New approaches for achieving more perfect transition metal oxide thin films

This perspective considers the enormous promise of epitaxial functional transition metal oxide thin films for future applications in low power electronic and energy applications since they offer wide-ranging and highly tunable functionalities and multifunctionalities, unrivaled among other classes of materials. It also considers the great challenges that must be overcome for transition metal oxide thin films to meet what is needed in the application domain. These challenges arise from the presence of intrinsic defects and strain effects, which lead to extrinsic defects. Current conventional thin film deposition routes often cannot deliver the required perfection and performance. Since there is a strong link between the physical properties, defects and strain, routes to achieving more perfect materials need to be studied. Several emerging methods and modifications of current methods are presented and discussed. The reasons these methods better address the perfection challenge are considered and evaluated

Direct Observation of Electrostatically Driven Band Gap Renormalization in a Degenerate Perovskite Transparent Conducting Oxide

We have directly measured the band gap renormalization associated with the Moss-Burstein shift in the perovskite transparent conducting oxide (TCO), La-doped BaSnO_{3}, using hard x-ray photoelectron spectroscopy. We determine that the band gap renormalization is almost entirely associated with the evolution of the conduction band. Our experimental results are supported by hybrid density functional theory supercell calculations. We determine that unlike conventional TCOs where interactions with the dopant orbitals are important, the band gap renormalization in La-BaSnO_{3} is driven purely by electrostatic interactions

Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling

A planar slab of negative index material works as a superlens with sub-diffraction-limited imaging resolution, since propagating waves are focused and, moreover, evanescent waves are reconstructed in the image plane. Here, we demonstrate a superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime. The combination of near-field microscopy with a tunable free-electron laser allows us to address precisely the polariton modes, which are critical for super-resolution imaging. We spectrally study the lateral and vertical distributions of evanescent waves around the image plane of such a lens, and achieve imaging resolution of wavelength/14 at the superlensing wavelength. Interestingly, at certain distances between the probe and sample surface, we observe a maximum of these evanescent fields. Comparisons with numerical simulations indicate that this maximum originates from an enhanced coupling between probe and object, which might be applicable for multifunctional circuits, infrared spectroscopy, and thermal sensors.Comment: 20 pages, 6 figures, published as open access article in Nature Communications (see http://www.nature.com/ncomms/

124I-HuCC49deltaCH2 for TAG-72 antigen-directed positron emission tomography (PET) imaging of LS174T colon adenocarcinoma tumor implants in xenograft mice: preliminary results

<p>Abstract</p> <p>Background</p> <p>¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) is widely used in diagnostic cancer imaging. However, the use of ¹⁸F-FDG in PET-based imaging is limited by its specificity and sensitivity. In contrast, anti-TAG (tumor associated glycoprotein)-72 monoclonal antibodies are highly specific for binding to a variety of adenocarcinomas, including colorectal cancer. The aim of this preliminary study was to evaluate a complimentary determining region (CDR)-grafted humanized C_H2-domain-deleted anti-TAG-72 monoclonal antibody (HuCC49deltaC_H2), radiolabeled with iodine-124 (¹²⁴I), as an antigen-directed and cancer-specific targeting agent for PET-based imaging.</p> <p>Methods</p> <p>HuCC49deltaC_H2 was radiolabeled with ¹²⁴I. Subcutaneous tumor implants of LS174T colon adenocarcinoma cells, which express TAG-72 antigen, were grown on athymic Nu/Nu nude mice as the xenograft model. Intravascular (i.v.) and intraperitoneal (i.p.) administration of ¹²⁴I-HuCC49deltaC_H2 was then evaluated in this xenograft mouse model at various time points from approximately 1 hour to 24 hours after injection using microPET imaging. This was compared to i.v. injection of ¹⁸F-FDG in the same xenograft mouse model using microPET imaging at 50 minutes after injection.</p> <p>Results</p> <p>At approximately 1 hour after i.v. injection, ¹²⁴I-HuCC49deltaC_H2 was distributed within the systemic circulation, while at approximately 1 hour after i.p. injection, ¹²⁴I-HuCC49deltaC_H2 was distributed within the peritoneal cavity. At time points from 18 hours to 24 hours after i.v. and i.p. injection, ¹²⁴I-HuCC49deltaC_H2 demonstrated a significantly increased level of specific localization to LS174T tumor implants (p = 0.001) when compared to the 1 hour images. In contrast, approximately 50 minutes after i.v. injection, ¹⁸F-FDG failed to demonstrate any increased level of specific localization to a LS174T tumor implant, but showed the propensity toward more nonspecific uptake within the heart, Harderian glands of the bony orbits of the eyes, brown fat of the posterior neck, kidneys, and bladder.</p> <p>Conclusions</p> <p>On microPET imaging, ¹²⁴I-HuCC49deltaC_H2 demonstrates an increased level of specific localization to tumor implants of LS174T colon adenocarcinoma cells in the xenograft mouse model on delayed imaging, while ¹⁸F-FDG failed to demonstrate this. The antigen-directed and cancer-specific ¹²⁴I-radiolabled anti-TAG-72 monoclonal antibody conjugate, ¹²⁴I-HuCC49deltaC_H2, holds future potential for use in human clinical trials for preoperative, intraoperative, and postoperative PET-based imaging strategies, including fused-modality PET-based imaging platforms.</p

Advanced synthesis techniques and routes to new single-phase multiferroics

We review recent developments and advances in the synthesis of thin-film multiferroic and magnetoelectric heterostructures. Driven by the promise of new materials with built-in useful phenomena (i.e., electric field control of ferromagnetism), extensive research has been centered on the search for and characterization of new single-phase multiferroic materials. In this review we provide a brief overview of recent developments in the synthesis of thin film versions of these materials. Advances in modern film growth processes have provided access to high-quality materials for in-depth study. We highlight the use of epitaxial thin-film strain to stabilize metastable phases, drive multiferroic properties, and produce new structures and properties in materials including case studies of EuTiO3 and BiFeO3. © 2012 Elsevier Ltd. All rights reserved

EPITAXIAL-GROWTH OF CUPRATE SUPERCONDUCTORS FROM THE GAS-PHASE

SCHLOM DG, Anselmetti D, BEDNORZ JG, GERBER C, MANNHART J. EPITAXIAL-GROWTH OF CUPRATE SUPERCONDUCTORS FROM THE GAS-PHASE. Journal of Crystal Growth. 1994;137(1-2):259-267.The growth mechanism of c-axis oriented thin epitaxial films of the most widely studied cuprate superconductor, YBa2Cu3O7-delta, formed by a variety of gas phase codeposition methods on common substrate materials is described. The evolution of the surface microstructure, as revealed by scanning tunneling microscopy (STM), indicates that growth is dominated by the accommodation of depositing species at ledges. These ledges, which provide energetically favorable positions for this process, lie either along growth spirals emanating from screw dislocations, or, when a vicinal substrate is used, separate the low energy (001) planes at the film surface. If the substrate is misoriented sufficiently, growth occurs by step propagation. Otherwise, a high density of screw dislocations (approximately 10(9) cm-2) is nucleated during the initial stages of growth, providing a continual supply of ledge incorporation sites for the depositing species. Two likely mechanisms for the generation of these screw dislocations are described. The surface evolution reported appears to be an intrinsic feature of c-axis oriented YBa2Cu3O7-delta, films for a wide range of growth conditions, irrespective of the substrate material or vapor phase deposition method

OBSERVATION OF SCREW DISLOCATIONS IN SPUTTERED YBA2CU3O7-DELTA FILMS

SCHLOM DG, Anselmetti D, BEDNORZ JG, GERBER C, MANNHART J, MULLER KA. OBSERVATION OF SCREW DISLOCATIONS IN SPUTTERED YBA2CU3O7-DELTA FILMS. Physica C Superconductivity. 1991;185-189:2007-2008.By imaging the as-grown surfaces of sputtered YBa2Cu3O7-delta films with scanning tunneling microscopy (STM), we have directly observed spiral-shaped growth terraces that emanate from screw dislocations. This surface morphology has important implications for Josephson junctions and superlattices. The density of screw dislocations observed is in the range of 10(9) cm-2. In addition to their importance as flux pinning sites, these screw dislocations act as growth centers by continually providing a growth step for the attachment of incident species by a step-propagation growth mechanism known as screw dislocation mediated growth. Growth parameters strongly influence the screw dislocation density: it decreases with increasing growth temperature, decreasing growth rate, and increasing substrate misorientation for SrTiO3 surface orientationn near {100}

PINNING CENTERS IN YBA2CU3O7-DELTA FILMS

MANNHART J, Anselmetti D, BEDNORZ JG, GERBER C, MULLER KA, SCHLOM DG. PINNING CENTERS IN YBA2CU3O7-DELTA FILMS. Superconductor Science and Technology. 1992;5(1S):S125-S128.Pinning centers in epitaxial YBa2Cu3O7-delta films have been investigated by scanning tunneling microscopy and transport studies. An astonishing surface morphology has been found which includes a high density congruent-to 10(9) cm-2 of screw dislocations and nanometer-sized holes. The density of screw dislocations can be controlled by varying the growth conditions of the YBa2Cu3O7-delta films, allowing correlations between critical currents and screw dislocation density to be investigated. Films with higher screw dislocation densities are observed to have higher critical current densities and a slower drop of J(c)(H)

CORRELATION BETWEEN JC AND SCREW DISLOCATION DENSITY IN SPUTTERED YBA2CU3O7-DELTA FILMS

MANNHART J, Anselmetti D, BEDNORZ JG, et al. CORRELATION BETWEEN JC AND SCREW DISLOCATION DENSITY IN SPUTTERED YBA2CU3O7-DELTA FILMS. Zeitschrift für Physik B Condensed Matter. 1992;86(2):177-181.Electric transport properties of sputtered YBa2Cu3O7-delta films were studied as a function of screw dislocation density, ranging from 5.10(7) cm-2 to 1.3.10(9) cm-2 as determined at the film surface. A correlation was found between the number of screw dislocations and the critical current density (J(c)). Films with higher screw dislocation densities have higher critical current densities and a slower drop of J(c) as a function of applied magnetic field H