Deposition and nonlinear optical properties of transition metal nitride/oxide thin films

非技术描述：光与物质的相互作用具有很高的科学和技术意义。光是一种电磁波，电场可以与材料中存在的电荷相互作用，产生正电荷和负电荷中心的分离，从而在材料体内产生电场。当光的强度较低时，感应电场也非常小，并与外加电场成正比（线性）。然而，当使用像激光这样的强光时，可能会获得非常高的（非线性）响应。这种对外部电场的强烈响应取决于材料的结构和成分，可以用来产生不同颜色的光，或者通过强度相关的折射率来调制光通过材料的传播。例如，能够保护传感器和裸眼免受高强度光（如激光）的伤害是非常理想的。虽然这些材料的军事意义是显而易见的，但它的好处可以影响日常生活的许多领域。已知具有非线性响应的大多数材料都是从大晶体或液体中切割出来的，并且不适合重复覆盖大面积，例如前面描述的应用所需的材料。在这个项目中，研究小组研究了一类新的非线性光学材料，这种材料基于薄膜，可以可靠地、可重复地沉积在大表面积上，包括复杂的几何形状，甚至具有原子尺度精度的光纤。该项目是在一个具有高技术重要性的领域培训两名研究生。技术描述：薄膜形式的非线性材料在片上快速全光开关器件，频率转换和光限制应用中是非常理想的，因为传统的非线性光学材料不适合与当代半导体工业工艺流程集成。该项目旨在通过设计和研究基于合理原理的新型非线性光学材料来解决这一不足。所研究的材料是基于钛和氮化钽播种的介质薄膜，其中钛氮或钽氮键在薄膜体积中的百分比可以用来控制非线性折射率和薄膜透明度的值。ALD作为一种成熟的薄膜沉积技术，可以通过控制工艺温度和前驱体传递温度等参数，通过单一的沉积过程，形成具有原子级厚度控制的结构。该项目包括设计具有可调成分的种子材料，以及采用z扫描和超快泵浦探针等光学技术来研究这些新颖的超薄结构。拟议的活动和跨学科研究团队寻求在电子材料和非线性光学社区之间结合和转移知识。这种交叉授粉有望推进这两个领域的技术水平，其目标是丰富片上快速全光开关、频率转换和光限制应用的材料工具包。本提案的主要成果是提供对控制一类新型半导体兼容非线性光学材料的物理的详细理解，这些材料可能解决对新颖，特性良好的材料的技术需求，以帮助实现新的器件范例。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。

Nontechnical description: The interaction of light with matter is of high scientific and technological interest. Light is an electromagnetic wave and the electric field may interact with the charges present in the material to produce separation of the positive and negative charge centers resulting in the appearance of an electric field within the body of the material. When the intensity of the light is low, then the induced electric field is also very small and proportional (linear) to the applied field. However, when intense light such as that from a laser is used then it is possible that a very high (nonlinear) response may be obtained. This intense response to the externally applied electric field depends on the structure and composition of the material and can be used to generate light of a different color, or to modulate the propagation of light through the material via an intensity dependent refractive index. For example, it is highly desirable to be able to protect sensors and the naked human eye from high intensity light such as lasers. While the military implications of such materials are obvious, the benefits can affect many areas of everyday life. Most of the materials known to have a nonlinear response are cut from large crystals or are liquids and are not suitable to cover large areas reproducibly such as those needed for the application described before. In this project, the research team study a new class of nonlinear optical materials that are based on thin films that can be deposited reliably and reproducibly on large surface areas including complex geometries and even optical fibers with atomic scale precision. The project is training of two graduate students in an area of high technological importance. Technical description: Nonlinear materials in thin film form are highly desirable for on chip fast all-optical switching devices, frequency conversion and optical limiting applications as conventional nonlinear optical materials are not suitable for integration with the contemporary semiconductor industry process flow. This project seeks to address this shortage by designing and investigating novel nonlinear optical materials based on rational principles. The materials investigated are based on titanium and tantalum nitride seeded dielectric thin films where the at% of titanium-nitrogen or tantalum-nitrogen bonding in the film volume can be used to control the value of the nonlinear index of refraction and film transparency. The maturation of ALD as a thin film deposition technique allows the formation of such structures with atomic level thickness control, through a single deposition process by just controlling parameters such as the process temperature and the precursor delivery temperature. This project includes design of seeded materials with tunable composition, as well as the adaptation of optical techniques such as Z-scan and ultrafast pump-probe to investigate these novel, ultrathin structures. The proposed activity and the interdisciplinary research team seek to combine and transfer knowledge between the electronics materials and nonlinear optics communities. Such cross pollination is expected to advance the state of the art in both fields, with the goal to enrich the materials toolkit available for on chip fast all-optical switching, frequency conversion and optical limiting applications. The main outcome for this proposal is to provide detailed understanding of the physics governing a new class of semiconductor compatible nonlinear optical materials that may address the technological need for novel, well-characterized materials to aid in the realization of new device paradigms.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.