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Showing papers in "Journal of Vacuum Science & Technology B in 1999"


Journal ArticleDOI
TL;DR: In this article, the Schottky barrier is described by two fitting parameters that are the effective barrier heights ΦBeff and the ideality factors n. Due to lateral inhomogeneities of the barrier height, both parameters differ from one diode to another.
Abstract: Most metal–semiconductor contacts are rectifying. For moderately doped semiconductors, the current transport across such Schottky contacts occurs by thermionic emission over the Schottky barrier. The current–voltage characteristics of real Schottky contacts are described by two fitting parameters that are the effective barrier heights ΦBeff and the ideality factors n. Due to lateral inhomogeneities of the barrier height, both parameters differ from one diode to another. However, their variations are correlated in that ΦBeff becomes smaller with increasing n. Extrapolations of such ΦBeff-versus-n plots to the corresponding image-force-controlled ideality factors nif give the barrier heights of laterally homogeneous contacts. They are then compared with the theoretical predictions for ideal Schottky contacts. Data of Si, GaN, GaAs, and CdTe Schottky contacts reveal that the continuum of metal-induced gap states is the fundamental mechanism that determines the barrier heights. However, there are additional b...

411 citations


Journal ArticleDOI
TL;DR: In this paper, the self-formation of periodic, supramolecular (micrometer scale) pillar arrays in a thin, single-homopolymer film melt, which was originally flat on a plate was observed.
Abstract: We observed, and believe it to be the first time, the self-formation of periodic, supramolecular (micrometer scale) pillar arrays in a thin, single-homopolymer film melt, which was originally flat on a plate. The self-formation was induced by placing a second plate (called a mask) a distance above the polymer film. The pillars, formed by rising against the gravitational force and surface tension, bridge the two plates. The pillar height is equal to the plate-mask separation, which is two to seven times the film’s initial thickness. If the surface of the mask has a protruding pattern (e.g., a triangle or rectangle), the pillar array can be formed only under the protruding pattern with the edge of the array aligned to the boundary of the mask pattern. We also discuss a model and novel applications of lithographically induced self-assembly.

364 citations


Journal ArticleDOI
TL;DR: In this paper, a new generation of ultra-high density patterned magnetic storage media has been proposed, and the magnetic properties of the particles and their mutual interactions have been measured.
Abstract: Arrays of discrete, lithographically patterned magnetic elements have been proposed as a new generation of ultrahigh density patterned magnetic storage media. Interferometric lithography has been used to make prototype arrays over large areas with periods of 100–200 nm. Arrays of magnetic pillars, pyramids, and dots have been made by electrodeposition, evaporation and liftoff, and etching processes, and the magnetic properties of the particles and their mutual interactions have been measured.

253 citations


Journal ArticleDOI
TL;DR: In this paper, an apparatus for deep-ultraviolet interferometric lithography is described, in which the interfering beams illuminate the substrate through a fused silica prism and a layer of index-matching liquid.
Abstract: An apparatus for deep-ultraviolet interferometric lithography is described, in which the interfering beams illuminate the substrate through a fused silica prism and a layer of index-matching liquid. The liquid-immersion technique was found to be compatible with a commercially available, chemically amplified photoresist. The apparatus was used with a 257 nm light source to write gratings having a period of 97 nm and linewidth of approximately 40 nm.

242 citations


Journal ArticleDOI
TL;DR: In this paper, the role of spontaneous and piezoelectric polarization in III-V nitride heterostructures is investigated and a detailed analysis of their influence in the field effect transistors is presented.
Abstract: The role of spontaneous and piezoelectric polarization in III–V nitride heterostructures is investigated Polarization effects and crystal polarity are reviewed in the context of nitride heterostructure materials and device design, and a detailed analysis of their influence in nitride heterostructure field-effect transistors is presented The combined effects of spontaneous and piezoelectric polarization are found to account well for carrier concentrations observed in AlGaN/GaN transistor structures with low to moderate Al concentrations, while the data for higher Al concentrations are consistent with defect formation in the AlGaN barrier Theoretical analysis suggests that incorporation of In into the barrier and/or channel layers can substantially increase polarization charge at the heterojunction interface The use of polarization effects to engineer Schottky barrier structures with large enhancements in barrier height is also discussed, and electrical characteristics of transistors with conventional a

202 citations


Journal ArticleDOI
TL;DR: In this paper, a 1 in. diameter curved surface with a 46 mm radius of curvature was demonstrated with step and flash imprint lithography (SFIL) using templates patterned by ion beam proximity printing (IBP).
Abstract: Submicron patterning of 1 in. diameter curved surfaces with a 46 mm radius of curvature has been demonstrated with step and flash imprint lithography (SFIL) using templates patterned by ion beam proximity printing (IBP). Concave and convex spherical quartz templates were coated with 700-nm-thick poly(methylmethacrylate) (PMMA) and patterned by step-and-repeat IBP. The developed resist features were etched into the quartz template and the remaining PMMA stripped. During SFIL, a low viscosity, photopolymerizable formulation containing organosilicon precursors was introduced into the gap between the etched template and a substrate coated with an organic transfer layer and exposed to ultraviolet illumination. The smallest features on the templates were faithfully replicated in the silylated layer.

202 citations


Journal ArticleDOI
TL;DR: In this paper, it was argued that the facile electron field emission from carbon systems occurs primarily because surface groups such as C-H can produce large changes in local electron affinity, so that electric fields from the anode can be focused toward unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer.
Abstract: It is argued that the facile electron field emission from carbon systems occurs primarily because surface groups such as C–H can produce large changes in local electron affinity, so that electric fields from the anode can be focused toward unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer. The resulting downward band bending creates large surface fields which allow Fowler–Nordheim emission, while not exceeding the material’s breakdown field.

191 citations


Journal ArticleDOI
TL;DR: In this article, a review of the current understanding of the spin relaxation of conduction electrons in nonmagnetic semiconductors and metals is presented in the perspective of current understanding.
Abstract: Prospect of building electronic devices in which electron spins store and transport information has revived interest in the spin relaxation of conduction electrons. Since spin-polarized currents cannot flow indefinitely, basic spin-electronic devices must be smaller than the distance electrons diffuse without losing its spin memory. Some recent experimental and theoretical effort has been devoted to the issue of modulating the spin relaxation. It has been shown, for example, that in certain materials doping, alloying, or changing dimensionality can reduce or enhance the spin relaxation by several orders of magnitude. This brief review presents these efforts in the perspective of the current understanding of the spin relaxation of conduction electrons in nonmagnetic semiconductors and metals.

161 citations


Journal ArticleDOI
TL;DR: In this article, the authors observed three distinct behavioral states in field emission from single-walled carbon nanotubes between temperatures of 300 and 1800 K and found that the stable behavior of clean nanotube states breakdown at extremely high currents and temperatures.
Abstract: We observe three distinct behavioral states in field emission from single-walled carbon nanotubes between temperatures of 300 and 1800 K. At room temperature, nanotubes emit through adsorbate states correlated to the presence of water. These states are removed above 900 K. After adsorbate removal, the apparently clean nanotube state shows lower emission current and substantially reduced emission noise. Current-temperature measurements identify a deviation from metallic tunneling behavior. Nanotube field emission undergoes a second, field-stabilized transition at high temperatures which reduces the current by as much as five orders of magnitude relative to the room temperature current. This current decrease is 100% recoverable. In addition, the stable behavior of clean nanotube states breakdown at extremely high currents and temperatures. Rings form around the field emission images, similar to those observed in metals at extreme current densities. Under these extreme conditions, we also find evidence for t...

160 citations


Journal ArticleDOI
TL;DR: In this paper, an improved understanding of the role of charging and surface recombination effects on cathodoluminescent intensity and efficiency is presented. But, the improved understanding is limited to the case of field emission displays (FEDs).
Abstract: Recent advances in the phosphors used for field emission displays (FEDs) are discussed. After reviewing the range of voltages and phosphors being used in first generation devices, the improved properties of future generation phosphors are reviewed. Specifically, next generation displays will require better low voltage efficiencies, chromaticity, saturation behavior, and maintenance. Possible routes to achieve these improvements are discussed. The improved understanding of the role of charging and surface recombination effects on cathodoluminescent intensity and efficiency is reviewed. An improved understanding of electron beam-stimulated surface chemical reaction effects on the degradation of phosphor is presented. It is concluded that recent research efforts have created a new level of understanding of FED phosphors, and this should lead to the necessary improvements in properties.

159 citations


Journal ArticleDOI
Abstract: This article takes a fresh look at the theoretical basis of methods for deriving emission area from the intercept of a Fowler–Nordheim (FN) plot. It sharpens the concepts involved, by defining a generalized FN equation, an intercept correction factor, and an emission-area extraction function. Some new general formulas are introduced. An improved version of the Charbonnier and Martin (CM) [F. M. Charbonnier and E. E. Martin, J. Appl. Phys. 33, 1897 (1962)] method for extracting emission area is discussed; this is numerically illustrated using formulas developed within the framework of Murphy and Good’s 1956 [E. L. Murphy and R. H. Good, Phys. Rev. 102, 1464 (1956)] treatment of the theory of cold field emission from metals at zero temperature. It is shown that uncertainties were underestimated in the methods introduced by CM and by Spindt and colleagues, [C. A. Spindt et al., J. Appl. Phys. 47, 5248 (1976)] but can be reduced by iterating the new method. Strictly, the numerical results presented apply only...

Journal ArticleDOI
TL;DR: In this paper, the synthesis and properties of a new generation of fine particle low voltage phosphors in field emission displays are reviewed and initial new results from novel synthetic methodology are presented and discussed.
Abstract: Factors affecting the synthesis and properties of a new generation of fine particle low voltage phosphors in field emission displays are reviewed. The morphology and particle size, the composition and stoichiometry, the stability, together with the nature and shape of the particle surface, all play important roles in the performance of the final phosphor. Initial new results from novel synthetic methodology are presented and discussed. Their implications in the light of the known literature point the way to the successful conclusion of the current thrust of phosphor research for good red, green, and blue low voltage, high definition phosphors.

Journal ArticleDOI
TL;DR: In this article, the process parameters in the ambient drying process affect the properties of a spin-coated xerogel film and the results of successful spin-on deposition of highly porous (>70%), thick (>1 μm), crack-free, and high porosity films was accomplished using a solvent saturated atmosphere during spinning and aging.
Abstract: SiO2-based xerogels are highly porous materials that may enhance the performance of microelectronic devices due to their extremely low dielectric constants (e=1.36–2.2). Conventional xerogel and aerogel manufacturing techniques include an expensive and hazardous supercritical drying step to deposit crack free, high porosity films. Ambient drying techniques have recently been developed and in this article, we discuss how the process parameters in the ambient drying process affect the properties of a spin-coated film. Successful spin-on deposition of highly porous (>70%), thick (>1 μm), crack-free, xerogel films was accomplished using a solvent saturated atmosphere during spinning and aging. The saturated atmosphere allowed for the isolation of each processing step and a better understanding of the effects of process variable changes. The film porosity was controlled by varying the extent of silylation (surface modification), the aging time, or the initial water/silane ratio. Fourier transform infrared spec...

Journal ArticleDOI
TL;DR: In this paper, a soft x-ray photoelectron spectroscopy with synchrotron radiation is used to study the interfaces of SiO2/Si(111), SiO 2/Si (100), Si O 2 /Si(100), and Si O 3 /Si 3 N 4 for device-quality ultrathin gate oxides and nitrides.
Abstract: High resolution soft x-ray photoelectron spectroscopy with synchrotron radiation is used to study the interfaces of SiO2/Si(111), SiO2/Si(100), Si(111)/Si3N4, and SiO2/Si3N4 for device-quality ultrathin gate oxides and nitrides. The thin oxides and nitrides were grown by remote plasma deposition at a temperature of 300 °C. Aftergrowth samples were further processed by rapid thermal annealing for 30 s at various temperatures from 700 to 950 °C. The Si(111)/Si3N4 samples were air exposed and formed a thin ∼6 A SiO2 layer with a Si(2p) core-level shift of 3.9 eV, thus allowing us to study both the Si(111)/Si3N4 and SiO2/Si3N4 interfaces with a single type of sample. We obtain band offsets of 4.54±0.06 eV for SiO2/Si(111) and 4.35±0.06 eV for SiO2/Si(100) with film thicknesses in the range 8–12 A. The Si(111)/Si3N4 nitrides show 1.78±0.09 eV valence-band offset for 15–21 A films. This value agrees using the additivity relationship with our independent photoemission measurements of the nitride–oxide valence-ba...

Journal ArticleDOI
TL;DR: The properties of titanium nitride deposited by atomic layer epitaxy (ALE) using three different deposition processes, i.e., TiI4+NH3, TiCl4+ NH3 and TiCl 4+Zn+NH 3, as a diffusion barrier between cop...
Abstract: The properties of titanium nitride deposited by atomic layer epitaxy (ALE) using three different deposition processes, i.e., TiI4+NH3, TiCl4+NH3 and TiCl4+Zn+NH3, as a diffusion barrier between cop ...

Journal ArticleDOI
TL;DR: In this paper, a two-step surface treatment is introduced to obtain low resistance Pt contacts to p-type GaN. The first step is performed after the mesa etching process using buffered oxide etch (BOE) and ammonium sulfide [(NH4)2Sx], and the second step using BOE.
Abstract: Two-step surface treatment is introduced to obtain low resistance Pt contacts to p-type GaN. The first step is performed after the mesa etching process using buffered oxide etch (BOE) and ammonium sulfide [(NH4)2Sx]. This is followed by the second step using BOE. The Pt contact, that was simply BOE treated, yields 2.1(±0.9)×10−2 Ω cm2. However, the contact which was treated sequentially using ultrasonically boiled BOE (10 min) and boiled (NH4)2Sx (10 min), produces a specific contact resistance of 2.0(±3.5)×10−5 Ω cm2. To the best of our knowledge, this is the lowest contact resistance reported hitherto for the contacts on p-GaN. The effective Schottky barrier heights (SBHs) of the differently surface-treated contacts were determined using the Norde and current–voltage methods. It is shown that the SBHs are dependent upon the surface treatment conditions.

Journal ArticleDOI
TL;DR: In this article, a glancing-angle deposition technique was used to produce regular lattices of submicrometer pillars and helices with a two-dimensional lattice constant below 1 μm and structure heights of 0.5-10 μm.
Abstract: We use a glancing-angle deposition technique to produce regular lattices of submicrometer pillars and helices with a two-dimensional lattice constant below 1 μm and structure heights of 0.5–10 μm. Possible applications of such structures include photonic crystals and magnetic-storage media.

Journal ArticleDOI
TL;DR: In this article, a double-layer 190 nm period metal grating at the interface between the waveguide core and waveguide cladding layer was fabricated, which can be applied to almost any waveguide structure.
Abstract: We fabricated a new waveguide polarizer, that has a double-layer 190 nm period metal grating at the interface between the waveguide core and waveguide cladding layer. Both silicon nitride and polymethylmethancrylate were used as waveguide cores. 190 nm period gratings were patterned by nanoimprint lithography. The new type waveguide polarizer works as a broadband and highly efficient transverse magnetic-pass polarizer with transverse electric-polarized light highly attenuated. The new polarizer structure can be applied to almost any waveguide structures. The simple fabrication process, which is compatible with conventional device processing, makes it very attractive for integrated optoelectronic system.

Journal ArticleDOI
TL;DR: In this paper, the waveguide bend is defined by removing a row of pillars in a two-dimensional photonic crystal of 5 μm long, 205 nm diameter pillars placed on a square lattice with a pitch of 570 nm.
Abstract: Fabrication process for sharp waveguide bends in a two-dimensional photonic band gap structure in silicon is developed The waveguide bend is defined by removing a row of pillars in a two-dimensional photonic crystal of 5 μm long, 205 nm diameter pillars placed on a square lattice with a pitch of 570 nm To meet the severe nanotolerance requirements in such a device the SF6/O2 electron cyclotron resonance plasma process at reduced temperature is tailored to extreme profile control The impact of main plasma parameters—ie, temperature, oxygen/fluorine content, and ion energy—on the sidewall passivation process is unraveled in detail Crystallographic orientation preference in the etch rate is observed

Journal ArticleDOI
TL;DR: In this article, the authors measured the sidewall roughness of a positive-tone, chemically amplified resist, Shipley APEX-E exposed by X-ray radiation and found that the overall roughness for fully developed nested lines, under normal processing conditions, is on the order of 4.3 nm root-mean-square (rms) and shows no dose dependence.
Abstract: As device critical dimensions continue to decrease, sidewall roughness will become increasingly important. To address this issue, we have measured the sidewall roughness of a positive-tone, chemically amplified resist, Shipley APEX-E exposed by X-ray radiation. We have also examined factors that contribute to the overall sidewall roughness such as mask roughness, the development process, variations in acid diffusion, shot noise, and the effects of acid volatility. The overall sidewall roughness for fully developed nested lines, under normal processing conditions, is on the order of 4.3 nm root-mean-square (rms) and shows no dose dependence. Isolated lines, however, do demonstrate a dose-dependent sidewall roughness. Samples exposed with doses of 60–100 mJ/cm2 exhibit a monotonically decreasing trend in roughness from 6.5 to about 4.5 nm rms, respectively. The development process, in tandem with pattern-specific parameters, appears to cause this difference in the roughness between nested and isolated lines...

Journal ArticleDOI
TL;DR: In this paper, a single and double pulse doped metamorphic high electron mobility transistor (MHEMT) structures have been grown on GaAs substrates by molecular beam epitaxy.
Abstract: Single and double pulse doped metamorphic high electron mobility transistor (MHEMT) structures have been grown on GaAs substrates by molecular beam epitaxy. A linear indium graded buffer layer was used to expand the lattice constant. Transmission electron microscopy cross sections showed planar interfaces. Threading dislocations were not observed along both cleavage directions. For a single pulse doped MHEMT structure with an In0.56Ga0.44As channel layer, the mobilities (10 030 cm2/V s at 292 K; 32 560 cm2/V s at 77 K) and sheet density (3.2×1012 cm−2) were nearly equivalent to values obtained for the same structure grown on an InP substrate. Secondary ion mass spectroscopy measurements of a double pulse doped structure indicated no measurable migration of the silicon doping pulses. MHEMT devices with 0.15 μm gates were fabricated, tested, and compared to GaAs pseudomorphic HEMT devices of the same geometries. Above 9 GHz, the MHEMT devices exhibited lower noise figure. From 3 to 26 GHz, the associated ga...

Journal ArticleDOI
TL;DR: In this paper, a porous polysilicon (PPS) diode with a structure of Au/PPS/n-type Si operates as an efficient stable surface-emitting cold cathode.
Abstract: It is demonstrated that a porous polysilicon (PPS) diode with a structure of Au/PPS/n-type Si operates as an efficient stable surface-emitting cold cathode. 1.5 μm of an nondoped polysilicon layer is formed on an n-type (100) silicon wafer and anodized in a solution of HF (50%): ethanol=1:1 at a current density of 10 mA/cm2 for 30 s under illumination by a 500 W tungsten lamp from a distance of 20 cm. Subsequently, a PPS layer is oxidized in a rapid thermal oxidation furnace for 1 h at a temperature of 700 °C. A semitransparent thin Au film (about 10 nm thick) is deposited onto the PPS layer as a positive electrode and an ohmic contact is formed at the back side of the silicon wafer as a negative electrode. When a positive bias is applied to the Au electrode in vacuum, the diode uniformly emits electrons. No electron emission is observed in the negatively biased region. Emission current is about 10−4 A/cm2 at a 20 V bias. It is further demonstrated that electrons are quasiballistically emitted from a PPS ...

Journal ArticleDOI
TL;DR: In this paper, the surface potential of a thin ferroelectric thin film was measured using scanning probe microscopy with a small oscillating voltage between the probe tip and the substrate.
Abstract: Scanning probe microscopy was used to form local polarized domains in ferroelectric thin films by applying a voltage between the gold-coated cantilever and the conductive substrate in contact mode. Two methods of visualizing the poled areas are described. The first is to detect the piezoelectric response of the films by applying a small oscillating voltage between the probe tip and the substrate. This measurement determines the local ferroelectric polarity and domain structure directly. The second method is to measure the surface potential of the poled films using scanning Maxwell stress microscopy. This does not directly address the ferroelectric behavior of the film, but rather the potential due to surface charge. We determined the surface potential dependence on pulse voltage and duration applied to the ferroelectric film. The results demonstrate that the charged area will increase rapidly, but the surface potential will saturate as the pulse voltage and duration are increased. The resultant stable loc...

Journal ArticleDOI
TL;DR: In this paper, a microwave plasma source that provides as high as 99.9% utilization removal efficiency (URE) of the reactant gas (NF3) during chamber clean is described.
Abstract: The semiconductor industry uses a large amount of perfluoro compounds (PFCs), and their impact on global warming has become a major environmental concern. In the semiconductor industry, PFC are used to periodically remove deposits from the chamber walls of chemical vapor deposition (CVD) reactors after film deposition. These chamber clean processes account for typically 50%–70% of the PFC usage in a semiconductor wafer fabrication site, the rest being mainly used for wafer-etching processes. With a conventional parallel plate radio frequency (rf) plasma reactor, the PFC gas utilization is incomplete and a large fraction of unreacted gas can be emitted in the atmosphere. This paper describes a microwave plasma source that provides as high as 99.9% utilization removal efficiency (URE) of the reactant gas (NF3) during chamber clean. This technology brings the million metric tons carbon equivalent (MMTCE) of a chamber clean to negligible levels and also enhances the chamber clean efficiency and the system thr...

Journal ArticleDOI
TL;DR: In this article, the nucleation and growth of NiAs-type MnAs was investigated in real time by reflection high-energy electron diffraction on different As-rich GaAs(001) templates, well characterized by reflectance difference spectroscopy, and the lattice mismatch accommodation is anisotropic with regularly arranged misfit dislocations along the [110] direction.
Abstract: On different As-rich GaAs(001) templates, well characterized by reflectance difference spectroscopy, nucleation and growth of NiAs-type MnAs is investigated in real time by reflection high-energy electron diffraction. Using very high As4/Mn flux ratios and low growth rates, one of the two occurring azimuthal alignments of the (1100) orientation can be nearly suppressed even in the nucleation stage, and it vanishes completely with further growth. Annealing is found to be very effective in surface smoothing. In dependence on the As/Mn ratio the MnAs(1100) surface develops different reconstructions. This finding is important for further investigations in the growth of double heterostructures. High-resolution transmission electron microscopy of as-grown MnAs/GaAs samples reveals an abrupt interface. The lattice mismatch accommodation is anisotropic with regularly arranged misfit dislocations along the [110] direction and less localized coherency strain in the [110] direction, consistent with a near-coincid...

Journal ArticleDOI
TL;DR: In this article, the possibility for wafer-scale nano-print lithography is addressed, and the results presented here are all obtained from 2 in. sized substrate and stamp wafers.
Abstract: Nanoimprint lithography is a promising technique for fabrication of nanometer-sized structures with an eventual throughput capacity similar to UV-lithography based production of integrated circuits. In this article we address the possibility for wafer scale nanoimprint lithography, and the results presented here are all obtained from 2 in. sized substrate and stamp wafers. Our nanoimprint lithography equipment is described and some of its characteristics are discussed. These include ultrafast imprint cycle times of less than 2 min, good temperature monitoring, and control possibility of the substrate temperature. We show complete results after imprint, removal of remaining resist, and liftoff for 2 in. wafers. Furthermore, in this article the relation between polymer sticking to the stamp applied pressure, stamp depth, etc. is studied in detail.

Journal ArticleDOI
TL;DR: In this article, negative-tone imaging was used to generate holes in photoresist, suitable for subsequent deposition or electroplating of magnetic material, and a negative i-line, chemically-amplified resist (OHKA THMR-iN PS1) was applied to form 200 nm period arrays of magnetic dots.
Abstract: Magnetic information storage density has increased at the rate of 60% per year for the past seven years. There is wide agreement that continuation of this trend beyond the physical limits of the continuous thin-film media currently used will likely require a transition to discrete, lithographically defined magnetic pillars. Interference lithography (IL) appears to be the most cost-effective means of producing two-dimensional arrays of such pillars. IL can rapidly expose large areas with relatively simple equipment, without the need for a mask, and with fine control of the ratio of pillar diameter to period. We show that negative-tone imaging yields three times the contrast of positive-tone imaging for the generation of holes in photoresist, suitable for subsequent deposition or electroplating of magnetic material. We use a negative i-line, chemically-amplified resist (OHKA THMR-iN PS1) to form 200 nm period arrays of magnetic dots in Co and Ni. Such arrays, with a variety of well controlled diameters, are used to study the effect of particle size on magnetic behavior.

Journal ArticleDOI
TL;DR: An effective gate recess etch process has been applied to AlGaN/GaN modulation-doped field effect transistors (MODFETs), utilizing low power Cl2 reactive ion etching as discussed by the authors.
Abstract: An effective gate recess etch process has been applied to AlGaN/GaN modulation-doped field-effect transistors (MODFETs), utilizing low power Cl2 reactive ion etching. In comparison to GaAs-based materials, GaN shows a greater robustness to ion damage under ion bombardment at very low ion energies (<70 V). It suggests that a viable gate recess etch process is possible. Recessed gate AlGaN/GaN MODFETs with gate to drain breakdown higher than −80 V have been demonstrated with an optimized lower power Cl2 reactive ion etching.

Journal ArticleDOI
TL;DR: In this article, the mask of a current EUV system is replaced by an array of micron-sized mirrors and patterns are achieved by modulating individual mirrors to create selected bright and dark spots.
Abstract: Masks have been identified as the high risk, high cost issue for extreme ultraviolet (EUV) lithography. Challenges in EUV mask technology such as providing a pellicle and correcting defects have prompted the search for a maskless technique. Here we describe two approaches in which the mask of a current EUV system is replaced by an array of micron-sized mirrors. Patterns are achieved by modulating individual mirrors to create selected bright and dark spots. In one approach, individual mirrors can be lowered by λ/4 to yield locally dark regions because of destructive interference. In another approach, each mirror is mounted on a cantilever. Selected cantilevers can be tilted such that incident light from those mirrors is out of the pupil of the imaging objective. The wafer is mechanically scanned and the object is electronically scrolled across the array of mirrors in order to build up the required pattern. We have simulated the mechanical properties of the micron-sized mirrors and some aerial images showin...

Journal ArticleDOI
TL;DR: In this paper, a nanocrystalline diamond films were deposited on p-type Si(100) substrates using plasma enhanced chemical vapor deposition (CVD) and showed good field emission properties with threshold fields of around 5 V'μm−1 (for 1 nA emission current).
Abstract: We have deposited nanocrystalline diamond films on p-type Si(100) substrates using plasma enhanced chemical vapor deposition (CVD). The diamond films were deposited at substrate temperatures between 950 and 980 °C using a high methane concentration of 5% in H2. The films obtained showed good field emission properties with threshold fields of around 5 V μm−1 (for 1 nA emission current). X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy showed that the nanocrystalline films still exhibit the basic electronic features of diamond with a band gap of 5.5 eV and a negative electron affinity when the surface is hydrogen plasma treated. The Fermi level position in these films is found to be 1±0.2 eV above the valence band maximum. The energy resolved field emission measurements show the typical asymmetric peak shape of Fowler-Nordheim (FN) tunneling through a surface potential barrier. The electrons emitted originate from a continuum of electronic states at the Fermi energy of the emitter...