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Ihlefeld, Jon

Publications and source records attributed to Ihlefeld, Jon.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Exploring leakage in dielectric films via automated experiments in scanning probe microscopy

Here electronic conduction pathways in dielectric thin films are explored using automated experiments in scanning probe microscopy (SPM). In this study, we use large field of view scanning to identify the position of localized conductive spots and develop an SPM workflow to probe their dynamic behavior at higher spatial resolution as a function of time, voltage, and scanning process in an automated fashion. Using this approach, we observe the variable behaviors of the conductive spots in a 20-nm-thick ferroelectric Hf 0.54 Zr 0.48 O 2 film, where conductive spots disappear and reappear during continuous scanning. There are also fresh conductive spots that develop during scanning. The automated workflow is universal and can be integrated into a wide range of microscopy techniques, including SPM, electron microscopy, optical microscopy, and chemical imaging.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effects of strain, disorder, and Coulomb screening on free-carrier mobility in doped cadmium oxide

Here, the interplay of stress, disorder, and Coulomb screening dictating the mobility of doped cadmium oxide (CdO) is examined using Raman spectroscopy to identify the mechanisms driving dopant incorporation and scattering within this emerging infrared optical material. Specifically, multi-wavelength Raman and UV-vis spectroscopies are combined with electrical Hall measurements on a series of yttrium (X = Y) and indium (X = In) doped X:CdO thin-films. Hall measurements confirm n-type doping and establish carrier concentrations and mobilities. Spectral fitting along the low-frequency Raman combination bands, especially the TA+TO(X) mode, reveals that the evolution of strain and disorder within the lattice as a function of dopant concentration is strongly correlated with mobility. Coupling between the electronic and lattice environments was examined through analysis of first- and second-order longitudinal–optical phonon–plasmon coupled modes that monotonically decrease in energy and asymmetrically broaden with increasing dopant concentration. By fitting these trends to an impurity-induced Fröhlich model for the Raman scattering intensity, exciton–phonon and exciton–impurity coupling factors are quantified. These coupling factors indicate a continual decrease in the amount of ionized impurity scattering with increasing dopant concentration and are not as well correlated with mobility. This shows that lattice strain and disorder are the primary determining factors for mobility in donor-doped CdO. In aggregate, the study confirms previously postulated defect equilibrium arguments for dopant incorporation in CdO while at the same time identifying paths for its further refinement.

42 ENGINEERING↗
DOE OSTI2021

Electroabsorption optical modulator

An electroabsorption modulator that operates based on electroabsorption of a surface plasmon polariton mode is improved by various structural changes and/or selection of different materials. For example, at least a portion of the waveguide may be made to be conductive, e.g., by doping. Also, layers that make up the modulator structure may be placed along sides of waveguides in addition to or instead of simply on the top thereof. High permittivity gate dielectric materials may be employed. Also, materials other than ITO may be employed as a transparent conductor. Such an improved plasmonic electroabsorption modulator can be fabricated using standard semiconductor processing techniques and may be integrated with standard photonic integrated circuits, including silicon photonics and compound semiconductor-based platforms. Advantageously, high-speed, low-voltage operation over a wide spectrum of wavelengths may be achieved.

Wood, Michael↗
DOE OSTI2021

Methods of epsilon-near-zero optical modulation

A method of optical modulation in a non-resonant epsilon-near-zero (EMZ) plasmonic electro-optical modulator is provided. An optical carrier is injected into a waveguide optically coupled to a layer of transparent conductive material having an epsilon-near-zero (ENZ) wavelength. The transparent conductive material layer constitutes a portion of a capacitive structure that includes a gate dielectric layer. A time-varying bias voltage applied across the gate dielectric layer shifts the ENZ wavelength toward the carrier wavelength, and thereby impresses a phase modulation pattern on the carrier wave.

Wood, Michael↗
DOE OSTI2019

Ion-implanted thermal barrier

Ion implantation can be used to define a thermal dissipation path that allows for better thermal isolation between devices in close proximity on a microelectronics chip, thus providing a means for higher device density combined with better performance.

42 ENGINEERING↗