Based on a structure model of mixture of phases, the crystal structure analysis of (Ba1−xLax)[Mg(1+x)/3Nb(2−x)/3]O3 (BLMN) (x = 0.9 and 1.0) by Rietveld refinements was carried out. The pure La(Mg2/3Nb1/3)O3 (LMN) and BLMN (x=0.9) actually consist of a two-phase mixture rather a single phase. One is Fm-3m, which is cubic and 1:1 ordered and the other is P21/n, which is monoclinic and has both 1:1 ordering and the antiphase and inphase tilting of oxygen octahedra with a−a−c+. The weight fraction of the Fm-3m phase is 17.5% at x=0.9 and further decreases to 7.5% in pure LMN. Meanwhile, that of the P21/n phase is 82.5% at x =0.9 and further increases to 92.5% in pure LMN. The I4/m phase, which is present as a minor phase from x=0.3 to 0.7, disappeared when x≥0.9. The abrupt change of the x-ray diffraction pattern at x=0.9 is caused by a change of major phase from Fm-3m to P21/n phase in the matrix.

Si/Si0.8Ge0.2/Si(001) structures were grown at various growth temperatures (250 ∼ 760 °C) using molecular beam epitaxy, and the variation of strain and microstructure of the film was investigated using double crystal X-ray diffractometry and transmission electron microscopy. SiGe films with good single crystallinity were obtained at the growth temperatures of 440 ∼ 600 °C. For the samples grown below 350 °C, an amorphous SiGe film was developed over the SiGe single crystalline layer with a jagged amorphous/crystalline (a/c) interface, and many defects such as stacking faults and microtwins were formed below the a/c interface. Dislocations were developed through out the films for the samples grown above 680 °C. In addition, for the samples grown below 680 °C, the amount of in-plane strain of the SiGe film was found to be about − 8×l0−3 without strain relaxation. However, the SiGe films grown at 760 °C have small in-plain strain of − 4×l0−3 and large strain relaxation of 50%.

Heterostructural properties of pseudomorphic (AlGaAs/GaAs), partially strained (GaInAs/GaAs), and highly strained (GaAs/Si) semiconductor systems have been studied using High Resolution Double-Crystal X-ray Diffraction (DXRD), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM). Using the high resolution DXRD with CuKα1 and two-reflection Si (220) monochromator, we obtained (004) symmetric and (115) or (224) asymmetric reflection rocking curves for samples grown by molecular beam epitaxy. With 0.5 μm thick samples, perpendicular and in-plane lattice mismatches were calculated using elastic theory and compared with each other. The different degree of relaxation for these samples was observed and correlated with the lattice mismatch, X-ray layer peak broadening (i.e., full width at half maximum), and SEM surface morphology. For a GaInAs/GaAs sample, the strain relaxation along one of the <110> directions was more than the other direction, that is, the strain relaxation is not isotrophic. Also we observed that the lines were mainly parallel in one direction, i.e., they did not form a cross-hatch pattern. TEM images from both cross-sectional and planar views of the samples will be presented.

An a-axis oriented YBa2Cu3O7-x (YBCO) thin film exhibiting zero resistance at 83 K and critical current density of 7.9x103 A/cm2 at 62 K was obtained on an 180 nm - thick PrBa2Cu3 O7-xx(PBCO) buffered SrTiO3(100) substrate by two step pulsed laser deposition (PLD). The volume fraction of a-axis orientation and the crystallinity(Xmin) of the 150 nm-thick YBCO thin films were increased with increasing the thickness of PBCO buffer layer, which was varied friom 0 nm to 180 nm. It is concluded that the thickness of PBCO buffer layer is one of the important parameters to control the structural and superconducting properties of the a-axis oriented YBCO thin films using the PBCO buffer layers.

The effect of growth interruption (GI) on the quality of interface between InGaAs quantum well (QW) and InP layer has been studied using transmission electron microscopy (TEM). The In1-xGaxAs (x=0.39) QW grown without GI has sharp and coherent interfaces. However, cellular structure instead of InGaAs QW was observed in the sample grown with 120 sec AsH3 purge during the first GI (before the growth of InGaAs QW). According to the composition analysis using energy dispersive X-ray (EDX), inside of cell is InP and boundary of cell is considered to be a mixture of In1-xGaxAs1-yPy and InAs1-xPx phases. Similar structure was observed in the sample grown with 30 sec AsH3 purge after 30 sec PH3 purge during the first GI. Our results indicate that long time AsH3 purge during the first GI is detrimental to the formation of InGaAs QW. For the sample grown with AsH3 purge less than 40 sec during the second GI (after the growth of InGaAs QW), InGaAs QW is formed with sharp and coherent interfaces. However, if the surface of InGaAs QW is exposed to AsH3 gas for long time (~ 120 sec), dislocations are generated at the interface bewteen InGaAs QW and InP cap layer.

For the GaAs buffer layer deposited on Si substrate at 80°C and annealed at 300°C for 10 min, the size of most GaAs islands was observed as ∼ 10 nm but large islands (∼ 40 nm) were also seen. According to the calculation of spacing of moire fringes, large GaAs islands are considered to be rotated about 4 ° with respect to the Si substrate normal. However, for the main GaAs film overgrown on the GaAs buffer layer at 580 °C, moire fringes with the spacing of 5 nm (GaAs film without rotation) completely covered the surface of Si substrate. Misfit dislocations and stacking faults were already formed at the growth stage of buffer layer. Stacking faults and misfit dislocations consisting of Lomer and 60 ° dislocations were observed in GaAs films grown at 580 °C. However, after rapid thermal annealing at 900 °C for 10 sec, only Lomer dislocations with 1/2[110] and 1/2[-110] Burgers vectors were observed.