Preparation and Properties of Layer Structured High-Tc Superconductors

1.层状结构的氮化物β-MnCl(M=Zr，Hf)可通过锂离子的嵌入实现电子掺杂，并转变为超导转变温度(T_c‘s)分别为14K和25.5K的超导体。通过极性溶剂分子与锂离子的共插层可以控制层间距，大大增强了超导电性的各向异性。核磁共振和介子自旋关系测量表明，电子掺杂层状结构氮化物超导体具有以下特点：(1)高度各向异性；(2)费米能级附近的低载流子密度，~10^&lt；21&gt；/cm^3；(3)很小的同位素效应。超导性是非常不寻常的。层状结构的氮化物β-MnCl(M=Zr，Hf)非常薄，晶体很软，很难用…进行X射线结构分析更多的物理性质测量。我们成功地开发了一种以氯化铵为助熔剂的高压合成厚单晶的新方法。合成了各种β-MnX(M=Zr，Hf；X=Cl，Br1，I)单晶，并用X射线单晶分析确定了其晶体结构。研究发现，化合物结晶为SMSi和YOF两种不同的多型结构。为了设计新型层状结构氮化物，在超高真空条件下，采用电子束蒸发和激光烧蚀的方法，以氮基为源制备了人工氮化薄膜。在MgO(100)衬底上外延生长了氮化钛、氮化钛、氮化钛薄膜，并用RHEED对生长过程进行了逐层监测。在Si(100)衬底上可以外延生长CrN，然后在CrN膜上生长外延NBN薄膜。这一发现表明，合成具有超结构的人工CrN-NBN薄膜是可能的。较少

1. The layer structured nitride chlorides, β-MNCl (M = Zr, Hf) can be electron-doped by the intercalation of lithium, and are changed into superconductors with the superconducting transition temperatures (Tc's) of 14 and 25.5 K for M = Zr and Hf, respectively. The interlayer spacing can be controlled by the co-intercalation of polar solvent molecules with lithium ions, and the anisotropy of the superconductivity is greatly enhanced. The NMR and muon spin relation measurements revealed that the electron-doped layer structured nitride superconductors have the following characteristics ; (i) highly anisotropic exotic superconductors, (ii) low carrier density near Fermi level, 〜10^<21>/cm^3, (iii) very small isotope effect on the replacement with ^<15>N, and (iv) low phonon excitation. The superconductivity is very unconventional.2. The layer structured nitride chlorides, β-MNCl (M = Zr, Hf) were so thin and so soft crystals that it was very difficult to use for X-ray structural analysis a … More nd physical property measurements. We have succeeded to develop a new high pressure synthesis method to obtain thick single crystals using ammonium chloride as flux. All kinds of β-MNX (M = Zr, Hf ; X = Cl, Br, I) were also obtained as single crystals, and the crystal structures were determined by X-ray single crystal analyses. It was found that the compounds were crystallized into the two different polytypes, the SmSI and the YOF structures.3. In an attempt to tailor new layer structured nitride compounds, thin artificial nitride films were prepared using electron-beam evaporation and lazer ablation methods with a nitrogen radical source under ultrahigh vacuum conditions. Titanium nitride, TiN, films were epitaxially grown on MgO (100) substrates, and the layer-by-layer growth was successfully monitored by RHEED. CrN could be epitaxially deposited on Si(100), and an expitaxial NbN film was subsequently grown on the CrN film. This finding suggests the possibility of the synthesis of artificial CrN-NbN films with superstructures. Less