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Showing papers on "Amorphous solid published in 1991"


Journal ArticleDOI
TL;DR: Amorphous films having a component of the stoichiometric GeTe-Sb2Te3 pseudobinary alloy system were found to have featuring characteristics for optical memory material presenting a large optical change and enabling high-speed one-beam data rewriting as mentioned in this paper.
Abstract: Amorphous films having a component of the stoichiometric GeTe‐Sb2Te3 pseudobinary alloy system, GeSb2Te4 or Ge2Sb2Te5 representatively, were found to have featuring characteristics for optical memory material presenting a large optical change and enabling high‐speed one‐beam data rewriting. The material films being sandwiched by heat‐conductive ZnS layers can be crystallized (low power) or reamorphized (high power) by laser irradiation of very short duration, less than 50 ns. The cooling speed of the sandwiched film is extremely high: more than 1010 deg/s, which permits the molten material to convert to the amorphous state spontaneously; whereas, a low‐power pulse irradiation of the same duration changed the exposed portion into the crystalline state. The optical constant changes between the amorphous state and the crystalline state of them were measured to be large: from 4.7+i1.3 to 6.9+i2.6 and from 5.0+i1.3 to 6.5+i3.5, respectively. The crystallized portion was known to have a GeTe‐like fcc structure ...

1,320 citations


Journal ArticleDOI
01 Jan 1991-Nature
TL;DR: In this paper, the synthesis of metallic glass powders using the microscopically extreme (yet macroscopically mild) conditions induced by high-intensity ultrasound was described, and the results showed that metallic glass powder is a highly active catalyst for the Fischer-Tropsch hydrogenation of carbon monoxide and for hydrogenolysis and dehydrogenation of saturated hydrocarbons.
Abstract: AMORPHOUS metallic alloys ('metallic glasses') lack long-range crystalline order and have unique electronic, magnetic and corrosion-resistant properties1–3. Their applications include use in power-transformer cores, magnetic storage media, cryothermometry and corrosion-resistant coatings. The production of metallic glasses is made difficult, however, by the extremely rapid cooling from the melt that is necessary to prevent crystallization. Cooling rates of about 105 to 107 K s−1 are generally required; for comparison, plunging red-hot steel into water produces cooling rates of only about 2,500 K s−1. Metallic glasses can be formed by splattering molten metal on a cold surface using techniques such as gun, roller or splat quenching4,5. Acoustic cavitation is known to induce extreme local heating in otherwise cold liquids, and to provide very rapid cooling rates6–11. Here we describe the synthesis of metallic-glass powders using the microscopically extreme (yet macroscopically mild) conditions induced by high-intensity ultrasound. The sonolysis of iron pentacarbonyl, a volatile organometallic compound, produces nearly pure amorphous iron. This amorphous iron powder is a highly active catalyst for the Fischer–Tropsch hydrogenation of carbon monoxide and for hydrogenolysis and dehydrogenation of saturated hydrocarbons.

1,149 citations


Journal ArticleDOI
TL;DR: In this article, a study of the structure and the morphology of a titanium dioxide photocatalyst (Degussa P25) reveals multiphasic material consisting of an amorphous state, together with the crystalline phases anatase and rutile in the approximate proportions 80 20.

1,001 citations


Journal ArticleDOI
TL;DR: A model is proposed which accounts for the formation and structure of ta-C films on the basis of the compressive stress generated by the shallow implantation of carbon ions, and an optimal range of beam energies between 15 and 70 eV, a high film stress, and a graphitic surface are predicted and confirmed by experimental evidence.
Abstract: Thin tetrahedrally coordinated amorphous carbon (ta-C) films have been grown using a filtered vacuum arc. ta-C is a new allotrope of carbon whose existence was previously thought to be unlikely. A model is proposed which accounts for the formation and structure of these films on the basis of the compressive stress generated by the shallow implantation of carbon ions. An optimal range of beam energies between 15 and 70 eV, a high film stress, and a graphitic surface are predicted and confirmed by experimental evidence. Computer simulation of the growth confirms that high compressive stress is generated by impact energies in this range.

825 citations


Journal ArticleDOI
07 Jun 1991-Science
TL;DR: Threedimensional antiferromagnetic exchange of the donor and acceptor spins resulting in ferrimagnetic behavior appears to be the mode of magnetic coupling.
Abstract: The reaction of bis(benzene)vanadium with tetracyanoethylene, TCNE, affords an insoluble amorphous black solid that exhibits field-dependent magnetization and hysteresis at room temperature. The critical temperature could not be estimated as it exceeds 350 kelvin, the thermal decomposition temperature of the sample. The empirical composition of the reported material is V(TCNE)x.Y(CH(2)Cl(2)) with x approximately 2 and Y approximately 1/2. On the basis of the available magnetic and infrared data, threedimensional antiferromagnetic exchange of the donor and acceptor spins resulting in ferrimagnetic behavior appears to be the mode of magnetic coupling.

802 citations


Journal ArticleDOI
TL;DR: Amorphous alloys exhibiting a wide supercooled liquid region above 100 K were found to form in a compositional range from 0 to 3%Co, 0 to 15%Ni and 10 to 23%Cu in Zr 65 Al 7.5 (Co 1-x-y Ni x Cu y ) 25 system by melt spinning as discussed by the authors.
Abstract: Amorphous alloys exhibiting a wide supercooled liquid region above 100 K were found to form in a compositional range from 0 to 3%Co, 0 to 15%Ni and 10 to 23%Cu in Zr 65 Al 7.5 Cu 2.5 (Co 1-x-y Ni x Cu y ) 25 system by melt spinning. The temperature span ΔT x (=T x -T g ) between glass transition temperature (T g ) and crystallization temperature (T x ) reaches as large as 127 K for Zr 65 Al 7.5 Ni 10 Cu 17.5

684 citations


Journal ArticleDOI
TL;DR: In this paper, a chemical bonding model is developed which describes the arrangement of these sites and which accounts for many of the electronic and mechanical properties of amorphous carbon, including elastic modulus, hardness, wear rate, friction and film adhesion.

683 citations


Journal ArticleDOI
TL;DR: In this paper, dehydrated sugar solutions were used as models of thermal behavior of amorphous foods, and of the effect of temperature, moisture content and time on physical state of such foods.
Abstract: Dehydrated sugar solutions were used as models of thermal behavior of amorphous foods, and of the effect of temperature, moisture content and time on physical state of such foods. The transition temperatures determined were glass transition (Tg), crystallization (Tcr) and melting (Tm) which all decreased with increasing moisture. Tg of a sucrose/ fructose model had a slightly lower value than the empirical “sticky point,” at all moisture contents studied. Crystallization of sucrose was delayed by addition of fructose or starch. Crystallization above Tg was time-dependent, and the relaxation time of this process followed the WLF equation.

626 citations


Journal ArticleDOI
12 Dec 1991-Nature
TL;DR: Despite their lack of long-range translational and orientational order, covalent amorphous solids can exhibit structural order over both short and medium length scales, the latter reaching to 20 A or so.
Abstract: Despite their lack of long-range translational and orientational order, covalent amorphous solids can exhibit structural order over both short and medium length scales, the latter reaching to 20 A or so. Medium-range order is difficult to measure experimentally and to interpret unambiguously, but a variety of techniques have allowed several types of characteristic structural ordering to be identified and their origin elucidated.

548 citations


Journal ArticleDOI
Akihisa Inoue1, Akira Kato1, Tao Zhang1, Sung Gyoo Kim1, Takeshi Masumoto1 
TL;DR: In this paper, a low pressure casting of Mg-Cu-Y melts into copper molds was found to cause amorphous bulks in a cylindrical form.
Abstract: A low pressure casting of Mg-Cu-Y melts into copper molds was found to cause amorphous bulks in a cylindrical form. The maximum diameter of the amorphous cylinder (D c ) shows a significantcompositional dependence and reaches a maximum value of 4.0 mm for Mg 65 Cu 25 Y 10 . The compositional dependence of the D c is similar to that for the temperature span of the supercooled liquid region, ΔT x (=T x -T g )

508 citations


Journal ArticleDOI
TL;DR: Optical constants for some samples of amorphous carbon are presented for the energy range 4.1 × 10 −3 to 3.5 × 10 3 eV, using a self-consistent method which combines extinction data in the infrared with other measurements of optical constants at higher energy as discussed by the authors.
Abstract: Optical constants for some samples of amorphous carbon are presented for the energy range 4.1 × 10 −3 to 3.5 × 10 3 eV, using a self-consistent method which combines extinction data in the infrared with other measurements of optical constants at higher energy. By construction, the optical constants satisfy the Kramers-Kronig relations. The effects of shape and clustering on the optical constants are examined and found to be significant. The CDE shape distribution mimics qualitatively the effects of compact clusters. Other data showing how the optical properties depend on the degree of hydrogenation and on the type of bonding in the amorphous carbon are discussed


Journal ArticleDOI
TL;DR: A mostly single bcc phase with nanoscale grain sizes of 10 to 20 nm was found to form by annealing amorphous Fe•Zr•B, Fe•Hf•B and Fe•M•B•Cu(M=Ti, Zr, Hf, Nb, and Ta) alloys for 36 ks in the range of 723 to 923 K as mentioned in this paper.
Abstract: A mostly single bcc phase with nanoscale grain sizes of 10 to 20 nm was found to form by annealing amorphous Fe‐Zr‐B, Fe‐Hf‐B, and Fe‐M‐B‐Cu(M=Ti, Zr, Hf, Nb, and Ta) alloys for 36 ks in the range of 723 to 923 K The high permeability (μe) above 10 000 at 1 kHz combined with high saturation magnetization (Bs) above 15 T was obtained for the bcc alloys The highest μe and Bs values reach 14 000 and 17 T for Fe91Zr7B2, 20 000 and 155 T for Fe87Zr7B5Cu1, and 48 000 and 152 T for Fe86Zr7B6Cu1 Magnetostriction (λs) decreases significantly by the phase transition from amorphous to bcc phase and is measured to be 1 × 10−6 for the bcc Fe86Zr7B6Cu1 alloy The small λs as well as the small grain size is concluded to be the reason for the good soft magnetic properties The lattice parameter of this bcc phase is 02870 nm being larger than that of pure α‐Fe The small λs seems to be achieved by the dissolution of solute elements above an equilibrium solubility limit The bcc Fe86Zr7B6Cu1 alloy also shows the l

Journal ArticleDOI
TL;DR: The silicon oxycarbide structure deduced from these results is a random network of silicon-oxygen tetrahedra, with some silicons bonded to one or two carbons substituted for oxygen as discussed by the authors.
Abstract: Silicon oxycarbide glass is formed by the pyrolysis of silicone resins and contains only silicon, oxygen, and carbon. The glass remains amorphous in x-ray diffraction to 1400 °C and shows no features in transmission electron micrographs (TEM) after heating to this temperature. After heating at higher temperature (1500–1650 °C) silicon carbide lines develop in x-ray diffraction, and fine crystalline regions of silicon carbide and graphite are found in TEM and electron diffraction. XPS shows that silicon-oxygen bonds in the glass are similar to those in amorphous and crystalline silicates; some silicons are bonded to both oxygen and carbon. Carbon is bonded to either silicon or carbon; there are no carbon-oxygen bonds in the glass. Infrared spectra are consistent with these conclusions and show silicon-oxygen and silicon-carbon vibrations, but none from carbon-oxygen bonds. 29Si-NMR shows evidence for four different bonding groups around silicon. The silicon oxycarbide structure deduced from these results is a random network of silicon-oxygen tetrahedra, with some silicons bonded to one or two carbons substituted for oxygen; these carbons are in turn tetrahedrally bonded to other silicon atoms. There are very small regions of carbon-carbon bonds only, which are not bonded in the network. This “free” carbon colors the glass black. When the glass is heated above 1400 °C this network composite rearranges in tiny regions to graphite and silicon carbide crystals. The density, coefficient of thermal expansion, hardness, elastic modulus, index of refraction, and viscosity of the silicon oxycarbide glasses are all somewhat higher than these properties in vitreous silica, probably because the silicon-carbide bonds in the network of the oxycarbide lead to a tighter, more closely packed structure. The oxycarbide glass is highly stable to temperatures up to 1600 °C and higher, because oxygen and water diffuse slowly in it.

Journal ArticleDOI
TL;DR: In this paper, the zinc blende and wurtzitic GaN films have been epitaxially grown onto (001)Si by electron cyclotron resonance microwave plasma assisted molecular beam epitaxy, using a two-step growth process.
Abstract: Zinc blende and wurtzitic GaN films have been epitaxially grown onto (001)Si by electron cyclotron resonance microwave plasma‐assisted molecular beam epitaxy, using a two‐step growth process. In this process a thin buffer layer is grown at relatively low temperatures followed by a higher temperature growth of the rest of the film. GaN films grown on a single crystalline GaN buffer have the zinc blende structure, while those grown on a polycrystalline or amorphous buffer have the wurtzitic structure.

Journal ArticleDOI
TL;DR: In this article, Annealing of initially amorphous FeCuNbSiB alloys at temperatures above their crystallization temperature leads to an ultrafine grain structure of α-FeSi with average grain sizes down to D ≈ 10 nm and random texture.
Abstract: Annealing of initially amorphous FeCuNbSiB alloys at temperatures above their crystallization temperature leads to an ultrafine grain structure of α-FeSi with average grain sizes down to D ≈ 10 nm and random texture. Owing to the nanocrystalline structure the magneto-crystalline anisotropy is randomly averaged out by exchange interaction. Moreover magnetostriction decreases on crystallization owing to the formation of α-FeSi. As a consequence the material reveals excellent soft magnetic properties.

Journal ArticleDOI
TL;DR: It is shown that amorphous Si formed by either implantation or deposition contains a large population of point defects and point-defect clusters, and structural relaxation, also known as short-range ordering, can be understood as annihilation of a large fraction of these defects.
Abstract: Thick amorphous Si layers have been prepared by MeV self-ion-implantation and the thermodynamic and structural properties examined by calorimetry, Raman-spectroscopy, and x-ray-diffraction techniques. Defects have been introduced into well-annealed amorphous and single-crystal Si by He, C, Si, and Ge bombardment. The defect structures are examined by these techniques and by transmission electron microscopy. The structure of amorphous Si in intermediate states of relaxation or annealing have been determined. It is shown that amorphous Si formed by either implantation or deposition contains a large population of point defects and point-defect clusters. Amorphous Si formed by laser quenching cannot be distinguished from well-annealed amorphous Si. Structural relaxation, also known as short-range ordering, can be understood as annihilation of a large fraction of these defects. Both structural relaxation in amorphous Si and defect annihilation in crystalline Si obey bimolecular reaction kinetics. The defect-formation and -annihilation processes are similar in amorphous and crystalline Si. Defect saturation occurs in amorphous Si at estimated defect concentrations of about 1 at. %. These formation and annihilation properties are intrinsic to pure amorphous Si. For hydrogenated amorphous Si, it is pointed out that the metastable-defect-creation and -annealing processes are essentially different from the annihilation processes in pure amorphous Si.

Journal ArticleDOI
TL;DR: In this article, the results of experimental investigations of the photodoping of amorphous chalcogenides by metals, and in particular by silver, are reviewed, and the results in the literature are analysed, giving answers to such fundamental questions as the following: where is the actinic light which is efficient for photodissolution absorbed? Which is the diffusion-limiting step? What is the state of the diffusing species (neutral atoms or ions)?
Abstract: The present paper reviews the results of experimental investigations of the photodoping of amorphous chalcogenides by metals, and in particular by silver. The kinetics of the photodissolution of the metal are described as also is the influence on the photodissolution rate of such factors as the wavelength and intensity of light, the composition and temperature of the semiconductor, and an external electric field. A separate section describes lateral diffusion. The properties of photodoped semiconductors (electrical, optical, photoelectric, etc.) are presented. The results in the literature are analysed, giving answers to such fundamental questions as the following. Where is the actinic light which is efficient for the photodissolution absorbed? Which is the diffusion-limiting step? What is the state of the diffusing species (neutral atoms or ions)? The dissolution of silver induced by electron or ion beams and the photodissolution of group II metals are mentioned. The experimental results are fol...

Journal ArticleDOI
Tsutomu Ikeda1, Hiroshi Satoh1
TL;DR: Hard Ti x N and (Ti 1− x Al x )N films were prepared using the cathodic arc ion plating method as discussed by the authors, and they exhibited a cubic structure.

Journal ArticleDOI
TL;DR: In this paper, optical and electrical measurements reveal uniform films over the thickness range 200-1000 A. They obtain optical absorption coefficients having values between those of Si and Ge and a relative permittivity having a value close to that of amorphous SiO2.
Abstract: Thermal sublimation of pure C60 and C70 has been used for depositing well‐characterized fullerene films on a variety of substrates. Film purity is determined by infrared absorption spectra and the extent of crystallinity of the face‐centered cubic structure by x rays. Thickness‐dependent optical and electrical measurements reveal uniform films over the thickness range 200–1000 A. We obtain optical absorption coefficients having values between those of Si and Ge and a relative permittivity having a value close to that of amorphous SiO2.

Journal Article
TL;DR: This article conducts studies on phase transitions of amorphous food materials and related Tg to composition, viscosity, stickiness, collapse, recrystallization, and ice formation, and proposed that some diffusion-limited deteriorative reactions are controlled by the physical state in the vicinity of Tg.
Abstract: The physical state of food components affects their properties during processing, storage, and consumption. Removal of water by evaporation or by freezing often results in formation of an amorphous state (Parks et al., 1928; Troy and Sharp, 1930; Kauzmann, 1948; Bushill et al., 1965; White and Cakebread, 1966; Slade and Levine, 1991). Amorphous foods are also produced from carbohydrate melts by rapid cooling after extrusion or in the manufacturing of hard sugar candies and coatings (Herrington and Branfield, 1984). Formation of the amorphous state and its relation to equilibrium conditions are shown in Fig. 1 [see text]. The most important change, characteristic of the amorphous state, is noticed at the glass transition temperature (Tg), which involves transition from a solid "glassy" to a liquid-like "rubbery" state. The main consequence of glass transition is an increase of molecular mobility and free volume above Tg, which may result in physical and physico-chemical deteriorative changes (White and Cakebread, 1966; Slade and Levine, 1991). We have conducted studies on phase transitions of amorphous food materials and related Tg to composition, viscosity, stickiness, collapse, recrystallization, and ice formation. We have also proposed that some diffusion-limited deteriorative reactions are controlled by the physical state in the vicinity of Tg (Roos and Karel, 1990, 1991a, b, c). The results are summarized in this article, with state diagrams based on experimental and calculated data to characterize the relevant water content, temperature, and time-dependent phenomena of amorphous food components.

Journal ArticleDOI
TL;DR: The dielectric constant was remarkably dependent upon the relative densities of the sintered bodies and the change of the lattice parameters, while Q value was mainly affected by the oxygen deficiency.
Abstract: Monosized spherical particles of (Zr, Sn)TiO4 with an average diameter of about 0.3 μm were synthesized by the controlled hydrolysis of metal alkoxides. The as-prepared, amorphous, particles were compacted without any sintering aid, crystallized, and then sintered at 1600°C for 3 h into bodies with >96.0% of theoretical density. The dense sintered bodies of (Zr0.80Sn0.20)TiO4 showed good microwave characteristics; ɛr= 40.0, Q= 5000, and τt= 3 ppm/°C at 10 GHz. The dielectric constant was remarkably dependent upon the relative densities of the sintered bodies and the change of the lattice parameters, while Q value was mainly affected by the oxygen deficiency. An increase of the dielectric constant with the substitution of Sn4+ in ZrTiO4 was attributable to the enhancement of ionic polarization with the increase of the c-axis length.

Journal ArticleDOI
TL;DR: In this paper, the effect of ambient oxygen pressure on the synthesis of epitaxial YBa2Cu3O7−x films on (100) SrTiO3 substrates by post-deposition annealing of amorphous precursor films was studied for oxygen partial pressures pO2 between 1.0 and 8.0×10−5 atm.
Abstract: The effect of ambient oxygen pressure on the synthesis of epitaxial YBa2Cu3O7−x films on (100) SrTiO3 substrates by post‐deposition annealing of amorphous precursor films was studied for oxygen partial pressures pO2 between 1.0 and 8.0×10−5 atm and annealing temperatures between 890 and 650 °C. A pO2−1/T diagram containing recent literature data regarding YBa2Cu3O7−x oxygen stoichiometry, phase stability, and liquid‐phase formation was compiled to provide guidance for the selection and interpretation of annealing conditions. The results evidence a strong dependency of growth properties on the oxygen pressure with enhanced c‐oriented epitaxy at lower pO2 values. A particularly interesting result is the formation of predominantly c‐oriented films at 740 °C and pO2=2.6×10−4 atm (0.2 Torr). Similar to YBa2Cu3O7−x films produced by in situ laser ablation at the same temperature and oxygen pressure, the films exhibited low ion channeling yields (χmin<0.1) and a dense (smooth) surface morphology, while critical ...

Journal ArticleDOI
TL;DR: The glass transition temperature of norbornene/ethene copolymers exceeds 130°C as discussed by the authors, which is the glass transition point of cyclopentene with propene.
Abstract: With homogenous catalysts on the basis of chiral metallocenes and methylaluminoxane it has become possible to polymerize cyclic olefins like cyclobutene, cyclopentene or norbornene. No ring opening reaction occurs. The crystalline polycycloalkenes show extremly high melting points between 400 and 600°C. Copolymers of cyclopentene with propene are amorphous. They have a low molecular weight and glass transition point. On the other hand the glass transition temperature of norbornene/ethene copolymers exceeds 130°C. These copolymers could be used as materials for optical discs and fibers.

Journal ArticleDOI
01 Jan 1991-Polymer
TL;DR: The system of this book of course will be much easier. No worry to forget bringing the physics of amorphous materials book as discussed by the authors, You can open the device and get the book by on-line.

Journal ArticleDOI
TL;DR: In this article, a model for the condensation of energetic carbon atoms into diamond-like films in which a quench-type surface accommodation mechanism is operative is proposed, and the degree of diamondlike film character is found to depend upon the deposition technique as well as the substrate temperature and thermal diffusivity.
Abstract: Trends in recently reported data on high sp3 fraction (up to 85%), nonhydrogenated amorphous diamond‐like carbon films deposited by ion beam sputtering and laser vaporization are examined. The degree of diamondlike film character is found to depend upon the deposition technique as well as the substrate temperature and thermal diffusivity. The data suggest that the combination of incident particle kinetic energy and surface accommodation determine the physical properties of the resultant film. A model is proposed for the condensation of energetic carbon atoms into diamondlike films in which a quench‐type surface accommodation mechanism is operative.


Journal ArticleDOI
TL;DR: The pyrolysis of a PCS precursor has been studied up to 1600 °C through the analysis of the gas phase and the characterization of the solid residue by thermogravimetric analysis, extended X-ray absorption fine structure, electron spectrocopy for chemical analysis, transmission electron microscopy, Xray diffraction, Raman and Auger electron spectroscopy microanalyses, as well as electrical conductivity measurements.
Abstract: The pyrolysis of a PCS precursor has been studied up to 1600 °C through the analysis of the gas phase and the characterization of the solid residue by thermogravimetric analysis, extended X-ray absorption fine structure, electron spectrocopy for chemical analysis, transmission electron microscopy, X-ray diffraction, Raman and Auger electron spectroscopy microanalyses, as well as electrical conductivity measurements. The pyrolysis mechanism involves three main steps: (1) an organometallic mineral transition (550 < T p < 800 °C) leading to an amorphous hydrogenated solid built on tetrahedral SiC, Si02 and silicon oxycarbide entities, (2) a nucleation of SiC (1000 < T p < 1200 °C) resulting in SiC nuclei (less than 3 nm in size) surrounded with aromatic carbon layers, and (3) a SiC grain-size coarsening (T p > 1400 °C) consuming the residual amorphous phases and giving rise simultaneously to a probable evolution of SiO and CO. The formation of free carbon results in a sharp insulator-quasimetal transition with a percolation effect.

Journal ArticleDOI
TL;DR: In this paper, a radio frequency glow discharge system for the deposition of amorphous thin-film semiconductors and insulators is presented, which is a multiplasma monochamber system consisting of three separated plasma chambers located inside the same isothermal vacuum vessel.
Abstract: We present a study on the development and the evaluation of a fully automated radio‐frequency glow discharge system devoted to the deposition of amorphous thin film semiconductors and insulators. The following aspects were carefully addressed in the design of the reactor: (1) cross contamination by dopants and unstable gases, (2) capability of a fully automated operation, (3) precise control of the discharge parameters, particularly the substrate temperature, and (4) high chemical purity. The new reactor, named ARCAM, is a multiplasma‐monochamber system consisting of three separated plasma chambers located inside the same isothermal vacuum vessel. Thus, the system benefits from the advantages of multichamber systems but keeps the simplicity and low cost of monochamber systems. The evaluation of the reactor performances showed that the oven‐like structure combined with a differential dynamic pumping provides a high chemical purity in the deposition chamber. Moreover, the studies of the effects associated with the plasma recycling of material from the walls and of the thermal decomposition of diborane showed that the multiplasma‐monochamber design is efficient for the production of abrupt interfaces in hydrogenated amorphous silicon (a‐Si:H) based devices. Also, special attention was paid to the optimization of plasma conditions for the deposition of low density of states a‐Si:H. Hence, we also present the results concerning the effects of the geometry, the substrate temperature, the radio frequency power and the silane pressure on the properties of the a‐Si:H films. In particular, we found that a low density of states a‐Si:H can be deposited at a wide range of substrate temperatures (100 °C≤Ts≤300 °C).

Journal ArticleDOI
TL;DR: In this article, sputter-deposited Ta, Ta36Si14, and Ta36 Si14N50 thin films are used as diffusion barriers between Cu overlayers and Si substrates.
Abstract: We have studied sputter-deposited Ta, Ta36Si14, and Ta36Si14N50 thin films as diffusion barriers between Cu overlayers and Si substrates. Electrical measurements on Si n + p shallow junction diodes demonstrate that a 180-nm-thick Ta film is not an effective diffusion barrier. For the standard test of 30-min annealing in vacuum applied in the present study, the Ta barrier fails after annealing at 500 °C. An amorphous Ta74Si26 thin film improves the performance by raising the failure temperature of a /Ta74Si26(100 nm)/Cu(500 nm) metallization to 650 °C. Unparalled results are obtained with an amorphous ternary Ta36Si14N50 thin film in the Si/Ta36Si14N50 (120 nm)/Cu(500 nm) and in the Si/TiSi2(30 nm)/Ta36SiN50 (80 nm)/Cu(500 nm) metallization that break down only after annealing at 900 °C. The failure is induced by a premature crystallization of the Ta36Si14N50 alloy (whose crystallization temperature exceeds 1000 °C) when in contact with copper.