| Summary: | 碩士 === 淡江大學 === 物理學系碩士班 === 98 === This dissertation presents the study of the surface and interface structures of thin films by means of x-ray reflectivity (XRR) and high resolution x-ray diffraction (HRXRD). One of the systems studied is the AlGaN/GaN multi-layers, which is used for the high electron mobility transistor (HEMT), grown on the Al2O3 and Si substrates by metal-organic chemical vapor deposition (MOCVD). Using XRR, we measured the thickness, roughness, and density of each layer and the concentrations of Al in AlxGa1-xN. From HRXRD measurements, the lattice constants were observed to change because of the lattice mismatch between substrate and nucleation layer (GaN).
The second case is the colossal magneto-resistance (CMR), Nd1-xCaxMnO3, thin films grown on LaAlO3 substrate by the pulsed-laser deposition (PLD). From the fitted results of XRR, top and interface layers were observed in all samples. The formation of interface layer is due to the lattice mismatch between the film and substrate, and the thickness of the interface layer becomes thicker as the lattice mismatch increased. From the calculation of the lattice constants, we further understand the strain effect produced by the substrate on the films.
|
|---|
