Real-time imaging of light-induced transformations in phase-change materials

在这个数字时代，我们在日常生活的许多方面都依赖于电脑。他们的表现不仅影响我们的沟通和工作方式，还影响我们的银行和医疗保健的效力。因此，投资于它们的发展，以保持在该领域的战略优势，符合加拿大的最佳利益。这项发现基金（DG）通过研究相变材料的动力学来实现这一目标，相变材料对计算机存储设备很重要，并且有可能实现更高效的计算机体系结构。今天的计算机遵循冯·诺伊曼架构，数据必须在物理上独立的处理和存储单元之间移动。由于处理器的速度已经超过了内存的速度，现在的瓶颈是来回传输数据所需的时间。这可以通过在单个设备中执行这两个操作来克服，称为内存计算。然而，这种器件的实际实现需要能够快速且不可逆地在状态之间切换的材料，以结合快速处理和非易失性存储功能。基于硫族合金的相变材料已经为此目的进行了大量的研究，并且已经在计算机工业中用于光学数据存储——Ge2Sb2Te5成分用于dvd， Ge8Sb2Te11成分用于蓝光光盘。数据可以在这些设备中写入，使用激光或电流局部加热一个小区域，并在绝缘非晶玻璃相和导电晶体相之间切换。所产生的相位由过程中吸收的热量决定，该过程由入射激光功率或电流控制。然而，目前最大的数据写入速度受到非晶到晶相变时间的限制。因此，利用INRS的动态透射电子显微镜（DTEM），探索如何提高这种转化速度并实时跟踪相应的材料结构演变是本DG的目标。这种独特的显微镜能够以接近原子的分辨率捕获一系列纳秒级的不可逆转换图像。具体而言，该DG将通过探索以下研究方向来解决有关相变材料结晶的关键突出问题：(1)成像快速冷却转变，(2)跟踪非晶相中的前体，以及(3)超定域纳米等离子体加热。这项研究预计将导致对这一技术上重要的转变的更深入的理解，这可能会影响未来的计算机设计。此外，通过该项目培训的高素质人才所获得的专业知识可以广泛地转移到加拿大技术产业的其他部门。

In this digital age, we rely on computers in many aspects of our daily life. Their performance not only influences how we communicate and work, but also the efficacy of our banks and medical care. It is then in the best interest of Canada to invest in their development to maintain a strategic advantage in this sector. This Discovery Grant (DG) contributes to this goal by studying the dynamics of phase-change materials that are important for computer memory devices and have the potential to enable more efficient computer architectures. Today's computers follow a von Neumann architecture, where data must be moved between physically separate processing and memory units. As the speed of processors has outpaced that of memory, the bottle neck is now the time it takes to shuttle data back and forth. This can be overcome by performing both actions in a single device, referred to as in-memory computing. However, practical realization of such devices requires materials that can both rapidly and irreversibly switch between states for combined fast processing and non-volatile memory functionality. Phase-change materials based on chalcogenide alloys have been largely investigated for this purpose, and are already used in the computer industry for optical data storage - the composition Ge2Sb2Te5 is used in DVDs, and Ge8Sb2Te11 is used in Blue-ray disks. Data can be written in these devices using a laser or electric current to locally heat a small region, and switch it between an insulating amorphous glass phase and a conductive crystalline phase. The resultant phase is determined by the amount of heat absorbed in the process that is controlled by the incident laser power or electric current. However, the maximum data writing speed is currently limited by the amorphous to crystalline phase transformation time. It is then the goal of this DG to explore ways to increase this transformation speed and track the corresponding material structural evolution in real time using the dynamic transmission electron microscope (DTEM) at INRS. This unique microscope has the capability to capture a sequence of nanosecond images of irreversible transformations with near-atomic resolution. Specifically, this DG will address critical outstanding questions about the crystallization of phase-change materials by exploring the following research directives: (1) imaging rapidly cooled transformations, (2) tracking precursors in the amorphous phase, and (3) ultra-localized nano-plasmonic heating. This research is expected to lead to a deeper understanding of this technologically important transformation, which can impact the future design of computers. Furthermore, the expertise gained by highly qualified personnel trained in this program is widely transferable to other sectors of the Canadian technology industry.