The Measurement of the Coating Uniformity of Lithium Iron Phosphate Cathodes on Metal Substrates with Terahertz Time-domain Spectroscopy

 Zarrinkhat, Faezeh, Alasdair Pentland, Carl Reynolds, Emma Kendrick, and Philip F. Taday. "The Measurement of the Coating Uniformity of Lithium Iron Phosphate Cathodes on Metal Substrates with Terahertz Time-domain Spectroscopy." In 2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), pp. 1-2. IEEE, 2023.

Abstract:

For the first time, the thickness uniformity of lithium iron phosphate (LFP) cathodes are measured using terahertz time-domain spectroscopy. Cathodes are widely manufactured with cobalt, however providing cobalt material comes with supply and health issues. LFP cathodes are introduced as an alternative to tackle this challenge. The aim is to use terahertz pulses to generate an on-line tool to undertake manufacturing process control. Different thickness of cathodes compressed to different densities is measured and the uniformity of their coating is inspected.

see https://ieeexplore.ieee.org/abstract/document/10299358

Self-referencing Reflection Sensor for Industrial Applications

Zarrinkhat, Faezeh, Bryan Cole, Alasdair Pentland, and Philip F. Taday. "Self-referencing reflection sensor for industrial applications." In 2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), pp. 1-2. IEEE, 2023. 

Abstract:

Terahertz sensors have found their way into many industrial applications, though undertaking regular reference measurements could be inconvenient on some occasions. A sensor with a self-referencing (SR) mechanism (in a linear configuration) is designed and manufactured to tackle the challenge. The sensor head is used on Lithium Iron Phosphate (LFP) cathodes to report the thickness and refractive index of the material.

see https://ieeexplore.ieee.org/abstract/document/10299020

Incorporating Time-Domain Reflectometry in Chip-Level Failure Analysis Workflow: Case Studies

 Liao, Joy Y., Khanh Giang, Timothy Pham, and Howard Lee Marks. "Incorporating time-domain reflectometry in chip-level failure analysis workflow: case studies." In International Symposium for Testing and Failure Analysis, vol. 84741, pp. 145-150. ASM International, 2023.

Abstract

Non-destructive electrical fault isolation (FI) techniques such as emission- and laser-based techniques have been utilized widely for chip-level failure analysis (FA). However, these techniques by themselves can sometimes be inadequate for certain failure modes. In this paper, we present six FA case studies using Time-domain Reflectometry (Electro-optical terahertz pulse reflectometry, EOTPR) in combination with the traditional FI techniques. We also present continuing development in making EOTPR accessible to the semiconductor process and packaging communities.

see https://dl.asminternational.org/istfa/proceedings-abstract/ISTFA2023/84741/145/28577

Recent Developments in EOTPR Towards a Fully Automated Tool for High Volume Failure Analysis

White, Tom, Jesse Alton, Brett Gibson, Martin Igarashi, Joy Liao, Timothy Pham, and Howard Marks. "Recent Developments in EOTPR Towards a Fully Automated Tool for High Volume Failure Analysis." In 2025 IEEE International Reliability Physics Symposium (IRPS), pp. 1-5. IEEE, 2025.

Abstract

Developments in backside power delivery (BPD) technology will become increasingly important for advanced semiconductors, but will present new challenges for failure analysis (FA) labs. Electro-Optical TeraHertz Pulsed Reflectometry (EOTPR) is a well-established electrical FA technique for package level open and leakage faults, but has comparatively little use for detecting die-level faults. Here, two case studies are presented that demonstrate how EOTPR can be used to localize faults within a die, highlighting how EOTPR could be utilized for BPD devices. Recent and future key developments in EOTPR are also presented.

see https://ieeexplore.ieee.org/abstract/document/10983830

Reduction in Reflection Signal Losses in Complex Terahertz Optical Elements Through Tailored Oil Application

 Kaluza, Mateusz, Adrianna Nieradka, Mateusz Surma, Wojciech Krauze, and Agnieszka Siemion. "Reduction in Reflection Signal Losses in Complex Terahertz Optical Elements Through Tailored Oil Application." Applied Sciences 15, no. 20 (2025): 11167.

Abstract

In complex terahertz (THz) systems, multiple optical elements are often combined to achieve advanced functionalities. However, unwanted Fresnel reflections at their interfaces and between components lead to parasitic interference effects and signal losses. This study presents oil-based refractive-index-matching fillers integrated with additively manufactured assemblies to suppress Fresnel reflections and enhance overall optical system performance. The optical properties of 20 plant-based, synthetic, and mineral oils were investigated using terahertz time-domain spectroscopy (THz TDS). Furthermore, a multilayer structure was designed and experimentally verified, fabricated via fused deposition modeling (FDM) using highly transparent cyclic olefin copolymer (COC). The results demonstrate that the use of tailored oils reduces Fresnel reflection signal losses and also mitigates parasitic interference within the system, thereby improving the effective efficiency of the optical system. Additionally, THz TDS measurements on multilayer structures revealed that, in imaging configurations, the application of refractive-index-matched oils increases the signal gain by 2.33 times. These findings highlight the potential of oil-based index-matching fillers for imaging multilayered objects and mitigating delamination effects in optical elements.

see https://www.mdpi.com/2076-3417/15/20/11167