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Baldo, P. M.

Publications and source records attributed to Baldo, P. M..

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

In-situ synchrotron x-ray studies of the microstructure and stability of In 2 O 3 epitaxial films

We report on the synthesis, stability, and local structure of In2O3 thin films grown via rf-magnetron sputtering and characterized by in-situ x-ray scattering and focused x-ray nanodiffraction. We find that In2O3 deposited onto (0 0 1)-oriented single crystal yttria-stabilized zirconia substrates adopts a Stranski-Krastanov growth mode at a temperature of 850 degrees C, resulting in epitaxial, truncated square pyramids with (1 1 1) side walls. We find that at this temperature, the pyramids evaporate unless they are stabilized by a low flux of In2O3 from the magnetron source. We also find that the internal lattice structure of one such pyramid is made up of differently strained volumes, revealing local structural heterogeneity that may impact the properties of In2O3 nanostructures and films.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Understanding Artifacts in Impedance Spectroscopy

Four-terminal measurements of impedance spectra have long been troubled by the presence of high frequency artifacts that typically indicate unphysically large inductive behavior. In this paper, we follow up on the observation of Fleig et al., that voltage and current are necessarily measured in different locations of the potentiostat circuit, and that, typically, the electrometer input is a virtual ground. In this case, the capacitance of coaxial cables that connect sample electrodes to the potentiostat provides a high frequency conduction path to ground, so that some of the current that passes through the sample bypasses the electrometer. In four-electrode measurements, this mechanism produces the observed inductive artifacts. We examine a variety of simulated samples, with calculations compared to measurements of relevant circuits, to quantitatively investigate the nature of the artifacts. Model results agree with measurements when the leakage capacitances are properly included in the circuit analyses. With understanding of the origin of the inductive artifacts, the four-electrode method can be effectively utilized, enabling a combination of two-, three- and four-electrode measurements to be used to best advantage. Finally, using this combination of electrode configurations, temperature dependent measurements of SrTiO 3 , Y 2 O 3 -stabilized ZrO 2 , and In 2 O 3 films deposited on YSZ substrates are presented.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Octahedral rotations in strained LaAlO{sub 3}/SrTiO{sub 3} (001) heterostructures

Many complex oxides display an array of structural instabilities often tied to altered electronic behavior. For oxide heterostructures, several different interfacial effects can dramatically change the nature of these instabilities. Here, we investigate LaAlO{sub 3}/SrTiO{sub 3} (001) heterostructures using synchrotron x-ray scattering. We find that when cooling from high temperature, LaAlO{sub 3} transforms from the Pm3{sup ¯}m to the Imma phase due to strain. Furthermore, the first 4 unit cells of the film adjacent to the substrate exhibit a gradient in rotation angle that can couple with polar displacements in films thinner than that necessary for 2D electron gas formation.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Modular instrument mounting system for variable environment in operando X-ray experiments

In the growing field of in operando and in situ X-ray experiments, there exists a large disparity in the types of environments and equipment to control them. This situation makes it challenging to conduct multiple experiments with a single mechanical interface to the diffractometer. Here, we describe the design and implementation of a modular instrument mounting system that can be installed on a standard six-circle diffractometer (e.g., 5021 Huber GmbH). This new system allows for the rapid changeover of different chambers and sample heaters and permits accurate sample positioning (x, y, z, and azimuthal rotation) without rigid coupling to the chamber body. Isolation of the sample motion from the chamber enclosure is accomplished through a combination of custom rotary seals and bellows. Control of the pressure and temperature has been demonstrated in the ranges of 10{sup -6}-10{sup 3} Torr and 25 Degree-Sign C-900 Degree-Sign C, respectively. We have utilized the system with several different modular instruments. As an example, we provide in situ sputtering results, where the growth dynamics of epitaxial LaGaO{sub 3} thin films on (001) SrTiO{sub 3} substrates were investigated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗