Integrated Field emission electron source analysis

• Applicant: Professor Dr. Rupert Schreiner
• Subject Area: Measurement Systems ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545035571

The aim of our international cooperation project INFASCOPE is to investigate new experimental methods and measurement procedures for spatially and temporally resolved electron detection from field emission (FE) cathode arrays and FE-electron sources. Research on field emitters, i.e., the fabrication methods, the nature of their operation, as well as their applications, have been extensively conducted by research groups worldwide, resulting in the research field of vacuum nanoelectronics. To gain a comprehensive understanding of the emission characteristics of modern FE-cathodes, especially emitters arranged in an array, it is necessary to understand how the individual emission sites on the cathode surface interact with each other and how the individual electron emission sites interact with the residual gas during operation in vacuum. However, this requires precise knowledge of which and how many emitters of an array contribute to the emission current during operation and how their emission characteristics change over time. To carry high emission currents, it is necessary for the total emission to be evenly distributed over the area of a field emission cathode. However, practice shows that even with high-precision fabricated FE- arrays, the emission is distributed only over a few dominant emitters, and these then degrade prematurely. Even slight changes in the shape of an individual emitter can already significantly change its output current. Currently available experimental methods do not provide sufficient observation possibilities of field emission arrays (FEA) in operation to determine the homogeneity of the emission or also to investigate the influence of conditioning processes on the homogeneity of the emission. Therefore, new experimental methods are needed to be able to investigate and understand the behavior of modern FE-cathodes, to improve their performance, and to develop improved theoretical models based on these experiments. We propose a new and easy to use approach, that largely overcomes the disadvantages of the common indirect electron detection methods (e.g., combinations of phosphor screens or scintillators with optical cameras). Instead of observing the illuminating phosphor screens with digital cameras, we will use the CMOS image sensor directly to measure the current distribution of FE-arrays in situ. As the CMOS sensor is a semiconductor device that in principle generates and traps electrons in its structure to accumulate signals from particular sensors in a matrix, it appears possible to collect electrons directly from the electron beam. The most significant advantage of this new method will be the high dynamic range in combination with the adjustable exposure time. This should allow spatially resolved detection of multiple emitting sites, whose emission current differs by orders of magnitude, without sacrificing near real-time observation.

• DFG Programme: Research Grants
• International Connection: Czech Republic, Poland
• Partner Organisation: Czech Science Foundation; Narodowe Centrum Nauki (NCN)
• Cooperation Partners: Privatdozent Dr.-Ing. Alexandr Knápek; Professor Dr.-Ing. Michal Krysztof