperature of 456 K.     

反应溅射法制备Y_2O_3种子层研究

采用直流磁控反应溅射法在双轴织构的镍钨合金(Ni-5%W)基带上生长Y2O3种子层。研究了由于水分压导致的金属靶材的氧化问题而引起反应溅射的迟滞效应,在其他最优工艺条件下通过水分压系列的试验,通过试验得出溅射电压和水分压的关系和溅射电流和水分压平衡点Pb的关系,以及水分压平衡点为反应溅射法制备Y2O3种子层薄膜的水分压最优化条件。在优化工艺条件下,反应溅射法可以制得C轴单一取向的Y2O3种子层,其面内外半高宽可达到3.874°和4.914°。     

Influence of charged particle bombardment and sputtering parameters on the properties of HfO2 films prepared by dc reactive magnetron sputtering

HfO₂ films prepared on glass substrates by dc reactive magnetron sputtering in an Ar + O₂ atmosphere are investigated. The films are polycrystallized with a pure monoclinic phase, and the crystallization strongly relates to the technology environment. Charged particle bombardment mainly caused by negative oxygen ions during sputtering on the films results in rougher surface morphology and worse crystalline property. Influence of sputtering pressure, substrate temperature and Ar:O₂ flow ratio is studied. The main orientations of the films are (−1 1 1) and (1 1 1). The (−1 1 1) orientation is stable, but (1 1 1) orientation is very sensitive to the sputtering condition, and it can be suppressed effectively by introducing charged particle bombardment, lowing sputtering pressure and increasing oxygen concentration.     

Structural and tribological properties of nitrogen doped amorphous carbon thin films synthesized by CFUBM sputtering method for protective coatings

Nitrogen doped amorphous carbon (a-C:N) films are a material that may successfully compete with DLC coatings, which have high hardness, high wear resistance, and a low friction coefficient. The a-C:N films were prepared on silicon substrate by a closed-field unbalanced magnetron sputtering method with a graphite target and using the Ar/N₂ mixture gases. And, we investigated the effects of various DC bias voltages from 0 to −300 V on the structural and tribological properties of the a-C:N films. This study was focused on improving physical properties of the a-C:N film by controlling process parameters like negative substrate DC bias voltage. The maximum hardness of the a-C:N film was 23 GPa, the friction coefficient was 0.08, and the critical load was 25 N on a Si wafer. Consequently, the structural and tribological properties of the a-C:N film showed a clear dependence on the energy of ions bombardment and the density of the sputtering and the reaction gases during film growth.