1 INTERRELATION OF PLANCK THERMAL GLOW WITH CURRENT SATURATION EFFECT OF CARBON NANOTUBE FIELD EMITTERS J. Wu, Z. Cheng, L. Sun Institute of Electron Device & Application, Hangzhou Dianzi University, Hangzhou, Zhejiang 310018, China wujun@hdu.edu.cn V. Labunov, B. Shulitski, I. Kashko, D. Grapov Belarusian State University of Informatics and Radioelectronics, Minsk, 220013, Belarus shulitski@bsuir.by N. Kargin National Research Nuclear University MEPhI, Moscow, 115409, Russia NIKargin@mephi.ru The interrelation of the emission current saturation effect with Planck glow in the visible spectral range of the matrix field emission carbon nanotube based cathodes was in- vestigated. It was found that the beginning of the glow in the visible spectral range corresponds to the beginning of the transition into the emission current saturation mode. It was found that the main reason for the emission current saturation is high internal resistance of carbon nanotubes and its contact with substrate. 1. Introduction Since the discovery of carbon nanotubes (CNTs) by Iijima in 1991, continuous research of them reveals more and more unique properties and new areas of application [1]. One of the promising and intensively studied fields of CNT application is field-emission cathodes (FECs). FECs can be used in a series of devices, such as high brightness flat-panel displays, compact X-ray sources, powerful microwave amplifiers, high-performance luminescent lamps, compact high-frequency electron sources, sources of synchrotron radiation etc. The attractiveness of CNTs for these applications is due to their electrical, chemical, thermal and mechanical properties, that are reached owing to quasi one- dimensional structure and naturally high aspect ratio. Regardless of the field of FECs application, a number of requirements to their characteristics must be satisfied. Among them are the high emission efficiency, low threshold and operating voltages, high homogeneity, density and stability of electron emission.