An AlGaN layer with good crystalline quality (χmin=2.1%) was grown by metalorganic vapor phase epitaxy on a sapphire (0001) substrate using a GaN intermediate layer. The Al composition, which cannot be unambiguously determined by x-ray diffraction (XRD) or by photoluminescence, was determined by Rutherford backscattering (RBS). The perpendicular and parallel elastic strain of the Al0.28Ga0.72N layer, e⊥=−0.16% and e∥=+0.39%, respectively, were derived using XRD and RBS/channeling. The small ratio |e⊥/e∥|=0.41 indicates that the Al0.28Ga0.72N lattice is much stiffer in the c-axis direction than in the a-axis direction. A comparison of the strain data for GaN, InGaN, and AlGaN layers is presented.

Superconducting Tl2Ba2CaCu2O8 thin films (Tl-2212) have been reproducibly fabricated on both sides of 2 inch LaAlO3(001) substrates by using a so-called two-step process. A simple and flexible horizontal arrangement inside the crucible during thallination has been proposed, to ensure a good convection of thallous oxide vapor around the film surface, and thus a high film quality on both sides. A good uniformity over the whole area of the films has been realized. The films are strongly textured, with the c-axis perpendicular to the substrate surface, and they show the fourfold symmetry of the tetragonal crystal structure. The full width at half maximum of the (002) peak for both films on the best sample is 0.43° and 0.55° respectively. The films exhibit flat terraces with particles and shallow holes, but free of microcracks. The superconducting critical temperatures fall in the range 105–108.5 K. The critical current densities are between 1.0 × 106 and 4.8 × 106 A cm−2 at 77 K. The microwave surface resistances at the central area of the films are around 500 μΩ at 77 K and 10 GHz. These films are suitable for microwave applications.