Superhard conductive carbon nanocrystallite films

Abstract

Carbon films whose hardness is comparable to diamond’s, but whose electrical conductivity is 19 orders of magnitude larger, have been discovered. The films were deposited onto silicon substrates by electron cyclotron resonance plasma sputtering. The bonding structure of the film was mainly sp2. The film consisted of sp2 nanocrystallites having parallel and curved graphene sheets vertically oriented to the film surface. The sp2 nanocrystallites were connected with adjacent crystallites by sp3 bonding, which gives the film both its high hardness and conductivity. These sp2 nanocrystallite films will have many applications.

Electron Energy-Loss Spectroscopy of Carbon Films Prepared by Electron-Cyclotron-Resonance Plasma Sputtering

“…In addition, a small bump started being visible at about 292 eV. Since the fraction of the sp 2 clusters is significantly large in the film, these evidences could suggest that a narrower energy band was formed; more fraction of the sp 2 clusters are ordered at the lower voltage i.e. V B = −75 and −120 V. Such an interpretation can be consistent with the low-loss spectroscopy.…”

“…The ECR film prepared on silicon substrate is also rich in sp 2 clusters. The atomic structures of the film based on the sp 2 clusters seem to be finely controlled by a simple experimental parameter such as a bias voltage V B .…”

“…3 and Table 1, the relative intensity of the peak for the ECR films was much higher than that for amorphous carbon, especially for V B = −120 V and −75 V, and was close to that for graphitized carbon. This implies that there is a significant fraction of sp 2 clusters. Similar to the behavior of the (π + σ ) plasmon peak, the π plasmon energy was the minimum when V B = −75 V. The energy of the π plasmon was 4.5, 4.0 and 4.2 for V B = −120, −75 and 0 V, respectively.…”

“…4) The degree of sp 2 clustering can be reflected also in a low-loss spectrum. These pieces of information are important since they are the keys to control mechanical and electrical properties of the protective film.…”

“…Using this technique, we recently succeeded in preparing a film that possessed both the wear durability as high as that of bulk diamond and the conductivity as high as that of graphite. 2) This was achieved when a negative voltage V B (−40 ≤ V B ≤ 140 V) was applied to the silicon substrate. It was found that the durability depended largely on V B .…”