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

Diamond may be grown at low pressures where it is the metastable form of carbon. Recent advances in a wide variety of plasma and electrical discharge methods have led to dramatic increases in growth rates. All of these methods have certain aspects in common, namely, the presence of atomic hydrogen and the production of energetic carbon-containing fragments under conditions that support high mobilities on the diamond surface. Some understanding of the processes taking place during nucleation and growth of diamond has been achieved, but detailed molecular mechanisms are not yet known. Related research has led to the discovery of a new class of materials, the "diamondlike" phases. Vapor-grown diamond and diamondlike materials may have eventual applications in abrasives, tool coatings, bearing surfaces, electronics, optics, tribological surfaces, and corrosion protection.

https://science.sciencemag.org/content/sci/241/4868/913.full.pdf

Low-Pressure, Metastable Growth of Diamond and "Diamondlike" Phases

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

This paper revies the preparation and properties of hard forms of amorphous carbon and hydrogenated amorphous carbon, often known as diamond-like carbon. Properties such as the hydrogen content, sp 3 content, optical gap, refractive index, hardness, elastic modulus and friction and their dependence on the deposition conditions are described. Models of the electronic structure and mechanical properties are used to relate the physical properties to the atomic structure.

Properties of diamond-like carbon

Hard amorphous (diamond-like) carbons

The deposition of amorphous hydrogenated hard carbon (a–C:H) thin films from benzene vapor in a rf plasma is described. a–C:H was deposited on glass, quartz, Si, Ge, and GaAs. Negative self‐bias VB and gas pressure P are shown to be the two significant parameters for an accurate control of the deposition process. The dependence of growth rate and deposition temperature on VB and P was determined; this gives an empirical relation for the average energy E of the ions forming the thin films. Refractive index (1.85–2.20 in the IR), optical gap (0.8–1.8 eV) and density (1.5–1.8 g/cm3) of a–C:H was measured. The optical gap varies linearly with the content of bonded hydrogen in the films. The density of a–C:H is proportional to the average ion energy E. We demonstrate the application of a–C:H as antireflective coating on Ge for 10.6 μm (reflection <0.2% at 10.6 μm) and as terminating layer of an optical multilayer stack.

rf‐plasma deposited amorphous hydrogenated hard carbon thin films: Preparation, properties, and applications

Continuous tuning over the entire 8–12 μm wavelength range is demonstrated for the intersubband absorption resonance in n‐doped GaAs/AlxGa1−xAs multiple quantum‐well structures following partial interdiffusion of the well and barrier layers via rapid thermal annealing. The data indicate that redshifting of the intersubband absorption resonance arises both from interdiffusion‐induced modification of the confining potential and from a decrease in the depolarization shift. The latter effect is due in part to a decrease in the free‐carrier concentration within the Si‐doped quantum wells following rapid thermal annealing. Significant diffusion of the localized Si dopant is also observed over the range of annealing temperatures investigated here. Calculated values of the Al‐Ga interdiffusion coefficient, as a function of anneal temperature, indicate that Si diffusion through the heterointerfaces contributes substantially to layer intermixing.

Intersubband transitions in partially interdiffused GaAs/AlGaAs multiple quantum-well structures

Hydrogenated amorphous carbon (a-C:H) thin films were prepared from hydrocarbons such as CH4, C2H4 and C6H6 in a capacitively coupled RF-discharge. a-C:H films which are electrically insulating (10 12 2Ωcm), transparent in the IR and very hard (on the order of 1400 kp/mm2 Knoop hardness) were deposited on glass, quartz, Si, Ge, SiC, GaAs and Gd3Ga5O12. This method allows large area (several inch diameter) homogeneous coatings and using C6H6 also gives high deposition rates on the order of 1000 A/min. The deposition process is described and the influence of various deposition parameters is discussed. It is shown that by means of the two parameters negative self bias and gas pressure coating properties such as refractive index can be easily tuned and controlled. The application of a-C:H as a single layer antireflection coating on Ge for 10.6 [im is demonstrated; the reflection at 10.6 pri is less than 0.2%.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

RF-Plasma Deposition Of Hydrogenated Hard Carbon Thin Films

Zusammenfassung Dieser Beitrag widmet sich im Anschluss an die Diskussion zur Entzerrung der „Rushhour des Lebens“ der Frage, ob es vorteilhaft für die berufliche Karriere von Akademikerinnen ist, wenn sie, anstatt nach dem Berufseinstieg, bereits vor dem Studienabschluss oder direkt im Anschluss daran Kinder bekommen. Während ein Aufschieben der Erstgeburt verschiedenen Studien zufolge durchaus positiv für den Karriereverlauf ist, ist der Zusammenhang zwischen einer frühen Familiengründung und dem Erreichen einer Führungsposition für Deutschland bislang kaum erforscht. Anhand von Absolventendaten des Deutschen Zentrums für Hochschul- und Wissenschaftsforschung (DZHW) wird mit logistischen Regressionsanalysen untersucht, wie wahrscheinlich das Erreichen einer Führungsposition für Mütter mit akademischem Abschluss in Abhängigkeit vom Geburtentiming ist. Die Befunde zeigen, dass Mütter, die bereits vor dem Berufseinstieg Kinder bekommen haben, zehn Jahre nach Studienabschluss mit höherer Wahrscheinlichkeit in Führungspositionen tätig sind als die Vergleichsgruppe der Mütter, die erst während des Erwerbsverlaufs eine Familie gegründet haben. Erstere weisen im Erwerbsverlauf weniger Vollzeitphasen, aber mehr Teilzeitphasen und weniger Unterbrechungsphasen auf. Die Ergebnisse stützen humankapital- und signaltheoretische Annahmen, wonach Akademikerinnen auf dem Arbeitsmarkt von einer Familiengründung vor dem Berufseinstieg profitieren, da längere Erwerbsunterbrechungen unwahrscheinlicher werden. 

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Karriere mit Kind – Wie wirkt sich frühe Mutterschaft auf das Erreichen von Führungspositionen bei Akademikerinnen aus?

In recent years amorphous carbon coatings found growing interest because of their optical and protective properties. We have deposited hydrogenated amorphous carbon films (a-C:H) from an RF excited discharge in benzene vapour. Substrates include germanium, glass and MgF2. The refractive index can be tuned between 1.8 and 2.2 and efficient antireflection coatings on Ge have been prepared. We have determined the optical absorption from the UV to the IR range (0.2 - 25 μm). A typical 1 µm thick a-C:H film is transparent (> 50% transmission) from 750 nm to the far infrared. Amorphous carbon films are harder than sapphire and are resistant to concentrated acids and bases.

G. Brandt

Papers

rf‐plasma deposited amorphous hydrogenated hard carbon thin films: Preparation, properties, and applications

Intersubband transitions in partially interdiffused GaAs/AlGaAs multiple quantum-well structures

RF-Plasma Deposition Of Hydrogenated Hard Carbon Thin Films

Karriere mit Kind – Wie wirkt sich frühe Mutterschaft auf das Erreichen von Führungspositionen bei Akademikerinnen aus?

Optical And Protective Properties Of Hard Carbon Coatings