Giant Impedance Transition in Lanthanum Hexaboride (LaB6) Thin Films

这个SBIR第一阶段项目将研究最近在UltraMet使用六硼化镧(LaB6)薄膜制造热电子发射器件时发现的一个新现象。LaB6是一种低功函数的热电子发射器。这种现象被称为巨阻抗转变(GIT)，表现为对外部电磁辐射和静电辐射的响应，阻抗(或直流电阻)发生了巨大且非常迅速的变化。应该指出的是，对GIT现象的所有观察都是非常初步的，只是作为正在进行的热离子发射工作的副产品而获得的，没有对该现象本身给予关注。因此，在进入器件设计阶段之前，需要进行大量额外的工作来了解GIT现象的物理原理并对其进行量化。在这个项目中，Ultramet将研究GIT现象，以了解其物理原理，进行定量分析，并将LaB6沉积物中阻抗变化的行为与其微观结构和加工技术联系起来。UltraMet将与犹他大学电气工程系合作，对UltraMet生产的LaB6薄膜的电学和光学特性进行表征。这项工作的成功完成将导致对GIT现象的理解和量化，并为后续工作中的器件设计和制造指明方向。

This SBIR Phase I project will investigate a new phenomenon discovered recently at Ultramet while fabricating thermionic emission devices using thin films of lanthanum hexaboride (LaB6), a low work function thermionic emitter. This phenomenon, designated giant impedance transition (GIT), is represented by a large and very fast change in impedance (or resistance in DC) in response to external electromagnetic and electrostatic radiation. It should be noted that all observations of the GIT phenomenon have been extremely preliminary, obtained merely as a byproduct of the thermionic emission work being performed, with no focus having been given to the phenomenon itself. As such, much additional work is required to understand the physics of the GIT phenomenon and quantify it before proceeding to the device design stage. In this program, Ultramet will investigate the GIT phenomenon to achieve an understanding of its physics, perform quantitative analysis, and relate the behavior of the impedance change in the LaB6 deposit to its microstructure and thus, the processing technique. Ultramet will team with the Electrical Engineering Department of the University of Utah for characterization of the electrical and optical properties of LaB6 thin films produced at Ultramet. The successful completion of this effort will result in an understanding and quantification of the GIT phenomenon, as well as a direction for device design and fabrication to be pursued in follow-on work.