Modification of emission properties of diamond films due to surface treatment process

摘要

The modification on the characteristics of the chemical vapor deposited (CVD) diamond films due to H_2-plasma post-treatment, SiO_2-coating and Cr-coating has been examined. A negatively biased H_2-plasma post-treatment process leads to pronounced modification on the morphology, Raman spectroscopy and electron field emission properties of the diamond films, whereas a positively biased H_2-plasma post-treatment process changes these characteristics insignificantly. The emission current density of the diamond films increased markedly to 162.1 #mu# A cm~(-2) due to negatively biased H_2-plasma etching, which is presumably caused by the formation of nano-sized columnar grains resulted from the etching of diamonds. On the other hand, the electron field emission capacity of the diamond films was completely suppressed due to the coating and chemical etching of SiO_2 layer, which is ascribed to the formation of a silicon-oxy-carbon (Si_(1-x-y)C_xO_(2y)) layer. Only when the SiO_2 layer is subjected to a negatively biased (-50 V) H_2-plasma etching process, can the electron field emission capacity of the diamond films be fully recovered. In contrast, emission current density (J_e) was increased substantially to 642 #mu# A cm~(-2) and the turn-on field (E_o) was lowered from 10.2 to 5.8 V #mu# m~(-1) due to Cr-coating. Scanning electron microscopic (SEM) and Auger electron spectroscopic (AES) examinations reveal that the main factor improving these behaviors for the Cr-coated diamond films is the formation of diamond-like carbon films on their top surface.