超高载流能力的干净极限MgB_2薄膜与超高上临界场的碳掺杂MgB_2薄膜  

Clean limit MgB_2 films with ultrahigh current carrying capability and carbon-doped MgB_2 films with extremely high upper critical field

作　　者：庄承钢[1] 孟胜[1] 张从尧[1] 马小柏 聂瑞娟[1] 王福仁[1] 杨欢[2] 贾颖[2] 闻海虎[2] 冯庆荣[1] 

机构地区：[1]北京大学物理学院及人工微结构与介观物理国家重点实验室,北京100871 [2]中科院物理研究所北京凝聚态物理国家实验室超导国家重点实验室,北京100080

出　　处：《前沿科学》2008年第1期6-12,共7页Frontier Science

基　　金：国家自然科学基金No.50572001;"973计划"No.2006CD601004;教育部优秀本科生基础科研基金No.J0630311

摘　　要：本本文报道了基于混合物理化学气相沉积方法制备高质量干净极限MgB2薄膜和碳掺杂MgB2薄膜的最新结果。c轴外延干净的MgB2薄膜具有高达41.4K的超导转变温度,低于0.3μΩcm的正常态剩余电阻率,样品处于干净极限。薄膜表面RMS粗糙度小于5nm,在150nm宽的纳桥上测量到了大于1×108A/cm2的临界电流密度,接近MgB2材料理论上的拆对电流密度,同样的结果也从对相同样品的磁性测量中推导得到。利用甲烷作为碳源,基于改进的热丝辅助混合物理化学气相沉积装置,高性能碳掺杂MgB2薄膜得以成功实现。不同程度的碳掺杂调制了MgB2双能带的带内和带间散射,进而明显增强了薄膜的上临界场。在重碳掺杂MgB2薄膜样品中,平行于样品表面的上临界场分量,Hc2//ab在临界温度(27K)附近对温度的斜率,-dHc2//ab/dT达到了3T/K,暗示了样品具有非常高的上临界场Hc2//ab(0)。碳掺杂同时使得样品的磁通钉扎能力得到很大增强,高场下具有比干净样品高出数个量级的临界电流密度,和更高的不可逆场。High quality epitaxial MgB2 film in clean limit with extremely high self-field critical current density JC(0),>108A/cm2,approaching the theoretical deparing current density of MgB2,in addition to very high critical transition temperature TC(0) ~ 41.4 K,low residual resistivity ρ(42K) down to 0.3 μΩcm and RMS roughness less than 5nm was reported in this article.Both I-V characteristics on a 150nm-wide nan-bridge and the magnetization measurement support this ultrahigh current density,indicating excellent current carrying capability in these clean films.Using a hot-filament assistant hybrid physical-chemical vapor depositon(HFA-HPCVD) technique with methane as doping source,carbon-doped MgB2 thin films with a significant enhancement in upper critical field HC2 and irreversibility field Hirr were fabricated.For the parallel field,a temperature derivative-dHC2//ab/dT value of 3 T/K near Tc was achieved in a heavily doped film.Carbon doping also enhanced flux pinning,resulting in much higher critical current density in magnetic field JC(H) than in undoped films.

关 键 词：混合物理化学气相沉积 MgB2薄膜 破对电流密度 碳掺杂 

分 类 号：TB383.2[一般工业技术—材料科学与工程]