基于FIB/HPCVD的MgB;超导微桥制备

Preparation of MgB;Superconducting Microbridge Based on FIB/HPCVD

超导微桥是决定超导热电子混频器性能的关键结构,为提高超导热电子混频器的工作温度并拓宽其中频带宽,用超导转变温度约40 K的MgB;超导薄膜制备超导微桥。研究了一种MgB;超导微桥的制备方法。首先利用聚焦离子束(FIB)直写技术在(0001)SiC衬底上制备出尺寸约1μm×1μm的微桥结构,然后采用混合物理化学气相沉积(HPCVD)法,在带有微桥结构的SiC衬底上生长厚度约20 nm的MgB;薄膜,从而得到MgB;超导微桥。扫描电子显微镜(SEM)和X射线衍射仪(XRD)的表征结果显示,微桥处的薄膜致密,晶粒沿垂直于衬底表面的c轴方向生长;原子力显微镜(AFM)分析薄膜的粗糙度约为0.8 nm;电阻-温度(R-T)测试结果表明,MgB;微桥的上超导转变温度约为40.43 K;由电流-电压(I-V)测试结果计算得到MgB;超导微桥的临界电流密度约为1.2×10^(7)A/cm^(2)。该工作对基于超导微桥结构的超导热电子混频器等超导电子学器件的制备具有重要的参考意义。

Superconducting microbridge is a key structure to determine the performance of superconducting hot-electron bolometer mixer. In order to increase the operating temperature of the superconducting hot-electron bolometer mixer and broaden its bandwidth, MgB;superconducting thin film with a high superconducting transition temperature of about 40 K was used to prepare the superconducting microbridges. A method for the fabrication of MgB;superconducting microbridges was studied. Firstly, a microbridge structure with a size of about 1 μm×1 μm was prepared by using the focused ion beam(FIB) direct writing technique on(0001) SiC substrate. MgB;thin film with a thickness of about 20 nm was grown on SiC substrates with microbridge structure by hybrid physical-chemical vapor deposition(HPCVD) method. Then, the MgB;superconducting microbridge was obtained. The characterization results of scanning electron microscope(SEM) and X-ray diffractometer(XRD) show that the thin film at the microbridge is dense, and the grains grow along the c-axis. The roughness of the thin film measured by atomic force microscope(AFM) is about 0.8 nm. The resistance-temperature(R-T) test result shows that the onset superconducting transition temperature of the MgB;superconducting microbridge is about 40.43 K, and the critical current density calculated from the current-voltage(I-V) test result is about 1.2×10^(7)A/cm^(2). The work is of important reference significance to the preparation of superconducting electronic devices such as the superconducting hot-electron bolometer mixer based on the superconducting microbridge structure.