High-barrier Al/p-Si Schottky diodes
Sequential implantation of argon ions and low-energy hydrogen ions has been found to yield Schottky barriers of exceptionally high values on p-type silicon. The interaction of these ions in Si is quite complex, involving donor defect generation, defect passivation, and acceptor dopant neutralization. The apparent synergism of these specific implants has resulted in Al/p-Si Schottky diodes with an effective barrier height as high as 0.83 eV, among the highest value reported for any metal/p-Si contact.
Effect of ion beam etching on metal-Si and metal-GaAs barriers
Abstract A hot filament ion source was used in this investigation. The ion beam acceleration system consisted of two graphite grids for extraction of a 1 mA cm −2 ion beam density of energy between 500 and 1000 eV. A very low energy ion beam [50–200 eV] with the same current density was obtained by using a 〈100〉 single-crystal silicon grid. I-V and C-V measurements of AlSi Schottky diodes pre-cleaned with a 100 eV ion beam before metal evaporation showed no change in the diode barrier height suggesting minimal surface damage (a barrier lowering). Ion etching of the Si surface at an energy higher than 100 eV leads to lowering of the barrier, with a tendency to saturation at a given energy. The induced damage in Si can be completely annealed at 700°C (as indicated by both I-V and C-V measurements) before metal evaporation. The GaAs surface is more sensitive to ion bombardment than Si. Only AlGaAs Schottky diodes pre-cleaned with a 50 eV ion beam did not change the barrier height. Any other higher ion energy drastically lowers the potential barrier of the metal-GaAs system.
An injectable and thermosensitive hydrogel: Promoting periodontal regeneration by controlled-release of aspirin and erythropoietin.
Periodontitis is an inflammatory disease induced by complex interactions between host immune system and plaque microorganism. Alveolar bone resorption caused by periodontitis is considered to be one of the main reasons for tooth loss in adults. To terminate the alveolar bone resorption, simultaneous anti-inflammation and periodontium regeneration is required, which has not appeared in the existing methods. In this study, chitosan (CS), β-sodium glycerophosphate (β-GP), and gelatin were used to prepare an injectable and thermosensitive hydrogel, which could continuously release aspirin and erythropoietin (EPO) to exert pharmacological effects of anti-inflammation and tissue regeneration, respectively. The releasing profile showed that aspirin and EPO could be continuously released from the hydrogels, which exhibited no toxicity both in vitro and in vivo, for at least 21 days. Immunohistochemistry staining and micro-CT analyses indicated that administration of CS/β-GP/gelatin hydrogels loaded with aspirin/EPO could terminate the inflammation and recover the height of the alveolar bone, which is further confirmed by histological observations. Our results suggested that CS/β-GP/gelatin hydrogels are easily prepared as drug-loading vectors with excellent biocompatibility, and the CS/β-GP/gelatin hydrogels loaded with aspirin/EPO are quite effective in anti-inflammation and periodontium regeneration, which provides a great potential candidate for periodontitis treatment in the dental clinic. Statement of Significance To terminate the alveolar bone resorption caused by periodontitis, simultaneous anti-inflammation and periodontium regeneration is required, which has not appeared in the existing methods. Here, (1) the chitosan (CS)/β-sodium glycerophosphate/gelatin hydrogels loaded with aspirin/erythropoietin (EPO) can form at body temperature in 5 min with excellent biocompatibility in vitro and in vivo; (2) The faster release of aspirin than EPO in the early stage is beneficial for anti-inflammation and provides a microenvironment for ensuring the regeneration function of EPO in the following step. In vivo experiments revealed that the hydrogels are effective in the control of inflammation and regeneration of the periodontium. These results indicate that our synthesized hydrogels have a great potential in the future clinical application.