CAREER: Melting-free Photonic Memory with Layered Chalcogenide Materials

非易失性存储器在除去外部驱动（如热、电场、电流或照明）后仍能保持其器件状态（电阻或折射率变化），是许多独立系统中不可缺少的部件。非易失性电子存储器有着丰富的历史，它们可以大致分为三大类：相变材料（PCM）、忆阻器和铁电存储器，分别通过热诱导原子重构、电流驱动离子动力学和电场定向极化来工作。在过去的半个世纪里，电子存储技术有了显著的发展，在可扩展性、耐用性和CMOS集成方面达到了很高的成熟度。由于能够在亚波长范围内进行均匀的相变，使得PCMs特别适合于光子应用。为了在非晶态和晶态之间转换，硫系pcm被加热到熔化温度以破坏共价键。冷却速率决定了最终状态。熔化温度高会影响时钟速率、集成密度和器件寿命的上限。本文将探索可替代的光学可逆调谐机制，解决新材料平台中的一些神话和挑战，并找到合适的光子存储器件原理图。CAREER项目将由毕业生进行，本科生和高中实习生参与。通过当地社会组织的夏令营，我们的本科生和高中实习生将与年轻一代，特别是女性和少数族裔分享他们选择STEM的举措和动机。本计划项目横跨层状材料物理、半导体制造及光子技术等领域，并加强量子力学、奈米制造、光电子学及光子系统工程的多学科教育。提出的工作探索了层状硫系材料的无熔化机制，用于集成光子学中的非易失性调谐和开关，这是由这些材料中独特的原子结构实现的。小的能量势垒有利于低温可逆相变，从而减少了元件偏析相关器件故障的机会。这个材料搜索从In2Se3开始。它的层状结构在室温下是可转换的和稳定的。此外，在环境条件下，通过光化学方法将探索层状硫属化物的损失不变大折射率调谐。通过对材料和器件响应的原位探测，将开发一个物理框架，用于描述相变过程中热和机械过程之间的复杂相互作用，了解原子尺度上瞬态动力学的细节，并优化器件的几何设计和制造步骤，以实现选择的光子应用，从高对比度相干光调制器，相控阵集成光子计算的多层超表面系统。该项目由电气、通信和网络系统部门（ECCS）和促进竞争研究的既定计划（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nonvolatile memories, which retain their device status (resistance or refractive index change) after removing the external drive (such as heat, electric field, current, or illumination), are indispensable components in many stand-alone systems. Nonvolatile electronic memories have a rich history, and they can be broadly categorized into three primary groups: phase change material (PCM), memristor, and ferroelectric memory, operating through thermal-induced atomic restructuring, current-driven ionic dynamics, and electric field-oriented polarization, respectively. Over the past half-century, electronic memory technologies have witnessed significant growth, achieving a high level of maturity in terms of scalability, endurance, and CMOS integration. Being able to perform uniform phase transitions over a subwavelength scale makes PCMs particularly suitable for photonic applications. For switching between amorphous and crystalline states, the chalcogenide PCMs are brought to a melting temperature to break the covalent bonds. The cooling rate determines the final state. The high melting temperature sets the upper limit of clock rate, integration density, and the device lifetime. The proposed works will explore alternative optical reversible tuning mechanisms, address a few myths and challenges in the new material platform, and locate proper photonic memory device schematics. The CAREER project will be carried out by graduates, with the involvement of undergraduates and high school interns. Through local society-organized summer camps, our undergraduate and high school interns will share their initiatives and motivations for choosing STEM with the younger generations, especially the females and minorities. The proposed projects bridge the fields of layered material physics, semiconductor manufacturing, and photonic technologies, and strengthen multidisciplinary education among quantum mechanics, nanofabrication, optoelectronics, and photonic system engineering.The proposed work explores melting-free mechanisms in layered chalcogenide materials for nonvolatile tuning and switching in integrated photonics, enabled by the unique atomic structures in these materials. The small energy barrier facilitates low temperature reversible phase transitions, which reduces the chance of element segregation-associated device failure. This material search started with In2Se3. Its layered structures are convertible and stable at room temperature. In addition, loss-invariant large refractive index tuning in layered chalcogenide through photochemistry will be explored in ambient conditions. Through in-situ probing of the material and device responses, a physical framework will be developed for describing the complex interplay between the thermal and mechanical processes in the phase transition process, understand the details of transient dynamics at atomic scale, and optimize device geometric design and fabrication steps towards selected photonic applications, from high contrast coherent optical modulator, phase array to integrated multi-layer metasurface system for photonic computing.This project is jointly funded by the Electrical, Communications and Cyber Systems division(ECCS), and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.