Electrical and Mechanical Properties of Three-Dimensional Tungsten Nanostructures

聚焦离子束（FIB）可以用来生长钨薄膜。这是通过扫描离子束（包含加速到30千伏的镓离子）在钨六羰基前体气体上完成的。气体分子被离子裂解，结果是钨沉积在衬底上。所得的钨薄膜是超导的，临界转变温度约为5开尔文。我们将扩展fib -钨生长技术，以制造各种三维纳米结构和器件。具体来说：(1)我们将制造半径小于10纳米的超导钨纳米线。我们将测量纳米线的电子特性，以确定它们是否表现为量子相滑移中心（QPSC）。QPSC是纳米线中的局部非超导区域，无论纳米线冷却到多低的温度都无法抑制该区域。（二）制作约瑟夫森结和超导量子干涉器件（squid）。约瑟夫森结是所有超导电子电路的基本组成部分。两个约瑟夫森结并联构成一个SQUID，是最灵敏的磁通探测器。我们将使用我们的三维FIB生长技术制作一个高灵敏度的梯度拾取线圈耦合到SQUID。（三）制作厚度小于10nm的钨薄膜。它们将被做成弯曲的线条，用作超导单光子探测器（SSPDs）。SSPD是量子通信和量子计算实验中光子探测的有力候选技术。（四）研究垂直生长纳米棒的力学性能。通过在安装在扫描电子显微镜上的压电台上振荡，我们将测量它们的杨氏模量和弹簧常数。这将使我们能够确定它们对纳米力学实验的适用性，包括开发用于单分子质量检测的超灵敏质量平衡。

A focussed ion beam (FIB) can be used to grow thin films of tungsten. This is done by scanning the ion beam (containing gallium ions accelerated to 30 kV) over a tungsten hexacarbonyl precursor gas. The gas molecules are cracked by the ions with the result that tungsten is deposited onto a substrate. The resulting tungsten film is superconducting, with a critical transition temperature of around 5 Kelvin. We will extend the FIB-tungsten growth technique to make a variety of three-dimensional nanostructures and devices. Specifically:(i) We will make superconducting tungsten nanowires of radius less than 10 nm. We will measure the electronic properties of the nanowires to determine if they are behaving as quantum phase slip centres (QPSC). A QPSC is a local non-superconducting region in a nanowire which cannot be suppressed no matter how low in temperature the nanowire is cooled to. (ii) We will make Josephson junctions and superconducting quantum interference devices (SQUIDs). The Josephson junction is the basic building block of all superconducting electronic circuits. Two Josephson junctions in parallel are a SQUID, which is the most sensitive detector of magnetic flux. We will use our three-dimensional FIB growth technique to make a highly sensitive gradiometric pick-up coil coupled to a SQUID. (iii) We will make tungsten thin films of thickness less than 10 nm. These will be patterned into meander lines and used as superconducting single photon detectors (SSPDs). The SSPD is a strong candidate technology for photon detection in quantum communication and quantum computation experiments.(iv) We will study the mechanical properties of vertically-grown nanorods. By oscillating them on a piezo-stage mounted in a scanning electron microscope we will measure their Young's modulus and spring constant. This will allow us to determine their suitability for nanomechanics experiments, including the development of an ultra-sensitive mass balance for single molecule mass detection.