Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp3 bonding. DLC is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This review will describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of DLCs. The films have widespread applications as protective coatings in areas, such as magnetic storage disks, optical windows and micro-electromechanical devices (MEMs).

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Diamond-like amorphous carbon

▪ Abstract The synthesis of nanocrystalline diamond films from carbon-containing noble gas plasmas is described. The nanocrystallinity is the result of new growth and nucleation mechanisms, which involve the insertion of C2, carbon dimer, into carbon-carbon and carbon-hydrogen bonds, resulting in hetereogeneous nucleation rates on the order 1010 cm−2 s−1. Extensive characterization studies led to the conclusion that phase-pure diamond is produced with a microstructure consisting of randomly oriented 3–15-nm crystallites. By adjusting the noble gas/hydrogen ratio in the gas mixture, a continuous transition from micro- to nanocrystallinity is achieved. Up to 10% of the total carbon in the nanocrystalline films is located at 2 to 4 atom-wide grain boundaries. Because the grain boundary carbon is π-bonded, the mechanical, electrical, and optical properties of nanocrystalline diamond are profoundly altered. Nanocrystalline diamond films are unique new materials with applications in fields as diverse as tribolo...

Nanocrystalline diamond films1

Current issues and problems in the chemical vapor deposition (CVD) of diamond are those which relate to its characterization, its nucleation on foreign surfaces, the question of its formation in preference to the other phases of solid carbon (for example, graphite, chaoite, or lonsdaleite), why different morphologies and crystallographic orientations (textures) are seen in different experiments or with different parameters in the same experiment, and finally whether well-crystallized metastable phases can be obtained by CVD in other material systems or are only a peculiarity of carbon chemistry. Whether a given carbon coating is justly described as diamond has been such an issue, and coatings should clearly show evidence for diamond by x-ray diffraction and Raman spectroscopy before the claim of diamond is made. Experimental results have not been consistent in many cases, and much work remains to be done before an accurate assessment can be made of the technological impact of the development.

https://science.sciencemag.org/content/sci/247/4943/688.full.pdf

Current Issues and Problems in the Chemical Vapor Deposition of Diamond

On etudie le depot chimique en phase vapeur et la croissance cristalline de revetement de diamant

/pdf/diamond-ceramic-coating-of-the-future-31m184yw0t.pdf

Diamond—Ceramic Coating of the Future

Wavelength modulation spectroscopy (WMS) and one-tone and two-tone frequency modulation spectroscopy (FMS) are compared by measuring the minimum detectable absorbances achieved using a mid-IR lead-salt diode laser. The range of modulation and detection frequencies spans over 5 orders of magnitude. The best results, absorbances in the low-to-mid 10−7 range in a 1-Hz bandwidth, are obtained by using high-frequency WMS (10-MHz detection frequency) and are limited by detector thermal noise. This sensitivity can provide species detection limits well below 1 part per billion for molecules with moderate line strengths if multiple-pass cells are used. High-frequency WMS is also tested by measuring the absorbance due to tropospheric N2O at 1243.795 cm−1. WMS at frequencies <100 kHz is limited by laser excess (1/f) noise. Both of the FMS methods, which require modulating the laser at frequencies ≥150 MHz, give relatively poor results due to inefficient coupling of the modulation waveform to the laser current. The results obtained agree well with theory. We also discuss the sensitivity limitations due to interference fringes from unintentional etalons and the effectiveness of etalon reduction schemes.

Frequency modulation and wavelength modulation spectroscopies:comparison of experimental methods using a lead-salt diode laser

Diamond Chemical Vapor Deposition

Infrared diode laser absorption spectroscopy is employed as an in situ method to examine gas phase species present during filament‐assisted deposition of diamond films. From a reactant mixture of 0.5% methane in hydrogen, methyl radical (CH3 ), acetylene (C2H2), and ethylene (C2H4 ) are detected above the growing surface, while ethane (C2H6 ), various C3 hydrocarbons, and methylene (CH2) radicals are below our sensitivity levels. The growth of polycrystalline diamond films on Si wafers and polycrystalline Ni is confirmed with x‐ray and Raman scattering, scanning electron microscopy, and Auger electron spectroscopy.

Infrared detection of gaseous species during the filament‐assisted growth of diamond

The resonance‐enchanced multiphoton ionization (REMPI) technique was employed for detection of gas phase atomic hydrogen in the filament‐asisted diamond growth environment. The H atom REMPI signal varied significantly with the reactant CH4/H2 fraction as well as with the filament temperature. We interpret these observations as evidence for the surface role of atomic hydrogen in the diamond growth mechanism. The spatial resolution of the REMPI technique allowed us to confirm that hydrogen atom transport in the deposition region occurs by diffusion.

F. G. Celii

Papers

Diamond Chemical Vapor Deposition

Infrared detection of gaseous species during the filament‐assisted growth of diamond

Hydrogen atom detection in the filament‐assisted diamond deposition environment