Graphene, the single-atom-thick form of carbon, holds promise for many applications, notably in electronics where it can complement or be integrated with silicon-based devices. Intense efforts have been devoted to develop a key enabling device, a broadband, fast optical modulator with a small device footprint. Now Liu et al. demonstrate an exciting new possibility for graphene in the area of on-chip optical communication: a graphene-based optical modulator integrated with a silicon chip. This new device relies on the electrical tuning of the Fermi level of the graphene sheet, and achieves modulation of guided light at frequencies over 1 gigahertz, together with a broad operating spectrum. At just 25 square micrometres in area, it is one of the smallest of its type. Integrated optical modulators with high modulation speed, small footprint and large optical bandwidth are poised to be the enabling devices for on-chip optical interconnects1,2. Semiconductor modulators have therefore been heavily researched over the past few years. However, the device footprint of silicon-based modulators is of the order of millimetres, owing to its weak electro-optical properties3. Germanium and compound semiconductors, on the other hand, face the major challenge of integration with existing silicon electronics and photonics platforms4,5,6. Integrating silicon modulators with high-quality-factor optical resonators increases the modulation strength, but these devices suffer from intrinsic narrow bandwidth and require sophisticated optical design; they also have stringent fabrication requirements and limited temperature tolerances7. Finding a complementary metal-oxide-semiconductor (CMOS)-compatible material with adequate modulation speed and strength has therefore become a task of not only scientific interest, but also industrial importance. Here we experimentally demonstrate a broadband, high-speed, waveguide-integrated electroabsorption modulator based on monolayer graphene. By electrically tuning the Fermi level of the graphene sheet, we demonstrate modulation of the guided light at frequencies over 1 GHz, together with a broad operation spectrum that ranges from 1.35 to 1.6 µm under ambient conditions. The high modulation efficiency of graphene results in an active device area of merely 25 µm2, which is among the smallest to date. This graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.

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A graphene-based broadband optical modulator

Learn the basic properties and designs of modern VLSI devices, as well as the factors affecting performance, with this thoroughly updated second edition. The first edition has been widely adopted as a standard textbook in microelectronics in many major US universities and worldwide. The internationally-renowned authors highlight the intricate interdependencies and subtle tradeoffs between various practically important device parameters, and also provide an in-depth discussion of device scaling and scaling limits of CMOS and bipolar devices. Equations and parameters provided are checked continuously against the reality of silicon data, making the book equally useful in practical transistor design and in the classroom. Every chapter has been updated to include the latest developments, such as MOSFET scale length theory, high-field transport model, and SiGe-base bipolar devices.

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Fundamentals of Modern VLSI Devices

Boron doses of 1×1012–5×1015/cm2 were implanted at 60 keV into 1‐μm‐thick polysilicon films. After annealing at 1100 °C for 30 min, Hall and resistivity measurements were made over a temperature range −50–250 °C. It was found that as a function of doping concentration, the Hall mobility showed a minimum at about 2×1018/cm3 doping. The electrical activation energy was found to be about half the energy gap value of single‐crystalline silicon for lightly doped samples and decreased to less than 0.025 eV at a doping of 1×1019/cm3. The carrier concentration was very small at doping levels below 5×1017/cm3 and increased rapidly as the doping concentration was increased. At 1×1019/cm3 doping, the carrier concentration was about 90% of the doping concentration. A grain‐boundary model including the trapping states was proposed. Carrier concentration and mobility as a function of doping concentration and the mobility and resistivity as a function of temperature were calculated from the model. The theoretical and ex...

The electrical properties of polycrystalline silicon films

The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.

Electronics based on two-dimensional materials

Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule-nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.

Integrated Nanoparticle–Biomolecule Hybrid Systems: Synthesis, Properties, and Applications

The strong electroabsorption modulation possible in Ge/SiGe quantum wells promises efficient, CMOS-compatible integrated optical modulators. We demonstrate surface-normal asymmetric Fabry-Perot and microdisk resonator modulators employing Ge quantum wells grown on silicon.

Ge quantum well resonator modulators

PROBLEM TO BE SOLVED: To provide a means for forming nano pores useful for aligning molecules. SOLUTION: In a technology for forming molecules (18) or an array of molecules (18) having a specified orientation for a substrate (10), or a technology for forming a die (16) to which a material (18) adheres internally, the array of molecules (18) is formed by an array of small aligned pores (nanopores) in the substrate (10) or by distributing the molecules (18) in the die (16). Typically, the material (14) internally formed with nanopores (16) is dielectric. The underlying substrate (10) may be conductive or dielectric. In the application of an electronic device, the substrate (10) is generally conductive and can be exposed at the bottom of the pore (16) and thereby one end of the molecule (18) in the nanopore (16) can be brought into electrical contact with the substrate (10). A single crystal silicon wafer is especially convenient as the substrate (10). COPYRIGHT: (C)2003,JPO

Method for forming one or a plurality of nano pores for aligning molecules for molecular electronics

Dense ensembles of silicon nanowires were prepared by metal-catalyzed chemical vapor deposition on silicon substrates. Some of these ensembles were doped with phosphorus during growth. The nanowires were characterized using scanning electron microscopy, x-ray diffraction, and mass spectroscopy. Field emission of electrons from these structures was studied at room temperature in ultrahigh vacuum. The measurements were carried out using a parallel-plate diode cell. At high applied fields, the current-voltage characteristics deviate from the Fowler-Nordheim law and exhibit a stepwise increase of the current with increasing voltage at 300K.

Field-electron emission at 300K in self-assembled arrays of silicon nanowires

Adding a phosphorus-containing species during chemical vapor deposition of Ge islands on Si (0 0 1) modifies the island sizes and shapes, primarily by changing the surface energies and the relative surface energies of different surface facets. Three distinct island shapes occur, but the island types and their sequence of formation differ from those found with undoped Ge islands. The addition of phosphorus decreases the size of the multifaceted “domes”—the island shape that has a favored island size, providing an additional method for controlling the islands. The largest islands have a steep pyramidal structure not seen for undoped islands.

Effect of phosphorus on island formation

To build efficient sensors a large sensing area can be achieved by forming a massively parallel set of nanostructures. We have grown laterally oriented, metal-catalyzed silicon nanowires bridging between vertical (111) Si planes formed by anisotropically etching a [110]-oriented silicon wafer. The surrounding silicon can be developed into electrodes. The bridges are mechanically robust and resist significant force. By employing only coarse optical lithography to form the electrodes ("top-down" formation) combined with self-assembled ("bottom-up") fabrication of nanostructures, a large array of nano-scale sensors can be fabricated between biasing electrodes.

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Theodore I. Kamins

Papers

Ge quantum well resonator modulators

Method for forming one or a plurality of nano pores for aligning molecules for molecular electronics

Field-electron emission at 300K in self-assembled arrays of silicon nanowires

Effect of phosphorus on island formation

Self-assembled silicon nano-bridges as an enabler for nano-sensors