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价值。光是一种电磁波，电场可以与材料中存在的电荷相互作用，产生正负电荷中心的分离，从而在材料体内出现电场。当光线强度较低时，感应电场也很小，并且与外加电场成正比(线性)。然而，当使用诸如来自激光的强光时，则有可能获得非常高的(非线性)响应。这种对外部施加电场的强烈响应取决于材料的结构和组成，并且可以用来产生不同颜色的光，或者通过依赖于强度的折射率来调制光通过材料的传播。例如，人们非常希望能够保护传感器和肉眼免受激光等高强度光的伤害。虽然这种材料的军事影响是显而易见的，但其好处可能会影响到日常生活的许多领域。大多数已知的具有非线性响应的材料是从大晶体切割而来的，或者是液体，不适合重复地覆盖大片区域，例如前面描述的应用所需的那些。在这个项目中，研究小组研究了一种新型的非线性光学材料，这种材料基于薄膜，可以可靠地和可重复地沉积在包括复杂几何结构甚至原子尺度精度的光纤在内的大表面积上。该项目是在一个具有高度技术重要性的领域培养两名研究生。技术描述：薄膜形式的非线性材料非常适合用于片上快速全光开关、频率转换和光限幅应用，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。本项目旨在通过基于有理原理设计和研究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籽晶的介质薄膜，其中钛-氮或钽-氮键在薄膜体积中的at%可以用来控制非线性折射率和薄膜透明度的值。AlD作为一种薄膜沉积技术的成熟，只需控制工艺温度和先驱体输送温度等参数，就可以通过单一的沉积过程形成原子级厚度控制的这种结构。该项目包括设计成分可调的种子材料，以及采用Z扫描和超快泵浦探测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小组寻求在电子材料和非线性光学社区之间结合和传递知识。这种交叉授粉有望推动这两个领域的技术水平，目标是丰富可用于芯片上快速全光交换、频率转换和光限幅应用的材料工具包。这项建议的主要成果是提供对管理一种新型半导体兼容非线性光学材料的物理学的详细了解，该材料可能满足对新的、特征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，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.