Advancements in Laser-Free UltraFast Electron Microscopy

Le résumé fourni par la source

TEMs are used to connect photonics, nanodevice architecture, and biophysics, each with their individual intrinsic response times on the nanoscale. The continued evolution of applications and maturation of basic TEM instruments have not only created additional sectors in the electron microscopy industry (life sciences, nanotechnology, and semiconductor), but have fostered significant growth in these areas that the new market sectors are comparable in size to the once dominant materials science market [1]. Due to the growing applications of temporally resolved electron microscopy for probing fundamental chemical and electronic phenomena as well as reducing beam-induced damage, temporally resolved electron microscopy has experienced a much broader adoption across many technical fields (see Fig. 1). Complex laser techniques with limited image acquisition times have been complemented by ultrafast rf and microwave-driven techniques that can be synchronized with any sample excitation (laser, rf, thermal) providing much faster image acquisition times (from days to mere minutes). These complementary ultrafast techniques can also be used as ‘fast’ beam blankers with larger pulse widths for observing phenomena on timescales larger than 100 picoseconds, providing more flexibility and therefore wider adoption of these laser-free electron beam modulation techniques. The flexibility of the commercially available laser-free beam modulation designs [2-5] provides seemingly endless possibilities to the users. Due to the increasing capabilities to operate from the ultrafast regime to much longer timescales with standard imaging technology, we expect even wider adoption of these beam modulation techniques. Of course, the details of the performance, flexibility and synchronization capabilities are extremely important when determining which of these complementary techniques are suitable for a particular laboratory or user facility. This talk will present the state-of-the-state of growing laser-free techniques that can provide gigahertz through dc performance while also providing beam pulse widths from picosecond to dc levels. Details of the modulation performance on the electron beam pulse shape, coherence at the sample and the subtleties of ‘sweeping’ vs. ‘chopping’ the beam will be discussed in depth. For aberration corrected (Cs) instruments, the modulation technique further requires additional beam compensation to maintain the native instrument performance. Such a system is shown in Fig. 2. To fully enable these technologies in research applications, the challenge to interface or synchronize these techniques with any stimuli (for pump/probe type of experiments) is also critical and will be considered for key applications. In particular, rf sample pump and probing throughout the rf cycle at various frequencies requires proper sample stage design and construction, which will also be covered. Over the past year or two, rf/microwave modulation techniques have demonstrated much wider ranges than used in typical ultrafast electron microscopy (UEM), making them versatile techniques that can access a large range of temporal phenomena in electron microscopy. These complementary methods and their ultimate performance, especially when integrated with ultrafast stimuli are rapidly emerging from the niche “UEM” community. This talk will be particularly geared towards electron microscope users to consider when trying to expand their research capabilities [6]. Time scales of various phenomena studied across various fields. UltraFast Pulser from Euclid Techlabs, with full compensation for ultrafast beam modulation in Cs TEM.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.