Showing papers on "Nitride published in 2005"

Preparation and Characterization of Well‐Ordered Hexagonal Mesoporous Carbon Nitride

Abstract: The synthesis and characteristic properties of a highly ordered mesoporous carbon nitride material (MCN-1), were analyzed. The ordered MCN-1 structure was investigated by powder X-ray diffraction (XRD) and nitrogen gas adsorption measurements. The X-ray diffraction pattern of the MCN-1 material showed three peaks, which can be assigned to the (100), (110), and (200) diffractions of a 2D hexagonal lattice. The MCN-1 exhibits a total pore volume of 0.55 cm 3g-1 and a specific Brunauer-Emmett-Teller (BET) surface area of 505 m2g-1. The results show that owing to its textural characteristics, MCN-1 material could be useful for applications such as catalytic supports, gas storage, and lubricants.

RuO2-Loaded β-Ge3N4 as a Non-Oxide Photocatalyst for Overall Water Splitting

Abstract: Germanium nitride β-Ge3N4 dispersed with RuO2 nanoparticles is presented as the first example of a non-oxide photocatalyst for the stoichiometric decomposition of H2O into H2 and O2. All of the successful photocatalysts developed for overall water splitting over the past 30 years have been based on oxides of metals. The discovery of a non-oxide photocatalyst, such as nitrides and oxynitrides, achieving the same function is therefore expected to stimulate research on non-oxide photocatalysts. New opportunities for progress in the development of visible light-driven photocatalysis can thus be expected, as the higher valence band positions of metal nitrides compared to the corresponding metal oxides provide narrower band gaps, which are suitable for visible light activity.

Vapor-solid growth and characterization of aluminum nitride nanocones

Abstract: Aluminum nitride nanostructures are attractive for many promising applications in semiconductor nanotechnology. Herein we report on vapor−solid growth of quasi-aligned aluminum nitride nanocones on catalyst-coated wafers via the reactions between AlCl3 vapor and NH3 gas under moderate temperatures around 700 °C, and the growth mechanism is briefly discussed. The as-prepared wurtzite aluminum nitride nanocones grow preferentially along the c-axis with adjustable dimensions of the sharp tips in the range of 20−60 nm. The photoluminescence spectrum reveals a broad blue emission band with a fine photon structure while the field emission study shows a notable emission current with a moderate turn-on field as expected, suggesting their potential applications in light and electron emission nanodevices.

High‐Thermal‐Conductivity Aluminum Nitride Ceramics: The Effect of Thermodynamic, Kinetic, and Microstructural Factors

Abstract: Improvement in the thermal conductivity of aluminum nitride (AlN) can be realized by additives that have a high thermodynamic affinity toward alumina (Al{sub 2}O{sub 3}), as is clearly demonstrated in the aluminum nitride-yttria (AlN-Y{sub 2}O{sub 3}) system. A wide variety of lanthanide dopants are compared at equimolar lanthanide oxide:alumina (Ln{sub 2}O{sub 3}:Al{sub 2}O{sub 3}, where Ln is a lanthanide element) ratios, with samaria (Sm{sub 2}O{sub 3}) and lutetia (Lu{sub 2}O{sub 3}) being the dopants that give the highest- and lowest-thermal-conductivity AlN composites, respectively. The choice of the sintering aid and the dopant level is much more important than the microstructure that evolves during sintering. A contiguous AlN phase provides rapid heat conduction paths, even at short sintering times. AlN contiguity decreases slightly as the annealing times increase in the range of 1--1,000 min at 1,850 C. However, a substantial increase in thermal conductivity results, because of purification of AlN grains by dissolution-reprecipitation and bulk diffusion. Removal of grain-boundary phases, with a concurrent increase in AlN contiguity, occurs at high annealing temperatures or at long times and is a natural consequence of high dihedral angles (poor wetting) in liquid-phase-sintered AlN ceramics.

Microstructural design of silicon nitride with improved fracture toughness: II. Effects of yttria and alumina additives

Abstract: Significant improvements in the fracture resistance of self-reinforced silicon nitride ceramics have been obtained by tailoring the chemistry of the intergranular amorphous phase. First, the overall microstructure of the material was controlled by incorporation of a fixed amount of elongated s-Si3N4 seeds into the starting powder to regulate the size and fraction of the large reinforcing grains. With controlled microstructures, the interfacial debond strength between the reinforcement and the intergranular glass was optimized by varying the yttria-to-alumina ratio in the sintering additives. It was found that the steady-state fracture toughness value of these silicon nitrides increased with the Y:Al ratio of the oxide additives. The increased toughness was accompanied by a steeply rising R-curve and extensive interfacial debonding between the elongated s-Si3N4 grains and the intergranular glassy phase. Microstructural analyses indicate that the different fracture behavior is related to the Al (and O) content in the s´-SiAlON growth layer formed on the elongated s-Si3N4 grains during densification. The results imply that the interfacial bond strength is a function of the extent of Al and Si bonding with N and O in the adjoining phases with an abrupt structural/chemical interface achieved by reducing the Al concentration in both the intergranular phase and the s´-SiAlON growth layer. Analytical modeling revealed that the residual thermal expansion mismatch stress is not a dominant influence on the interfacial fracture behavior when a distinct s´-SiAlON growth layer forms. It is concluded that the fracture resistance of self-reinforced silicon nitrides can be improved by optimizing the sintering additives employed.

Molecular octa-uranium rings with alternating nitride and azide bridges.

Abstract: Uranium nitrides offer potential as future nuclear fuels and as probes of metal ligand multiple bonding involving the f-block actinide metals. However, few molecular examples are available for study owing to the difficulties in synthesis. Recent advances in organoactinide chemistry have provided a route to uranium nitride complexes that expands the options for developing UN chemistry. Several 24-membered uranium nitrogen rings, (UNUN3)4, have been synthesized by reduction of sodium azide with organometallic metallocene derivatives, [(C5Me4R)2U][(μ-Ph)2BPh2] (R = Me, H; Me = methyl, Ph = phenyl). The nanometer-sized rings contain unusual UNU nitride linkages that have short U-N distances within the double-bond range.

Covalent functionalization: towards soluble multiwalled boron nitride nanotubes.

Abstract: (Figure Presented) Playing with the band: Long alkyl chains are bound to boron nitride nanotubes (BNNTs) from the reaction of stearoyl chloride with amino groups on the BNNTs; the resulting functionalized BNNTs (see picture) are soluble in many organic solvents. Cathodoluminescence and UV/Vis absorption experiments indicate that the long alkyl chains may induce drastic changes in the band structure of BNNTs.

Silicon nitride etching methods

Abstract: Methods of etching silicon nitride material, and more particularly, etching nitride selective to silicon dioxide or silicide, are disclosed. The methods include exposing a substrate having silicon nitride thereon to a plasma including at least one fluorohydrocarbon and a non-carbon containing fluorine source such as sulfur hexafluoride (SF 6 ). The plasma may also include oxygen (O 2 ) and the fluorohydrocarbons may include at least one of: trifluoromethane (CHF 3 ), difluoromethane (CH 2 F 2 ), and methyl fluoride (CH 3 F). In an alternative embodiment, the plasma includes one of hydrogen (H 2 ) and nitrogen trifluoride (NF 3 ) and one of tetrafluoromethane (CF 4 ) and octafluorocyclobutane (C 4 F 8 ). The methods are preferably carried out using a low bias voltage, e.g. <100 V.

Method of producing thin films

Abstract: A process for producing metal nitride thin films comprising doping the metal nitride thin films by atomic layer deposition (ALD) with silicon or boron or a combination thereof. The work function of metal nitride thin films, which are used in metal electrode applications, can efficiently be tuned.

XPS investigations of chromium nitride thin films

Abstract: Cr–N film coatings were prepared by magnetron sputter deposition at different nitrogen partial pressures. The film characterisation by XRD and DTG gives average bulk compositions of Cr2N and CrN for the coatings. Highly sensitive XPS investigations were performed and the chemical and phase compositions of a film surface range of about 10 nm thickness was estimated quantitatively from the deconvoluted peak intensities. It is demonstrated that the composition of the surface of chromium nitride thin films differs from the core and is more complex in constitution. Not only chromium nitrides (Cr2N and CrN) but also chromium oxynitrides and chromium oxides (CrOx and CrOxHy) were detected. Metallic chromium was also found in films prepared at higher nitrogen flow. The concentration of the estimated phases shows dependence on film preparation and additional heat treatment.

Glow-discharge nitriding of AISI 316L austenitic stainless steel: influence of treatment temperature

Abstract: Nitriding treatments of austenitic stainless steels can be performed only at relatively low temperatures in order to avoid a decrease of corrosion resistance due to chromium nitride formation. These conditions promote the formation of the so-called S phase, which shows high hardness and good corrosion resistance. In the present paper, the influence of the treatment temperature of glow-discharge nitriding process on the microstructural and mechanical characteristics of AISI 316L steel samples was evaluated. Glow-discharge nitriding treatments were performed at temperatures in the range 673–773 K for 5 h at 10 3 Pa. The modified surface layer of the nitrided samples consists mainly of the S phase and, according to metallographic technique analysis, it seems to be essentially a modification of the austenite matrix. All the nitrided sample types show a peculiar surface morphology due to both plasma etching during nitriding and the presence of slip steps and relieves at grain boundaries, the latter features presumably due to the formation of the nitrided layer. X-ray diffraction analysis shows that for the samples nitrided at temperatures up to 723 K, besides the S phase, small chromium nitride precipitates are present at the surface, while using higher treatment temperatures both chromium (CrN) and iron (γ'-Fe 4 N) nitrides precipitate along the grain boundaries and in the middle of the grains, and their amount increases as treatment temperature increases. High hardness values (from ∼1450 to ∼1550 HK 0.01 , depending on nitriding conditions) are observed in the modified layer with a steep decrease to matrix values. Preliminary corrosion resistance tests, carried out in 5% NaCl aerated solution with the potentiodynamic method, show that with the used treatment parameters a substantial improvement of corrosion resistance can be achieved when glow-discharge nitriding treatments are performed at temperatures in the range 703–723 K.

Progresses in III‐Nitride Distributed Bragg Reflectors and Microcavities Using AlInN/GaN Materials

Abstract: We propose to use lattice-matched AlInN/GaN to replace the Al(Ga)N/GaN material system for III-nitride Bragg reflectors, despite the poor material quality of AlInN reported until very recently. We report an improvement of AlInN material that allowed for successful fabrication of a microcavity light emitting diode, a distributed Bragg reflector with 99.4% reflectivity and microcavities with a quality factor over 800. These results establish state-of-the-art values for III-nitrides, and announce the future importance of AlInN in GaN-based optoelectronics. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Mesoporous BN and BCN exhibiting Large Surface Areas via Templating Methods

Abstract: The synthesis of mesoporous boron nitride (MBN) and mesoporous carbon nitride (MBCN) with a very high surface area and pore volume, was analyzed. The samples were prepared by crushing the as-synthesized flakes in an agate mortar, mixing them with ethanol, sonication, and spreading the resultant mixture on a carbon film supported on a Cu grid. MBCN ands MBCN materials possess relatively high surface areas of 740 and 650 m2/g and large pore volumes of 0.69 and 0.60 cm3/g. The results show that these materials could be used as catalytic supports operating at high temperature in anoxidative atmosphere.

A printable form of single-crystalline gallium nitride for flexible optoelectronic systems.

Abstract: This work was supported by the DARPA-funded AFRL-managed Macroelectronics Program and used the Center for Microanalysis of Materials and the Laser and Spectroscopy Facility of the Frederick Seitz Materials Research Laboratory, supported by the Department of Energy (DEFG02-96ER45439). K.L. thanks Prof. Jae Min Myoung in the Department of Materials Science and Engineering at Yonsei University for valuable information related to the processing of GaN thin films.

Metal nitride carbide deposition by ALD

Abstract: The present methods provide tools for growing conformal metal thin films, including metal nitride, metal carbide and metal nitride carbide thin films. In particular, methods are provided for growing such films from aggressive chemicals. The amount of corrosive chemical compounds, such as hydrogen halides, is reduced during the deposition of transition metal, transition metal carbide, transition metal nitride and transition metal nitride carbide thin films on various surfaces, such as metals and oxides. Getter compounds protect surfaces sensitive to hydrogen halides and ammonium halides, such as aluminum, copper, silicon oxide and the layers being deposited, against corrosion. Nanolaminate structures incorporating metallic thin films, and methods for forming the same, are also disclosed.

An analytical retention model for SONOS nonvolatile memory devices in the excess electron state

Abstract: We present an analytical retention model for scaled SONOS devices in the excess electron state. In this model, trap-to-band tunneling and thermal excitation discharge mechanisms are considered to be responsible for the temperature-dependent electron decay behaviors in SONOS devices. We assume an arbitrary trap distribution in energy within the charge-storage silicon nitride. Simulated retention characteristics are compared with experiment results measured on SONOS devices with a gate dielectric stack consisting of a 1.8 nm tunnel oxide, a 10 nm oxynitride and a 4.5 nm blocking oxide. We obtain good agreement between simulations and measurements for temperatures from 22 to 225 °C. We also extract the trap distribution in the nitride with this model. Finally, we discuss the influence of the gate dielectric properties (thickness, trap energy, etc.) and temperature on data retention of SONOS devices.

Spherical Aluminum Nitride Fillers for Heat‐Conducting Plastic Packages

Abstract: It is necessary for encapsulants to have not only a suitable coefficient of thermal expansion (CTE) compatible to IC devices and a low dielectric constant to reduce the device propagation delay, but also a high thermal conductivity to dissipate large amounts of heat from power-hungry, high-speed IC and high-density packages. Fillers such as silica have been mixed with polymers to improve their properties. Aluminum nitride (AlN) is considered as an alternative one, because it has a higher theoretical thermal conductivity of ∼320 W/mK 1 , a compatible CTE with silicon chips and a low dielectric constant. Commercial AlN fillers are angular in shape, because they are prepared via grinding coarse AlN powders synthesized by direct nitridation of aluminum metal and classification. The angular AlN are not expected to have high fluidity when mixed with polymers and hence low packing density. Recently, we successfully obtained single-crystalline spherical AlN fillers. Furthermore, polymer composites filled with the spherical AlN showed excellent thermal conductivity (>8 W/mK) as encapsulants for dissipating the heat generated in electronic devices.

Light emitting apparatus and method for manufacturing the same

Abstract: The purpose of the invention is to improve reliability of a light emitting apparatus comprising TFTs and organic light emitting elements. The light emitting apparatus according to the invention having thin film transistors and light emitting elements, comprises; a second inorganic insulation layer on a gate electrode, a first organic insulation layer on the second inorganic insulation layer, a third inorganic insulation layer on the first organic insulation layer, an anode layer formed on the third inorganic insulation layer, a second organic insulation layer overlapping with the end of the anode layer and having an inclination angle of 35 to 45 degrees, a fourth inorganic insulation layer formed on the upper surface and side surface of the second organic insulation layer and having an opening over the anode layer, an organic compound layer formed in contact with the anode layer and the fourth inorganic insulation layer and containing light emitting material, and a cathode layer formed in contact with the organic compound layer containing the light emitting material, wherein the third inorganic insulation layer and the fourth inorganic insulation layer are formed with silicon nitride or aluminum nitride.

Turbostratic carbon nitride prepared by pyrolysis of melamine

Abstract: Since the theoretical calculations predicted that the hardness of C3N4 covalent compound might be comparable to or even higher than that of diamond [1, 2], many attempts have been made to synthesis this novel substance. Due to the great thermodynamic stability of N2, however, the ideal structural transition from precursor to crystalline carbon nitride is difficult to realize. In most cases, only amorphous products with low nitrogen content were obtained [3]. To solve this problem, it is good to prepare carbon nitride in graphitic or turbostratic form firstly, and then using it as precursor to synthesize other carbon nitride crystalline phases. Therefore, graphitic C3N4 have recently attracted more attention. Through different routes, graphitic C3N4 has been synthesized [4–6]. For previous work, the claimed graphitic-like C3N4 with unique (002) diffraction peak has the turbostratic structure actually [7–10], for the lake of other peaks in their XRD patterns. Meanwhile, the (002) spacing of those obtained turbostratic carbon nitrides are in the range of 0.32–0.33 nm. The graphitic C3N4 predicted by Teter and Hemley [11] can be described as a perfect de-ammonation polycondensate of melamine, therefore, melamine was often chosen as the carbon nitride precursor to synthesize graphitic C3N4 by electrodeposition [6] and solvothermal method [7]. Pyrolysis of melamine was investigated [12] in 1988, however, the authors focused their attention only on its thermal behavior, and they didn’t consider the possibility as potential candidate for carbon nitrides after complete polycondensate. Recently, pyrolysis of melamine under high pressure was studied at the temperatures up to 700 ◦C [13]. Obvious nitrogen loss made the attempt unsuccessful. In this letter, we report an improved pyrolysis route to prepare turbostratic carbon nitride from melamine. The pyrolysis was performed in two steps: first, the temperature was maintained at 300 ◦C in order to realize the primary condensation (melamine → melam) as complete as possible; and then it was risen to 650 ◦C to perform the advanced condensation. In the experimental, melamine was pyrolyzed in a quartz tube with a diameter of 35 mm, and an outer-thimble-shape heater was used. Melamine was placed at the middle of the quartz tube. The pyrolysis was conducted at 300 ◦C for 1 hr, then at 600◦ for 2 hr in atmosphere; after milling, the obtained powder was maintained at 300 ◦C for 0.5 hr, then at 650 ◦C for 1 hr in vacuum. Finally, a kind of brown carbon nitride powder was obtained. The chemical composition was analyzed by using elemental analyzer (LECO, CHN-1000) and EDX (EDAX INC., Phoenix). The product was characterized by X-ray diffraction (XRD) with Cu-Kα radiation (JEOL, ROTEX JRX-12), fourier transfer infrared (FTIR) spectroscopy (Bruker, EQUINOX55), scanning electron microscopy (SEM) (TOPCON, SM520), and transmission electron microscopy (TEM) coupled with selected area diffraction (SAED) (JEOL, JEM-2010) and thermogravimetry (TG) (NETZSCH, STA449C/6/G). The composition of the product characterized by elemental analysis and EDX is listed in Table I. SEM observation found that the particles dimension ranged from 5 μm to 20 μm. Most of the particles show the flake-like morphology. Fig. 1 shows a typical XRD pattern of the product. There is a single main peak at the position of 27.62 ◦, which suggests that the product was turbostratic. Its corresponding d-spacing is 0.321 nm similar to the (002) plane of the turbostratic/graphitelike carbon nitrides obtained in previous work [9, 14]. The FTIR spectrum of the prepared turbostratic carbon nitride and melamine are shown in Fig. 2. The IR spectrum of melamine presents three absorption bonds: 3000–3650 cm−1, 1100–1700 cm−1, and the last one centered at about 810 cm−1. The 3000– 3650 cm−1 band is assigned to N H stretching vibration modes, the 1100–1650 cm−1 band corresponds to the stretching vibrations related to C N, C N, and is generally associated with the skeletal stretching vibrations of these aromatic rings. The absorption at 810 cm−1 is characteristic of out-of-plane bending modes of these rings. The 460–850 cm−1 band is linked to the C NH2 group and the ring breadth or bending vibration modes [15]. Comparing the FTIR spectrum of the turbostratic carbon nitride with that of melamine, it reveals that after pyrolysis, the previous strong absorption peaks in the range of 3000–3650 cm−1 have disappeared, only a board absorption bond is left, which suggest that most of the N H bonds have been destroyed during the de-ammonation condensation. While the increased number of absorption peaks ranging from 1100 to 1700 cm−1 implies the condensation of 1,3,5-s-triazine rings making the related chemi-

Integration of pre-S/D anneal selective nitride/oxide composite cap for improving transistor performance

Abstract: The present invention facilitates semiconductor device operation and fabrication by providing a cap-annealing process that improves channel electron mobility without substantially degrading PMOS transistor devices. The process uses an oxide/nitride composite cap to alter the active dopant profile across the channel regions. During an annealing process, dopants migrate out of the Si/SiO2 in a channel region thereby altering the dopant profile of the channel region. This altered profile generally improves channel mobility thereby improving transistor performance and permitting smaller density designs.

Atomic layer deposition of Hf3N4/HfO2 films as gate dielectrics

Abstract: The use of atomic layer deposition (ALD) to form a dielectric layer of hafnium nitride (Hf 3 N 4 ) and hafnium oxide (HfO 2 ) and a method of fabricating such a combination gate and dielectric layer produces a reliable structure for use in a variety of electronic devices. Forming the dielectric structure includes depositing hafnium oxide using precursor chemicals, followed by depositing hafnium nitride using precursor chemicals, and repeating to form the laminate structure. Alternatively, the hafnium nitride may be deposited first followed by the hafnium nitride. Such a dielectric layer may be used as the gate insulator of a MOSFET, a capacitor dielectric in a DRAM, or a tunnel gate insulator in flash memories, because the high dielectric constant (high-k) of the film provides the functionality of a thinner silicon dioxide film, and because of the reduced leakage current when compared to an electrically equivalent thickness of silicon dioxide.

Static and Dynamic Compressive Behavior of Aluminum Nitride under Moderate Confinement

Abstract: An experimental technique for imposing lateral confinement on specimens subjected to dynamic or quasi-static uniaxial compression has been developed. Lateral confinement is provided by a shrink-fit metal sleeve installed on the lateral surface of a cylindrical ceramic specimen. Experiments using this technique were performed on sintered aluminum nitride (A1N). The results show that the failure mode changes from fragmentation by axial splitting under conditions of uniaxial stress to localized faulting under moderate lateral confinement. The compressive failure strength of the AlN increases with the increase of confinement pressure under both static and dynamic loading conditions. The effect of strain rate on the failure strength appears to be independent of the confinement pressure.

Nanocomposite Ti-Si-N, Zr-Si-N, Ti-Al-Si-N, Ti-Al-V-Si-N thin film coatings deposited by vacuum arc deposition

Abstract: Thin films of Ti–Si–N, Zr–Si–N, Ti–Al–V–Si–N and Ti–Al–Si–N have been synthesized by reactively evaporating a metal or metal alloy cathode by a vacuum arc in a background of nitrogen gas and tetramethylsilane. The amount of silicon in the films was varied from 0 to 19 at.%. With increasing silicon content, the Ti–Si–N, Ti–Al–V–Si–N and Zr–Si–N films were found to increase in hardness, the maximum recorded value being 42 GPa. The Ti–Al–Si–N films showed either a slight increase or decrease in hardness with silicon content. Structural studies showed that the increased hardness was accompanied by a reduction in the grain size, in the case of Ti–Al–V–Si–N, from 24 to 7.7 nm. Transmission electron microscopy (TEM) studies confirmed the X-ray diffraction (XRD) results and showed that the major diffraction lines were associated with the nitride phases. X-ray photoelectron spectroscopy (XPS) studies indicated the presence of Si 3 N 4 and also small amounts of carbide which may be amorphous and possibly located at the grain boundaries.

Purification of endohedral trimetallic nitride fullerenes in a single, facile step.

Abstract: A major hurdle hampering the development of fullerenes, endohedral metallofullerenes, and nanotubes has been the difficulty of obtaining high purity samples. Soots prepared in the usual manner via ...

Crack-free fully epitaxial nitride microcavity using highly reflective AlInN∕GaN Bragg mirrors

Abstract: We report the growth over 2 in. sapphire substrates of crack-free fully epitaxial nitride-based microcavities using two highly reflective lattice-matched AlInN∕GaN distributed Bragg reflectors (DBRs). The optical cavity is formed by an empty 3λ∕2 GaN cavity surrounded by AlInN∕GaN DBRs with reflectivities close to 99%. Reflectivity and transmission measurements were carried out on these structures, which exhibit a stopband of 28 nm. The cavity mode is clearly resolved with a linewidth of 2.3 nm. These results demonstrate that the AlInN∕GaN system is very promising for the achievement of strong light–matter interaction and the fabrication of nitride-based vertical cavity surface emitting lasers.