Compact Ion-Sources based on Surface-Patterned Atom Chips

在这个项目中，我将使用最近开发的激光冷却原子技术来改善聚焦离子束（FIB）。FIB用于广泛的应用;从半导体行业的电路编辑和缺陷检查，到故障分析，样品制备，表面分析等等。FIB可用于成像、研磨（去除材料）和沉积（添加材料）JIB的大多数目前使用镓液态金属离子源（LMIS），并且在约10 pA的低电流下常规地实现< 10 nm的光斑尺寸。虽然FIB使用LMIS已经取得了巨大的成功，但也有一些严重的局限性。例如，斑点尺寸基本上受到源处离子的能量扩散的限制，并且源物质由于其独特的性质组合而限于镓。镓在用于成像时是破坏性的，但对于许多应用来说不够重或反应性不够。镓离子注入也会污染样品，造成不必要的影响。最近，研究人员已经开始研究使用激光冷却原子作为FIB应用的源。通过激光将原子冷却到微开尔文温度，然后将其光电离，我们可以在neV范围内实现固有的低能量扩散。由于激光冷却原子的超冷温度导致离子横向运动速度很小，因此可以得到较低的束发散角，使光束聚焦更紧密。可以被激光冷却的物质的范围很大，包括碱金属、碱土金属、亚稳态诺贝尔气体以及一系列过渡金属和稀土金属; Al，Cr，Ag，Cd，Hg，Dy，Ho，Er，Tm，Yb，潜在地在纳米技术中开辟全新的可能性。虽然离子源基于激光-冷却已经被证明是有用的，并且是冷原子物理学的真实的技术实现的候选者，但是实验的绝对规模和复杂性使得将它们嵌入FIB系统不切实际。真空系统往往又大又重，冷却和光电离需要几个激光频率，我打算使用新开发的表面图案化（光栅）原子芯片技术来形成冷离子源的MOT，从而大大减少设备的尺寸和复杂性。这种光栅MOT离子源（GMIS）可以作为FIB系统的离子源，为普遍存在的LMIS提供替代方案。

In this project I will use recently developed techniques in laser-cooling of atoms to improve focused ion beams (FIBs).FIBs are used across a vast range of applications; from circuit editing and defect review in the semiconductor industry, to failure analysis, sample preparation, surface analysis and much more. FIBs can be used for imaging, milling (removing material) and deposition (adding material).The majority of FIBs currently use a gallium liquid metal ion source (LMIS) and spot sizes of < 10 nm are routinely achieved at low currents of around 10 pA. Although FIBs using LMIS have been spectacularly successful, there are some serious limitations. For example, the spot size is fundamentally limited by the energy spread of the ions at the source and the source species is limited to gallium because of its unique combination of properties. Gallium is destructive when used for imaging but not heavy or reactive enough for many applications. Gallium implantation can also contaminate samples, causing unwanted effects.Recently, researchers have begun to investigate using laser-cooled atoms as a source for FIB applications. By laser cooling atoms down to microKelvin temperatures and then photoionising them, we can achieve inherently low energy spreads in the neV range. Because the ultracold temperatures of laser cooled atoms result in small transverse ion velocities, we get low beam divergence and can focus the beam more tightly. The Range of Species that could be laser-cooled is large and includes the alkali metals, alkaline earths, metastable Nobel gases and also a range of transition and rare earth metals; Al, Cr, Ag, Cd, Hg, Dy, Ho, Er, Tm, Yb, potentially opening up brand new possibilities in nanotechnology.Although ion sources based upon laser-cooling have proven to be useful and are a candidate for real technological implementation of cold atoms physics, the sheer scale and complexity of the experiments makes embedding them into FIB systems impractical. The vacuum systems tend to be large and heavy and several laser frequencies are required for cooling and photoionisation.I intend to use newly-developed surface-patterned (grating) atom chip technology to form the MOT for a cold ion source, thereby considerably reducing the size and complexity of the apparatus. This grating MOT ion source (GMIS) could then realistically be implemented as the ion source for a FIB system, providing an alternative to the ubiquitous LMIS.