REDUCTION OF CRYSTALLINE DISORDER IN MOLECULAR-BEAM EPITAXY GAAS ON SI BY MEV ION-IMPLANTATION AND SUBSEQUENT ANNEALING

Molecular beam epitaxy GaAs films on Si, with thicknesses ranging from 0.9-2.0-mu-m, were implanted with Si ions at 1.2-2.6 MeV to doses in the range 10(15)-10(16) cm-2. Subsequent rapid infrared thermal annealing was carried out at 850-degrees-C for 15 s in a flowing N2 atmosphere. Crystalline quality was analyzed by using Rutherfold backscattering/channeling technique and Raman scattering spectrometry. The experimental results show that the recrystallization process greatly depends on the dose and energy of implanted ions. Complete recrystallization with better crystalline quality can be obtained under proper implantation and subsequent annealing. In the improved layer the defect density was much lower than in the as-grown layer, especially near the interface.

Measurement of respiratory acoustic impedance in children by a modified forced oscillation method

An introduction to a modified forced oscillation method, square-wave excitation technique, including fundamentals and methods, as used in respiratory function examination. On the basis of experimental results and theoretical predictions, we suggest that Respiratory Acoustic Impedance (RAI) measurement by spectral analysis can significantly improve estimation of contribution to RAI from different part of respiratory tract. The outcome is of considerable interest in the study of lung disease, such as COPD and asthma in young children.