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Damage accumulation in 4H–SiC under 1.1 MeV Al22+ irradiation is investigated as a function of dose at temperatures from 150 to 450 K. Based on Rutherford backscattering spectroscopy and nuclear reaction analysis channeling spectra, the damage accumulation on both the Si and C sublattices have been determined, and a disorder accumulation model has been fit to the data. The model fits indicate that defect-stimulated amorphization is the primary amorphization mechanism in SiC over the temperature range investigated. The temperature dependence of the cross section for defect-stimulated amorphization and the critical dose for amorphization indicate that two different dynamic recovery processes are present, which are attributed to short-range recombination and long-range migration of point defects below and above room temperature, respectively. As the irradiation temperature approaches the critical temperature for amorphization, cluster formation has an increasing effect on disorder accumulation, and ion flux plays an important role on the nature and evolution of disorder. Dislocation loops, which are mostly formed under high ion flux, act as sinks for point defects, thereby reducing the disorder accumulation rate.

Stoichiometric, epitaxial LaCrO 3 films have been grown on TiO 2 -terminated SrTiO 3 (001) substrates by molecular beam epitaxy using O 2 as the oxidant. Film growth occurred in a layer-by-layer fashion, giving rise to structurally excellent films and surfaces which preserve the step-terrace structure of the substrate. The critical thickness is in excess of 500 Å. Near-surface Cr(III) is highly susceptible to further oxidation to Cr(V), leading to the formation of a disordered phase upon exposure to atomic oxygen. Recovery of the original epitaxial LaCrO 3 phase is readily achieved by vacuum annealing. 2Complex oxides exhibit a range of physical properties unparalleled by any other class of materials. Their electronic, magnetic, and optical characteristics span the field of possibilities, and a wealth of applications awaits our ability to understand and control these properties. Materials synthesis is key to realizing the full potential of complex oxides, particularly in thin-film form. In the bulk, this perovskite exhibits an orthorhombic structure (space group Pbnm) with lattice parameters a = 5.513 Å, b = 5.476 Å, c = 7.759 Å. 4 However, isolation of a pseudocubic cell within the orthorhombic structure yields a = b = c = 3.885 Å (see structural models in Fig. 1). Thus, LCO is a candidate for heteroepitaxy on SrTiO 3 (001), for which a = b = c = 3.905 Å.In this Letter, we describe the epitaxial growth of LCO on SrTiO 3 (001) by MBE. 5 Atomically flat, TiO 2 -terminated SrTiO 3 (STO) substrates were prepared as described previously. 6 La and Cr were evaporated from an effusion cell and an electron beam evaporator, respectively, and the O 2 partial pressure was kept constant at ~6 × 10 -8 Torr.The La flux was measured before and after deposition by a quartz crystal oscillator (QCO), and the Cr flux was monitored and controlled during deposition by atomic with an AFM image and a line profile. The surface periodicity evolves from (1×1) for the substrate to (2×2) for the film surface. Moreover, the film surface exhibits a well-defined terrace-step structure with typical step heights of ~ 4 Å, the c value for pseudocubic LCO.This result confirms the layer-by-layer growth mode revealed by RHEED oscillations and the presence of a single surface termination, which we expect is CrO 2 , based on the fact that all growths were terminated after an integral number of oscillations were recorded.We show in Fig. 2