Triple-Beam Focussed-Ion-Beam Microscope

伦敦大学学院的卡尔蔡司XB1540交叉光束聚焦离子束显微镜是一种独特的仪器，位于独特的位置。该仪器位于位于首都中心的伦敦纳米技术中心的一个全新的专门建造的10,000级洁净室。该仪器不仅配备了用于无镓成像的原位场发射扫描电子显微镜，还配备了用于无镓纳米加工的原位低压氩离子米勒器。我们相信这是英国唯一的三光束组合。FIB的致命弱点是镓束不可避免地会损坏任何研磨或成像样品的表面。损伤包括镓注入和非晶化。在某种程度上，这可以通过使用低光束电流（以更长的铣削时间为代价）和/或低电压（以更差的成像对比度为代价）来改善。一种更强大的技术是使用传统的FIB研磨纳米级特征，然后使用宽束氩离子研磨机抛光样品，以去除镓植入和非晶层。与镓相比，氩不仅是惰性的，流动性更低，因此对样品的破坏要小得多，而且离子能量可以降低到30 eV。这大大减少了对样品的破坏深度。当使用FIB制造功能器件和材料时，重要的是要获得关于何时完成制造的某种反馈。使用扫描电镜对结构进行成像显然是一种反馈方法，但拓扑结构并不是全部。人们真正想要的是功能反馈/换句话说，在FIB铣削过程中测量设备功能，以向铣削过程提供反馈。对于电子设备，这可以通过使用与设备的电气连接直接完成。然而，许多功能纳米电子器件只能在低温下工作，例如大多数自旋电子、铁电、量子比特、多铁性和超导器件。因此，在伦敦大学学院，我们安装了一个液氦冷却的样品支架，具有多个馈线用于电气测量。这使我们能够在FIB制造超导器件时实时测量其电流-电压特性。由于XB1540 FIB无与伦比的性能和这两个独特的实验能力，我们相信英国材料科学，物理科学和生命科学学术界将从该仪器的使用中受益匪浅。

The Carl Zeiss XB1540 Cross-Beam focussed-ion-beam microscope at University College London is a unique instrument in a unique location. The instrument is located in a brand new purpose-built class 10,000 cleanroom in the basement level of the London Centre for Nanotechnology in the heart of the capital city. The instrument is equipped not only with an in situ field-emission scanning electron microscope for gallium-free imaging, but also an in situ low-voltage argon-ion-miller for gallium-free nanofabrication. We believe this to be the only such triple-beam combination in the UK.The Achilles' heel of the FIB is that the gallium beam inevitably damages the surface of any milled or imaged sample. The damage consists of both gallium implantation and amorphisation. To some extent this can be ameliorated by using low beam currents (at a cost of longer milling times) and/or low voltages (at a cost of worse imaging contrast). A much more powerful technique is to mill nanoscale features using the conventional FIB and then polish the sample using a broad-beam argon ion miller so as to remove the gallium-implanted and amorphised layer. Not only is argon inert and less mobile than gallium and therefore will do much less damage to the sample, but also the ion energy can be reduced to as low as 30 eV. This greatly reduces the depth of damage done to the sample. When fabricating functional devices and materials using FIB it is important to get some kind of feedback as to when the fabrication is complete. Using the SEM to image the structure is clearly one feedback method, but topology is not the whole story. What one really wants is functional feedback / in other words measuring the device functionality during FIB milling to give feedback to the milling process. For electronic devices this can be done straightforwardly by using electrical connections to the device. Many functional nanoelectronic devices, however, only work at low temperatures / examples include most spintronic, ferroelectric, qubit, multiferroic and superconducting devices.At UCL we have therefore installed a liquid-helium-cooled sample holder with multiple feedthroughs for electrical measurements. This has allowed us to measure in real-time the current-voltage characteristics of superconducting devices as they are being fabricated by FIB.As a result of both the unrivalled performance of the XB1540 FIB and these two unique experimental capabilities, we believe that the UK academic community in materials science, the physical sciences and the life sciences will benefit greatly from access to this instrument.