The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Electrochemical capacitors, also called supercapacitors, store energy in two closely spaced layers with opposing charges, and are used to power hybrid electric vehicles, portable electronic equipment and other devices¹. By offering fast charging and discharging rates, and the ability to sustain millions of ²⁻⁵, electrochemical capacitors bridge the gap between batteries, which offer high energy densities but are slow, and conventional electrolytic capacitors, which are fast but have low energy densities. Here, we demonstrate microsupercapacitors with powers per volume that are comparable to electrolytic capacitors, capacitances that are four orders of magnitude higher, and energies per volume that are an order of magnitude higher. We also measured discharge rates of up to 200 V s⁻¹, which is three orders of magnitude higher than conventional supercapacitors. The microsupercapacitors are produced by the electrophoretic deposition of a several micrometre-thick layer of nanostructured carbon onions⁶‚⁷ with diameters of 6-7 nm. Integration of these nanoparticles in a microdevice with a high surface-to-volume ratio, without the use of organic binders and polymer separators, improves performance because of the ease with which ions can access the active material. Increasing the energy density and discharge rates of supercapacitors will enable them to compete with batteries and conventional electrolytic capacitors in a number of applications.

/pdf/ultrahigh-power-micrometre-sized-supercapacitors-based-on-28alaqlic6.pdf

Ultrahigh-power micrometre-sized supercapacitors based on onion-like carbon

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas–solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic–organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.

Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends

Nanostructured devices have the potential to serve as the basis for next-generation energy systems that make use of densely packed interfaces and thin films 1 . One approach to making such devices is to build multilayer structures of large area inside the open volume of a nanostructured template. Here, we report the use of atomic layer deposition to fabricate arrays of metal–insulator–metal nanocapacitors in anodic aluminium oxide nanopores. These highly regular arrays have a capacitance per unit planar area of 10 m Fc m 22 for 1-mm-thick anodic aluminium oxide and 100 m Fc m 22 for 10-mm-thick anodic aluminium oxide, significantly exceeding previously reported values for metal–insulator–metal capacitors in porous templates 2–6 . It should be possible to scale devices fabricated with this approach to make viable energy storage systems that provide both high energy density and high power density. The nanocapacitor structures in this Letter are formed of metal electrodes separated by a dielectric film; therefore they behave in the same manner as conventional electrostatic capacitors, in which charge is stored on opposing electrode surfaces. A characteristic feature of electrostatic capacitors is high power. This is because charge can be moved rapidly, with speeds limited only by external circuit RCs. However, energy storage is limited because only surface charge is used. In contrast, conventional electrochemical supercapacitors store charge in electric double layers or in faradic reactions, permitting larger energy density storage on the electrode surfaces. Power density is limited in these devices because of the requirement for mass transport of ions and/or redox reactions 7 . The use of highly regular nanostructures promises both high energy and high power density. For the nanocapacitors described in this Letter, the nanostructure significantly enhances capacitance density. The nanocapacitors demonstrate the high power (up to � 1 � 10 6 Wk g 21 ) typical of electrostatic capacitors while achieving the much higher energy density (� 0.7 Wh kg 21 ) characteristic of electrochemical supercapacitors. As a result, electrostatic nanocapacitors are attractive for high-burst-power applications requiring the energy density of supercapacitors. To obtain energy devices that achieve dense packing of active interfaces and thin films, nanoporous structures are required that have internal surfaces on which highly uniform films can be reproducibly formed. We make use of the self-assembly of regular nanopore arrays available from anodic aluminium oxide (AAO) formation together with multilayer atomic layer deposition (ALD) to form highly controlled, self-aligned nanocapacitors. ALD has become the leading process used to achieve such coatings, yielding a high degree of thickness control and conformality in the most demanding nanostructures, with features that are either highly ordered 8–10 or are random porous networks 11–13 . Nanostructures fabricated with AAO and ALD show a high degree of uniformity across massive arrays, imparting the regularity that is a key factor in the viability of any technology 8 . Our fabrication strategy makes use of AAO nanopore templates in combination with metal–insulator–metal (MIM) structures deposited in the nanopores by ALD. The anodization process produces an ultrahigh density (� 1 � 10 10 cm 22 ) of hexagonally arranged, uniform, self-assembled nanopores in AAO film on Al tens of micrometres deep, which provides a good template for

Nanotubular metal–insulator–metal capacitor arrays for energy storage

Nanotubes are fabricated by atomic layer deposition (ALD) into nanopore arrays created by anodic aluminum oxide (AAO). A transmission electron microscopy (TEM) methodology is developed and applied to quantify the ALD conformality in the nanopores (thickness as a function of depth), and the results are compared to existing models for ALD conformality. ALD HfO2 nanotubes formed in AAO templates are released by dissolution of the Al2O3, transferred to a grid, and imaged by TEM. An algorithm is devised to automate the quantification of nanotube wall thickness as a function of position along the central axis of the nanotube, by using a cylindrical model for the nanotube. Diffusion-limited depletion occurs in the lower portion of the nanotubes and is characterized by a linear slope of decreasing thickness. Experimentally recorded slopes match well with two simple models of ALD within nanopores presented in the literature. The TEM analysis technique provides a method for the rapid analysis of such nanostructures in general, and is also a means to efficiently quantify ALD profiles in nanostructures for a variety of nanodevice applications.

TEM-Based Metrology for HfO2 Layers and Nanotubes Formed in Anodic Aluminum Oxide Nanopore Structures

A recently reported ruthenium molecule, bis(2,6,6-trimethyl-cyclohexadienyl)ruthenium, has been developed and characterized as a precursor for atomic layer deposition (ALD) of ruthenium. This molecule, which has never been reported as an ALD precursor, was developed to address low growth rates, high nucleation barriers, and undesirable precursor phases commonly associated with other Ru precursors such as RuCp and Ru(EtCp)2. The newly developed precursor has similar vapor pressure to both RuCp and Ru(EtCp)2 but offers significant improvement in stability as evaluated by thermogravimetric analysis and differential scanning calorimetry. In an ALD process, it provides good self-limiting growth, with a 0.5 A/cycle growth rate under saturated dose conditions in a temperature between 250 and 300 °C. Furthermore, the precursor exhibits considerably better nucleation characteristics on SiO2, TiO2, and H-terminated Si surfaces, compared to RuCp2 and Ru(EtCp)2.

Atomic Layer Deposition of Ruthenium Using the Novel Precursor bis(2,6,6-trimethyl-cyclohexadienyl)ruthenium

Most conventional chemical vapor deposition (CVD) systems do not have the spatial actuation and sensing capabilities necessary to control deposition uniformity or to intentionally induce nonuniform deposition patterns for single-wafer combinatorial CVD experiments. In an effort to address these limitations, a novel CVD reactor system has been developed that can explicitly control the spatial profile of gas-phase chemical composition across the wafer surface. This paper discusses the construction of a prototype reactor system featuring a three-zone, segmented showerhead design. Experiments are performed to assess the ability of this reactor system to deposit tungsten films by the hydrogen reduction process; segment-to-segment process recipes are controlled to deposit spatially nonuniform W films. The capabilities of this reactor system for materials discovery research are discussed.

/pdf/development-of-a-spatially-controllable-chemical-vapor-26dfpdtm56.pdf

Development of a spatially controllable chemical vapor deposition reactor with combinatorial processing capabilities

In situ quadrupole mass spectrometry (QMS) has been integrated to an atomic layer deposition (ALD) reactor to achieve real-time chemical diagnostic and wafer-state metrology. The process investigated was tungsten ALD using WF6 and SiH4. The UHV-based substrate-heated ALD reactor incorporated a minireactor chamber to simulate the small reaction volume anticipated for manufacturing tools in order to achieve adequate throughput. Mass spectrometry revealed essential surface reaction dynamics through real-time signals associated with by-product generation as well as reactant introduction and depletion for each ALD half-cycle. The by-product QMS signal was then integrated in real time over each exposure and plotted against process cycle number to directly observe ALD film growth, leading to two valuable metrologies. First, the integrated by-product QMS value changes with cycle number, directly reflecting the nucleation kinetics. Specifically, QMS values increase with cycle number during the nucleation phase and...

Laurent Henn-Lecordier

Papers

Nanotubular metal–insulator–metal capacitor arrays for energy storage

TEM-Based Metrology for HfO2 Layers and Nanotubes Formed in Anodic Aluminum Oxide Nanopore Structures

Atomic Layer Deposition of Ruthenium Using the Novel Precursor bis(2,6,6-trimethyl-cyclohexadienyl)ruthenium

Development of a spatially controllable chemical vapor deposition reactor with combinatorial processing capabilities

Real-time sensing and metrology for atomic layer deposition processes and manufacturing