Charge Transfer at Metal Dielectric Interfaces under Extreme Environments

Project: Research project

Project Details

Description

Charge Transfer at Metal Dielectric Interfaces under Extreme Environments Statement of Work - Arizona State University State-of-the-art transmission electron microscopy techniques will be used to probe the atomic structure of the metal dielectric interfaces as well as their chemical and electronic nature. In order to achieve atomic-resolution imaging and to extract chemical information simultaneously, the metal/oxide and oxide/oxide interfaces will be imaged in the STEM mode. Elements with high atomic number elements generate strong Z-contrast in high-angle annulardark- field (HAADF) images, while inelastically-scattered electrons containing chemical information about the materials being examined can be simultaneously recorded with a spectrometer after passing through the sample. Sub-angstrom electron probes will be available for this purpose using two recently acquired aberration-corrected scanning transmission electron microscopes housed at the Cowley Center (ASU). One of these instruments is equipped with a novel type of monochromator, which should permit probing of the electronic structure across interfaces with ~0.025eV energy resolution, while the other is equipped with Xray (energydispersive) and electron-energy-loss spectrometers capable of spectrum or elemental mapping at the atomic scale. Thus, composition profiles and bonding information from electron energy loss spectroscopy (EELS) will provide complementary chemical characterization of the fabricated structures with atomic resolution. In addition, we will study the interfaces using off-axis electron holography. This technique represents a unique and powerful electron-interference approach able to visualize and quantify changes in phase of the incident electron beam caused by interaction with the electromagnetic fields of a thin, electron-transparent object. These phase changes can be related back to specific object features with spatial resolutions approaching the nanometer scale. The holography technique can thus be used to determine 2-D variations in electrostatic potential across metal/oxide heterostructures, in conjunction with the electron microscopy techniques being used to probe the atomic structure and chemical bonding across the interfaces. Holography could, in principle, also allow us to make direct measurements of the ferroelectric fields on the nanometer scale although preparing a cross-sectional sample suitable for measurement purposes could prove to be challenging.
StatusFinished
Effective start/end date6/1/1411/30/17

Funding

  • DOD-USAF-AFRL: Air Force Office of Scientific Research (AFOSR): $294,611.00

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