arXiv subjects

Aidan A. Taylor

Publications and source records attributed to Aidan A. Taylor.

3 recordsLinked to original sources

arXiv2026

A correlation of structural changes with nanomechanical properties in TiN-AlN multilayer films

The present work investigates the changes in overall nanomechanical properties of reactively sputtered TiN-AlN multilayer films arising due to phase transformation in the AlN layers. Multilayered TiN-AlN films were sputter deposited with constant TiN layer thickness of 5 nm while the AlN layer thickness varied between 1-5 nm. The AlN underwent a phase transition from cubic rock salt to hexagonal wurtzite above 3 nm thickness due to the lattice strains. The hardness and indentation modulus of the multilayers decreased with increasing AlN film thickness, up to 3 nm, due to increased volume fraction of softer AlN layer and then stabilized for 4 nm and 5 nm thickness films. Micropillar compression of these multilayers showed a transition from columnar brittle to partially ductile failure associated with crack deflection with increasing AlN film thickness. Interestingly, nanoindentation scratch resistance of 3 nm AlN multilayer was observed to be superior compared to all other films. The crack propagation behavior in scratching showed increased microcracking tendency towards higher AlN film thickness. This shows that cubic to hexagonal transformation in AlN is beneficial for improving the damage tolerance of the multilayer system.

cond-mat.mtrl-sci↗

arXiv2020

Electron Backscattered Diffraction using a New Monolithic Direct Detector: High Resolution and Fast Acquisition

A monolithic active pixel sensor based direct detector that is optimized for the primary beam energies in scanning electron microscopes is implemented for electron back-scattered diffraction (EBSD) applications. The high detection efficiency of the detector and its large array of pixels allow sensitive and accurate detection of Kikuchi bands arising from primary electron beam excitation energies of 4 keV to 28 keV, with the optimal contrast occurring in the range of 8-16 keV. The diffraction pattern acquisition speed is substantially improved via a sparse sampling mode, resulting from the acquisition of a reduced number of pixels on the detector. Standard inpainting algorithms are implemented to effectively estimate the information in the skipped regions in the acquired diffraction pattern. For EBSD mapping, a speed as high as 5988 scan points per second is demonstrated, with a tolerable fraction of indexed points and accuracy. The collective capabilities spanning from high angular resolution EBSD pattern to high speed pattern acquisition are achieved on the same detector, facilitating simultaneous detection modalities that enable a multitude of advanced EBSD applications, including lattice strain mapping, structural refinement, low-dose characterization, 3D-EBSD and dynamic in situ EBSD.

cond-mat.mtrl-sci↗

arXiv2020

Defect filtering for thermal expansion induced dislocations in III-V lasers on silicon

Epitaxially integrated III-V semiconductor lasers for silicon photonics have the potential to dramatically transform information networks, but currently, dislocations limit performance and reliability even in defect tolerant InAs quantum dot (QD) based lasers. Despite being below critical thickness, QD layers in these devices contain previously unexplained misfit dislocations, which facilitate non-radiative recombination. We demonstrate here that these misfit dislocations form during post-growth cooldown due to the combined effects of (1) thermal-expansion mismatch between the III-V layers and silicon and (2) precipitate and alloy hardening in the active region. By incorporating an additional sub-critical thickness, indium-alloyed misfit dislocation trapping layer, we leverage these mechanical hardening effects to our advantage, successfully displacing 95% of misfit dislocations from the QD layer in model structures. Unlike conventional dislocation mitigation strategies, the trapping layer reduces neither the number of threading dislocations nor the number of misfit dislocations. It simply shifts the position of misfit dislocations away from the QD layer, reducing the defects' impact on luminescence. In full lasers, adding a misfit dislocation trapping layer both above and below the QD active region displaces misfit dislocations and substantially improves performance: we measure a twofold reduction in lasing threshold currents and a greater than threefold increase in output power. Our results suggest that devices employing both traditional threading dislocation reduction techniques and optimized misfit dislocation trapping layers may finally lead to fully integrated, commercially viable silicon-based photonic integrated circuits.

physics.app-ph↗