We fabricated high-output-power 255 and 280 nm light-emitting diodes (LEDs) using direct bonding. The LED chips were bonded to sapphire lenses at room temperature using either atomic diffusion bonding or surface-activated bonding. The LEDs with lenses had a higher light extraction efficiency than conventionally structured LEDs. As a result, at a forward current of 350 mA, the output power of the 255 nm LED increased by a factor of 2.8, reaching 73.6 mW, while that of the 280 nm LED increased by a factor of 2.3, reaching 153 mW.
Effect of 3 d , 4 d , and 5 d transition metal doping on damping in permalloy thin filmsBonding between two flat wafers with thin metal films was studied for 14 thin metal films with various crystal structures and self-diffusion coefficients. Thin nanocrystalline metal films were fabricated on two flat wafers' surfaces using sputter deposition. Bonding of the two metal films on the wafers was accomplished immediately after film deposition in vacuum. For the films, Al, Au, Ag, Cu, Si, Co, Ni, Pt, Ti, Ru, Fe, Cr, Mo, and Ta were used. The wafers were bonded at room temperature over the entire bonded area ͑1 or 2 in. wafers of either Si or SiO 2 ͒ using these metal films. Transmission electron microscopic cross-section images revealed that complete crystalline grains were formed across the original surfaces of the films, probably because of recrystallization occurring at the bonded interface when Al-Al, Ag-Ag, Au-Au, Cu-Cu, and Ti-Ti nanocrystalline films were bonded. A clear interface corresponding closely to the original film surface was visible in the bonded Pt-Pt films. However, fcc-͑111͒ lattices were formed continuously across the films' original surfaces. A thin amorphous layer was formed at the interfaces of Cr-Cr, Fe-Fe, and Ta-Ta bonded films. Experimental results revealed that the two films' bonded structure was related closely to the self-diffusion coefficients of the metals used for bonding. A high atomic diffusion coefficient at the grain boundaries and film surfaces is likely to have enabled bonding at room temperature. Moreover, results obtained using Cu-Cu, Al-Al, Ti-Ti, Cr-Cr, and Ta-Ta films demonstrated that the wafers were bonded even with only 0.2-nm-thick films on both sides. Bonding films of different materials was also achieved, e.g., Ta-Cu films. The bonding technique described herein is promising for use with bonding wafers to fabricate new thin film devices and microelectromechanical systems.
Room temperature bonding between two flat wafers using thin metal films was studied. Thin nanocrystalline metal films (0.2-20 nm thick) were fabricated on two flat wafers' surfaces using sputter deposition. Bonding of the two metal films on the wafers was accomplished immediately after film deposition in vacuum. The wafers were bonded at room temperature over the entire bonded area using metal films of 16 kinds including W films. The two films' bonded structure was related closely to the self-diffusion coefficients of the metal films. The very high atomic diffusion coefficient at the grain boundaries and film surfaces is likely to have enabled bonding at room temperature. The wafers were bonded even with films of 0.2 nm thickness on each side. The potential of the bonding for applications to device fabrication is examined. Moreover, bonding in air using noble metal films is examined according to experimental results.
Room temperature bonding using thin metal films uses two flat wafer surfaces with sputter deposition. Then two films on wafers are bonded in vacuum or in air. Bonding in vacuum can be accomplished using almost any metal film, even with film thickness of a few angstroms on each side. The bonding energy is greater than the surface energy of metal films at thicknesses greater than the critical film thickness, which is related to the formation of thin reactive layers between metal films and wafers. Bonding in air using Au films also shows a bonding energy greater than the surface energy of Au films, even with an exposure time of Au films to air of 168 h (1 week). Bonding of wafers and mirror-polished metals was also achieved, which is effective for enhancing the heat dissipation efficiency.
Dietary seaweed fucoidan delays the onset of disease of enterally infected mice with scrapie when given orally for 6 days after infection, but not when given before the infection. This effect was not modified at a tested fucoidan dose range and appeared to reach the maximum level at a concentration of 2.5% or less in feed. Daily uptake of fucoidan might be prophylactic against prion diseases caused by ingestion of prion-contaminated materials, although further evaluation of its pharmacology remains to be done.Transmissible spongiform encephalopathies, or prion diseases, are fatal neurodegenerative disorders that include Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker syndrome in humans and scrapie, bovine spongiform encephalopathy (BSE), and chronic wasting disease in animals. Recent outbreaks of BSE and variant CJD (vCJD), both of which are considered to occur through ingestion of BSE-contaminated materials (reviewed in reference 21), have necessitated the development of preventive measures against these diseases.Sulfated polysaccharides, such as heparin, dextran sulfate, and pentosan polysulfate (PPS), are known either to prolong incubation periods in animals with prion diseases or to inhibit formation of pathogen-related abnormal prion protein (PrP) in prion-infected cells (reviewed in reference 3). Their therapeutic effects are attributed to inhibition of the conversion of normal PrP to abnormal PrP by either competitively binding to the normal PrP (4) or reducing normal PrP on the cell surface through stimulation of endocytosis (20). These large-molecule compounds are not taken up well from the gut to blood or from blood to the brain (a target organ of prion diseases). Therefore, these compounds are effective in cases of peripheral infection when given intraperitoneally, intravenously, or subcutaneously (8) and even in cases of intracranial infection when given intracerebroventricularly (5). Recently, PPS intracerebroventricular injection has been utilized for clinical trials of patients; the clinical outcome remains to be determined (17).Fucoidans, complex sulfated fucosylated polysaccharides, are known to have various biological activities: anticoagulant, antiviral, antiparasital, anti-inflammatory, contraceptive, and so on, because of their ability to imitate patterns of sulfate substitution on glycosaminoglycans and other sulfated glycans (2). Some fucoidans are present in large quantities in dietary brown seaweed food products, which are eaten frequently in Asian countries (9). Here, we report that fucoidan from popularly eaten brown algae has antiprion activity and delays disease onset when it is ingested after the enteral prion infection.Fucoidan was prepared from the brown seaweed Cladosiphon okamuranus Tokida (Fig. 1A) and subsequently tested as described previously (15). Briefly, the brown seaweed was suspended in distilled water adjusted to pH 3.0 with 30% HCl and heated at 100°C for 30 or 60 min. The suspension was centrifuged (10,000 ϫ g) at room temperature, and the supernat...
We reviewed the structural and optical properties of high output power 255 and 280 nm light-emitting diodes (LEDs) bonded with hemispherical lenses made of inorganic materials. [This is described as a full paper (and not a review). Is this your intended meaning?][This is my intended] The optimal LED structure with a lens to improve the output power for deep ultraviolet LEDs was designed using Monte Carlo simulation. The LED chips were bonded to sapphire lenses at room temperature using either atomic diffusion bonding or surface activated bonding. The bonding of the lenses to the LEDs is experimentally shown to improve the light extraction efficiency, and the light output power of the LEDs with lenses was significantly higher than that of conventional structure LEDs. The output power of a 255 nm LED with a lens was 2.8 times larger than that without a lens, with a maximum external quantum efficiency of 4.56%, and that of the 280 nm LED with a lens was larger by a factor of 2.3.
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