本文报导了利用混合物理化学气相沉积法(Hybrid physical-chemical vapor deposition, HPCVD)在SiC(0001)衬底上制备干净的MgB_2超薄膜.在背景气体压强、载气H_2流量等条件一定的情况下,改变B_2H_6流量及沉积时间,制备不同厚度的MgB_2超薄膜样品,并研究了超导转变温度Tc、剩余电阻率ρ(42K)、上临界场H_(c2)等与膜厚的关系.这系列超薄膜生长沿c轴外延,随膜厚度的变小T_(c(0))降低,ρ(42K)升高,膜在衬底上的生长遵循Volmer-Weber岛状生长模式,对于10nm厚的膜,T_(c(0))～32. 4K, ρ(42K) ～124. 92μΩ·cm,其表面连接性良好,平均粗糙度为2. 72nm,上临界磁场H_(c2(0K)0 ～12T,零场4K时的临界电流密度Jc～107 A/cm2,为迄今为止所观测到的10nm厚MgB_2超薄膜的最高Jc值,这也证明了10nm厚的MgB_2膜在超导纳米器件上具有很强的应用潜力.
We fabricated MgB_2 ultra-thin films via hybrid physical-chemical vapor deposition (HPCVD) technique. Under the same background pressure, the same H_2 flow rate, by changing B_2H_6 flow rate and deposition time, we made a series of ultra-thin films, thickness ranging from 5nm to 80nm. These films grew on SiC substrate,all c-axis epitaxial. The film formation obeys the Volmer-Weber mode. As the thickness increases, critical transition temperature T_(c(0)) also increases, the residual resistivity decreases. Especially,a very high T_(c(0)) ～32. 4K,low residucritical resistivity ρ(42K)～124. 92μΩ·cm, and extremely high critical current density Jc～107A/cm_2 (0T,4K), upper critic field H_(c2(0)) for 10nm film was reported Moreover, the smooth surface of the epitaxial films, with root-meansquare (RMS) roughness～2. 72nm, makes them well qualified for device applications.
参考文献
| [1] | R. Espiau de Lamaeestre;Ph. Odier;J.-C. Villegier .Microstructure of NbN epitaxial ultrathin films grown on A-, M-, and R-plane sapphire[J].Applied physics letters,2007(23):232501.1-232501.3. |
| [2] | 庄承钢 .干净MgB<,2>薄膜与碳掺杂MgB<,2>薄膜的制备与超导电性研究[D].北京大学,2008. |
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