Doped Amorphous Carbon Research Articles

Low cycle fatigue of doped tetrahedral amorphous carbon coatings by repetitive micro scratch tests

In contrast to the conventional progressive scratch testing where load is increased up to a critical damage level, the repetitive scratch testing is an assessment of coating behavior under repeatedly applied subcritical load. It often represents a better approximation to actual application conditions of well-designed coating systems where overcritical conditions typically do not occur. In this work, the cyclic micro scratch behavior of differently doped amorphous carbon coatings with similar coating thicknesses were studied using repetitive scratch tests at loads that correspond to 40 %, 60 % and 80 % of the critical loads from progressive scratch testing. Depending on the doping element, the structural and mechanical properties changed, in some cases considerably, which also had a clear effect on the test results. The damage progression was examined using optical microscopy, friction coefficient, and residual depth measurements. The progression of failure phenomena was categorized into different stages. Furthermore, the critical number of cycles for coating failure was recorded at the various load levels. For the identification of the critical cycles, the use of the deviation of the friction coefficient from its mean value has proven to be a valuable parameter. The approach of testing at different load levels allows the creation of low cycle fatigue curves to evaluate the coating behavior. It was found that the hardness and residual stresses of the coatings had different effects on the lifetime of the coatings at the various load levels, i.e. higher hardness and residual compressive stresses were only beneficial for moderate stress levels with low plastic substrate deformation. The results demonstrate that the cyclic scratch test is a powerful tool for comparative damage assessment at different load scenarios.

Characteristics of Palladium Doped Amorphous Carbon Films Fabricated by Unbalanced Magnetron Sputtering System

Generally, hydrogenated amorphous carbon (a-C:H) has been shown to have a low friction coefficient, high hardness, and low abrasive wear rate. In this study, Pd doped hydrogenated amorphous carbon (a-C:H:Pd) fabricated by the closed-field unbalanced magnetron sputtering (CFUBMS) system with two targets of carbon and palladium in Ar/C2H2 plasma. The tribological and lubricant characteristics for a-C:H:Pd fabricated with various DC bias voltage from 0 to −200 V were investigated. We obtained a hardness up to 27.5 GPa and friction coefficient lower than 0.1. The atomic percentage of Pd related to the lubricant properties increased up to 22% at −200 V. In the results, the Pd doping in the a-C:H films improved the tribological and lubricant properties. The friction coefficient value of a-C:H:Pd films was decreased, the hardness and elastic modulus were increased, and also the adhesion properties was improved with the increase of negative DC bias voltage.

Hierarchical Self‐Supported Carbon Nanostructure Enables Superior Stability of Highly Nitrogen‐Doped anodes

AbstractAs the primary anode for both lithium‐ and sodium‐ion batteries, carbonaceous anodes store more energy and own a higher rate capacity through nitrogen doping. Nevertheless, achieving a high nitrogen content in a carbonaceous anode is challenging because it tends to result in anode instability, owing to high‐level structural defects. Here, by doping biotic ispaghula with nitrogen from melamine through hydrothermal and carbonization treatments, we design and prepare a nitrogen‐enriched carbonaceous anode with a record‐high 30 % nitrogen content primarily in pyridinic and pyrrolic forms. The anode owns a self‐supported architecture that contains a highly‐defected (ID : IG=1.34) nanosheet structure sandwiched and supported with carbon nanospheres. Through surface defects, Li and Na ions are stored and transported efficiently in both highly doped graphitic carbon and amorphous carbon. In situ Raman spectroscopy reveals that amorphous carbon can be crystallized in the Li storage process to contribute reversible capacity. The highly doped anode delivers capacities of 551 mAh g−1 for 500 cycles for lithium storage and 278 mAh g−1 for 2000 cycles of sodium storage at a current density of 1 A g−1, surpassing those of the‐state‐of‐the‐art at an identical current density and with the same cycle number.

Electrical Characterization of N- and B- Doped Amorphous Carbon Film from Palmyra Sugar

Structure of amorphous carbon can be composed of sp2 (graphite), or sp3 (diamond), or a combination of both, depending on their fractions. Therefore, many researchers were exploring to use it as solar cell material. This research used the amorphous carbon of bio-product as a basic material in the form of palmyra sugar which was synthesized through the heating and doping process to produce n-type and p-type semiconductors. This research aims to analyze the effect of dopant and deposition time on electrical properties. The heating process was carried out at 250°C and the doping process was carried out by adding NH4OH for a-C:N and H3BO3 for a-C:B. The deposition process was carried out by the nano-spray method using a variety of deposition time on the ITO substrate. The result of scanning electron microscopy (SEM) showed that the film thickness increased with the increase of deposition time. Besides, the result of four-point probe (FPP) showed that the dopant can increase electrical conductivity, but the film thickness did not influence it. The electrical conductivity obtained was 5x10-1 - 6x10-1 S/cm. And the result of further analysis, it can be concluded that electrical conductivity was still in the range of semiconducting material.

Structure and mechanical properties of Ni and Cr binary doped amorphous carbon coatings deposited by magnetron sputtering and pulse cathodic arc

This paper studies the structure and mechanical properties of amorphous carbon coatings (a-C) modified by Ni and Cr binary doping. The a-C:(Nix+Cry) coatings were deposited using pulsed cathodic carbon arc technique with direct current magnetron sputtering.Microstructure, surface morphology and chemical composition of the a-C:(Nix+Cry) coatings were analyzed via Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy. Friction parameters of the coating were studied under the condition of dry sliding using a "sphere-plane" method. It has been established that the structure of binary doped coatings mainly consists of an amorphous carbon matrix, primarily with sp2 bonds, chromium carbide and nickel metal clusters. The dependence of the Сsp3/Сsp2 ratio and microhardness on the composition in the coating has been specified. The Ni/Cr ratio in the coating with the optimal content of Csp2 and C-Cr carbide phases resulting in a decrease in the wear rate of the counterbody has been determined. At the same time, binary doping of carbon coatings substantially changes in both the phase compositions and surface morphology, which leads to the stabilization of the friction coefficient and reduces the counterbody wear rate.

Ag Doped Amorphous Carbon Films: Structure, Mechanical and Electrical Behaviors

Ag Doped Amorphous Carbon Films: Structure, Mechanical and Electrical Behaviors

Formation of a highly doped ultra-thin amorphous carbon layer by ion bombardment of graphene

Ion bombardment of graphene leads to the formation of defects which may be used to tune properties of the graphene based devices. In this work, however, we present that the presence of the graphene layer on a surface of a sample has a significant impact on the ion bombardment process: broken sp2 bonds react with the incoming ions and trap them close to the surface of the sample, preventing a standard ion implantation. For an ion bombardment with a low impact energy and significant dose (in the range of 1014 atoms cm−2) an amorphization of the graphene layer is observed but at the same time, most of the incoming ions do not penetrate the sample but stop at the surface, thus forming a highly doped ultra-thin amorphous carbon layer. The effect may be used to create thin layers containing desired atoms if no other technique is available. This approach is particularly useful for secondary ion mass spectrometry where a high concentration of Cs at the surface of a sample significantly enhances the negative ionization probability, allowing it to reach better detection limits.

Hydrogenated nanostructure boron doped amorphous carbon films by DC bias

Hydrogenated nanostructure-boron doped amorphous carbon thin film carbon was deposited at different negative bias using custom-made deposition bias assisted-CVD. Solid of boron and palm oil were used as dopant and carbon source, respectively. The hydrogenated nanostructure amorphous films were characterized by Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, while the photo-response studies of thin film is done by I-V measurement under light measurement. The results showed the carbon film were in nanostructure with hydrogen and boron might be incorporated in the film. The Raman spectra observed the increase of upward shift of D and G peaks as negative bias increased which related to the structural change as boron incorporated in carbon network. These structural changes were further correlated with photo-response study and the results obtained are discussed and compared.

Unusual ZFC and FC magnetic behavior in thin Co multi-layered structure

The observation of unusual magnetic phenomena in a Ni -based magnetic memory device ([4] O. Ben-Dor et al., 2013) encouraged us to conduct a systematic research on Co based multi-layered structure which contains a α-helix L polyalanine (AHPA-L) organic compound. The constant Co thickness is 7nm and AHPA-L was also replaced by non-chiral 1-Decanethiol organic molecules. Both organic compounds were chemisorbed on gold by a thiol group. The dc magnetic field (H) was applied parallel and perpendicular to the surface layers. The perpendicular direction is the easy magnetization axis and along this orientation only, the zero-field-cooled (ZFC) plots exhibit a pronounced peak around 55–58K. This peak is suppressed in the second ZFC and field-cooled (FC) runs performed shortly after the virgin ZFC one. Thus, around the peak position ZFC>FC a phenomenon seldom observed. This peak reappears after measuring the same material six months later. This behavior appears in layers with the non-chiral 1-Decanethiol and it is very similar to that obtained in sulfur doped amorphous carbon. The peak origin and the peculiar ZFC>FC case are qualitatively explained.

Peculiar Magnetic Features and Superconductivity in Sulfur Doped Amorphous Carbon

We report on magnetic studies of inhomogeneous commercial and synthesized amorphous carbon (a-C) and a-C doped with sulfur (a-CS) powders which exhibit (i) peculiar magnetic behavior and (ii) traces of two superconducting (SC) phases TC ~ 33 and at 65 K. (i) The temperature dependence of zero-field-cooled (ZFC) curves measured up to room temperature show well distinguished elusive peaks at around 50–80 K, and their origin is not yet known. These peaks are totally washed-out in the second ZFC sweeps and in the FC branches as well. As a result, in the vicinity of the peaks, the FC curves lie below the ZFC peaks (FC < ZFC), a phenomenon which is rarely observed. These magnetic anomalies are intrinsic properties of a-C and a-CS materials (ii) SC was observed in three different a-C sources: (a) The commercial a-C powder contains 0.21% of sulfur and it is suggested that two different a-CS phases (at 33 and 65 K) are the origin of the two SC states observed. The compositions of these two phases are not yet unknown. The small SC volume fractions of the 33 K phase can be enhanced by a solid reaction with additional sulfur at 250 °C; (b) the synthesized (a-C) powder (obtained from decomposition of sucrose) is not SC. However, when mixed with sulfur and heated at 400 °C under a protective atmosphere, the a-CS powder obtained also show traces of a SC phase at TC = 42 K; (c) The same occurs in a-C thin films. The as-grown films are not SC but a SC phase at TC = 34 K emerges after the films were reacted with sulfur at elevated temperatures. It is concluded, therefore, that all SC phases observed are due to different unknown a-CS phases. Since the a-C and a-CS powders possess SC and magnetic states, we believe that these powders resemble the high TC curates and Fe-As based systems in which the SC and the magnetic states are closely related to each other.

UV Laser Annealing Effect on Mechanical Properties of Boron Doped Amorphous Carbon Films As Hardmasks

The hard forms of amorphous carbon (a-C, diamond like carbon) include hydrogenated amorphous carbon (a-C:H) and tetrahedral amorphous carbon have raised interest as coating materials. Recently, boron doped amorphous carbon films have been studied as hardmask materials. The hardmasks are utilized to fabricate advanced semiconductor devices, including dynamic random access memory (DRAM) and vertical NAND flash memory. As decreasing of feature sizes on DRAM and NAND, the hardmask materials need to exhibit a high etch selectivity with low internal stress and good mechanical strength. In this work, we have prepared boron doped amorphous carbon film deposited with the fixed B2H6 flow rate as a function of the process temperature using plasma enhanced chemical vapor deposition (PECVD). Boron has been widely known efficient dopant for passivating the oxidation of various carbon materials. We investigated the physical and optical properties of film with the refractive index, hardness and chemical bonding configuration. Especially, the effect of ultraviolet (UV) laser annealing on the hardness was studied using nano-indentation. UV annealing caused a change of chemical bonding configuration, i.e., sp2/sp3 bonding ratio and C-H bonds, through analysis of the Fourier transform-infrared (FT-IR) and RAMAN spectrum. UV annealed boron doped amorphous carbon thin films exhibited an enhanced hardness, which leads to high etch selectivity. Our results could provide a route to high etch selective hardmask materials development.

WEAR OF Si OR B DOPED AMORPHOUS CARBON COATINGS

The paper describes a complex wear research on DLC (amorphous carbon) doped with boron (B) and silicone (Si). The tests were carried out in two different sliding systems: flat–on–flat (ring contact, unidirectional sliding) and ball–on–flat (reciprocating sliding). Water and medical saline solutions were used as lubricants. A comparative analysis of the results revealed differences in the initiation and progress of wear and the endurance with regard to coating’s composition, lubricant and contact geometry. The results obtained from the tests show the influence of the additive element on the wear resistance and the high dependency of coatings’ performance in the type of contact and of the lubricant used. In all cases analysed, the use of medical saline solution resulted in accelerated wear or an increased result scatter in comparison to pure water lubrication.

Value-added functional textiles by plasma-based surface modification

Event Abstract Back to Event Value-added functional textiles by plasma-based surface modification Ranna Tolouei1, Sondes Sondes Gargoubi2, Lucie Levesque1, Pascale Chevallier1, Stephane Turgeon1 and Diego Mantovani1 1 CHU de Quéebec Research Centre, Laval University, Lab. for Biomaterials & Bioengineering (CRC-I), Dept. Min-Met-Materials Engineering, Canada 2 ISET Ksar-Hellal, Textile Engineering Laboratory, Tunisia Recently, there has been a strong interest in providing fabrics with greater wearing comfort while remaining fresh and odor free as well as the ability to impart antimicrobial properties[1]. The innovative combination of controllable topographical and chemical modifications of the material will be a step forward for surface engineering towards real life application: to make surfaces less liable to microbial adhesion, or easier to be cleaned, with the addition of an antimicrobial agent. The fabric surfaces are not only exposed to abrasion and wear caused by daily contacts, but also to aggressive laundry procedures. So far, many different methods have been studied using approaches such as polymeric grafting or polymeric coating accompanied by lack of stability[2]. Thus, higher mechanical and chemical stabilities become mandatory properties for such materials and need to be taken into consideration during the design process. Using plasma-based process techniques, thereby obtaining a highly stable and homogenous functional surface could be a potential alternative. Materials and Methods Cotton knit fabric samples were were cut into size of 1×1 cm2 and cleaned in successive baths of acetone and diethyl ether anhydrous for 10 minutes before being used. Surface modifications were performed using a hybrid plasma enhanced chemical vapor deposition (PE-CVD) reactor, operating at 13.56 MHz at room temperature. Hydrogen and nitrogen (N2:H2) were used as gas precursors for plasma pre-treatment of cotton fabric to enhance antimicrobial dye uptake. Methane was used for deposition of biocidal doped amorphous carbon (aC) nanocoating on the cotton fabric. Chemical state of surface was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The wettability of the surfaces after each modification has been measured using static water contact angle (WCA). The antibacterial activity of the treated fabric was estimated against Escherichia coli (ATCC 11229). To evaluate durability of wash, a hospital laundry process was chosen[3]. Results: The morphological changes due to plasma treatments were investigated by SEM as shown in Figure 1. It reveals a fairly smooth surface for untreated and N2:H2 pretreated samples, whereas nanocoating deposition caused a significant morphological change. Surface chemical composition analyses, by XPS, exhibited that the aC deposition was efficient as carbon became the major component of the surface: 95.4 at.% for nanocoated sample versus 67 at.% for untreated one. N2:H2 pretreated samples displayed high amount of nitrogen (at.%). Depending on plasma modification process the wetting behavior of cotton fabric could be tailored. Indeed, the WCA demonstrate the effect of plasma treatment by changing untreated cotton fabric wettability from ~ 100° to hydrophobic state (~145°) or hydrophilic state (~ 80°) by aC nanocoating and N2:H2 pretreatment, respectively. Antibacterial test revealed that nanocoated samples as well as N2:H2 pretreated samples with antimicrobial agents shown antibacterial activity against E. Coli as compared to untreated cotton fabric before and after laundry. Discussion and Conclusions: Our results clearly show the feasibility of low temperature plasma based process to modify the surface of fabric towards tuning the wetting behavior and antibacterial property. Moreover, stable antibacterial activity has been achieved by deposition of nanocoating on the surface of cotton fabric. The goal of the present work was to propose an appropriate treatment for functionalization of cotton fabric, which can be applied by textile industry using ecofriendly and non-toxic agents and processes. This work was partially supported by NSERC-Canada, CIHR-Canada, CFI-Canada, FRQ-NT-Quebec, and MRI-Quebec.

Unusual magnetic behavior in a chiral-based magnetic memory device

In recent years chiral molecules were found to act as efficient spin filters. Using a multilayer structure with chiral molecules magnetic memory was realized. Observed rare magnetic phenomena in a chiral-based magnetic memory device was reported by O-Ben Dor et. al in Nature Commun, 4, 2256 (2013). This multi-layered device is built from α-helix l-polyalanine (AHPA-L) adsorbed on gold, Al2O3 (7nm) and Ni (30nm) layers. It was shown that certain temperature range the FC branch crosses the magnetic peak (at 55K) observed in the ZFC curve thus ZFC>FC. We show here that in another similar multi-layered material, at low applied field, the ZFC curve lies above the FC one up to 70K. The two features have the same origin and the crucial necessary components to exhibit them are: AHPA-L and 30nm Ni layered thick. Similar effects were also reported in sulfur doped amorphous carbon. A comparison between the two systems and the ingredients for these peculiar observations is discussed.

Properties of Boron Doped Amorphous Carbon Films at -30 V and -50 V for Carbon Based Solar Cell Applications

The a-C:B film were prepared by mixing vapor of hydrocarbon palm oil, boron dopant, carrier gas, and argon in the chamber deposited at -30 V and -50 V of negative bias voltage. The effect of these negative bias voltage on the thickness, electrical and electronic properties of a-C:B film were investigated. It was observed, the optical band gap slightly changed (2.0 eV to 2.04 eV). The fabricated solar cell with the configuration of Au/p-C:B/n-Si/Au achieved conversion efficiency (η) of 0.192% at applied bias voltage of -50 V. This result showed by the applied of negative bias voltage can controlled the interstitial doping of boron in the amorphous carbon films network.

Doped Amorphous Carbon Films Prepared by Liquid Phase Electrodeposition

It has theoretical significance and practical value to synthetize and modify amorphous carbon films by liquid electro-deposition technique due to its low cost, simple equipment, and better operability in uniform deposition of the films with large-area and complex shape work pieces. This article introduces the research situation of the carbon films prepared by liquid phase electrochemical deposition according to the applied voltage, discusses the influence of experimental parameters on the film properties, and describes possible reaction mechanisms. It summarizes the research progress of amorphous carbon films doped with metal and nonmetals. Finally, existing problems have been demonstrated and suggestions on research hotspots in the future are given.

Semiconducting Properties of Nanostructured Amorphous Carbon Thin Films Incorporated with Iodine by Thermal Chemical Vapor Deposition

Nanostructured iodine-post doped amorphous carbon (a-C:I) thin films were prepared from camphor oil using a thermal chemical vapor deposition (TCVD) technique at different doping temperatures. The structural properties of the films were studied by field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), Raman, and Fourier transform infrared (FTIR) studies. FESEM and EDS studies showed successful iodine doping. FTIR and Raman studies showed that the a-C:I thin films consisted of a mixture of sp2- and sp3-bonded carbon atoms. The optical and electrical properties of a-C:I thin films were determined by UV–vis–NIR spectroscopy and current–voltage (I–V) measurement respectively. The optical band gap of a-C thin films decreased upon iodine doping. The highest electrical conductivity was found at 400 °C doping. Heterojunctions are confirmed by rectifying the I–V characteristics of an a-C:I/n-Si junction.

Synthesis of Antimony Doped Amorphous Carbon Films

We report the effects of antimony (Sb) doping on the electrical and optical properties of amorphous carbon (a-C:H) films grown on silicon and copper substrates by magnetron sputtering deposition. For film deposition, the mixture targets fabricated from carbon and antimony powders was used. The atomic concentration of carbon, hydrogen, and antimony, in the film deposited from the 1.0 mol% Sb containing target were 81, 17, 2 at.%, respectively. These elements were homogeneously distributed in the film. On the structural effect, the average continuous sp2 carbon bonding networks decreased with Sb concentration increasing, and defects in the films were increased with the Sb incorporation because atomic radius of Sb atoms is twice larger size than that of carbon. The optical gap and the electrical resistivity were carried out before and after the Sb doping. The results show that optical gap dropped from 3.15 to 3.04 eV corresponding to non-doping to Sb-doping conditions, respectively. The electrical resistivity reduced from 10.5 to 1.0 MΩm by the Sb doping. These results suggest the doping level was newly formed in the forbidden band.

Search for Superconductivity in Doped Amorphous Carbon Thin Films

In this paper, we have searched for superconductivity by measuring ohmic resistivity as a function of temperature in amorphous carbon films deposited by pulsed laser deposition and doped by ion implantation with sulfur and phosphorus ions. The doping concentrations were varied from 0.0003 to 4 Vol% for sulfur and 0.0003 to 1 Vol% for phosphorus. Previous efforts have studied doping of carbon-family materials such as highly oriented pyrolytic graphite, diamond-like carbon, and graphite/graphene, which have yielded critical temperatures lower than 20 K. In this study, amorphous carbon films doped with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$2.55 \times 10^{12}\ \hbox{ions/cm}^{2}$</tex></formula> phosphorus concentration showed a distinct change from semiconducting to metallic behavior and a dramatic 10 000-fold decrease in resistivity below 100 K as compared to undoped films. Sulfur-doped films with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$2.55 \times 10^{12}\ \hbox{ions/cm}^{2}$</tex> </formula> concentration showed up to a 100-fold decrease in resistivity below 100 K as compared to undoped samples. While evidence of superconductivity was not observed, significant improvements in conductivity were noted below 100 K.

Properties of Iodine Doped Amorphous Carbon Thin Films Grown by Thermal CVD

Thin film of undoped and doped amorphous carbon has been achieved using the simple thermal CVD system in an ambient gas of Ar and Ar with I2, respectively. The electrical and optical properties of the iodine doped amorphous carbon (a-C:I) thin films were studied. The incorporation of iodine into the amorphous carbon thin film results in increase of electrical conductivity as doping temperature increase up to 400°C, which indicates that doping effect of iodine. Heterojuction is confirmed by rectifying current-voltage characteristics of a-C:I/n-Si junction. The decreasing of optical band gap from 0.54 to 0.25 eV after iodine doping was determined which contribute to induce graphitization in the films. Raman result indicates that sp2 and sp3 bonded carbon atoms were dominated in the both with and without iodine doped thin films.