Resistivity Of Carbon Films Research Articles

Resistivity of Thin Carbon Films with Different sp-Bonds Fractions

Carbon films with different extents of sp hybridization have been grown by ion–plasma pulsed arc sputtering of graphite in a methane atmosphere. Using Raman scattering and transmission electron microscopy data, it has been shown that the content of the phase including carbon chains with sp hybridization grows with increasing methane concentration in the working volume. The resistivity of carbon films correlates well with the fraction of sp-hybridized carbon in the films.

The Effect of the Ion Assistance Energy on the Electrical Resistivity of Carbon Films Prepared by Pulsed Plasma Deposition in a Nitrogen Atmosphere

Thin carbon films prepared by pulsed plasma ion-assisted deposition of graphite in an atmosphere of a mixture of argon and nitrogen are studied. The results of characteristic electron energy loss spectroscopy and electron diffraction indicate the increase in the graphite component with increasing ion assistance energy. The use of ion assistance during the film deposition makes it possible to control their resistivity by changing it from 105 to 102 Ω cm.

Self-passivating carbon film as bipolar plate protective coating in polymer electrolyte membrane fuel cell

The effects of W doping on the microstructure, ICR, and corrosion resistance of carbon films are systematically investigated. The W-doped carbon film has a compact structure and the surface topography changes slightly with W concentration. W exists in mainly the metallic state when the concentration is small, but amorphous WC is formed in the CW2(A) and CW3(A) samples. The ICR at a typical compaction force of 150 N cm−2 increases marginally in the range of 6.25–7.21 mΩ-cm2 as the W concentration is varied. The carbon films with smaller W concentrations have better corrosion resistance and even the self-passivating ability. During pulse polarization, the bare SS316L shows a very large current density of 150 μA cm−2 due to breakdown of the passive film, but CW1(A) shows a stable and low current density of about 0.6 μA cm−2 due to the good self-passivating ability. The self-passivating ability originates from oxidation of metallic state W in the carbon film and so a proper W concentration can yield the desirable self-passivating effect.

Thermal properties of modified carbon films

Purpose – The purpose of this paper is to present thermal properties of palladium-carbon films prepared by physical vapour deposition (PVD)/chemical vapour deposition (CVD) methods. Design/methodology/approach – Thin palladium-carbon films were prepared at Tele- and Radioresearch Institute. Test structures containing palladium-carbon films and titanium electrodes were made. Temperature-resistance characteristics were measured. Findings – The results show strong temperature dependence of modified carbon film resistance. The dependence is stable, and so modified carbon films can be applied for various electronic applications. Originality/value – The paper presents thermal properties of thin palladium-carbon prepared by original PVD/CVD method at Tele- and Radioresearch Institute.

Corrosion and Wear Resistance of Carbon Films Obtained by Electrodeposition on Ferritic Stainless Steel

In improving the corrosion and hardness proprieties of ferritic stainless steel, the use of protective coatings becomes an interesting alternative. In this study, a carbon layer was deposited on AISI 430 by electrodeposition using N,N-dimethylformamide with the addition of an organic dopant as the electrolyte. The AISI 430 stainless steel was pretreated by anodization aiming to optimize the film anchoring. The obtained films were characterized by atomic force microscopy, by scanning electron microscopy and by optical interferometry. The microstructural characterization of the films was obtained by Raman Spectroscopy. The corrosion resistance was evaluated by open circuit potential and by potentiodynamic polarization. The friction test and the scratch test were performed to evaluate the mechanical properties. The Raman spectroscopy showed the presence of an amorphous carbon film. The films improved the corrosion resistance of stainless steel. In addition, on the wear analysis the coating showed a good adhesion on the substrate.

Change of electrical resistance of carbon films during the adsorption of acetone and other molecules

Carbon films were prepared from polyimide films (Kapton and Upilex-s with thickness of 50 μm) by heat treatment at 750 °C under Ar atmosphere. The electrical resistance of the carbon films was remarkably increased with the adsorption of acetone and decreased with its desorption. The magnitude of the resistance change increased with increasing vapor pressure of acetone and with decreasing temperature. The weight and resistance changes during the adsorption of acetone were simultaneously determined. A linear relationship was confirmed between them. It was also found that similar resistance changes were observed for adsorption of aqueous ammonia and nitric acid. [TANSO 2013 (No. 257) 141–144]

カーボンフィルムへの分子吸着と電気抵抗変化

カーボンフィルムへの分子吸着と電気抵抗変化

H2/N2 Plasma Etching Rate of Carbon Films Deposited by H-Assisted Plasma Chemical Vapor Deposition

Etching resistance of carbon films deposited by plasma chemical vapor deposition (CVD) is one of the concerns to fabricate nanostructures using such carbon films as protective coating films and dummy films. We have carried out H2/N2 plasma etching of carbon films deposited by using an H-assisted plasma CVD method. The etching rate of carbon films decreases exponentially with increasing the mass density of carbon films from 1.51 to 2.27 g/cm3. The mass density of carbon films is the key parameter to tune the etching resistance.

Physical properties of sputtered amorphous carbon coating

Abstracts In this study the effect of deposition temperature and thickness on the physical properties of carbon films deposited by magnetron sputtering PVD was investigated. The results of Raman spectra and grazing incidence XRD (GIXRD) patterns show that the graphitization increases by increasing the deposition temperature. There is a change in deposition mechanism at 400 °C from amorphous carbon deposition to nano-structured graphite deposition. Also by increasing substrate temperature the electrical resistance of carbon films reduces significantly up to 300 °C and then remains largely constant. High intrinsic compressive stress in low temperature deposited carbon films causes cracks and delaminating in carbon films.

Modification of carbon films by high-power proton-carbon ion beam of nanosecond duration

The effect of a high-power proton-carbon ion beam on the surface morphology and resistance of carbon films synthesized by plasma-enhanced chemical vapor deposition has been investigated. Possible mechanisms of the surface morphology changes and increase in the carbon film resistance due to irradiation have been discussed.

Temperature Dependence on Structural, Tribological, and Electrical Properties of Sputtered Conductive Carbon Thin Films

Conductive carbon films were prepared at room temperature by unbalanced magnetron sputtering (UBMS) on silicon substrates using argon (Ar) gas, and the effects of post-annealing temperature on the structural, tribological, and electrical properties of carbon films were investigated. Films were annealed at temperatures ranging from <TEX>$400^{\circ}C$</TEX> to <TEX>$700^{\circ}C$</TEX> in increments of <TEX>$100^{\circ}C$</TEX> using a rapid thermal annealing method by vacuum furnace in vacuum ambient. The increase of annealing temperature contributed to the increase of the ordering and formation of aromatic rings in the carbon film. Consequently, with increasing annealing temperature the tribological properties of sputtered carbon films are deteriorated while the resistivity of carbon films significantly decreased from <TEX>$4.5{\times}10^{-3}$</TEX> to <TEX>$1.0{\times}10^{-6}\;{\Omega}-cm$</TEX> and carrier concentration as well as mobility increased, respectively. This behavior can be explained by the increase of sp2 bonding fraction and ordering <TEX>$sp^2$</TEX> clusters in the carbon networks caused by increasing annealing temperature.

Carbon films deposited by low frequency plasma as inter-metal dielectric

We present a study of the correlation between deposition conditions, microstructure, dielectric constant and resistivity of carbon films prepared by low frequency plasma enhanced chemical vapor deposition (LF PE CVD). The carbon films were deposited at relatively high temperature ( T=350 °C). The microstructure of the films was studied by IR spectroscopy. The electrical properties were characterized by the measurement of current–voltage characteristics. The correlation between CC, C–H X bonding, resistivity ρ, and dielectric constant K has been found. The effect of isothermal annealing on the structure and dielectric properties has been studied and a correlation between CC and CH X bonding behavior and ρ and K was observed. Ultra low concentration of impurities, resulting from out-gassing of the reactor walls was found to have a great influence on the concentration of CC and CH X bonds, and causes changes in the K and ρ values. For all of the above experiments it is observed the correlation between CC and CH X bonding characteristics with the dielectric properties of the carbon films.

탄소계 박막의 성장과 특성에 대한 나노 Buffer Layer의 영향

Using Platinum-silicide (PtSi) formed between silicon substrate and carbon film, we have improved the field emission of electrons from carbon films. Pt films were deposited on n-Si(100) substrates at room temperature by DC sputter technique. After deposition, these PtSi thin films were annealed at 400 ~ <TEX>$600^{\circ}C$</TEX> in a vacuum chamber, and the carbon films were deposited on those Pt/Si substrates by laser ablation at room temperature. The field emission property of C/Pt/Si system is found to be better than that of C/Si system and it is showed that property was improved with increasing annealing temperature. The reasons why the field emission from carbon film was improved can be considered as follows, (1)the resistance of carbon films was decreased due to graphitization, (2)electric field concentration effectively occurred because the surface morphology of carbon film deposited on Pt/si substrates with rough surface, (3)it is showed that annealing induced reaction between Pt film and Si substrate, as a consequence that the interfacial resistance between Pt film and Si substrate was decreased.

Multimedia keyboard with instrument playing device

A multimedia keyboard with instrument playing device comprising a case, a connector and flexible protruding plate mounted on one end of the case. A protruding plate can be inserted into an available slot in the multimedia keyboard, providing a signal connection and a flexible clip. Playing elements such as guitar strings, piano keys, or a drumhead are mounted on the exterior of the case. Several series of flexible conducting elements connected to the playing elements are mounted within the case. When the playing elements are struck or plucked, the conducting elements will deform in direct proportion to the amount of force that has been applied. One signal pickup circuit board including several carbon film resistance plates is mounted on the top or bottom of each flexible conducting elements. When a flexible conducting elements deforms, the changing area of contact between its deformed portion and the carbon film resistance plates can be used to generate analog signals in direct proportion to the amount of force applied to the playing elements. These signals allow the computer to generate sound length, tone, and volume corresponding to those of the playing elements.

Lithographic printing of force-sensitive resistors

Prototype force sensitive resistors were made using powder-filled inks by offset lithography, a high speed printing process. A carbon-based lithographic ink that dries to form a film with a carbon content close to the percolation threshold for electrical conduction was formulated. Silver-filled, electrically conducting ink was prepared for the electrodes and connecting leads. The substrate was white gloss-art A4 paper. The carbon film resistance was 23 kΩ while the combined resistance of electrodes and leads was less than 2 Ω. The force sensor was tested by repeated loading and unloading.

The effect of film resistance on electron field emission from amorphous carbon films

The effects of film resistance on the electron field emission properties of carbon films were systematically investigated by combining electron emission and DC current-voltage ( I– V) measurements. The field emission follows the Fowler–Nordheim law at lower fields. However, at high fields the emission current becomes limited by the resistance of the carbon film and deviates from the Fowler–Nordheim law. Using the emission I– V curves in this range, the carbon film resistance was estimated, and this agrees well with the resistance derived from the DC I– V curve. It is also shown how the film resistance can be used to effectively control the emission current across a wide range of applied voltage. This concept can be extended to confining the emission current for each emission site, hence achieving more uniform emission current over a large emission area.

Time dependence of the resistance of sputtered carbon films

The electrical resistance of carbon films sputtered under high Ar pressure and low bias was observed to increase by as much as 200% when the films were exposed to the atmosphere for a period of several days. Substrate temperature and sputtering power had no effect on the time dependence of the resistance. The time dependence of the resistance appears to be related to the formation of a porous structure when films are sputtered under high Ar pressure and low bias. The increase in resistance noted when sputtered carbon films were exposed to air bears some similarity to aging behavior observed for discontinuous metal films. The initial resistivity of the films was dependent on Ar pressure, bias, substrate temperature and power.

Energetic neutral particles behind the PLT pumped limiter

A carbon film resistance probe was used to measure the energy and flux of energetic neutral deuterium in the pumping duct of the pumped limiter on the PLT tokamak. The particle flux at the back of the pumping duct increased from about 1012 to 4 × 1013 cm−2·s−1 as the limiter was moved into the plasma edge. With the limiter in the plasma edge, the mean particle energy measured at the back of the pumping duct was 160–300 eV. Gas pressures in the pumping duct up to about 1 mtorr were measured but were found to have little effect on the energetic neutrals reaching the back of the pumping duct. Particle transport calculations indicate that pressures more than an order of magnitude higher than observed would be necessary to stop the particles. The measured flux of energetic neutrals is estimated to be large enough to contribute significantly to the particle removal rate achieved by the pumped limiter.

Search for exponentially damped surface solutions to the Boltzmann transport equation for He II

A search for exponentially damped surface solutions to the Boltzmann transport equation has been made for the case of heat flow across a copper-liquid-He-II interface. Measurements were made by two different techniques involving a carbon film resistance thermometer that could be displaced with respect to the interface. No evidence was found, in all the measurements down to 100 mK, for the existence of exponentially damped surface solutions.

Electrical resistivity of carbon films

The electrical resistivity along 500 Å thick carbon films has been measured from 1.2 to 1100°K. The electrical resistivity measurements at high temperature indicate a change in the structure of the film beginning at about 670°K. In the theory of non-crystalline solids by Mott, the temperature dependence of the electrical conductivity σ, at low temperature, is given by In σ = A —BT − 1 4 where A and B are constants. Whereas previous investigators have shown general agreement with Mott's relation, the present result at low temperature shows deviation from the In σ α T − 1 4 relation.