CAREER: Melting-free Photonic Memory with Layered Chalcogenide Materials

非易失性存储器在移除外部驱动器(如热、电场、电流或照明)后保持其设备状态(电阻或折射率变化)，是许多独立系统中不可缺少的组件。非易失性电子存储器有着丰富的历史，大致可以分为三大类：相变材料(PCM)、忆阻器和铁电存储器，它们分别通过热致原子重组、电流驱动的离子动力学和电场取向的极化来工作。在过去的半个世纪里，电子存储技术经历了显著的发展，在可扩展性、耐用性和CMOS集成方面实现了高度的成熟。能够在亚波长范围内进行均匀的相变，使相变材料特别适合于光子应用。为了在非晶态和晶态之间切换，硫化物相变材料被带到熔化温度，以打破共价键。冷却速度决定了最终状态。较高的熔化温度设置了时钟频率、集成密度和器件寿命的上限。建议的工作将探索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。就业项目将由毕业生实施，本科生和高中实习生将参与其中。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的倡议和动机。拟议的项目跨越了层状材料物理、半导体制造和光子技术领域，并加强了量子力学、纳米制造、光电子学和光子系统工程等多学科的教育。拟议的工作探索了层状硫化物材料中的免熔化机制，用于集成光子学中的非易失性调谐和开关，利用这些材料中独特的原子结构。较小的能垒促进了低温可逆相变，从而减少了与元素偏析相关的器件故障的机会。这一材料搜索始于第三季。它的层状结构在室温下是可转换和稳定的。此外，还将探索在环境条件下通过光化学在层状硫化物中实现损耗不变的大折射率调谐。通过对材料和器件响应的原位探测，将建立一个物理框架，用于描述相变过程中热过程和机械过程之间的复杂相互作用，了解原子尺度上的瞬变动力学细节，并针对选定的光子应用，从高对比度相干光学调制器、相位阵列到用于光子计算的集成多层亚表面系统，优化器件几何设计和制造步骤。该项目由电气、通信和网络系统司(ECCS)联合资助，和既定的激励竞争性研究计划(EPSCoR)。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，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.