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

The recent development in the field of superhard materials with Vickers hardness of ⩾40 GPa is reviewed. Two basic approaches are outlined including the intrinsic superhard materials, such as diamond, cubic boron nitride, C3N4, carbonitrides, etc. and extrinsic, nanostructured materials for which superhardness is achieved by an appropriate design of their microstructure. The theoretically predicted high hardness of C3N4 has not been experimentally documented so far. Ceramics made of cubic boron nitride prepared at high pressure and temperature find many applications whereas thin films prepared by activated deposition from the gas phase are still in the stage of fundamental development. The greatest progress has been achieved in the field of nanostructured materials including superlattices and nanocomposites where superhardness of ⩾50 GPa was reported for several systems. More recently, nc-TiN/SiNx nanocomposites with hardness of 105 GPa were prepared, reaching the hardness of diamond. The principles of de...

https://mediatum.ub.tum.de/doc/958917/file.pdf

The search for novel, superhard materials

A general framework for the interpretation of infrared and Raman spectra of amorphous carbon nitrides is presented. In the first part of this paper we examine the infrared spectra. The peaks around 1350 and 1550 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ found in the infrared spectrum of amorphous carbon nitride or hydrogenated and hydrogen-free amorphous carbon are shown to originate from the large dynamic charge of the more delocalized \ensuremath{\pi} bonding which occurs in more ${\mathrm{sp}}^{2}$ bonded networks. The IR absorption decreases strongly when the \ensuremath{\pi} bonding becomes localized, as in tetrahedral amorphous carbon. Isotopic substitution is used to assign the modes to $\mathrm{C}=\mathrm{C}$ skeleton modes, even those modes around 1600 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ which become strongly enhanced by the presence of hydrogen. The infrared spectrum of carbon nitride may resemble the Raman spectrum at some excitation energy, but the infrared activity does not primarily result from nitrogen breaking the symmetry. In the second part we examine the Raman spectra. A general model is presented for the interpretation of the Raman spectra of amorphous carbon nitrides measured at any excitation energy. The Raman spectra can be explained in terms of an amorphous carbon based model, without need of extra peaks due to CN, NN, or NH modes. We classify amorphous carbon nitride films in four classes, according to the corresponding N-free film: $a\ensuremath{-}\mathrm{C}:\mathrm{N},$ $a\ensuremath{-}\mathrm{C}:\mathrm{H}:\mathrm{N},$ $ta\ensuremath{-}\mathrm{C}:\mathrm{H}:\mathrm{N},$ and $ta\ensuremath{-}\mathrm{C}:\mathrm{N}.$ We analyze a wide variety of samples for the four classes and present the Raman spectra as a function of N content, ${\mathrm{sp}}^{3}$ content, and band gap. In all cases, a multiwavelength Raman study allows a direct correlation of the Raman parameters with the N content, which is not generally possible for single wavelength excitation. The G peak dispersion emerges as a most informative parameter for Raman analysis. UV Raman enhances the ${\mathrm{sp}}^{1}$ CN peak, which is usually too faint to be seen in visible excitation. As for N-free samples, UV Raman also enhances the C-C ${\mathrm{sp}}^{3}$ bonds vibrations, allowing the ${\mathrm{sp}}^{3}$ content to be quantified.

/pdf/interpretation-of-infrared-and-raman-spectra-of-amorphous-4qk3s6kov2.pdf

Interpretation of infrared and Raman spectra of amorphous carbon nitrides

A review of the preparation of carbon nitride films

The Nature of Nitrogen‐Modified Titanium Dioxide Photocatalysts Active in Visible Light

Thin carbon–nitrogen films have been formed by direct impingement of 5–100 eV C+ and N+ or N+2 ions upon solid surfaces, as well as by 5–350 eV N+ bombardment of graphite surfaces. The influences of ion energy, N+/C+ arrival rate, and type of substrate have been studied. The films deposited in this manner are found to be essentially amorphous, with some graphitic regions on the scale of a few nm. Two distinct types of C–N bonding, one attributed to graphitelike local structure (C–N π bonds) and one attributed to C3N4‐like local structure (C–N σ bonds), have been detected by x‐ray photoelectron spectroscopy. Films deposited by dual‐beam deposition and single‐beam nitridation at 75 eV or less exhibit differences in the single‐bonded structure. Total nitrogen concentrations of up to 47 at. % have been measured by Auger electron spectroscopy (AES) and Rutherford backscattering spectrometry. The C KVV Auger line shapes of the two phases have been determined by factor analysis. These line shapes are consistent ...

Formation of C–N thin films by ion beam deposition

A dynamic trim‐based computer simulation program that includes treatment of post‐cascade atomic motion has been used to model the ion beam deposition of carbon nitride and boron carbide thin films at energies below 100 eV. Simulations of chemically enhanced phenomena are based on describing the motion of the atoms as a sequence of ballistic steps followed by a chemically guided step. In the case of B–C films, a satisfactory description of the experimental results is achieved by including only ballistic effects in the simulation. For C–N, agreement between experiment and simulation requires the inclusion of a mechanism of preferential nitrogen re‐emission into the program. This mechanism is modeled by the formation of nitrogen‐containing dimers which are considered volatile and are readily released through the surface. The probability of dimer formation depends on the local N concentration. The simulation reproduces well both as‐deposited composition measurements and Auger sputter depth profiling. The mode...

Computer simulation of the ion beam deposition of binary thin films: Carbon nitride and boron carbide

Homoepitaxy and controlled oxidation of silicon at low temperatures have been achieved using a dual source, mass‐selected, low‐energy, ion beam deposition system. For Si homoepitaxy, 28Si+ ions in the energy range 8–40 eV were used to grow films on Si{100} in the temperature range of 50–750 °C. The films were analyzed in situ by reflection high‐energy electron diffraction and Auger electron spectroscopy (AES) and ex situ by high‐resolution transmission electron microscopy, Rutherford backscattering spectrometry, and atomic force microscopy. For silicon oxidation, films of SiO2 on Si{100} at room temperature were grown by using 25 eV beams of 28Si+ and 16O+. Fast switching of the magnetic sectors allows deposition of these ions in alternating pulses. The pulse increments used were 1×1014 cm −2 for Si+ and 4×1014 cm−2 for O+. Analysis of the oxide films by in situ AES and ex situ x‐ray photoelectron spectroscopy show that the films are SiO2, that the suboxides are localized at the interface, and that there ...

D. Marton

Papers

Formation of C–N thin films by ion beam deposition

Computer simulation of the ion beam deposition of binary thin films: Carbon nitride and boron carbide

Homoepitaxy and controlled oxidation of silicon at low temperatures using low-energy ion beams