Alfred Grill

100-GHz Transistors from Wafer-Scale Epitaxial Graphene

The maximum switching frequency of these devices exceeds that of silicon transistors with similar gate-electrode dimensions. The high carrier mobility of graphene has been exploited in field-effect transistors that operate at high frequencies. Transistors were fabricated on epitaxial graphene synthesized on the silicon face of a silicon carbide wafer, achieving a cutoff frequency of 100 gigahertz for a gate length of 240 nanometers. The high-frequency performance of these epitaxial graphene transistors exceeds that of state-of-the-art silicon transistors of the same gate length.

DIAMOND-LIKE CARBON : STATE OF THE ART

Abstract Diamond-like carbon films, amorphous hydrogenated or non-hydrogenated forms of carbon, are metastable amorphous materials characterized by attractive mechanical, optical, electrical, chemical and tribological properties. The films can be prepared at low temperatures by different techniques using a large variety of precursors and can be modified by incorporation of different elements such as N, F, Si or metals. The diversity of methods used for the deposition of diamond-like carbon films provides the flexibility to tailor their properties according to specific needs and potential applications. The hydrogenated form of DLC appears to reach a maturity in understanding its properties and finding old and new practical applications for it. The non-hydrogenated diamond-like carbon, or tetrahedral carbon, is at a much younger state of preparation and characterization and practical applications have yet to be proven. The paper will review the state of the art of the preparation of the different types of diamond-like carbon films, the characterization and understanding of their properties, and their practical applications.

Wafer-Scale Graphene Integrated Circuit

Components such as inductors were fabricated alongside graphene transistors to create integrated radio-frequency mixers. A wafer-scale graphene circuit was demonstrated in which all circuit components, including graphene field-effect transistor and inductors, were monolithically integrated on a single silicon carbide wafer. The integrated circuit operates as a broadband radio-frequency mixer at frequencies up to 10 gigahertz. These graphene circuits exhibit outstanding thermal stability with little reduction in performance (less than 1 decibel) between 300 and 400 kelvin. These results open up possibilities of achieving practical graphene technology with more complex functionality and performance.

Structure of low dielectric constant to extreme low dielectric constant SiCOH films: Fourier transform infrared spectroscopy characterization

Carbon doped oxide dielectrics comprised of Si, C, O, and H (SiCOH) have been prepared by plasma enhanced chemical vapor deposition (PECVD) from mixtures of tetramethylcyclotetrasiloxane (TMCTS) and an organic precursor. The films have been analyzed by determining their elemental composition and by Fourier transform infrared spectroscopy with deconvolution of the absorption peaks. The analysis has shown that PECVD of TMCTS produces a highly crosslinked networked SiCOH film. Dissociation of TMCTS appears to dominate the deposition chemistry as evidenced by the multitude of bonding environments and formation of linear chains and branches. Extensive crosslinking of TMCTS rings occurs through Si–Si, Si–CH2–Si, Si–O–Si, and Si–CH2–O–Si moieties. The films deposited from mixtures of TMCTS and organic precursor incorporate hydrocarbon fragments into the films. This incorporation occurs most probably through the reaction of the organic precursor and the Si–H bonds of TMCTS. Annealing the SiCOH films deposited fro...

Diamond-like carbon coatings as biocompatible materials—an overview

Amorphous hydrogenated diamond-like carbon (DLC) and tetrahedral carbon (taC) films are characterized by high wear resistance, low friction coefficients and chemical inertness, thus high-corrosion resistance. The properties of DLC and taC can further be modified by incorporating other elements in the films, such as N, F, Si and metals, thus tailoring them for specific applications. The films can be deposited as conformal, very smooth layers. These properties make the films good candidates as biocompatible coatings for biomedical devices and tools. The paper presents on overview of the biomedical characteristics of different varieties of amorphous carbon and their potential applications.

Tribology of diamondlike carbon and related materials: an updated review

Diamondlike carbon (DLC) has been studied for many years as a wear-resistant material with low friction coefficient. Its tribological behavior is strongly affected by the tribotesting environment and is controlled by tribochemical effects, which may in turn be dependent on the technique used for the deposition of the films. New variations of DLC films, with various dopings, and new deposition methods have been investigated in recent years. The paper presents an updated review of the tribological properties of DLC and related materials, and discusses the mechanisms suggested for the explanation of the wear and friction behavior of these materials.

Ultralow-k dielectrics prepared by plasma-enhanced chemical vapor deposition

Carbon-doped oxide materials (SiCOH films) with ultralow dielectric constants have been prepared by plasma-enhanced chemical vapor deposition (PECVD) from mixtures of SiCOH precursors with organic materials. The films have been characterized by Rutherford backscattering and forward recoil elastic scattering analysis, Fourier transform infrared spectroscopy and index of refraction measurements, and measurement of step heights in the films. The electrical properties of the films have been measured on metal–insulator–silicon structures. By proper choice of the precursor and deposition conditions, the dielectric constants of the SiCOH films can be reduced to values below 2.1, demonstrating the extendibility of PECVD-prepared carbon-doped oxides as the interconnect dielectrics for future generation of very large scale integrated chips.

Plasma enhanced chemical vapor deposited SiCOH dielectrics: from low-k to extreme low-k interconnect materials

Carbon doped oxide dielectrics comprised of Si, C, O, and H (SiCOH) have been prepared by plasma enhanced chemical vapor deposition. Low-k films with a dielectric constant (k) of about 2.8 have been deposited from tetramethylcyclotetrasiloxane (TMCTS). The dielectric constant has been further reduced to extreme low-k values of k<2.1 by admixing an organic precursor to TMCTS and annealing the films to remove the organic fragments and create porosity in the films. The entire range of SiCOH films is characterized by relatively low coefficients of thermal expansion of about 12×10−6 K and mechanical properties that make them suitable for integration as the interconnect dielectric in ultralarge scale integration (ULSI) devices. The range of dielectric constants makes the films potentially useful for several generations of ULSI chips.

Picosecond optical studies of amorphous diamond and diamondlike carbon: Thermal conductivity and longitudinal sound velocity

A picosecond pump‐probe technique is used to measure the room‐temperature thermal conductivity κ and longitudinal sound velocity cl of amorphous diamond (a‐D) and diamondlike carbon (DLC) thin films. Both κ and cl were found to decrease with film hydrogen content. Depending on the film deposition technique, κ is in the range 5–10×10−2 W cm−1 K−1 for a‐D, and 3–10×10−3 W cm−1 K−1 for DLC. Values of cl were found to be in the range 14–18×105 cm s−1 for a‐D, and 6–9×105 cm s−1 for DLC.

Electrical and optical properties of diamond-like carbon

Abstract Diamond-like carbon (DLC) films, amorphous hydrogenated or nonhydrogenated forms of carbon, are metastable amorphous materials characterized by a range of attractive mechanical, chemical, tribological, as well as optical and electrical properties. The films can be prepared at low temperatures, from a large variety of precursors, by a diversity of techniques, and their characteristics can be modified by incorporation of different elements such as N, F, Si, or metals. The diversity of methods used for the deposition of DLC films provides the flexibility to tailor their properties according to specific needs and potential applications. The optical gap of these materials is in the range of 1–4 eV and the electrical resistivity spans 14 orders of magnitude. The dielectric constant of DLC films covers the range of 2.5–6. The talk will review the optical and electrical characteristics of DLC and discuss the actual and potential applications based on these properties.