Electron-energy-loss characterization of laser-depositeda-C,a-C:H, and diamond films

Abstract

Electron-energy-loss spectroscopy has been used to identify microcrystalline diamond films produced by laser ablation of graphite. The production of the diamond phase results from varying the deposition geometry and parameters from those of an earlier configuration that produced diamondlike carbon films. A complete study of these crystalline and amorphous materials indicates a plasmon energy variation for films produced in different environments.Spectra taken with different primary energies show variation in the plasmon energy in hydrogenated carbon films. These changes were interpreted as a variation in the bonding nature of the sample with depth. The spectra of all samples were analyzed to determine sp /sp +sp fraction, dielectric functions, and optical band gap.

Structural properties of highly conductive ultra-nanocrystalline diamond films grown by hot-filament CVD

“…Notably, while the core-loss EELS spectrum shows different feature for diamond (σ * -band near 289.5 eV) and the sp 2 -bonded carbon (π * -band near 284.5 eV), it is the plasmon-loss EELS spectrum, which can unambiguously differentiate the a-C (the noncrystalline sp 2 -bonded carbon) and the graphite phases (the crystalline sp 2 -bonded carbon) in sp 2 -bonded carbon. [19][20][21][22] In plasmon-loss EELS spectrum, a-C phase exhibits a peak near 22 eV (ω a -band), whereas the graphite phase shows a peak near 27 eV (ω g -band). [19][20][21][22] In contrast, the diamond phase exhibits a peak at 33 eV (ω d2 -band) corresponding to bulk plasmon with a shoulder at 23 eV (ω d1 -band) corresponding to surface plasmon and the ω d1 /ω d2 peak ratio is ∼1/ √ 2.…”

“…[19][20][21][22] In plasmon-loss EELS spectrum, a-C phase exhibits a peak near 22 eV (ω a -band), whereas the graphite phase shows a peak near 27 eV (ω g -band). [19][20][21][22] In contrast, the diamond phase exhibits a peak at 33 eV (ω d2 -band) corresponding to bulk plasmon with a shoulder at 23 eV (ω d1 -band) corresponding to surface plasmon and the ω d1 /ω d2 peak ratio is ∼1/ √ 2. [19][20][21][22] The core-loss EELS spectrum of highly conducting nanocrystalline diamond films ( figure 6(a)) exhibits an abrupt rise near ∼289.5 eV (σ * -band) and a deep valley near 302 eV with a smaller peak near ∼284.5 eV (π * -band).…”

“…[19][20][21][22] In contrast, the diamond phase exhibits a peak at 33 eV (ω d2 -band) corresponding to bulk plasmon with a shoulder at 23 eV (ω d1 -band) corresponding to surface plasmon and the ω d1 /ω d2 peak ratio is ∼1/ √ 2. [19][20][21][22] The core-loss EELS spectrum of highly conducting nanocrystalline diamond films ( figure 6(a)) exhibits an abrupt rise near ∼289.5 eV (σ * -band) and a deep valley near 302 eV with a smaller peak near ∼284.5 eV (π * -band). These bands indicate the presence of predominantly sp 3 -bonded carbon, the diamond, along with some proportion of sp 2 -bonded carbon.…”

Pulsed laser deposited tetrahedral amorphous carbon with high sp3 fractions and low optical bandgaps

“…To understand the growth mechanism, the dynamics of a confined carbon plume ablated using a laser from a graphite target was studied using optical emission spectroscopy and ultrafast charge-coupled device imaging. 6 Amorphous carbon films deposited using PLD have been studied using electron energy loss spectroscopy ͑EELS͒ to provide information about their sp 2 fraction and their density 7 with the degree of sp 2 clustering obtained from Raman spectroscopy. 8 The concentration and the chemical bonding in the films based on x-ray photoelectron spectroscopy have also been reported.…”

Vertically aligned diamond-graphite hybrid nanorod arrays with superior field electron emission properties

“…Both carbon K-edge spectra exhibit a typical EELS spectrum of diamond with an Fd3m structure for DGH nanorods, as they contain an abrupt rise in σ*-band (near 290 eV) and a large valley near 302 eV. 44,45 Moreover, there presence a small hump near 284.5 eV (π*-band). Such an observation revealed the existence of a significant proportion of sp 2 phases at the top portion and at the grain boundaries of the DGH nanorods, which is in accord with the Raman studies of patterned DGH nanorods [spectrum I of Fig.…”