TEM Investigation of Nitrogen-Doped Amorphous Carbon Coated Field Emitters

Abstract Amorphous carbon coatings, including highly sp3-bonded amorphous diamond (a-D), also referred to as tetrahedral amorphous carbon (ta-C), and diamond-like carbon (DLC), have recently been explored for field emission applications [1-3]. These coatings can be deposited uniformly at low temperatures, and possess chemical and mechanical properties similar to those of diamond. They also can be doped with nitrogen to form n-type semiconductors [4]. Diamond coatings, on the other hand, are microscopically nonuniform, usually require deposition temperatures greater than 600 °C, and cannot be doped to produce shallow donor levels [2]. Diamond, a-D, and DLC coated emitters all show enhanced electron emission properties [1-3]. The major emphasis of the work presented here is on the parallel electron energy loss spectroscopy (PEELS) characterization of the sp2 and sp3 bonded carbon in the coatings. PEELS spectra and TEM images were recorded with a Philips CM300 FEG TEM, equipped with a Gatan model 666 parallel acquisition EELS spectrometer. The operating voltage was 300 keV.