Showing papers on "Silicon published in 2003"

High Performance Silicon Nanowire Field Effect Transistors

Abstract: Silicon nanowires can be prepared with single-crystal structures, diameters as small as several nanometers and controllable hole and electron doping, and thus represent powerful building blocks for nanoelectronics devices such as field effect transistors. To explore the potential limits of silicon nanowire transistors, we have examined the influence of source-drain contact thermal annealing and surface passivation on key transistor properties. Thermal annealing and passivation of oxide defects using chemical modification were found to increase the average transconductance from 45 to 800 nS and average mobility from 30 to 560 cm 2 /V‚s with peak values of 2000 nS and 1350 cm 2 /V‚s, respectively. The comparison of these results and other key parameters with state-of-the-art planar silicon devices shows substantial advantages for silicon nanowires. The uses of nanowires as building blocks for future nanoelectronics are discussed.

Thermal conductivity of individual silicon nanowires

Abstract: The thermal conductivities of individual single crystalline intrinsic Si nanowires with diameters of 22, 37, 56, and 115 nm were measured using a microfabricated suspended device over a temperature range of 20–320 K. Although the nanowires had well-defined crystalline order, the thermal conductivity observed was more than two orders of magnitude lower than the bulk value. The strong diameter dependence of thermal conductivity in nanowires was ascribed to the increased phonon-boundary scattering and possible phonon spectrum modification.

Fabrication of solid-state nanopores with single-nanometre precision.

Abstract: Single nanometre-sized pores (nanopores) embedded in an insulating membrane are an exciting new class of nanosensors for rapid electrical detection and characterization of biomolecules. Notable examples include α-hemolysin protein nanopores in lipid membranes1,2 and solid-state nanopores3 in Si3N4. Here we report a new technique for fabricating silicon oxide nanopores with single-nanometre precision and direct visual feedback, using state-of-the-art silicon technology and transmission electron microscopy. First, a pore of 20 nm is opened in a silicon membrane by using electron-beam lithography and anisotropic etching. After thermal oxidation, the pore can be reduced to a single-nanometre when it is exposed to a high-energy electron beam. This fluidizes the silicon oxide leading to a shrinking of the small hole due to surface tension. When the electron beam is switched off, the material quenches and retains its shape. This technique dramatically increases the level of control in the fabrication of a wide range of nanodevices.

Etch rates for micromachining processing-Part II

Abstract: Samples of 53 materials that are used or potentially can be used or in the fabrication of microelectromechanical systems and integrated circuits were prepared: single-crystal silicon with two doping levels, polycrystalline silicon with two doping levels, polycrystalline germanium, polycrystalline SiGe, graphite, fused quartz, Pyrex 7740, nine other preparations of silicon dioxide, four preparations of silicon nitride, sapphire, two preparations of aluminum oxide, aluminum, Al/2%Si, titanium, vanadium, niobium, two preparations of tantalum, two preparations of chromium, Cr on Au, molybdenum, tungsten, nickel, palladium, platinum, copper, silver, gold, 10 Ti/90 W, 80 Ni/20 Cr, TiN, four types of photoresist, resist pen, Parylene-C, and spin-on polyimide. Selected samples were etched in 35 different etches: isotropic silicon etchant, potassium hydroxide, 10:1 HF, 5:1 BHF, Pad Etch 4, hot phosphoric acid, Aluminum Etchant Type A, titanium wet etchant, CR-7 chromium etchant, CR-14 chromium etchant, molybdenum etchant, warm hydrogen peroxide, Copper Etchant Type CE-200, Copper Etchant APS 100, dilute aqua regia, AU-5 gold etchant, Nichrome Etchant TFN, hot sulfuric+phosphoric acids, Piranha, Microstrip 2001, acetone, methanol, isopropanol, xenon difluoride, HF+H/sub 2/O vapor, oxygen plasma, two deep reactive ion etch recipes with two different types of wafer clamping, SF/sub 6/ plasma, SF/sub 6/+O/sub 2/ plasma, CF/sub 4/ plasma, CF/sub 4/+O/sub 2/ plasma, and argon ion milling. The etch rates of 620 combinations of these were measured. The etch rates of thermal oxide in different dilutions of HF and BHF are also reported. Sample preparation and information about the etches is given.

Single-crystal gallium nitride nanotubes.

Abstract: Since the discovery of carbon nanotubes in 1991 (ref. 1), there have been significant research efforts to synthesize nanometre-scale tubular forms of various solids. The formation of tubular nanostructure generally requires a layered or anisotropic crystal structure. There are reports of nanotubes made from silica, alumina, silicon and metals that do not have a layered crystal structure; they are synthesized by using carbon nanotubes and porous membranes as templates, or by thin-film rolling. These nanotubes, however, are either amorphous, polycrystalline or exist only in ultrahigh vacuum. The growth of single-crystal semiconductor hollow nanotubes would be advantageous in potential nanoscale electronics, optoelectronics and biochemical-sensing applications. Here we report an 'epitaxial casting' approach for the synthesis of single-crystal GaN nanotubes with inner diameters of 30-200 nm and wall thicknesses of 5-50 nm. Hexagonal ZnO nanowires were used as templates for the epitaxial overgrowth of thin GaN layers in a chemical vapour deposition system. The ZnO nanowire templates were subsequently removed by thermal reduction and evaporation, resulting in ordered arrays of GaN nanotubes on the substrates. This templating process should be applicable to many other semiconductor systems.

Small-Diameter Silicon Nanowire Surfaces

Abstract: Small-diameter (1 to 7 nanometers) silicon nanowires (SiNWs) were prepared, and their surfaces were removed of oxide and terminated with hydrogen by a hydrofluoric acid dip. Scanning tunneling microscopy (STM) of these SiNWs, performed both in air and in ultrahigh vacuum, revealed atomically resolved images that can be interpreted as hydrogen-terminated Si (111)-(1 × 1) and Si (001)-(1 × 1) surfaces corresponding to SiH 3 on Si (111) and SiH 2 on Si (001), respectively. These hydrogen-terminated SiNW surfaces seem to be more oxidation-resistant than regular silicon wafer surfaces, because atomically resolved STM images of SiNWs were obtained in air after several days9 exposure to the ambient environment. Scanning tunneling spectroscopy measurements were performed on the oxide-removed SiNWs and were used to evaluate the electronic energy gaps. The energy gaps were found to increase with decreasing SiNW diameter from 1.1 electron volts for 7 nanometers to 3.5 electron volts for 1.3 nanometers, in agreement with previous theoretical predictions.

Photovoltaic materials, history, status and outlook

Abstract: This paper reviews the history, the present status and possible future developments of photovoltaic (PV) materials for terrestrial applications. After a brief history and introduction of the photovoltaic effect theoretical requirements for the optimal performance of materials for pn-junction solar cells are discussed. Most important are efficiency, long-term stability and, not to be neglected, lowest possible cost. Today the market is dominated by crystalline silicon in its multicrystalline and monocrystalline form. The physical and technical limitations of this material are discussed. Although crystalline silicon is not the optimal material from a solid state physics point of view it dominates the market and will continue to do this for the next 5–10 years. Because of its importance a considerable part of this review deals with materials aspects of crystalline silicon. For reasons of cost only multicrystalline silicon and monocrystalline Czochralski (Cz) crystals are used in practical cells. Light induced instability in this Cz-material has recently been investigated and ways to eliminate this effect have been devised. For future large scale production of crystalline silicon solar cells development of a special solar grade silicon appears necessary. Ribbon growth is a possibility to avoid the costly sawing process. A very vivid R&D area is thin-film crystalline silicon (about 5–30 μm active layer thickness) which would avoid the crystal growing and sawing processes. The problems arising for this material are: assuring adequate light absorption, assuring good crystal quality and purity of the films, and finding a substrate that fulfills all requirements. Three approaches have emerged: high-temperature, low-temperature and transfer technique. Genuine thin-film materials are characterized by a direct band structure which gives them very high light absorption. Therefore, these materials have a thickness of only one micron or less. The oldest such material is amorphous silicon which is the second most important material today. It is mainly used in consumer products but is on the verge to also penetrate the power market. Other strong contenders are chalcogenides like copper indium diselenide (CIS) and cadmium telluride. The interest has expanded from CuInSe 2 , to CuGaSe 2 , CuInS 2 and their multinary alloys Cu(In,Ga)(S,Se) 2 . The two deposition techniques are either separate deposition of the components followed by annealing on one hand or coevaporation. Laboratory efficiencies for small area devices are approaching 19% and large area modules have reached 12%. Pilot production of CIS-modules has started in the US and Germany. Cadmium telluride solar cells also offer great promise. They have only slightly lower efficiency and are also at the start of production. In the future other materials and concepts can be expected to come into play. Some of these are: dye sensitized cells, organic solar cells and various concentrating systems including III/V-tandem cells. Theoretical materials that have not yet been realized are Auger generation material and intermediate metallic band material.

ReaxFFSiO Reactive Force Field for Silicon and Silicon Oxide Systems

Abstract: To predict the structures, properties, and chemistry of materials involving silicon and silicon oxides; interfaces between these materials; and hydrolysis of such systems, we have developed the ReaxFFSiO, reactive force field. The parameters for this force field were obtained from fitting to the results of quantum chemical (QC) calculations on the structures and energy barriers for a number of silicon oxide clusters and on the equations of state for condensed phases of Si and SiO2 from QC. We expect that ReaxFFSiO will allow accurate dynamical simulations of bond breaking processes in large silicon and silicon oxide systems. ReaxFFSiO is based closely on the potential functions of the ReaxFFCH reactive force field for hydrocarbons, so that it should also be useful for describing reactions of organics with Si and SiO2 systems.

Highly Reversible Lithium Storage in Nanostructured Silicon

Abstract: Anode materials of nanostructured silicon have been prepared by physical vapor deposition and characterized using electrochemical methods. The electrodes were prepared in thin-film form as nanocrystalline particles (12 nm mean diameter) and as continuous amorphous thin films (100 nm thick). The nanocrystalline silicon exhibited specific capacities of around 1100 mAh/g with a 50% capacity retention after 50 cycles. The amorphous thin-film electrodes exhibited initial capacities of 3500 mAh/g with a stable capacity of 2000 mAh/g over 50 cycles. We suggest that the nanoscale dimensions of the silicon circumvents conventional mechanisms of mechanical deterioration, permitting good cycle life.

Liquid-liquid phase transition in supercooled silicon.

Abstract: Silicon in its liquid and amorphous forms occupies a unique position among amorphous materials. Obviously important in its own right, the amorphous form is structurally close to the group of 4–4, 3–5 and 2–6 amorphous semiconductors that have been found to have interesting pressure-induced semiconductor-to-metal phase transitions1,2. On the other hand, its liquid form has much in common, thermodynamically, with water and other ‘tetrahedral network’ liquids that show density maxima3,4,5,6,7. Proper study of the ‘liquid–amorphous transition’, documented for non-crystalline silicon by both experimental and computer simulation studies8,9,10,11,12,13,14,15,16,17, may therefore also shed light on phase behaviour in these related materials. Here, we provide detailed and unambiguous simulation evidence that the transition in supercooled liquid silicon, in the Stillinger–Weber potential18, is thermodynamically of first order and indeed occurs between two liquid states, as originally predicted by Aptekar10. In addition we present evidence to support the relevance of spinodal divergences near such a transition, and the prediction3 that the transition marks a change in the liquid dynamic character from that of a fragile liquid to that of a strong liquid.

Molecular Memories That Survive Silicon Device Processing and Real-World Operation

Abstract: If molecular components are to be used as functional elements in place of the semiconductor-based devices present in conventional microcircuitry, they must compete with semiconductors under the extreme conditions required for processing and operating a practical device. Herein, we demonstrate that porphyrin-based molecules bound to Si(100), which exhibit redox behavior useful for information storage, can meet this challenge. These molecular media in an inert atmosphere are stable under extremes of temperature (400°C) for extended periods (approaching 1 hour) and do not degrade under large numbers of read-write cycles (10 12 ).

Six-band k⋅p calculation of the hole mobility in silicon inversion layers: Dependence on surface orientation, strain, and silicon thickness

Abstract: A six-band k⋅p model has been used to study the mobility of holes in Si inversion layers for different crystal orientations, for both compressive or tensile strain applied to the channel, and for a varying thickness of the Si layer. Scattering assisted by phonons and surface roughness has been accounted for, also comparing a full anisotropic model to an approximated isotropic treatment of the matrix elements. Satisfactory qualitative (and in several cases also quantitative) agreement is found between experimental data and theoretical results for the density and temperature dependence of the mobility for (001) surfaces, as well as for the dependence of the mobility on surface orientation [for the (011) and (111) surfaces]. Both compressive and tensile strain are found to enhance the mobility, while confinement effects result in a reduced hole mobility for a Si thickness ranging from 30 to 3 nm.

Light transmission in quasiperiodic multilayers of porous silicon

Abstract: Porous silicon is an efficient photo- and electro-luminescent material and represents a promising candidate for opto-electronic applications On the other hand, quasiperiodic structures have been shown to be effective media for light localization and third harmonic generation In this work, we present a photonic model for quasiperiodic multilayer structures, which are built experimentally by alternating porous silicon layers with high and low refractive indices The analysis of the light propagation through these structures is based on the transfer matrix theory The theoretical reflectance spectrum is compared with experimental data, observing a good agreement

High Capacity, Reversible Silicon Thin-Film Anodes for Lithium-Ion Batteries

Abstract: The properties of amorphous 250 nm and 1 μm silicon films deposited by radio-frequency (rf) magnetron sputtering on copper foil are investigated using X-ray diffractιon, scanning electron microscopy (SEM), and electrochemical methods. Galvanostatic half-cell electrochemical measurements conducted between 0.02 and 1.2 V using a lithium counter electrode have shown that the 250 nm Si thin films exhibit an excellent reversible specific capacity of nearly 3500 mAh/g when tested for 30 cycles. The high reversible capacity and excellent cyclability of the 250 nm sputtered silicon thin films suggest excellent adhesion between Si and Cu leading to high capacity retention. SEM analysis conducted on the 250 nm Si films after the 30th charge suggests the good adhesion of the ∼2 μm diam "plates" of silicon to the copper substrate.

Polymer replicas of photonic porous silicon for sensing and drug delivery applications.

Abstract: Elaborate one-dimensional photonic crystals are constructed from a variety of organic and biopolymers, which can be dissolved or melted, by templating the solution-cast or injection-molded materials in porous silicon or porous silicon dioxide multilayer (rugate dielectric mirror) structures. After the removal of the template by chemical dissolution, the polymer castings replicate the photonic features and the nanostructure of the master. We demonstrate that these castings can be used as vapor sensors, as deformable and tunable optical filters, and as self-reporting, bioresorbable materials.

Semiconductor transistor having a stressed channel

Abstract: A process is described for manufacturing an improved PMOS semiconductor transistor. Recesses are etched into a layer of epitaxial silicon. Source and drain films are deposited in the recesses. The source and drain films are made of an alloy of silicon and germanium. The alloy is epitaxially deposited on the layer of silicon. The alloy thus has a lattice having the same structure as the structure of the lattice of the layer of silicon. However, due to the inclusion of the germanium, the lattice of the alloy has a larger spacing than the spacing of the lattice of the layer of silicon. The larger spacing creates a stress in a channel of the transistor between the source and drain films. The stress increases IDSAT and IDLIN of the transistor. An NMOS transistor can be manufactured in a similar manner by including carbon instead of germanium, thereby creating a tensile stress.

Dendrite-Assisted Growth of Silicon Nanowires in Electroless Metal Deposition

Abstract: This article concerns the detailed investigations on the silver dendrite-assisted growth of single-crystalline silicon nanowires, and their possible self-assembling nanoelectrochemistry growth mechanism. The growth of silicon nanowires was carried out through an electroless metal deposition process in a conventional autoclave containing aqueous HF and AgNO3 solution near room temperature. In order to explore the mechanism and prove the centrality of silver dendrites in the growth of silicon nanowires, other etching solution systems with different metal species were also investigated in this work. The morphology of etched silicon substrates strongly depends upon the composition of the etching solution, especially the metal species. Our experimental results prove that the simultaneous formation of silver dendrites is a guarantee of the preservation of free-standing nanoscale electrolytic cells on the silicon substrate, and also assists in the final formation of silicon nanowire arrays on the substrate surface.

Structured Silicon Anodes for Lithium Battery Applications

Abstract: Pillar arrays fabricated on silicon substrates have been tested as potential anodes for lithium batteries. Electrodes of array characteristics, diameter 580 ′ 150 nm: fractional surface coverage 0.34: height 810 nm are reported here. Cyclic voltammetry (CV) and cyclic galvanostatic tests of alloying/dealloying of electrochemically produced lithium with silicon were carried out, and results correlated with SEM studies. Aerial current densities in the low and fractional mA cm - 2 , and voltage 25 mV to 2 V (vs. L/Li + ) were used. CV features correspond to various Zintl phase compounds (ZPCs). Structured electrodes of Si pillars maintained their structural integrity throughout cycling; planar Si electrodes showed cracks (2 μm features) after 50 cycles. A model is advanced in which lithium diffuses through a layer of ZPC to react with Si: growing ZPCs plastically deforms where necessary. Upon lithium dealloying vacancies coalesce to form voids at the ZPC/Si interface, Si rejoins the substrate. or precipitates out as a nanocrystalline material, and the voids appear as a fine pattern of cracks, looking like dried mud. The extra surface area that a pillar structure can confer on Si electrodes is essential and makes it practical to consider the possible eventual use of such anodes in integrated battery structure;.

Metalorganic Chemical Vapor Deposition Route to GaN Nanowires with Triangular Cross Sections

Abstract: High-quality gallium nitride nanowires have been synthesized via metal-initiated metalorganic chemical vapor deposition for the first time. Excellent substrate coverage was observed for wires prepared on silicon, c-plane, and a-plane sapphire substrates. The wires were formed via the vapor−liquid−solid mechanism with gold, iron, or nickel as growth initiators and were found to have widths of 15-200 nm. Transmission electron microscopy confirmed that the wires were single-crystalline and were oriented predominantly along the [210] or [110] direction. Wires growing along the [210] orientation were found to have triangular cross-sections. Transport measurements confirmed that the wires were n-type and had electron mobilities of ∼65 cm2/V·s. Photoluminescence measurements showed band edge emission at 3.35 eV (at 5 K), with a marked absence of low-energy emission from impurity defects.

High-Performance Nanowire Electronics and Photonics on Glass and Plastic Substrates

Abstract: The merger of nanoscale building blocks with flexible and/or low cost substrates could enable the development of high-performance electronic and photonic devices with the potential to impact a broad spectrum of applications. Here we demonstrate that high-quality, single-crystal nanowires can be assembled onto inexpensive glass and flexible plastic substrates to create basic transistor and light-emitting diode devices. In our approach, the high-temperature synthesis of single-crystal nanowires is separated from ambient-temperature solution-based assembly to enable the fabrication of single-crystal-like devices on virtually any substrate. Silicon nanowire field-effect transistors were assembled on glass and plastic substrates and display device parameters rivaling those of single-crystal silicon and exceeding those of state-of-the-art amorphous silicon and organic transistors currently used for flexible electronics on plastic substrates. Nanowire transistor devices have been configured as low-threshold logi...

Pinpoint and bulk electrochemical reduction of insulating silicon dioxide to silicon.

Abstract: Silicon dioxide (SiO2) is conventionally reduced to silicon by carbothermal reduction, in which the oxygen is removed by a heterogeneous–homogeneous reaction sequence at approximately 1,700 °C. Here we report pinpoint and bulk electrochemical methods for removing oxygen from solid SiO2 in a molten CaCl2 electrolyte at 850 °C. This approach involves a 'contacting electrode', in which a metal wire supplies electrons to a selected region of the insulating SiO2. Bulk reduction of SiO2 is possible by increasing the number of contacting points. The same method was also demonstrated with molten LiCl-KCl-CaCl2 at 500 °C. The novelty and relative simplicity of this method might lead to new processes in silicon semiconductor technology, as well as in high-purity silicon production. The methodology may be applicable to electrochemical processing of a wide variety of insulating materials, provided that the electrolyte dissolves the appropriate constituent ion(s) of the material.

Determining the material structure of microcrystalline silicon from Raman spectra

Abstract: An easy and reliable method to extract the crystalline fractions in microcrystalline films is proposed. The method is shown to overcome, in a natural way, the inconsistencies that arise from the regular peak fitting routines. We subtract a scaled Raman spectrum that was obtained from an amorphous silicon film from the Raman spectrum of the microcrystalline silicon film. This subtraction leaves us with the Raman spectrum of the crystalline part of the microcrystalline film and the crystalline fraction can be determined. We apply this method to a series of samples covering the transition regime from amorphous to microcrystalline silicon. The crystalline fractions show good agreement with x-ray diffraction (XRD) results, in contrast to crystalline fractions obtained by the fitting of Gaussian line profiles applied to the same Raman spectra. The spectral line shape of the crystalline contribution to the Raman spectrum shows a clear asymmetry, an observation in agreement with model calculations reported previo...

Handbook of Infrared Spectroscopy of Ultrathin Films

Abstract: PrefaceAcronyms and SymbolsIntroduction1 Absorption and Reflection of Infrared Radiation byUltrathin Films11 Macroscopic Theory of Propagation of ElectromagneticWaves in Infinite Medium12 Modeling Optical Properties of a Material13 Classical Dispersion Models of Absorption14 Propagation of IR Radiation through Planar Interface between Two Isotropic Media141 Transparent Media142 General Case15 Reflection of Radiation at Planar Interface Covered by Single Layer16 Transmission of Layer Located at Interface between Two Isotropic Semi-infinite Media17 System of Plane-Parallel Layers: Matrix Method18 Energy Absorption in Layered Media181 External Reflection: Transparent Substrates182 External Reflection: Metallic Substrates183 ATR19 Effective Medium Theory110 Diffuse Reflection and TransmissionAppendixReferences2 Optimum Conditions for Recording Infrared Spectra of Ultrathin Films21 IR Transmission Spectra Obtained in Polarized Radiation22 IRRAS Spectra of Layers on Metallic Surfaces ("Metallic" IRRAS)23 IRRAS of Layers on Semiconductors and Dielectrics231 Transparent and Weakly Absorbing Substrates ("Transparent" IRRAS)232 Absorbing Substrates233 Buried Metal Layer Substrates (BML-IRRAS)24 ATR Spectra25 IR Spectra of Layers Located at Interface251 Transmission252 Metallic IRRAS253 Transparent IRRAS254 ATR26 Choosing Appropriate IR Spectroscopic Method for Layer on Flat Surface27 Coatings on Powders, Fibers, and Matte Surfaces271 Transmission272 Diffuse Transmittance and Diffuse Reflectance273 ATR274 Comparison of IR Spectroscopic Methods for Studying Ultrathin Films on PowdersReferences3 Interpretation of IR Spectra of Ultrathin Films31 Dependence of Transmission, ATR, and IRRAS Spectra of Ultrathin Films on Polarization (Berreman Effect)32 Theory of Berreman Effect321 Surface Modes322 Modes in Ultrathin Films323 Identification of Berreman Effect in IR Spectra of Ultrathin Films33 Optical Effect: Film Thickness, Angle of Incidence, and Immersion331 Effect in "Metallic" IRRAS332 Effect in "Transparent" IRRAS333 Effect in ATR Spectra334 Effect in Transmission Spectra34 Optical Effect: Band Shapes in IRRAS as Function of Optical Properties of Substrate35 Optical Property Gradients at Substrate-Layer Interface: Effect on Band Intensities in IRRAS36 Dipole-Dipole Coupling37 Specific Features in Potential-Difference IR Spectra of Electrode-Electrolyte Interfaces371 Absorption Due to Bulk Electrolyte372 (Re)organization of Electrolyte in DL373 Donation/Backdonation of Electrons374 Stark Effect375 Bipolar Bands376 Effect of Coadsorption377 Electronic Absorption378 Optical Effect38 Interpretation of Dynamic IR Spectra: Two-Dimensional Correlation Analysis39 IR Spectra of Inhomogeneous Films and Films on Powders and Rough Surfaces Surface Enhancement391 Manifestation of Particle Shape in IR Spectra392 Coated Particles393 Composite, Porous, and Discontinuous Films394 Interpretation of IR Surface-Enhanced Spectra395 Rough Surfaces310 Determination of Optical Constants of Isotropic Ultrathin Films: Experimental Errors in ReflectivityMeasurements311 Determination of Molecular Packing and Orientation in Ultrathin Films: Anisotropic Optical Constants of Ultrathin Films3111 Order-Disorder Transition3112 Packing and Symmetry of Ultrathin Films3113 Orientation3114 Surface Selection Rule for Dielectrics3115 Optimum Conditions for MO StudiesReferences4 Equipment and Techniques 30741 Techniques for Recording IR Spectra of Ultrathin Films on Bulk Samples411 Transmission and Multiple Transmission412 IRRAS413 ATR414 DRIFTS42 Techniques for Ultrathin Films on Powders and Fibers421 Transmission422 Diffuse Transmission423 Diffuse Reflectance424 ATR43 High-Resolution FTIR Microspectroscopy of Thin Films431 Transmission432 IRRAS433 DRIFTS and DTIFTS434 ATR435 Spatial Resolution and Smallest Sampling Area436 Comparison of -FTIR Methods44 Mapping, Imaging, and Photon Scanning Tunneling Microscopy45 Temperature-and-Environment Programmed Chambers for In Situ Studies of Ultrathin Films on Bulk and Powdered Supports46 Technical Aspects of In Situ IR Spectroscopy of Ultrathin Films at Solid-Liquid and Solid-Solid Interfaces461 Transmission462 In Situ IRRAS463 ATR464 Measurement Protocols for SEC Experiments47 Polarization Modulation Spectroscopy48 IRRAS of Air-Water Interface49 Dynamic IR Spectroscopy491 Time Domain492 Frequency Domain: Potential-Modulation Spectroscopy410 Preparation of Substrates4101 Cleaning of IREs4102 Metal Electrode and SEIRA Surfaces4103 BML SubstrateReferences5 Infrared Spectroscopy of Thin Layers in Silicon Microelectronics51 Thermal SiO2 Layers52 Low-Temperature SiO2 Layers53 Ultrathin SiO2 Layers54 Silicon Nitride, Oxynitride, and Carbon Nitride Layers55 Amorphous Hydrogenated Films551 a-Si:H Films552 a-SiGe:H553 a-SiC:H Films56 Films of Amorphous Carbon, Boron Nitride, and Boron Carbide561 Diamondlike Carbon562 Boron Nitride and Carbide Films57 Porous Silicon Layers58 Other Dielectric Layers Used in Microelectronics581 CaF2, BaF2, and SrF2 Layers582 GeO2 Film583 Metal Silicides584 Amorphous Ta2O5 Films585 SrTiO3 Film586 Metal Nitrides59 Multi- and Inhomogeneous Dielectric Layers: Layer-by-Layer EtchingReferences6 Application of Infrared Spectroscopy to Analysis of Interfaces and Thin Dielectric Layers in Semiconductor Technology61 Ultrathin Oxide Layers in Silicon Schottky-Type Solar Cells62 Control of Thin Oxide Layers in Silicon MOS Devices621 CVD Oxide Layers in Al-SiOx -Si Devices622 Monitoring of Aluminum Corrosion Processes in Al-PSG Interface623 Determination of Metal Film and Oxide Layer Thicknesses in MOS Devices63 Modification of Oxides in Metal-Same-Metal Oxide-InP Devices64 Dielectric Layers in Sandwiched Semiconductor Structures641 Silicon-on-Insulator642 Polycrystalline Silicon-c-Si Interface643 SiO2 Films in Bonded Si Wafers644 Quantum Wells65 IR Spectroscopy of Surface States at SiO2 -Si Interface66 In Situ Infrared Characterization of Si and SiO2 Surfaces661 Monitoring of CVD of SiO2662 Cleaning and Etching of Si Surfaces663 Initial Stages of Oxidation of H-Terminated Si SurfaceReferences7 Ultrathin Films at Gas-Solid, Gas-Liquid, and Solid-Liquid Interfaces71 IR Spectroscopic Study of Adsorption from Gaseous Phase: Catalysis711 Adsorption on Powders712 Adsorption on Bulk Metals72 Native Oxides: Atmospheric Corrosion and Corrosion Inhibition73 Adsorption on Flat Surfaces of Dielectrics and Semiconductors74 Adsorption on Minerals: Comparison of Data Obtained In Situ and Ex Situ741 Characterization of Mineral Surface after Grinding: Adsorption of Inorganic Species742 Adsorption of Oleate on Calcium Minerals743 Structure of Adsorbed Films of Long-Chain Amines on Silicates744 Interaction of Xanthate with Sulfides75 Electrochemical Reactions at Semiconducting Electrodes: Comparison of Different In Situ Techniques751 Anodic Oxidation of Semiconductors752 Anodic Reactions at Sulfide Electrodes in Presence of Xanthate76 Static and Dynamic Studies of Metal Electrode-Electrolyte Interface: Structure of Double Layer77 Thin Polymer Films, Polymer Surfaces, and Polymer-Substrate Interface78 Interfacial Behavior of Biomolecules and Bacteria781 Adsorption of Proteins and Model Molecules at Different Interfaces782 Membranes783 Adsorption of BiofilmsReferencesAppendixReferencesIndex

Process for preparing macroscopic quantities of brightly photoluminescent silicon nanoparticles with emission spanning the visible spectrum

Abstract: Silicon nanoparticles with bright visible photoluminescence have been prepared by a new combined vapor phase and solution phase process, using only inexpensive commodity chemicals. CO2 laser induced pyrolysis of silane was used to produce Si nanoparticles at high rates (20−200 mg/h). Particles with an average diameter as small as 5 nm were prepared directly by this vapor phase (aerosol) synthesis. Etching these particles with mixtures of hydrofluoric acid (HF) and nitric acid (HNO3) reduced the size and passivated the surface of these particles such that after etching they exhibited bright visible luminescence at room temperature. The wavelength of maximum photoluminescence (PL) intensity was controlled from above 800 nm to below 500 nm by controlling the etching time and conditions. Particles with blue emission (maximum PL intensity at 420 nm) were prepared by rapid thermal oxidation of orange-emitting particles. The particle synthesis methods; steady-state photoluminescence spectra; results of their cha...

Supercritical Fluid–Liquid–Solid (SFLS) Synthesis of Si and Ge Nanowires Seeded by Colloidal Metal Nanocrystals

Abstract: Semiconductor nanowires, 5 to 20 nm in diameter and micrometers in length, appear to be promising candidates for a variety of new technologies, including computing, memory, and sensor applications. Suitable for these applications, silicon (Si) and germanium (Ge) nanowires ranging from 4 to 30 nm in diameter and micrometers in length can be produced in high temperature supercritical fluids by thermally degrading organosilane or organogermane precursos in the presence of organic-monolayer-protected gold nanocrystals. Although gas phase vapor-liquid-solid (VLS) methods can be used to produce a variety of different nanowire materials, high temperature supercritical fluids provide wire size control through nanocrystal size selection prior to synthesis, and high product yields due to the high precursor solubility.

Field-emission studies on thin films of zinc oxide nanowires

Abstract: Studies on field emission (FE) from thin films of zinc oxide (ZnO) nanowires found that both the turn-on voltage and emission current density depend on the areal density of nanowires. The density of ZnO nanowires is controlled by the gold (Au) nanoparticle density deposited on the silicon substrates. The growth of ZnO nanowires was achieved by the thermal evaporation/condensation method. It is shown that the same screening effect observed on carbon nanotube field emitters also affects the FE from thin films of ZnO nanowires. Thin films with the lowest areal density of ZnO nanowires showed much better FE characteristics, comparable to that of carbon nanotubes. More importantly, the FE characteristics of ZnO nanowire thin film were further improved with annealing in hydrogen.