Effect of Power Density on the Electrochemical Properties of Undoped Amorphous Carbon (a‐C) Thin Films

Abstract

Undoped a‐C thin films were deposited with varying power density from 10 to 25 W/cm2 using unbalanced closed‐field magnetron sputtering (CFUBMS). The effect of power density on the physical and electrochemical properties was investigated by experimental characterization methods and atomistic simulations. XPS indicated that the films were composed mostly of sp2‐bonded carbon (55–58 at.%) with a small amount of oxygen (8–9 at.%) in the surface region. The films appeared completely amorphous in XRD. The ID/IG ratio obtained by Raman spectroscopy indicated an increase from 1.76 to 2.34 with power density. The experimental and simulated data suggested a possible ordering and/or clustering of the sp2 phase with power density as the cause of the improved electrical properties of the a‐C films. The electrochemical properties of a‐C were between those of glassy carbon and tetrahedral amorphous carbon with potential windows ranging from 2.77 to 2.93 V and double‐layer capacitance values around 0.90 μF cm−2. Electron transfer for Ru(NH3)63+/2+ and FcMeOH+1/0 was reversible whereas that for IrCl62−/3− was quasi‐reversible. Peak potential separation of dopamine and oxidation potential of ascorbic acid decreased with power density, correlating with the structural and electrical changes of the films. The a‐C thin films deposited by CFUBMS are inherently conductive and their physical properties can be adjusted by varying the deposition parameters to a wide range of electrochemical applications.

Trends in Carbon, Oxygen, and Nitrogen Core in the X-ray Absorption Spectroscopy of Carbon Nanomaterials: A Guide for the Perplexed

“…A 60 μL drop of this solution was then drop cast on a Si substrate and dried overnight. A 200 nm thick a-C layer was deposited by closed-field unbalanced magnetron sputtering (CFUBMS) as described in refs and . Seven nanometer thick tetrahedral a-C (ta-C) samples were deposited using a pulsed filtered cathodic vacuum arc (p-FCVA).…”

Gaussian Process Regression for Materials and Molecules

“… 268 Another study included the generation of many individual a-C model structures by GAP-driven quenching and a subsequent link to experimental properties. 269 A computational study of plasticity in large structural models of a-C, again using a combination of GAP and a faster empirical potential, was reported in ref ( 270 ).…”

“…A detailed study of structural and elastic properties of different a-C networks, obtained by quenching, was carried out by Jana et al, who compared simulations using an existing empirical potential with simulations using the C-GAP-17 model . Another study included the generation of many individual a-C model structures by GAP-driven quenching and a subsequent link to experimental properties . A computational study of plasticity in large structural models of a-C, again using a combination of GAP and a faster empirical potential, was reported in ref .…”

“…268 Another study included the generation of many individual a-C model structures by GAP-driven quenching and a subsequent link to experimental properties. 269 A computational study of plasticity in large structural models of a-C, again using a combination of GAP and a faster empirical potential, was reported in ref 270. Another direction in the atomistic modeling of carbon materials is the thermal annealing of more disordered structures to gradually generate more ordered ones, following an early study in 2009 that used C-EDIP.…”

Room‐Temperature Micropillar Growth of Lithium–Titanate–Carbon Composite Structures by Self‐Biased Direct Current Magnetron Sputtering for Lithium Ion Microbatteries

“…GIXRD was carried out (Figure b) to identify phases present in the LTO‐C pillars. Silicon wafer diffraction peaks have been documented in the same GIXRD setup in previous work . The scan shown in Figure b indicates the presence of multiple Li 2 O–TiO 2 phases at 18.5° 2θ, likely a mix of β‐Li 2 TiO 3 (COD 96‐151‐5996) and Li 4 Ti 5 O 12 (96‐100‐1099).…”