arXiv subjects

Frank W. DelRio

Publications and source records attributed to Frank W. DelRio.

4 recordsLinked to original sources

arXiv2026

Connecting Microseismicity to Lithology via a Model of Slip Avalanches

Fluid injection into the earth's crust can induce small and frequent earthquakes in the subsurface. Predicting their sizes and temporal occurrences via statistical analysis is crucial for safe operations in unconventional oil and gas recovery, enhanced geothermal systems, and geologic carbon storage. Here we show that a simple micromechanical model of slip avalanches in slowly deforming solids predicts the slip statistics observed over drastically different spatial scales, namely meter-scale microseismic observations and nanometer- to micrometer-scale nanoindentation experiments can be described with this model. Microseismic catalogs extracted from high-pressure fluid injection operations into geological basins with various lithologies and nanoindentation experiments on shale across a wide range of temperatures and mineral compositions yield statistics consistent with model predictions. This universality across materials, temperatures, and scales is consistent with the prediction that the slip statistics result from only a few basic properties. Previously debated deviations of the statistics in layered sedimentary formations are explained by finite-size and stress-integrative effects resulting from mechanically weak bedding planes. The slip statistics therefore provide important information about the structure and scales of the bedding planes. Conversely, the basin structure can also be used to predict the probability distribution for the sizes of triggered microseismic events.

cond-mat.other↗

arXiv2024

Refining microstructures in additively manufactured Al/Cu gradients through TiB$_2$ inclusions

The additive manufacture of compositionally graded Al/Cu parts by laser engineered net shaping (LENS) is demonstrated. The use of a blue light build laser enabled deposition on a Cu substrate. The thermal gradient and rapid solidification inherent to selective laser melting enabled mass transport of Cu up to 4 mm away from a Cu substrate through a pure Al deposition, providing a means of producing gradients with finer step sizes than the printed layer thicknesses. Printing graded structures with pure Al, however, was prevented by the growth of Al$_2$Cu$_3$ dendrites and acicular grains amid a matrix of Al$_2$Cu. A combination of adding TiB$_2$ grain refining powder and actively varying print layer composition suppressed the dendritic growth mode and produced an equiaxed microstructure in a compositionally graded part. Material phase was characterized for crystal structure and nanoindentation hardness to enable a discussion of phase evolution in the rapidly solidifying melt pool of a LENS print.

physics.app-ph↗

arXiv2023

Unlocking High Performance, Ultra-Low Power Van der Waals Transistors: Towards Back-End-of-Line In-Sensor Machine Vision Applications

Recent reports on machine learning (ML) and machine vision (MV) devices have demonstrated the potentials of 2D materials and devices. Yet, scalable 2D devices are being challenged by contact resistance and Fermi Level Pinning (FLP), power consumption, and low-cost CMOS compatible lithography processes. To enable CMOS+2D, it is essential to find a proper lithography strategy that can fulfill these requirements. Here, we explore modified van der Waals (vdW) deposition lithography and demonstrate a relatively new class of van-der-Waals-Field-Effect-Transistors (vdW-FETs) based on 2D materials. This lithography strategy enables us to unlock high performance devices evident by high current on-off ratio (Ion/Ioff), high turn-on current density (Ion), and weak Fermi Level Pinning (FLP). We utilize this approach to demonstrate a gate-tunable near-ideal diode using MoS2/WSe2 heterojunction with an ideality factor of ~1.65 and current rectification of 102. We finally demonstrate a highly sensitive, scalable, and ultra-low power phototransistor using MoS2/ WSe2 vdW-FET for Back-End-of-Line (BEOL) integration. Our phototransistor exhibits the highest gate-tunable photoresponsivity achieved to date for white light detection with ultra-low power dissipation, enabling ultra-sensitive, ultra-fast, and efficient optoelectronic applications such as in-sensor neuromorphic machine vision. Our approach shows the great potential of modified vdW deposition lithography for back-end-of-line CMOS+2D applications.

cond-mat.mtrl-sci↗

arXiv2023

Exploring Layer Thinning of Exfoliated \b{eta}-Tellurene and Room Temperature Photoluminescence with Large Exciton Binding Energy Revealed in TeO2

Due to its tunable band gap, anisotropic behavior, and superior thermoelectric properties, device applications using layered tellurene (Te) are becoming attractive. Here, we report a thinning technique for exfoliated tellurene nanosheets using thermal annealing in an oxygen environment. We characterize different thinning parameters including temperature and annealing time. Based on our measurements, we show that controlled layer thinning occurs in the narrow temperature range of 325 oC to 350 oC. We also show a reliable method to form \b{eta}-tellurene oxide (\b{eta}- TeO2), which is an emerging wide band gap semiconductor with promising electronic and optoelectronic properties. This wide band gap semiconductor exhibits a broad photoluminescence (PL) spectrum with multiple peaks covering the range 1.76 eV to 2.08 eV. This PL emission coupled with Raman spectra are strong evidence of the formation of 2D \b{eta}- TeO2. We discuss the results obtained and the mechanisms of Te thinning and \b{eta}-TeO2 formation at different temperature regimes. We also discuss the optical band gap of \b{eta}-TeO2 and show the existence of pronounced excitonic effects evident by the large exciton binding energy in this 2D \b{eta}-TeO2 system that reach 1.54 eV to 1.62 eV for bulk to monolayer, respectively. Our work can be utilized to have better control over Te nanosheet thickness. It also sheds light on the formation of well-controlled \b{eta}-TeO2 layered semiconductor for electronic and optoelectronic applications.

cond-mat.mtrl-sci↗