Influence of Sr deficiency on structural and electrical properties of SrTiO3 thin films grown by metal–organic vapor phase epitaxy

Homoepitaxial growth of SrTiO3 thin films on 0.5 wt% niobium doped SrTiO3 (100) substrates with high structural perfection was developed using liquid-delivery spin metal–organic vapor phase epitaxy (MOVPE). Exploiting the advantage of adjusting the partial pressures of the individual constituents independently, we tuned the Sr/Ti ratio of the gas phase for realizing, stoichiometric, as well as Sr deficient layers. Quantitative energy dispersive X-ray spectroscopy in a scanning transmission electron microscope confirm Sr deficiency of up to 20% in nominally off-stoichiometrically grown films. Our MOVPE process allows to grow such layers in phase pure state and without extended defect formation. Indications for oxygen deficiency could not be identified. Sr deficient layers exhibit an increased permittivity of ɛr = 202 and a larger vertical lattice parameter. Current–voltage characteristics (IVCs) of metal–oxide–semiconductor (Pt/SrTiO3/SrTiO3:Nb) structures reveal that Sr deficient SrTiO3 films show an intrinsic resistive switching with on–off ratios of three orders of magnitude at RT and seven orders of magnitude at 10 K. There is strong evidence that a large deviation from stoichiometry pronounces the resistive switching behavior. IVCs conducted at 10 K indicate a defect-based mechanism instead of mass transport by ion diffusion. This is supported by in-situ STEM investigations that show filaments to form at significant higher voltages than those were resistive switching is observed in our samples.

Shear Pleasure: The Structure, Formation, and Thermodynamics of Crystallographic Shear Phases

A renaissance of interest in crystallographic shear structures and our recent work in this remarkable class of materials inspired this review. We first summarize the geometrical aspects of shear plane formation and possible transformations in ReO3, rutile, and perovskite-based structures. Then we provide a mechanistic overview of crystallographic shear formation, plane ordering, and propagation. Next we describe the energetics of planar defect formation and interaction, equilibria between point and extended defect structures, and thermodynamic stability of shear compounds. Finally, we emphasize the remaining challenges and propose future directions in this exciting area. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is July 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Systemic Lupus Erythematosus with Unusual Manifestations

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown etiology, presenting with variable clinical picture. Having a high heterogeneity and lacking pathognomonic features, very often the diagnosis poses a great challenge for the clinician. Several unusual clinical manifestations such as nasal septal perforation and digital gangrene can occur in LES patients. Case report. We report the case of a 42-year-old woman, known with SLE, hospitalized in our department for a clinical presentation consisting of a recent major epistaxis, physical asthenia and acral necrosis of the upper limbs. Physical examination revealed an afebrile patient, with a cushingoid facies, facial telangiectasias, and necrotic scars localized on the distal phalanges, bilaterally. A diagnostic nasal endoscopy showed a large septal perforation with the absence of the cartilaginous nasal septum. CT highlighted an extended defect at the level of the cartilaginous part of the nasal septum. Conclusion. Nasal septal perforation remains an underdiagnosed invalidating complication of lupus and treated and discovered early could have an important impact on the general health of an already burdened by disease patient.

From Wafers to Bits and Back again: Using Deep Learning to Accelerate the Development and Characterization of SiC

A non-destructive, fast and accurate extended defect counting method on large diameter SiC wafers is presented. Photoluminescence (PL) signals from extended defects on 4H-SiC substrates were correlated to the specific etch features of Basal Plane Dislocations (BPDs), Threading Screw Dislocations (TSDs), and Threading Edge Dislocations (TED). For our non-destructive technique (NDT), automated defect detection was developed using modern deep convolutional neural networks (DCNN). To train a robust network, we used our large volume data set from our selective etch method of 4H-SiC substrates, already established based on definitive correlations to Synchrotron X-Ray Topography (SXRT) [1]. The defect locations, classifications and counts determined by our DCNN correlate with the subsequently etch-delineated features and counts. Once our network is sufficiently trained we will no longer need destructive methods to characterize extended defects in 4H-SiC substrates.

Tumor Control and Quality of Life in Skin Cancer Patients With Extensive Multilayered Nasal Defects

Objectives. The reconstruction after nasal skin cancer (NSC) resection is often practiced differently. The objective of this study is to evaluate the influence of patient-, tumor- and management-related factors on the role of surgery and choice of reconstruction.Methods. This was a monocentric retrospective study of patients who were diagnosed with a NSC (squamous cell or basal cell carcinoma) and suffered from an extended defect after ablative surgery between 2003 and 2013. Twenty-five patients were included. Tumors were staged using the Union for International Cancer Control (eighth edition) TNM classification for primary cutaneous skin cancer of the head and neck. Preferred treatment was surgery in all patients. Health-related quality of life (HRQoL) measurement was evaluated by one generic (36-Item Short Form Health Survey [SF-36]) and two organ-specific questionnaires (Rhinoplasty Outcome Evaluation [ROE] and Functional Rhinoplasty Outcome Inventory 17 [FROI-17]) after therapy. Survival data were estimated by the Kaplan-Meier method and statistical analysis was performed by log-rank, analysis of variance, Levene’s and t-tests. The median follow-up time was 2.1 years.Results. According to the Union for International Cancer Control classification, 13 of 25 tumors were staged as pT1 (52%), four as pT2 (16%), seven as pT3 (28%) and one as pT4a (4%). Seventy-two percent of patients (n=18) chose plastic reconstruction, and for the remaining 28% (n=7) of the patients opted for an implant-retained prosthesis. The overall survival was 69.5% after 5 years, the 5-year recurrence-free survival was 90.9% and the 5-year disease-specific survival was 100%. There was no significant difference in the HRQoL outcome between both rehabilitation methods.Conclusion. Surgery in NSC gives an excellent oncologic prognosis. Nasal reconstruction and prostheses are both very viable options depending on tumor stage and biology, the patient’s wishes as well as the experience of the surgeon.