Preparation and Superconducting Properties of NbN Filaments Formed on Carbon Fibers

碳纤维NbN细丝的制备及其超导性能

• 批准号: 60550220
• 负责人: WAKIVAMA Tokuo
• 金额: $ 1.34万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1986
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60550220/
• 关键词: Superconducting Properties; Niobium Nitride; Carbon Fibers; 反応性スパッタリング

Preparation of NbN is usually carried out by reactive sputtering with controlling the N2 gas partial pressure( <P_N2> ). In the present investigation, besides <P_N2> , the <N_2> gas flow-rate( <Gf_N2> ) and the Ar gas flow-rate( <Gf_Ar> ) were controlled, and also the relationship between the plasma temperature(Tp) and the discharge current( <I_p> ) was clarified. In this way, the preparation condition of Bl-type NbN was obtained.NbN was deposited onto carbon fibers(fiber diameter of 7 <micro> m, Toray, Japan) by DC reactive magnetron sputtering with two opposed Nb-plate targets, under <P_N2> =2.4mTorr, <Gf_N2> =2.5cc/min, <Gf_(Ar)> =4.0cc/min, and <I_p> =350-600mA. X-ray diffraction analysis showed that these samples have the Bl-type crystal structure. Morphology of NbN-coated carbon fiber filaments was observed by a scanning electron microscope. The dependence of the superconducting transition temperature(Tc) on <I_p> was investigated. Under <P_N2> =2.2mTorr and <Gf_N2> =2.5cc/min, it was found that Tc increases with increasing <I_p> . In the region of <I_p> =500-600mA, Bl-type NbN films with Tc(middle point)=17K were formed on carbon fibers. A Tc of 17K is the highest Tc in NbN films deposited onto carbon fibers.The critical current became larger for the samples prepared at higher <I_p> . This result corresponds to the fact that Bl-type NbN with higher Tc was formed at higher <I_p> . The dependence of the critical current density(Jc) on the transverse external magnetic field(Hex) was obtained at 4.2K. For example, Jc=9x <10^4> A/ <cm^2> at Hex=0, or Jc=4x <10^4> A/ <cm^2> at Hex=10T. These Jc values are about one tenth of those of NbN films deposited onto sapphire substrates. The origin of this result is thought to be due to inhomogeneity and microstructure in the samples. It was found that Bl-type NbN was synthesized in the presence of N2 (excited N2 molecule) in a plasma.

NbN的制备通常通过控制N2气体分压的反应溅射进行（<P_N2>）。此外，在本研究中<P_N2>，还控制了<N_2>气体流量（<Gf_N2>）和Ar气体流量（<Gf_Ar>），并阐明了等离子体温度（Tp）与放电电流（）之间的关系<I_p>。采用<micro>直流反应磁控溅射技术，在碳纤维（直径7 μ m，日本东丽）上沉积NbN，溅射条件为：Ar =2.4mTorr，Ar <P_N2><Gf_N2>=2.5cc/min，Gf_（Ar）=4.0cc/min，<I_p>电流为350- 600 mA。X射线衍射分析表明，样品具有B1型晶体结构。用扫描电子显微镜观察了碳纤维表面NbN涂层的形貌。研究了超导转变温度（Tc）随温度的变化规律<I_p>.在<P_N2>~ 2.2mTorr和<Gf_N2>~ 2.5cc/min下，发现Tc随温度的升高而增加<I_p>。在<I_p>~ 500- 600 mA范围内，在碳纤维上形成了Tc（中点）为17 K的B1型NbN薄膜。在碳纤维上沉积的NbN薄膜的最高Tc为17 K，随着温度的升高，临界电流增大<I_p>。这一结果对应于具有较高Tc的B1型NbN在较高温度下形成的事实<I_p>。在4.2K下得到了临界电流密度Jc随横向外磁场Hex的变化关系。例如，在Hex=0时，Jc= 9 x &lt;10^4&gt; A/ &lt;cm^2&gt;，或在Hex= 10 T时，Jc=4x &lt;10^4&gt; A/ &lt;cm^2&gt;。这些Jc值约为沉积在蓝宝石衬底上的NbN膜的Jc值的十分之一。这一结果的起源被认为是由于样品中的不均匀性和微观结构。发现在等离子体中在N2（激发的N2分子）存在下合成B1型NbN。

项目成果

S. Ohshima: "Structure and Superconducting Properties of NbN Deposited on Carbon Fibers by DC Magnetron Sputtering" Jpn. J. Appl. Phys.

S. Ohshima：“通过直流磁控溅射在碳纤维上沉积 NbN 的结构和超导性能”Jpn。

S.Ohshima: Jpn.J.Appl.Phys.

S.Ohshima：Jpn.J.Appl.Phys。