Electron Emission Through Tetrahedral Amorphous Carbon Coatings on Mo and Si Emitters

1997 ◽  
Vol 498 ◽  
Author(s):  
W. B. Choi ◽  
A. F. Myers ◽  
M. Q. Ding ◽  
A. K. Sharma ◽  
J. Narayan ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Columnar Structure ◽  
Hydrogen Atmosphere ◽  
Carbon Coatings ◽  
Field Emission Properties ◽  
Tetrahedral Amorphous Carbon ◽  
Low Field ◽  
Improved Stability ◽  
Thick Coatings ◽  
Amorphous Carbon Coatings

ABSTRACTThe field emission properties of molybdenum and silicon emitter coated with tetrahedral amorphous carbon (or amorphous diamond) were studied. The tetrahedral amorphous carbon was deposited by laser ablation and showed a uniformly coated columnar structure over the entire emitter. In general, current conditioning improved stability and increased the current density. Coatings of ta-C on Mo emitters with and without nitrogen incorporated both yielded significantly higher emissivity than uncoated emitters. Nitrogen incorporation reduced the effective workfunction and the sp3/sp2 ratio. However similar depositions on Si emitters reduced the emissivity, and may be attributable to the residual oxide at the ta-C/Si interface. Annealing in a hydrogen atmosphere enhanced emissivity from both ta-C/Mo and ta-C/Si emitters. In general, thick coatings lowered the emissivity and the slope of the I-V curves. A temperature dependence of emission was observed only in the low field regions.

Micro/nanomechanical and tribological characterization of ultrathin amorphous carbon coatings

1999 ◽  
Vol 14 (6) ◽  
pp. 2328-2337 ◽  
Author(s):  
Xiaodong Li ◽  
Bharat Bhushan
Keyword(s):  
Wear Resistance ◽  
Amorphous Carbon ◽  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
Carbon Coatings ◽  
Load Carrying ◽  
Tribological Characterization ◽  
Thick Coatings ◽  
Amorphous Carbon Coatings

Micro/nanomechanical and tribological characterization of ultrathin amorphous carbon coatings, deposited by filtered cathodic arc (FCA), direct ion beam (IB), electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD), and sputter (SP) deposition processes on Si substrate have been conducted using a nanoindenter with a nanoscratch attachment and an accelerated ball-on-flat tribometer. Coating thicknesses of 20, 10, 5 nm and, for the first time, 3.5 nm coatings have been investigated. It was found the FCA coating exhibits the highest hardness and elastic modulus, followed by the ECR-CVD, IB, and SP coatings. In general, the thicker coatings exhibited better scratch/wear performance than the thinner coatings due to their better load-carrying capacity as compared to the thinner coatings. At 20 nm, the FCA and ECR-CVD coatings show the best scratch and wear resistance, while the IB and ECR-CVD coatings show the best scratch and wear resistance at 10 nm. Five nanometer thick coatings show reasonable scratch and wear resistance, while 3.5 nm thick coatings show extremely low load-carrying capacity and poor scratch and wear resistance. It appears that the 3.5 nm coatings studied are unfeasible for scratch and wear resistance applications as of now.

scholarly journals Effect of Energy and Temperature on Tetrahedral Amorphous Carbon Coatings Deposited by Filtered Laser-Arc

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2176
Author(s):  
Frank Kaulfuss ◽  
Volker Weihnacht ◽  
Martin Zawischa ◽  
Lars Lorenz ◽  
Stefan Makowski ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
High Hardness ◽  
Significant Loss ◽  
Normal Direction ◽  
Medium Temperature ◽  
Carbon Coatings ◽  
Tetrahedral Amorphous Carbon ◽  
Bias Pulse ◽  
Arc Evaporation ◽  
Amorphous Carbon Coatings

In this study, both the plasma process of filtered laser-arc evaporation and the resulting properties of tetrahedral amorphous carbon coatings are investigated. The energy distribution of the plasma species and the arc spot dynamics during the arc evaporation are described. Different ta-C coatings are synthesized by varying the bias pulse time and temperature during deposition. An increase in hardness was observed with the increased overlapping of the bias and arc pulse times. External heating resulted in a significant loss of hardness. A strong discrepancy between the in-plane properties and the properties in the film normal direction was detected specifically for a medium temperature of 120 °C during deposition. Investigations using electron microscopy revealed that this strong anisotropy can be explained by the formation of nanocrystalline graphite areas and their orientation toward the film’s normal direction. This novel coating type differs from standard amorphous a-C and ta-C coatings and offers new possibilities for superior mechanical behavior due to its combination of a high hardness and low in-plane Young’s Modulus.

scholarly journals Amorphous Carbon Coatings for Total Knee Replacements—Part I: Deposition, Cytocompatibility, Chemical and Mechanical Properties

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1952
Author(s):  
Benedict Rothammer ◽  
Kevin Neusser ◽  
Max Marian ◽  
Marcel Bartz ◽  
Sebastian Krauß ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Amorphous Carbon ◽  
Detailed Characterization ◽  
Carbon Coatings ◽  
Dlc Coatings ◽  
Total Knee Replacements ◽  
Knee Replacements ◽  
Total Knee ◽  
Amorphous Carbon Coatings

Diamond-like carbon (DLC) coatings have the potential to reduce implant wear and thus to contribute to avoiding premature failure and increase service life of total knee replacements (TKAs). This two-part study addresses the development of such coatings for ultrahigh molecular weight polyethylene (UHMWPE) tibial inlays as well as cobalt–chromium–molybdenum (CoCr) and titanium (Ti64) alloy femoral components. While a detailed characterization of the tribological behavior is the subject of part II, part I focusses on the deposition of pure (a‑C:H) and tungsten-doped hydrogen-containing amorphous carbon coatings (a‑C:H:W) and the detailed characterization of their chemical, cytological, mechanical and adhesion behavior. The coatings are fabricated by physical vapor deposition (PVD) and display typical DLC morphology and composition, as verified by focused ion beam scanning electron microscopy and Raman spectroscopy. Their roughness is higher than that of the plain substrates. Initial screening with contact angle and surface tension as well as in vitro testing by indirect and direct application indicate favorable cytocompatibility. The DLC coatings feature excellent mechanical properties with a substantial enhancement of indentation hardness and elastic modulus ratios. The adhesion of the coatings as determined in modified scratch tests can be considered as sufficient for the use in TKAs.

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