Vapor deposition processes for amorphous carbon films with <i>sp</i>3 fractions approaching diamond

Cuomo, J. J.; Pappas, David; Bruley, J.; Doyle, J. P.; Saenger, K. L.

doi:10.1063/1.349540

Cited by 271 publications

(79 citation statements)

References 18 publications

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“…1͑b͒ the data for all the research groups lie above the line joining that of diamond and graphite. Cuomo et al 21 used a ''rule of mixtures'' to give a relationship between the sp 2 /sp 3 bonds and density shown by the dashed line in the figure. Again, the fit to the data is not perfect and an overestimation of the density is predicted.…”

mentioning

confidence: 99%

Nanocrystallites in tetrahedral amorphous carbon films

Ravi

Silva

et al. 1996

Applied Physics Letters

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The microstructure of filtered cathodic vacuum arc deposited tetrahedral amorphous carbon films is studied as a function of ion energy. An optimum energy window in the density and C-C sp 3 content at an ion energy of ϳ90 eV observed in this study. It is shown that the density of the amorphous carbon films are closely related to the sp 3 content. The observation of nanocrystals embedded in the amorphous carbon matrix is reported. Most of the crystals observed by transmission electron microscopy can be indexed to graphite, but some of the crystals can be indexed to cubic diamond. The chemical composition of the crystals is analyzed using electron energy loss spectroscopy ͑EELS͒. The only discernible EELS edge is that of C at an energy of 285 eV. © 1996 American Institute of Physics. ͓S0003-6951͑96͒03230-5͔Filtered cathodic vacuum arc ͑FCVA͒ deposited carbon films have the unique property of producing high quality diamondlike amorphous carbon films with a high sp 3 content. 1,2 The film properties are critically dependent on the ion energy of the species. The carbon plasma initiated from a graphite target by the vacuum arc is sustained during the deposition and macroparticles associated with the arc process are filtered using a 90°bend toroidal solenoid in the deposition system. We have investigated the relationship between the bonding structure in the films and the ion energy of the C species. At a particular threshold ion energy the particles found in the tetrahedral amorphous carbon ͑ta-C͒ films have been studied using transmission electron microscopy ͑TEM͒ and electron energy loss spectroscopy ͑EELS͒. Although there are reports that diamond nanocrystallites have been observed in diamondlike carbon ͑DLC͒ films deposited under low temperature and low pressure conditions, 3-6 direct observation of diamond crystals in deposition techniques that do not operate at high temperatures and high pressures is not common. This is because graphite is the stable crystalline form of carbon under these conditions.Highly tetrahedrally bonded ta-C films have also been deposited using laser initiated vacuum arcs, and pulsed cathodic arcs, 7,8 and hydrogenated ta-C films deposited using a plasma beam source. 9 There is much interest in all of these films due to their unique mechanical properties. 7,10 Recently, Yin et al. 11 have found cauliflower-like growths ͑nanocrys-tals͒ which cannot be indexed to graphite in their FCVA deposited films, which are considered to be precursors for diamond growth. 12 However, there has been no published literature on the observation of diamond nanocrystallites in ta-C films deposited using the FCVA. In this letter, we report on the observation of nanocrystallites that index to diamond, deposited under low temperature/low pressure conditions using such a system.The FCVA films were deposited with a base pressure of 2ϫ10 Ϫ6 Torr which increased to 1ϫ10 Ϫ5 Torr during deposition. The substrate bias is varied from 0 to Ϫ120 V, while the arc current remained constant at ϳ60 A. A toroidal magnetic field ...

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confidence: 99%

Nanocrystallites in tetrahedral amorphous carbon films

Ravi

Silva

et al. 1996

Applied Physics Letters

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“…Yet, questions as to the validity of a thermal spike at ion energies of a few hundred electron volts in a low elemental mass material remains unanswered. Nevertheless, at such impact energies several thousand vibrations are involved for a time period of the order of 10 Ϫ12 s. 14 Dense and highly tetrahedral amorphous carbon films have also been deposited by the laser ablation technique, 15,16 by dual ion beam technique, 17 and recently by magnetron sputtering together with intense ion plating ͑MS/IP͒. 18,19 This MS/IP technique differs from other techniques since the film forming particles are low energy neutral carbon atoms ͑sput-tered from a graphite target͒, and the necessary energy for densification of the film is transferred by the argon ion plating process.…”

Section: Introductionmentioning

confidence: 99%

Stress-induced formation of high-density amorphous carbon thin films

Schwan

Ulrich

Theel

et al. 1997

Journal of Applied Physics

115

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Amorphous carbon films with high sp 3 content were deposited by magnetron sputtering and intense argon ion plating. Above a compressive stress of 13 GPa a strong increase of the density of the carbon films is observed. We explain the increase of density by a stress-induced phase transition of sp 2 configured carbon to sp 3 configured carbon. Preferential sputtering of the sp 2 component in the carbon films plays a minor role compared to the sp 2 ⇒sp 3 transition at high compressive stress formed during the deposition process. Transmission electron microscopy shows evidence of graphitic regions in the magnetron sputtered/Ar plated amorphous carbon thin films. Differences in the microstructure of the tetrahedral amorphous carbon ͑ta-C͒ films deposited by filtered arc and mass selected ion beam; and those films deposited using magnetron sputtering combined with intense ion plating can be used to explain the different electronic and optical properties of both kinds of ta-C films. © 1997 American Institute of Physics. ͓S0021-8979͑97͒09422-X͔ INTRODUCTIONCarbon films have been of considerable research interest since Aisenberg and Chabot 1 deposited the first hard, diamondlike amorphous carbon films. Amorphous carbon films with a high fraction of sp 3 hybridized carbons have been deposited by filtered cathodic vacuum arc ͑FCVA͒ 2-4 and mass selected ion beams. 5-8 C ϩ ions are used to deposit the amorphous carbon films by both techniques. Different mechanisms for the formation of the sp 3 rich phase have been proposed such as the shallow implantation process ͑subplantation͒ by Lifshitz et al.,5,6 selective sputtering processes by Reinke and Kuhr 9 ͑discussed for c-BN͒, and stressinduced phase transition processes by McKenzie et al. 3,10 Analytical expressions for the subplantation process describing the formation of stress and the densification have been proposed by Davis 11 and Robertson. 12 The basic idea of the models by Davis and Robertson is that a carbon ion needs at least the displacement energy to penetrate into the carbon film leading to a densification of subsurface layers of the evolving film. 6 But, not all the energy of the energetic carbon ion is used for penetration ͑displacement processes͒. Part of the ion energy is used by momentum transfer collisions which results in a thermal spike. Davis 11 and Robertson 12 modified calculations of Windischmann 13 by allowing implanted carbon atoms to relax to the film surface, due to the high localized temperature generated by the impinging C ϩ ions in the thermal spike. Yet, questions as to the validity of a thermal spike at ion energies of a few hundred electron volts in a low elemental mass material remains unanswered. Nevertheless, at such impact energies several thousand vibrations are involved for a time period of the order of 10 Ϫ12 s. 14 Dense and highly tetrahedral amorphous carbon films have also been deposited by the laser ablation technique, 15,16 by dual ion beam technique, 17 and recently by magnetron sputtering together with intense ion plating ͑MS/I...

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“…Properties such as sp 3 content, hardness, Young's modulus, density, and stress have a maximum when ions have a kinetic energy of about 100 eV [6,[58][59][60]. While in most experiments the energy could be manipulated by substrate biasing, the second generation twist filter system had a permanently grounded, rotating substrate holder.…”

Section: Synthesis and Properties Of A-c Films Synthesized By Fimentioning

confidence: 99%

Ultrathin diamond-like carbon films deposited by filtered carbon vacuum arcs

Anders

Fong

Kulkarni

et al. 2001

IEEE Trans. Plasma Sci.

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Ultrathin (< 5 nm) hard carbon films are of great interest to the magnetic storage industry as the areal density approaches 100 Gbit/in 2 . These films are used as overcoats to protect the magnetic layers on disk media and the active elements of the read-write slider. Tetrahedral amorphous carbon films can be produced by filtered cathodic arc deposition, but the films will only be accepted by the storage industry only if the "macroparticle" issue has been solved. Better plasma filters have been developed over recent years. Emphasis is put on the promising twist filter system -a compact, open structure that operates with pulsed arcs and high magnetic field. Based on corrosion tests it is shown that the macroparticle reduction by the twist filter is satisfactory for this demanding application, while plasma throughput is very high. Ultrathin hard carbon films have been synthesized using Sfilter and twist filter systems. Film properties such as hardness, elastic modulus, wear, and corrosion resistance have been tested. Index Terms: diamond-like carbon, cathodic vacuum arc, macroparticle filtering, magnetic storage, carbon overcoats 3 I. INTRODUCTIONUltrathin (< 5 nm) hard carbon films are used as protective overcoats on hard disks and readwrite heads. The tribological properties of the head-disk interface are not only of mechanical but also of chemical nature: the overcoat should protect the magnetic layers against wear and corrosion [1, 2]. The areal density of information stored in disk drive products increased at an amazing rate of over 65% for many years rate, and continues to accelerate to even greater rates [3]. To accomplish this, the "magnetic spacing" between the magnetic layers of the disk and read/write sensor of the head must continue to decrease. The magnetic spacing includes the overcoats, lubrication, and the fly height. Thinner overcoats allow the read-write head to be closer to the magnetic layer of the disk, and hence, the size of individual bits on the disk to be smaller. As we work toward an areal density of 100 Gbit/in 2 , the magnetic spacing approaches the sub-10-nm regime (pseudo-contact recording) and overcoat thickness must shrink to 1-2 nm. Overcoats currently used are sputtered or ion-beam deposited diamond-like carbon films, typically doped with hydrogen or nitrogen. They cease to provide acceptable levels of corrosion protection when the film thickness is less than 5 nm.Overcoats need to be tough (hard and elastic), chemically inert, pinhole-free, and compatible with the lubricant. The challenge of ultrathin film synthesis is to make the films as thin as possible and still continuous, as opposed to an assembly of islands.Nucleation and growth of ultrathin films is a field of intense research. For carbon, it is well known that films that are rich in sp 3 (diamond) bonds should be grown in a kinetic mode at low temperature (less than 200°C, preferably room temperature), with film-forming carbon atoms or ions having an energy of about 100 eV. This energy is optimized for subplantat...

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Vapor deposition processes for amorphous carbon films with sp3 fractions approaching diamond

Cited by 271 publications

References 18 publications

Nanocrystallites in tetrahedral amorphous carbon films

Nanocrystallites in tetrahedral amorphous carbon films

Stress-induced formation of high-density amorphous carbon thin films

Ultrathin diamond-like carbon films deposited by filtered carbon vacuum arcs

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