Carbon Thin Films Research Articles

Suppression of Transition Metal Dissolution in Mn-Rich LayeredOxide Cathodes with Graphene Nanocomposite Dry Coatings

Abstract The growing demand for lithium-ion batteries (LIBs) and the reliance on scarce metals in cathode active materials (CAMs) have prompted a search for sustainable alternatives. However, the performance of Mn-rich CAMs formulated with less Co suffer from transition metal dissolution (TMD).
TMD can be suppressed by applying a thin film of carbon or oxide to the CAM but the assumed need for a continuous film necessitates bottom-up coating methods. This has been a challenge for LIB production as well as limiting material choices. Here we show that particulate coatings can also suppress TMD, allowing for scalable, material-independent, dry coating methods. Dry coating the Mn-rich CAM surfaces with graphene encapsulated nanoparticles (GEN) (1 wt\%) suppresses TMD while nearly doubling the cycle life and improving rate capacities up to 42\% under stressful conditions. The ability to suppress TMD is attributed to the unique chemical and electronic properties of the GEN produced by plasma enhanced chemical vapor deposition. The method is general and could provide a scalable path to CAM with less Co.

Development of smart molecularly imprinted tetrahedral amorphous carbon thin films for in vitro dopamine sensing

This study investigates how varying the thickness of tetrahedral amorphous carbon (ta-C) thin films and incorporating a titanium adhesion layer influences the structural and electrochemical properties of molecularly imprinted ta-C thin film-based sensing platforms, aiming to develop a molecularly imprinted ta-C electrochemical sensor for dopamine (DA) detection with physiologically relevant sensitivity. This electrochemical sensing platform was designed by integrating ta-C with molecularly imprinted polymers (MIPs). The process involved depositing a ta-C thin film onto boron-doped p-type silicon wafers through a filtered cathodic vacuum arc (FCVA) system. Subsequently, the ta-C sensing platforms were electrochemically coated with the MIP layer (DA-imprinted polypyrrole). We evaluated three configurations: (i) a 15 nm ta-C layer, (ii) a 7 nm ta-C layer with a 20 nm titanium adhesion layer, and (iii) a 15 nm ta-C layer with a 20 nm titanium adhesion layer. Comprehensive structural and electrochemical characterization was performed to understand how these modifications affect sensor performance. The optimized MIP/ta-C sensor demonstrated a sensitivity of 0.16 μA μM−1 cm−2 and a limit of detection (LOD) of 48.6 nM, suitable for detecting DA at physiological levels. Leveraging the synergistic effects of ta-C coatings and molecular imprinting, as well as its compatibility with common complementary metal–oxide–semiconductor (CMOS) processes underlines its potential for integration into microanalytical systems, paving the way for miniaturized and high-throughput sensing platforms.

Influence of carbon ionization increment by adding ne on the bonding, electrical, and tribological properties of carbon thin films deposited by HiPIMS

In this work, we use mass quadrupole spectroscopy to analyze the ion energy distribution function for C+ ions from different gas composition discharges (20, 40, 60, 80, and 90% Ne) + Ar in a plasma sputtering process. Carbon films were obtained for each gas composition discharge. The carbon bonding structure of films was analyzed by Raman spectroscopy using deconvolution fitting of the G and D Raman peaks. The C-sp3 content was correlated with the electrical and tribological properties of the carbon films. Our results further corroborate the enhancement of carbon ionization in HiPIMS processes by adding neon in conventional argon gas during the deposition process. Furthermore, we found that excessive levels of carbon ionization were detrimental in the formation of C-sp3 decreasing the resistivity, and indicating the decrement of the elastic modulus of the samples. In addition, the use of neon in the gas working mixture increased the deposition rate significantly compared to argon-only processes from 1.7 to 3.22 nm/min for the highest deposition rate cases. Tribology showed that an intermediate C-sp3 content in the carbon films developed desirable tribological behaviors with lower friction coefficients and wear rates, revealing that higher values of C-sp3 content are not necessarily for robust solid lubricious and wear resistance.

Synergistic effect of synthesized green nanocomposite of chitosan-activated carbon thin film (ACTF)@opuntia ficus-indica shell for removal of Sn (II) and As (V) ions from aqueous solution

Synergistic effect of synthesized green nanocomposite of chitosan-activated carbon thin film (ACTF)@opuntia ficus-indica shell for removal of Sn (II) and As (V) ions from aqueous solution

Influence of the Metallic Sublayer on Corrosion Resistance in Hanks' Solution of 316L Stainless Steel Coated with Diamond-like Carbon.

The purpose of the study was to ascertain the corrosion resistance in Hanks' solution of Cr-Ni-Mo stainless steel (AISI 316L) coated with diamond-like carbon (DLC) coatings to establish its suitability for biomedical applications, e.g., as temporary implants. The influence of the carbon coating thickness as well as the correlated effect of the metallic sublayer type and defects present in DLC films on corrosion propagation were discussed. The results obtained were compared with findings on the adhesion of DLC to the steel substrate. The synthesis of carbon thin films with Cr and Ti adhesive sublayers was performed using a combined DC and a high-power-impulse vacuum-arc process. Evaluation of the corrosion resistance was carried out by means of potentiodynamic polarisation tests and scanning electron microscopy. Adhesive properties of the sublayer/DLC coating systems were measured using a scratch tester. It was found that systems with Ti sublayers were less susceptible to the corrosion processes, particularly to pitting. The best anti-corrosion properties were obtained by merging Ti with a DLC coating with a thickness equal to 0.5 μm. The protective properties of the Cr/DLC systems were independent of the carbon coating thickness. On the other hand, the DLC coatings with the Cr sublayer showed better adhesion to the substrate.

Impact of Diamond-like Carbon Films on Reverse Torque: Superior Performance in Implant Abutments with Internal Conical Connections

The loosening or fracture of the prosthetic abutment screw is the most frequently reported complication in implant dentistry. Thin diamond-like carbon (DLC) films offer a low friction coefficient and high wear resistance, functioning as a solid lubricant to prevent the weakening of the implant–abutment system. This study evaluated the effects of DLC nanofilms on the reverse torque of prosthetic abutments after simulated chewing. Abutments with 8° and 11° taper connections, with and without DLC or silver-doped DLC coatings, were tested. The films were deposited through the plasma enhanced chemical vapor deposition process. After two million cycles of mechanical loading, reverse torque was measured. Analyses with scanning electron microscopy were conducted on three samples of each group before and after mechanical cycling to verify the adaptation of the abutments. Tribology, Raman and energy-dispersive spectroscopy analyses were performed. All groups showed a reduction in insertion torque, except the DLC-coated 8° abutments, which demonstrated increased reverse torque. The 11° taper groups experienced the most torque loss. The nanofilm had no significant effect on maintaining insertion torque, except for the DLC8 group, which showed improved performance.

Corrosion-Resistant Ultrathin Cu Film Deposited on N-Doped Amorphous Carbon Film Substrate and Its Use for Crumpleable Circuit Board.

Copper (Cu) is widely used as an industrial electrode due to its high electrical conductivity, mechanical properties, and cost-effectiveness. However, Cu is susceptible to corrosion, which degrades device performance over time. Although various methods (alloying, physical passivation, surface treatment, etc.) are introduced to address the corrosion issue, they can cause decreased conductivity or vertical insulation. Here, using the nitrogen-doped amorphous carbon (a-C:N) thin film is proposed as a substrate on which Cu is directly deposited. This simple method significantly inhibits corrosion of ultrathin Cu (<20nm) films in humid conditions, enabling the fabrication of ultrathin electronic circuit boards without corrosion under ambient conditions. This study investigates the origin of corrosion resistance through comprehensive microscopic/spectroscopic characterizations and density-functional theory (DFT) calculations: i) diffusion of Cu atoms into the a-C:N driven by stable C-Cu-N bond formation, ii) diffusion of N atoms from the a-C:N to the Cu layer heading the top surface, which is the thermodynamically preferred location for N, and iii) the doped N atoms in Cu layer suppress the inclusion of O into the Cu lattice. By leveraging the ultrathinness and deformability of the circuit board, a transparent electrode and a crumpleable LED lighting device are demonstrated.

Boron-doped carbon nano dot anchored thin film coating on cobalt vanadium oxide for ultrafast energy storage devices

Lithium-ion capacitors (LICs) with ultrafast rate capabilities are required to increase the applicability of rechargeable energy storage devices. Considering that the power density of an LIC is primarily determined by the anode properties, carbon coating onto the anode material is a promising method of accelerating electron transfer between particles and alleviating structural collapse during repeated charge–discharge cycles. In this study, a new coating configuration featuring a boron-doped carbon nano dot-anchored thin film on cobalt vanadium oxide (BC-CVO) was demonstrated. The coating morphology, wherein the carbon nano dots were connected by a thin carbon film, induced nano-scale surface roughness on CVO, expanding the contact area between the functional groups on the coating layer and electrolyte. The boron-doped carbon lattice structure provided ultrafast electron transfer inside the CVO particles, which allowed reversible electron transfer even under ultrafast charge–discharge cycles. This morphological and chemical combination significantly improved the ultrafast-rate capability of the LIC anodes (429.6 mAh/g at 4000 mA/g and 534.3 mAh/g after 1000 cycles at 2000 mAh/g) compared to that of bare CVO. Furthermore, an LIC full cell fabricated with a BC-CVO anode and an activated carbon cathode showed high energy and power densities.

Carbon Thin-Film Electrodes as High-Performing Substrates for Correlative Single Entity Electrochemistry.

Correlative methods to characterize single entities by electrochemistry and microscopy/spectroscopy are increasingly needed to elucidate structure-function relationships of nanomaterials. However, the technical constraints often differ depending on the characterization techniques to be applied in combination. One of the cornerstones of correlative single-entity electrochemistry (SEE) is the substrate, which needs to achieve a high conductivity, low roughness, and electrochemical inertness. This work shows that graphitized sputtered carbon thin films constitute excellent electrodes for SEE while enabling characterization with scanning probe, optical, electron, and X-ray microscopies. Three different correlative SEE experiments using nanoparticles, nanocubes, and 2D Ti3C2Tx MXene materials are reported to illustrate the potential of using carbon thin film substrates for SEE characterization. The advantages and unique capabilities of SEE correlative strategies are further demonstrated by showing that electrochemically oxidized Ti3C2Tx MXene display changes in chemical bonding and electrolyte ion distribution.

Metal Acetylene Dicarboxylates as Catalyst for Printable Low Temperature Carbon Precursors

The synthesis of various metal acetylene dicarboxylates (MxADC, M = Cu, Ag, Fe, Co, Ni) via new methods are reported. The previously unknown crystal structures for Ag2ADC and FeADC are presented. The behaviour of the different metal dicarboxylates and their role as graphitization catalysts in a printable highly energetic carbon precursor is investigated in detail. Despite the copper compound has the lowest decomposition temperature of all studied acetylene dicarboxylates and is significantly enhancing the conductivity of carbon thin films obtained at low pyrolysis temperatures, the catalytic effect of cobalt and iron on graphitizing carbon results in a superior conductivity in carbon thin films pyrolyzed at lower temperatures down to 600°C. The newly designed precursors are demonstrated to produce micro‐supercapacitors with a 3D‐piezoelectric inkjet technique at low pyrolysis temperature.

Operando Stress Evolution in Hard Carbon Anodes – Insight into the Mechanical Degradation Induced Failure Mode in Rechargeable Sodium Ion Batteries

Microstructural instabilities in electrodes arising from cycling induced stress is a primary failure mode in rechargeable batteries. Therefore, a quantitative knowledge of the cycling induced stress evolution in rechargeable battery electrodes is important for understanding the electrode microstructural instabilities during cycling that can potentially inform the electrode design to prolong battery cycle life. The cycling induced stress in electrodes typically arises from the volume changes associated with insertion/extraction of the electroactive species in the electrode matrix. For example, operando measurement of lithiation-delithiation induced stress in graphite electrodes that typically show 10% volume change has previously resulted in useful information that correlates well with the lithiation-delithiation mechanism in graphite anodes1. The size of the shuttling-electroactive species can be taken as an indicator of the cycling induced stress magnitude that drives the electrode microstructural instabilities. In this regard, quantification of the cycling induced stress in rechargeable Na-ion battery electrodes is warranted for understanding mechanical degradation induced failure modes owing to the larger size of the electroactive species, i.e., Na ions (vs. Li-ion).Hard carbons as potential anodes in rechargeable sodium ion batteries has gained considerable attention in the recent past due to their superior Na-ion storage capability (vs. graphite that is a canonical anode in rechargeable lithium-ion batteries). However, hard carbon anodes typically show significant capacity fade that can potentially arise from cycling induced mechanical degradation of the anodes. Operando stress measurements coupled with comprehensive electrode microstructural characterization will provide valuable insights in this context. Here we report on the operando stress evolution in hard carbon anodes in rechargeable sodium ion batteries as probed by Multiple Optical-beam Sensing (MOS) technique that basically involves monitoring the spacings among a group of laser spot (Fig. 1). Preliminary measurements have shown that the stress correlates with the potential with a maximum around 12 MPa in compression during sodiation and tensile stress of ~ 2MPa during desodiation. Operando stress measurements are performed in hard carbon anodes in two different electrode configurations – typical composite anodes (with binder and conductive agents) and hard carbon thin film anodes (without binder and conductive agents). The thin film configuration is considered to evaluate intrinsic stress response in hard carbon anodes in absence of any secondary phase. A comparison of operando stress response in these two types of hard carbon anodes along with comprehensive electrode microstructural characterization will be presented. Additionally, attempts will be made to shed light on the current debate in the mechanism of sodium storage in hard carbon anodes by comparing operando stress response of hard carbons from multiple sources along with their structural characterization (Raman, XPS, surface area etc.). V. A. Sethuraman, N. Van Winkle, D. P. Abraham, A. F. Bower, and P. R. Guduru, Journal of Power Sources, 206, 334–342 (2012). Figure 1

Renewable symmetric supercapacitors assembled with lignin nanoparticles-based thin film electrolyte and carbon aerogel electrodes

Lignin as a natural biopolymer is becoming increasingly in demand due to its eco-friendly properties, while lignin-based electrolyte with high conductivity and reliable durability for applications in supercapacitors is still challenging. Herein, a facile method to prepare lignin nanoparticles (LNPs)-based solid electrolyte thin film (LF) was proposed through chemical cross-linking reaction. The fabricated LF exhibited a distinctive spongy porous structure with the ionic conductivity of 3.26 mS cm−1, demonstrating the exceptional flexibility and favorable mechanical properties. Moreover, the assembly of all-LNPs-based symmetric supercapacitor (SSC) devices was achieved using LF electrolyte and LCA electrodes for the first time, confirming the LF3 electrolyte superior to commercial cellulose separator in capacitive behaviour. This SSC device exhibited a specific capacitance of 122.7 F g−1 at 0.5 A g−1 and the maximum energy density of 17.04 W h kg−1. Furthermore, the incorporation of sodium alginate (SA) significantly enhanced the ionic conductivity of SA/LF3 electrolyte, and the resulting SSC device delivered a higher specific capacitance of 174.5 F g−1 at 0.5 A g−1 and the maximum energy and power densities of 24.24 W h kg−1 and 5023 W kg−1, respectively. This study proposes a promising approach for sustainable utilization of lignin in energy storage applications.

Contact fatigue of thin hard diamond-like carbon films on M50 steels under cyclic spherical micro-indentation

Contact fatigue behaviors of thin hard diamond-like carbon (DLC) films on M50 steels during cyclic spherical micro-indentations were investigated. The stress-strain evolution of the entire system was analyzed by finite element methods. The film fracture mechanisms and interfacial bearing responses under monotonic and repeated contacts were comprehensively explored. Concentrated tensile and shear stresses were found to, respectively, govern the initiation and propagation of the surface ring cracks. Elevated tensile stresses at the initiation and epilogue of each indentation cycle enhanced bottom radial cracking. At the interfaces, the maximum tensile (σnmax) and shear (σtmax) stresses occurred at the end of unloading and loading processes, respectively. With increasing maximum indentation forces, σnmax initially increased and then gradually decreased, while σtmax increased monotonically.

Fabrication of device equipped with rope-like axon bundles by diamond-like carbon thin film patterning deposition

The aim of this research is to fabricate plane-type devices possessing straight longer axons individually and regularly arrayed for evaluating the axon behavior of neuronal cells in vitro toward the development of brain-on-chip models, utilizing diamond-like carbon (DLC) thin film patterning deposition. The DLC thin films were deposited on a polydimethylsiloxane (PDMS) plate with a plasma CVD method under four conditions, with/without stretching of and a metal mask on the plate, and the fabricated substrates were used to culture human neuroblastoma cells, SH-SY5Y, for up to 21 days. In the case of the stretched PDMS plate with the mask covered, extremely peculiar structures were created on the DLC deposited areas of the substrate, with multiple 20 μm-thick rope-like axons aligned straight at the length of millimeter-level at intervals of about 200 μm. It was found that the rope-like axons consisted of plenty of thinner axons, and were supported by the clusters of cells at both ends. It was strongly suggested that the linear wrinkle structures created by the DLC deposition played an important role in the formation of the rope-like axons. This device can be fabricated by means of not conventional lithographic techniques, but only DLC thin film deposition.

Structuring of the Surface of Thin Carbon Films During Activation by Microsecond Current Pulses

The influence of current activation by electric pulse breakdown on changes in surface morphology and emission characteristics of a field emission cathode made on the basis of carbon films obtained by deposition in a microwave gas discharge plasma was studied. Current activation of these films was carried out by applying voltage pulses of microsecond duration until an electrical breakdown occurred. It is shown that during activation, the morphology of the film surface in the breakdown region changes with the formation of a micro-sized emitting structure, which significantly improves the field emission characteristics of cathodes based on carbon films.

Antiviral and antibacterial efficacy of nanocomposite amorphous carbon films with copper nanoparticles

Copper compound-rich films and coatings are effective against widespread viruses and bacteria. Even though the killing mechanisms are still debated, it is agreed that the metal ion, nanoparticle release, and surface effects are of paramount importance to the antiviral and antibacterial efficacy of the surfaces. In this work we have investigated the behavior of the reactive magnetron sputtered nanocomposite diamond-like carbon thin films with copper nanoparticles (DLC:Cu). The films were etched employing oxygen plasma and/or exposed to ultra-pure water, aiming to investigate the differences of the Cu release in the medium and changes in film morphology. The presence of metallic copper and Cu2O phases was confirmed by multiple analytical methods. Pristine films were more effective in the Cu release reaching up to 1.3 mg/L/cm2 concentration. Plasma processing resulted in the oxidation of the films which released less Cu, but after exposure to water, their average roughness increased more, up to 5.5 nm. Pristine and O2 plasma processed DLC:Cu films were effective against both model coronavirus and herpesvirus after 1-hour contact time and reached virus reductions of up to 2.23 and 1.63 log10, respectively. Pristine DLC:Cu films were more effective than plasma-processed ones against herpesvirus, while less expressed difference was found for coronavirus. The virucidal efficacy over up to 24 h exposures in the aqueous medium was validated. A bactericidal study confirmed that pristine DLC:Cu films were effective against gram-negative E. coli and gram-positive E. faecalis bacteria. After 3 h, 100 % antibacterial efficiency (ABE) was obtained for E. coli and 99.97 % for E. faecalis. After 8 h and longer exposures, 100 % ABE was reached. The half-life inactivation of viruses was 8.10–11.08 min and for E. faecalis 15.1–72.2 min.

Thermal and Electrical Properties Depending on the Bonding Structure of Amorphous Carbon Thin Films

Thermal and Electrical Properties Depending on the Bonding Structure of Amorphous Carbon Thin Films

Polymer-like hydrogenated amorphous carbon thin films fabricated by plasma-enhanced chemical vapor deposition of cyclohexane precursor

Hydrogenated amorphous carbon (a-C:H) films were fabricated by plasma-enhanced chemical vapor deposition (PECVD) of a cyclohexane precursor at ambient temperature at varying deposition pressures from 19.73 to 38.00 Pa and varying plasma powers from 20 to 80 W. The deposition rate of the a-C:H films was strongly dependent on the deposition conditions. The films were all optically transparent with extinction coefficient below 0.0042. The refractive index as an indicator of the film's density varied depending on the deposition conditions. Their surfaces were all hydrophobic regardless of the deposition conditions. The a-C:H films had wide optical bandgaps ranging from 3.09 to 3.69 eV. The refractive index and FTIR spectra were consistent with those of polymer-like a-C:H films. As the deposition pressure decreased and plasma power increased, the intensity of a dominant peak of CHx stretching mode in the FTIR spectra decreased. The relative hydrogen content of the a-C:H films was estimated from an FTIR analysis and determined to have an inverse relationship with refractive index. These results indicated that the formation of more energetic plasmas during deposition at lower pressures and higher plasma powers led to the a-C:H films with reduced hydrogen content and increased density. The observed film properties could be advantageous for several applications, particularly as protective, wear-resistant, low-friction, or anti-reflective coatings for optical windows.

Synthesis, characterization, and application of PVDF-PZT composite thin film separator for self-charging supercapacitors

This work utilizes a simple ball milling and heating process to synthesize lead zirconium titanate (PZT). The thin film PVDF-PZT separator is fabricated with the use of dimethyl sulfoxide (DMSO) solvent. The separator's characterization is accomplished by using conventional characterization tools to examine its crystallinity, morphology, chemical composition, and other parameters. According to X-ray diffraction (XRD), Energy dispersive spectroscopy (EDS), and Elemental mapping, the separator is extremely pure and free of any impurities. The separator's surface is found to be uniform with minimal porosity. An analysis of the application of the fabricated thin film separator in a supercapacitor is conducted by placing it in between the previously prepared carbon and NiO thin film electrodes. Upon bending, twisting, and applying force, the device displayed output voltage. Twisting results in a maximum output potential of 140 mV, which is higher than some previously reported works. The results show that the PVDF-PZT thin film separator could potentially be utilized in self-charging supercapacitor applications.

Enhancing sp3 content in diamond-like carbon thin film electrodes by pulsed laser annealing for durable charge storage performance

In this work, diamond-like carbon (DLC) thin film electrodes were grown on Si substrate by pulsed laser deposition (PLD) technique, and the implication of pulsed laser annealing (PLA) treatment on their electrochemical supercapacitor performance was examined by three electrode systems in 1 M Na2SO4 electrolyte solutions. The SEM micrographs exhibit a sheet-like wrinkled surface of DLC film on Si which later transformed into tiny hierarchical heap-like structures with enhanced surface roughness. The Raman spectra confirm signature of the D and G peaks of pristine DLC film at ∼1352 cm−1 (1356 cm−1 after PLA) and 1591 cm−1 (1589 cm−1 after PLA), and appearance of minor T2g (diamond) (1332 cm−1) peaks with an increment of the sp3 content after PLA treatment. The X-ray photoelectron spectroscopy (XPS) spectra were deconvoluted into three different contributions CC (sp2), CC (sp3), and CO, and their sp3 percentages were estimated ∼48.9 %, and 64.7 % before and after annealing. The area under cyclic voltammetry (CV) curve and galvanostatic charging discharging (GCD) performance of PLA-treated DLC film were improved and the highest areal-specific capacitance was obtained to be ∼48.25 mF/cm2 for scan rate of 5 mV/s and 36.01 mF/cm2 for current density of 2 mA/cm2, respectively. Excellent charging discharging cyclic stability of PLA treated electrode was observed over 5000 cycles, and Coulombic efficiency and capacitance retention were determined to be ∼93.5 % and ∼ 97.3 %, respectively. The electrochemical impedance spectroscopy (EIS) was performed to obtain the Nyquist plot (Z′vs.Z′′) of both electrodes before and after the stability test, and a small degradation in impedance was observed. The Nyquist plots were fitted with the well-known Randles equivalent circuit model Rs(Cdl(RctZw)) and substantial curtailment of Warburg resistance (Zw) in PLA-induced DLC electrode signifies the dominance of the diffusion-controlled region in the charging-discharging process. Minor changes in the Nyquist plot before and after the stability test manifest the enduring charge kinetics of both electrodes and PLA-treated DLC exhibits better cyclic stability. PLA techniques have a great impact on upgrading the areal-specific capacitance, capacitance retention with high Coulombic efficiency, and stability with negligible impedance loss of the DLC film electrodes.