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

Abstract

A protective carbon film, prepared by electron-cyclotron-resonance (ECR) plasma sputtering, has attracted considerable interest because the film can possess both the high wear durability and the high conductivity without doping. Such properties can be obtained, for example, when a negative bias voltage V B (−40 ≤ V B ≤ −140 V) is applied to a substrate made of silicon. Little is known, however, about the atomic structure and bonding state of the ECR films for such a bias region, so that the physical origins of the macroscopic properties are not fully understood. In the present study, electron energy-loss spectroscopy (EELS) in a transmission electron microscope has been applied to investigate such ECR films that were deposited on a sodium chloride substrate for three different bias voltages: 0 V, −75 V and −120 V. The physical density of each ECR film was found to be lower than that of graphitized carbon and that of amorphous carbon. For each of the ECR films, the fraction of sp 2 bonding was estimated to be more than 90%. The carbon clusters with sp 2 bonding were considered to be more ordered for V B = −75 V and −120 V than for V B = 0 V. The averaged density of valence electrons did not change much for each film, but the band structure is considered to vary depending on a local area. For the film prepared by the ECR technique, the macroscopic properties of the film such as electronic and mechanical ones may be controlled by controlling the ordering of sp 2 clusters.

Multifunctional Bi-Layered Tribofilm Generated on Steel Contact Interfaces under High-Temperature Melt Lubrication

“…Regarding C, the resultant spectrum from the interface suggests the formation of amorphous carbon while according spectrum is featureless in the melt reference. The peak located at 286eV is due to the transitions from core 1s state to the π* state followed by a broad peak which is associated to the transition from 1s to σ* state [22][23] . It is noted that spikey appearance might be due to partial radiation damages despite reduced operating voltage in STEM-EELS mode.…”

Unusual Competitive and Synergistic Effects of Graphite Nanoplates in Engine Oil on the Tribofilm Formation

“…The electron energy loss spectroscopy (EELS) spectrum of the carbon K‐edge (Figure b) taken from the boxed region in Figure a, confirms the presence of carbon and permits its bonding state to be assessed. The carbon K‐edge comprises a sharp peak at around 285.5 eV (π*) followed by a broad peak ranging from 290 to 300 eV (σ*), which is explained to be the transition from the core 1s state to the π* state and σ* state, respectively . In Figure b, the ratio of I π* /( I π* + I σ* ) is found to be 0.094 with the relative sp 2 bonding fraction as 32%, which indicates the dominant sp 3 coordination of carbon within the amorphous polyphosphate tribofilm matrix.…”

Electron beam induced radiation damage in the catalyst layer of a proton exchange membrane fuel cell

“…An EELS spectrum including the zero‐loss peak is also included in Figure b for the reader to have an idea of the sample thickness. The reason we believe that the 6 eV transition peak in the low loss EELS spectrum is a fingerprint for Nafion is based on the fact that the other two components in our sample do not have this characteristic peak according to their existing low loss EELS spectra (Ahn et al ; Murooka et al ).…”