Porous Silicon Coated with Ultra-Thin Diamond-Like Carbon Film Cathodes
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Porous Silicon Coated With Ultra-Thin Diamond-Like Carbon Film Cathodes Anatoli A. Evtukh, Volodimir G. Litovchenko, Yurii M. Litvin, Dmitrii V. Fedin, Yurii V. Rassamakin, Andrey V. Sarikov, Andrei G. Chakhovskoi1, Charles E. Hunt1 , Thomas E. Felter2 Institute of Semiconductor Physics, 45 Prospekt Nauki, Kiev 03028 , UKRAINE. 1 ECE Department, University of California, Davis, CA 95616, USA. 2 Lawrence Livermore National Laboratory, Livermore, USA.
ABSTRACT The main requirements to electron field emission cathodes are their efficiency, stability and uniformity. In this work we combined the properties of porous silicon layers and diamond-like carbon (DLC) film to obtain emission cathodes with improved parameters. The layered structures of porous silicon and DLC film were formed both on flat n-Si surface and silicon tips created by chemical etching. The conditions of the anodic and stain etching of silicon in HF containing solution under the illumination have been widely changed. The influence of thin (≤10nm) DLC film coating of the porous silicon layer on electron emission has been investigated. The parameters of emission efficiency such as field enhancement coefficient, effective emission areas and threshold voltages have been estimated from currentvoltage dependencies to compare and characterize different layered structures. The improvement of the emission efficiency of silicon tip arrays with porous layers coated with thin DLC film has been observed. These silicon-based structures are promising for flat panel display applications. INTRODUCTION There are many investigations directed toward the improvement of the emission properties of cathodes. For low voltage applications the tip radii should be made very small in order to achieve a high field enhancement coefficient. The processes required to manufacture very sharp and uniform emitters are relatively complicated. The porous silicon (PS) layers are perspective for the improvement of electron field emission. The stability of the emission current as well as its density can be increased and the applied voltage can be decreased for silicon cathodes by depositing or forming a PS layer on their surface [1–6]. The lowering of the emission voltage is caused by the electric field enhancement due to the presence of the sharp asperities (also referred as fibrils or protrusions) of porous silicon. Due to the variation of the formation conditions the density of asperities, which act as separate emission centers, can be in the range of 108–1011 asperities per mm2 [1]. On the other hand, due to the distribution of radii of the tips in the array most of the emission current flows through the tips having small radii. If the tip is very small its thermal resistance is very high and the equilibrium temperature necessary to dissipate the power may be greater than the melting point [7]. As a result some tips can be overheated and blunted. In the case of porous layer on the silicon tip surface the blunting and destruction of some asperities does not influence the emission significant
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