Instrumentation

International Thermal Conductivity & International Thermal Expansion Society Conference 2024, October 29, 2024, Charlottesville, VA. Organized by Joshua Martin (NIST) and Dylan Kirsch (NIST).

Thermoreflectance instruments are generally home-built; they can be difficult to construct, align, and maintain, especially for the novice. The goal of this workshop was to provide practical advice from a pool of institutional knowledge beyond theory. Speakers shared their insights and tips for optimizing thermoreflectance instrument design, methods, and data analysis.

• Pump-Probe Thermoreflectance: Then and Now | Patrick Hopkins | Co-Founder Laser Thermal & Whitney Stone Professor, UVA
• Time Domain Thermoreflectance: Tips, Tricks, and a few Extensions | Brian Donovan | Associate Professor, USNA
• Frequency Domain Thermoreflectance (FDTR) Instrumentation: Common Challenges and Practical Guidance | Dylan Kirsch | Materials Research Engineer, NIST
• A Practical Guide to Steady-State Thermoreflectance | Jeffrey Braun | Vice President of Strategy and Programs, Laser Thermal
• Advanced Measurement Configurations: TR-MOKE | Xiaojia “XJ” Wang | Associate Professor, University of Minnesota

Link to Download: FDTR Instrumentation Guide

Dylan Kirsch, Joshua B. Martin, Ronald Warzoha, Mark McLean, Donald Windover, Ichrio Takeuchi

Abstract: Frequency Domain Thermoreflectance (FDTR) is a versatile and rapidly developing technique used to measure the thermal properties of thin films, multilayer stacks, and interfaces that govern the performance and thermal management in semiconductor microelectronics. Reliable thermal property measurements at these length scales, where the physics of thermal transport and phonon scattering at interfaces both grow in complexity, are increasingly relevant as electronic components continue to shrink. While FDTR is a promising measurement technique, FDTR instruments are generally home built; they can be difficult to construct, align, and maintain, especially for the novice. We provide a detailed account of unpublished insights and institutional knowledge that are critical for obtaining accurate and repeatable measurements of thermal properties using FDTR. We discuss component selection and placement, alignment procedures, data collection parameters, common challenges, and our efforts to increase measurement automation. In FDTR, the unknown thermal properties of interest are fit by minimizing the error between the phase lag at each frequency and the solution to a multilayer diffusive thermal model. For data fitting and uncertainty analysis, we compare common numerical integration methods, and we compare multiple approaches for fitting and uncertainty analysis, including Monte Carlo simulation, to demonstrate their reliability and relative speed. Since the transducer thermal properties and thickness are input parameters in the thermal model, we also discuss the deposition and characterization of high-quality transducer films. The instrument is validated with substrates of known thermal properties over a wide range of isotropic thermal conductivities, including Borofloat silica, quartz, sapphire, and silicon.

Link to Download: P. Jiang, X. Qian, and R. Yang, J. Appl. Phys. 124, 161103 (2018)

Abstract: Measuring thermal properties of materials is not only of fundamental importance in understanding the transport processes of energy carriers (electrons and phonons in solids) but also of practical interest in developing novel materials with desired thermal properties for applications in energy conversion and storage, electronics, and photonic systems. Over the past two decades, ultrafast laser-based time-domain thermoreflectance (TDTR) has emerged and evolved as a reliable, powerful, and versatile technique to measure the thermal properties of a wide range of bulk and thin film materials and their interfaces. This tutorial discusses the basics as well as the recent advances of the TDTR technique and its applications in the thermal characterization of a variety of materials. The tutorial begins with the fundamentals of the TDTR technique, serving as a guideline for understanding the basic principles of this technique. Several variations of the TDTR technique that function similarly as the standard TDTR but with their own unique features are introduced, followed by introducing different advanced TDTR configurations that were developed to meet different measurement conditions. This tutorial closes with a summary that discusses the current limitations and proposes some directions for future development.

Link to Download: Mohan, R., Khan, S., Wilson, R.B. et al. Time-domain thermoreflectance. Nat Rev Methods Primers 5, 55 (2025). 

Abstract: Time-domain thermoreflectance (TDTR) has been instrumental in measuring the heat transfer properties of bulk and nanostructured materials over the past two decades. In this Primer, we describe the optical and thermal aspects of TDTR, with an in-depth discussion on the theory, apparatus design and implementation. We present examples that illustrate the ability of TDTR to measure thermal conductivity tensors, thermal conductance across material interfaces, and volumetric heat capacity of thin films, 2D materials and bulk materials. The ability of TDTR to spatially resolve thermal properties is useful for studying heterogeneous material systems, such as materials processed in or subjected to extreme environments. We consider current limitations of pump–probe metrologies and discuss recent advancements of TDTR, such as time-resolved magneto-optic Kerr effect (TR-MOKE), beam-offset TDTR/TR-MOKE, steady-state thermoreflectance, frequency-domain thermoreflectance and laser-flash TDTR. Finally, we present an outlook on anticipated technological developments to further expand the ability of TDTR to measure nanoscale thermal properties.

Link to Website: Joseph Feser's TDTR Training – Short Course

"This website contains a series of materials to help train new users (and hopefully, new builders) of time domain thermoreflectance (TDTR) systems.  Because the potential audience for this is quite diverse, information is given at wide range of detail-level that hopefully accommodates everyone from the complete newcomer to TDTR gurus; some of the information is generic but in many cases I’ve tried to include quantitative performance examples and give specific examples of model numbers/equipment.  Information is given about a wide variety of different TDTR systems/layouts in use, though most of my own experience is with two-tint TDTR a la David Cahill’s design at UIUC, so there is some bias in that direction."

-Text from linked website.

Link to Website: PennState Electronics and Thermography Laboratory | Sukwon Choi

Link to Website: ExSiTE Lab (Experiments and Simulations in Thermal Engineering)

This website contains a virtual lab tour, links to publications, presentations, and code.

Link to Presentations 

Over 50 presentations, including Time-Domain Thermoreflectance 1.0: Fundamentals and Time-Domain Thermoreflectance 2.0: Advanced Techniques.  

Link to Software and Data

MATLAB scripts, LabVIEW automation code, and thermal property data for various materials.