The enhanced optical property of chemical passivated n type GaSb
In the paper, Te-doped n type GaSb was passivated by (NH4)2S, the optical and surface properties of passivated GaSb were investigated by PL and AFM. After passivation treatment, the luminescence intensity of GaSb was enhanced. The passivation time would also affect luminescence intensity and the surface smooth of GaSb.
Characterization of sulfur passivated n-GaSb using transmission electron microscopy and the influence of passivationon ohmic contact resistance
Transmission electron microscopy has been used to study sulfur passivation of (100) n-GaSb. An amorphous Ga-S layer forms during passivation, with a thickness dependent on the duration of passivation. Minimal oxygen is present in the sulfide layer. The sulfide layer remains amorphous when annealed at 350°C for 10min. After 20min at 500°C, the layer becomes nanocrystalline and is enriched with Ga from the GaSb, with voids and Sb precipitates forming at the sulfide/GaSb interface. If used as a premetallization surface preparation, sulfur passivation can inhibit reaction between a contact metallization and GaSb; however, with an appropriate choice of passivation conditions to minimize the thickness of the sulfide layer, it can instead promote a more uniform reaction between the metal and semiconductor than is achieved with a conventional surface preparation. It can also lead to a reduced ohmic contact resistance.
In search of optimum chest radiography techniques.
A nation-wide study of chest radiography in Sweden had previously revealed a large variation in the physical and technical factors involved, in particular the radiation dose. In this study the image quality could not be assessed unambiguously. The aim of the present study was to try to establish a correlation between visual grading of radiographs and physical and technical factors in order to find the optimum chest X-ray system. The physical and technical performance of 24 chest units was evaluated. Radiographs were taken of an anthropomorphic chest phantom supplied with test structures simulating various pathologies. Image quality was assessed by visual grading analysis of the radiographs. The physical and technical parameters of the units rated best were used to exemplify good radiographic practice. The results were in agreement with the recommendations issued by the Commission of the European Communities (CEC). It was also shown that low radiation dose is compatible with high-quality radiographic imaging of the chest.