Stabilized field emission behavior of diamond-like carbon-coated Si tips

Micromachined Si tips have been considered as a strong candidate for cold c athode materials. However, as-prepared Si tips showed unstable emission beh avior, presumably due to native oxide, chemical reaction with residual gase s or changes in tip geometry during operation. In order to stabilize the em ission behavior, diamond-like carbon (DLC) films were deposited on the Si t ips by DC magnetron sputtering of high purity graphite. We focused on the s tability of the emission behavior by repeating the I-V measurement with ano de voltages ranging from 100 to 2500 V. With increasing number of I-V measu rements, the onset electric field decreased in both as-prepared and DLC-coa ted Si tips. However, the emission current of as-prepared Si tips decreased with increasing number of I-V measurements and eventually could not be obs erved after 10 measurements. On the other hand, DLC-coated tips exhibited i mproved emission behavior by repeating the I-V measurement. These results s howed that the DLC coating can prevent the Si tips from oxidation or from b eing contaminated, which stabilized the field emission behavior. Furthermor e, the DLC coating seems to reduce the effect of the changes in tip apex mo rphology by reducing the sharpness of the tip apex. (C) 1999 Elsevier Scien ce S.A. All rights reserved.