DETERMINATION OF THE OXYGEN CONTENT IN YBa2Cu3O7-y FILMS

A method for determination of the oxygen content (y) in YBa₂Cu₃O_7-y films has been established, in which the lattice conetant difference (b-a) of the films was measured and used to fit the function of (b-a) vs y for the experimental data of bulk YBaaCuaO?-y given in the literature. It is suggested that the function of (b-a) vs y can indeed be used in the case of film. In this process the twin structure of the YBa₂Cu₃O_7-y films was used.     

THE SCREENING EFFECT OF PHONON MODES IN HIGH-Tc OXIDE SUPERCONDUCTOR

This paper presents three different kinds of infrared (IR) spectra of oxide materials. The first one is the IR reflection spectra of Ti₂Ba₂Ca₂Cu₃O₁₀ superconducting film at the incident angles 7°, 12° and 30°. The second one is the IR spectra of nonsuperconducting ceramic materials YBa₂Cu₃O₆ and PrBa₂Cu₃O₇. The third one is the IR spectra of superconductor YBa₂Cu₃O_7-δ and of its film with the c-axis perpendicular to the film plane, as well as the changes in the spectra of these materials after annealing at different temperatures. It is found that in the spectra of high-T_c oxide superconductor, only the phonon modes along c-axis can be observed while the modes in a-b plane are absent. But in the spectra of nonsuperconductors the modes in a-b plane can be observed, particularly in the absorption spectra of the semiconductor YBa₂Cu₃O₆, all eleven allowed IR active modes have been detected. We suggest that the above experimental phenomena may result from the fact that the phonon modes vibrating in the a-b plane of the high-T_c oxide superconducting materials are almost screened by the free carriers which can move only in a-b plane.     

DETERMINATION OF THE OXYGEN CONTENT IN YBa2Cu3O7-y FILMS

A method for determination of the oxygen content (y) in YBa₂Cu₃O_7-y films has been established, in which the lattice conetant difference (b-a) of the films was measured and used to fit the function of (b-a) vs y for the experimental data of bulk YBaaCuaO?-y given in the literature. It is suggested that the function of (b-a) vs y can indeed be used in the case of film. In this process the twin structure of the YBa₂Cu₃O_7-y films was used.     

LaAlO_3衬底上磁控溅射的大面积YBa_2Cu_3O_（7－x）薄膜微观组织

用分析电镜和高分辨电镜对在３０ｍｍ×３０ｍｍＬａＡｌＯ３衬底上，采用中空柱状阴极直流磁控溅射的高ＪｃＹＢａ２Ｃｕ３Ｏ７－ｘ（ＹＢＣＯ）薄膜的微观组织结构进行了研究。薄膜为ｃ轴取向ＹＢＣＯ，含有少量Ｙ２ＢａＣｕＯ５颗粒和纺锤状Ｙ２Ｏ３。膜内主要晶体缺陷为［００１］刃位错和螺位错、堆垛层错、（００１）晶面弯曲带、小于１５ｎｍ的晶格畸变区和阳离子空位。ＬａＡｌＯ３衬底表面呈阶梯状并有小坑。衬底表面第一层膜原子为ＣｕＯ和ＣｕＯ２层，以致在界面形成ＢａＣｕＯ２和ＹａＢａＣｕ２Ｏ５相。ＬａＡｌＯ３衬底表层有较多位错，对薄膜外延生长和缺陷的形成有明显影响。     

THE SCREENING EFFECT OF PHONON MODES IN HIGH-Tc OXIDE SUPERCONDUCTOR

This paper presents three different kinds of infrared (IR) spectra of oxide materials. The first one is the IR reflection spectra of Ti₂Ba₂Ca₂Cu₃O₁₀ superconducting film at the incident angles 7°, 12° and 30°. The second one is the IR spectra of nonsuperconducting ceramic materials YBa₂Cu₃O₆ and PrBa₂Cu₃O₇. The third one is the IR spectra of superconductor YBa₂Cu₃O_7-δ and of its film with the c-axis perpendicular to the film plane, as well as the changes in the spectra of these materials after annealing at different temperatures. It is found that in the spectra of high-T_c oxide superconductor, only the phonon modes along c-axis can be observed while the modes in a-b plane are absent. But in the spectra of nonsuperconductors the modes in a-b plane can be observed, particularly in the absorption spectra of the semiconductor YBa₂Cu₃O₆, all eleven allowed IR active modes have been detected. We suggest that the above experimental phenomena may result from the fact that the phonon modes vibrating in the a-b plane of the high-T_c oxide superconducting materials are almost screened by the free carriers which can move only in a-b plane.     

Ho替代Y的YBCO外延薄膜制备及超导电性

利用直流磁控溅射技术制备了Ｈｏ替代的ＹＢＣＯ超导薄膜，Ｘ射线技术（θ－２θ扫描：θ－θ扫描及—扫描）、ＳＥＭ和电子通道花样（ＥＣＰ）测试表明，所制备的掺杂薄膜具有高平面内外延性和平面外外延性。发现掺杂薄膜的临界电流密度Ｊｃ比ＹＢＣＯ薄膜的有不同程度的提高，掺杂量ｘ＝０４时有最大值。     

高Tc超导薄膜/砷化镓场效应器件混合微波振荡器的研制

研制了一种高T_c超导薄膜/砷化镓场效应器件混合的微波振荡器,整个电路采用微带电路形式,制备在一片10mm×15mm的YBa₂Cu₃O_7-δ超导薄膜上。该振荡器采用共源和栅结串联反馈电路结构,以GaAs MESFET(NE72084)为负阻元件,利用高品质因数的超导微带谐振器作为稳频元件。通过提高谐振器的品质因数和调节它与MESFET的耦合强度,降低了振荡器的相位噪声。相位噪声在偏离载频(10.6GHz)为10kHz时达到-87dBc/Hz。     

用DC-磁控溅射制备的高T_c A15 Nb_3Ge超导薄膜的研究

用直流平板磁控溅射装置在不同的溅射条件下制备了一系列Nb-Ge薄膜.在最佳条件下(溅射电压V_s～200V,溅射电流I_s～450mA,氩气压力P_(Ar)1—2×10~(-1)托,基体温度T_s780—810℃)重复制备了T_(c0)>23k的样品.T_c最高的样品的T_(c0)为23.5k,△T_c1.5k.用X-射线衍射仪测定了相组成以及晶格参数.研究了T_c与沉积参数、化学计量比、相组成以及晶格参数的关系.结果表明少量的Nb_2Ge_3存在于接近或等于化学计量比的A15相占优势的薄膜中,有利于高T_c亚稳A15相的稳定化,使样品呈现高T_c.结论指出:用磁控溅射技术研究高T_c亚稳A15材料的实用化是有意义的.