Name: The Frequency Domain Thermoreflectance Technique for Thermal Property Measurements (Video) | JoVE Journal
Uploaded: 2025-12-05T13:25:00.000+00:00
Duration: 9 min 10 s
Description: Learn the Frequency Domain Thermoreflectance technique for thermal property measurements using laser-based methods. This approach enables nondestructive microscale characterization of grain boundaries and thermal connectivity.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

playerTrialDesktop

Some of the authors were supported by partial funding from the Northwestern University Center for Engineering Sustainability and Resilience through a seed-funded project entitled &#34;Toward Engineering Metamaterials for Sustainable Energy Solutions: Local Thermal Properties of Grain Boundaries in Polycrystalline Materials&#34;.

The authors disclose no conflicts of interest.

The FDTR technique presented here is used to characterize the local substrate &#954; of a single-crystal silicon substrate and to map the &#954; distribution around an interface between two plasma-sintered silicon substrates. One critical aspect of the measurement is the use of the modeling fitting to determine the unknown thermal properties of the substrate and the transducer-substrate interface. The accuracy of the measurement depends on the proper selection of the spot size and modulation frequencies of the pump laser...

Thermal metrology and characterization tools are critical to the design and optimization of advanced materials used in, for example, thermoelectric generators and refrigeration applications1,2. Materials with low thermal conductivity and high electrical conductivity are generally preferred in these applications to maintain a large temperature gradient between hot and cold junctions and for efficient thermal-to-electrical energy conversion. Realizing these disparate properties in bulk crystalline materials is challenging. However, microstructure engineering through the introduction of point and interfacial defects (such as grain boundaries) is a promising direction to design high-performance thermoelectric materials1. A majority of the grain boundary (GB)-controlled thermal conductivity studies have mainly focused on the grain size as the fundamental structural property of importance2,3,4,5, as they lack the spatial resolution to probe a GB's local thermal environment.Thermal metrology at the micro- and nano-scale can provide local information on how heat flows near individual GBs. For example, recent microscale thermal imaging measurements by Isotta et al.6,7 revealed that the bulk thermal conductivity (κ) is locally suppressed near individual GBs in polycrystalline tin telluride (SnTe) and silicon. The observed κ suppression was correlated with different GB properties, including misorientation angle, roughness of the GB plane, nanotwinning density, and porosity. These types of measurements can facilitate tuning the bulk κ by providing local information on the microstructure-κ relationship. As interest in the local effects of defects on κ continues to grow, both computational8 and experimental9,10 approaches that provide insight into these contributions will become increasingly relevant.
Optical thermoreflectance methods11,12,13,14,15 are widely used for nondestructive thermal metrology of bulk solids, thin film superlattices, and interfaces. The methods use ultrafast or intensity-modulated lasers to locally heat a sample and probe their thermal response with high frequency or temporal resolution16, making them ideal for characterizing thermophysical properties. Thermoreflectance techniques, including time-domain thermoreflectance (TDTR)13,16 and frequency-domain thermoreflectance (FDTR)17,18, are the most common high-resolution thermal metrology methods. FDTR uses a focused intensity-modulated pump laser to generate a local periodic heat source in the sample. The resulting sample temperature change is transduced into a modulation frequency-dependent thermoreflectance signal that is recorded with a lock-in amplifier. To facilitate the measurement, a thin transducer layer with a large thermoreflectance coefficient19 at the probe laser wavelength is deposited on the sample. The TDTR technique, on the other hand, utilizes ultrafast pump and probe lasers, and the transient thermoreflectance signal of the transducer layer is monitored at different time delays between the pump and probe lasers, with picosecond time resolution.
Thermoreflectance techniques offer microscale lateral spatial resolution for probing thermophysical properties, and the measurements can be configured to characterize both isotropic and anisotropic κ of materials. Recently, Sood et al.10 used the TDTR technique to map local κ inhomogeneities in boron-doped polycrystalline diamond that were correlated with electron-backscatter diffraction imaging. In their measurements, regions in the sample with small grains had a lower κ compared to the bulk value. However, their measurements did not show whether the κ suppression was due to the small grain sizes or resistive GBs. Following this work, Isotta et al. showed that the local κ suppression around individual GBs, observed in microscale FDTR maps of SnTe, a mid-temperature thermoelectric material, is directly correlated to the GB misorientation angle6, so far only predicted theoretically 20,21,22,23 or rarely measured in fabricated GBs 24. Compared to the TDTR approach used by Sood et al., FDTR is less expensive and allows for the measurement of multiple properties, such as the substrate κ and constant-pressure heat capacity (C), and the film-substrate interface thermal conductance, in a single measurement that spans a broad frequency range25. Two-dimensional thermoreflectance phase maps obtained at multiple pump laser modulation frequencies with the highest sensitivity to the sample's thermal properties are converted to a κ image.
The thermoreflectance phase represents the phase shift between the periodic temperature oscillations at the surface of a transducer layer and the modulated heat source produced by the absorbed pump laser. In a standard FDTR approach, the pump and probe lasers are focused to the same point on the sample surface, and the thermoreflectance phase at that point is measured with a lock-in amplifier at different pump laser modulation frequencies. A layered heat conduction model is fitted to the measured data to determine the sample's thermal properties (i.e., κ, C, and the transducer-sample interface conductance)14. Variations of the standard FDTR approach allow for improved sensitivity of the measured thermoreflectance phase to the sample's anisotropic κ. These include the use of (i) spatially offset pump and probe lasers26, (ii) elliptical27 or line28 shaped pump laser-generated heat sources, and (iii) FDTR measurements with variable pump laser spot sizes29. Beyond thermal characterization of bulk properties, the FDTR technique can be used to characterize interface thermal properties30,31,32,33,34,35, since the thermal penetration depth of the heat source, defined as <img alt="Thermal penetration depth formula, \(d = \sqrt{\kappa/\pi fC}\), in heat transfer study." src="/files/ftp_upload/68908/68908eq1.jpg" style="opacity: 0.9; margin: 0px;" data-altupdatedat="1783396841000" data-alt="Equation 1"> depends on the pump laser modulation frequency (f). The interface causes a thermal resistance due to the transmission and reflection of heat carriers (i.e., electrons and phonons)36. The resistance is characterized in FDTR experiments in terms of an interface thermal conductance. FDTR measurements of the interface thermal conductance of self-assembled monolayers33,35, metal-substrate interfaces37,38,and thin interface layers39 have been reported in the literature. Finally, FDTR measurements with thin magnetic transducer films were recently shown to allow for the characterization of anisotropic κ of two-dimensional materials40.
This article provides a detailed description of the procedures involved in a FDTR measurement that utilizes coaxially focused pump and probe lasers on the transducer surface. Representative measurements of local κ of a bulk silicon substrate are provided, and the measurement uncertainties are quantified. Finally, we provide a simple example that illustrates the FDTR imaging of the local κ near a single vertical interface between two (100) single-crystal silicon substrates bonded by surface activated bonding (SAB).

<table><tbody><tr><td>3-Axis NanoMax Stage, Stepper Motor Drives</td><td>Thorlabs</td><td>MAX383</td><td>Sample translation stage</td></tr><tr><td>532 nm Continuous Wave Laser</td><td>SpectraPhysics</td><td>SPFL 532-20</td><td>Probe laser</td></tr><tr><td>Achromatic Doublet, f=150mm, 2&quot;</td><td>Thorlabs</td><td>AC508-150-C-ML</td><td>Relay lenses in the 4-f optical imaging system used to image the center of the Gimbal scanner to the back aperture of the microscope objective</td></tr><tr><td>Beamsplitter Cube</td><td>Thorlabs</td><td>BS019</td><td>Optics</td></tr><tr><td>Broadband Power/Energy Meter</td><td>Melles Griot</td><td>13PEM001</td><td>To measure laser powers</td></tr><tr><td>Closed-Loop Picomotor Controller</td><td>New Focus</td><td>8743-CL</td><td>For scanning the pump beam on the sample surface</td></tr><tr><td>Color CMOS Camera</td><td>Thorlabs</td><td>CS165CU1</td><td>For imaging the sample surface</td></tr><tr><td>Current-Limited Power Supply</td><td>New Focus</td><td>901</td><td>To power the high-speed photodetector</td></tr><tr><td>Fiber Amplifier</td><td>IPG Photonics</td><td>LDR-3U</td><td>Pump laser</td></tr><tr><td>Free-Space Isolator, 1550 nm</td><td>Thorlabs</td><td>IO-5-1550-HP</td><td>For preventing back reflections of the pump laser into the fiber amplifier</td></tr><tr><td>Free-Space Isolator, 532 nm</td><td>Thorlabs</td><td>IO-3-532-LP</td><td>For preventing back reflections of the probe laser into the diode laser</td></tr><tr><td>Function / Arbitrary Waveform Generator</td><td>Agilent</td><td>33220A</td><td>For modulating the pump laser intensity</td></tr><tr><td>Gimbal Optic Mount</td><td>Newport</td><td>605-2</td><td>For scanning the pump beam on the sample surface</td></tr><tr><td>Gold Mirrors, 1&quot;</td><td>Thorlabs</td><td>PF10-03-M01</td><td>High reflectivity mirrors for the pump laser</td></tr><tr><td>Half Waveplate (1550)</td><td>Thorlabs</td><td>WPH05M-1550</td><td>Polarization optics</td></tr><tr><td>Half Waveplate (532 nm)</td><td>Thorlabs</td><td></td><td>Polarization optics</td></tr><tr><td>IR 1 GHz Low Noise Photoreceiver</td><td>New Focus</td><td>1611</td><td>For monitoring the modulated intensity of the pump laser</td></tr><tr><td>Laser Diode Controller</td><td>ILX Lightwave&amp;nbsp;</td><td>LDC-3742B</td><td>For controlling the seed pump laser intensity</td></tr><tr><td>Lock-In Amplifier</td><td>Stanford Research&lt;br/&gt; Systems</td><td>SR844</td><td>For high-frequency measurements</td></tr><tr><td>Lock-In Amplifier</td><td>Stanford Research&lt;br/&gt; Systems</td><td>SR830</td><td>For low-frequency measurements</td></tr><tr><td>Mechanical Chopper Controller</td><td>Stanford Research Systems</td><td>SR540</td><td>For modulating the probe beam intensity</td></tr><tr><td>MgO:PPLN Crystal</td><td>Covesion</td><td></td><td>Second harmonic generation crystal for frequency doubling the 1550 nm pump laser to the 775 nm reference light source</td></tr><tr><td>Polarizing Beamsplitter Cube</td><td>Thorlabs</td><td>PBS254</td><td>Polarization optics</td></tr><tr><td>RF Signal Generator</td><td>Agilent</td><td>N9310A</td><td>For modulating the pump laser intensity</td></tr><tr><td>Stepper Motor Controller</td><td>Thorlabs</td><td>BSC200</td><td>Controller for the sample translation stage</td></tr><tr><td>Temperature Controller</td><td>Covesion</td><td>OC1</td><td>For controlling the MgO:PPLN Crystal temperature</td></tr><tr><td>Visible 1 GHz Low Noise Photoreceiver</td><td>New Focus</td><td>1601</td><td>For monitoring the thermoreflectance signal</td></tr></tbody></table>

the frequency domain thermoreflectance technique for thermal property measurements

The Frequency Domain Thermoreflectance Technique for Thermal Property Measurements

The frequency domain thermoreflectance (FDTR) technique is a nondestructive method for thermal characterization and imaging with microscale spatial resolution. The technique relies on a pump laser to generate a modulated temperature change in a sample and a probe laser to monitor the sample&#39;s local thermal response. The sample&#39;s thermal properties are determined by fitting a thermal model to the sample&#39;s thermoreflectance response. This article presents detailed protocols for implementing the technique and conducting local measurements of a substrate&#39;s local thermal conductivity. Special attention is devoted to discussing how the measurement is influenced by the laser source parameters, error sources in an FDTR measurement, and quantifying the measurement uncertainty. Finally, we discuss a thermal conductivity imaging experiment conducted near a single vertical interface between two surface-activated bonded single-crystal silicon substrates. The thermal conductivity at the interface is suppressed by 3% compared to the bulk value in the adjoining single crystals. The ability to probe interface thermal properties with the FDTR technique may facilitate local studies of heat flow around individual grain boundaries, particularly in thermoelectric materials, where they can be tuned to optimize the performance of thermoelectric devices.

Point measurements
The goal of the point measurement presented here is to determine the room-temperature thermal conductivity (κ) of (100) single-crystal silicon based on the measured thermoreflectance phase of the gold transducer film on the sample. A two-layer heat conduction model is fitted to the measured phase data to determine the best-fit substrate κ and the transducer-silicon interface thermal conductance (G). The measured transducer thickness, thermal conduct...

This article presents the Frequency Domain Thermoreflectance (FDTR) technique for local nondestructive thermal characterization and imaging.

The frequency domain thermoreflectance (FDTR) technique is a nondestructive method for thermal characterization and imaging with microscale spatial ...

We study how microscale defects in materials, such as grain boundaries, affect a material thermal connectivity with micron scale spatial resolution. The continuum scale assumption that thermal properties are size independent breaks down as small length scales. To begin, turn the power switch of the 532 nanometer diode laser to the on position to activate the power supply.Wait until the enable light turns on, indicating that the laser crystal's temperature is stable. Then, turn the laser switch to initiate the emission of the 532 nanometer laser and use a power meter to confirm that the input probe laser power is between 20 and 30 milliwatts before proceeding. Next, turn on the pump laser diode controller.Enable thermoelectric cooling by setting the correct resistance value according to the diode laser specifications. After the temperature stabilizes, switch on the laser current, then turn on the Erbium-Doped Fiber Amplifier, or EDFA and set the output power to the desired value in watts. Press the emission button.Set the radio frequency, or RF, RF amplitude and bias voltage on the signal generator to modulate the pump laser intensity. Now, turn on the lock-in amplifier and photo de

the-frequency-domain-thermoreflectance-technique-for-thermal-property

Research

JoVE Journal

Engineering

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials.

Characterization of Thermal Transport in One-dimensional Solid Materials

Here, we present three protocols for thermal measurements in microfluidic devices.

Thermal Measurement Techniques in Analytical Microfluidic Devices

Europium thenoyltrifluoroacetonate (EuTFC) has an optical luminescence line at 612 nm, whose activation efficiency decreases strongly with temperature. If a sample coated with a thin film of this material is micro-imaged, the 612 nm luminescent response intensity may be converted into a direct map of sample surface temperature.

High-resolution Thermal Micro-imaging Using Europium Chelate Luminescent Coatings

We demonstrate use of a fiber optic distributed sensor for mapping the temperature field of mixing air jets. The Rayleigh scattering-based sensor generates thousands of data points along a single fiber to provide exceptional spatial resolution that is unattainable with traditional sensors such as thermocouples.

Fiber Optic Distributed Sensors for High-resolution Temperature Field Mapping

A technique utilizing wavelengths of 1150 and 1412 nm to measure the temperature of water surrounding an induction-heated small magnetic sphere is presented.

Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere

This manuscript describes methods aimed at measuring the local instantaneous convective heat transfer coefficients in a single or two-phase pipe flow. A simple optical method to determine the length and the propagation velocity of an elongated (Taylor) air bubble moving at a constant velocity is also presented.

Measurements of Local Instantaneous Convective Heat Transfer in a Pipe - Single and Two-phase Flow

This protocol describes how to install an infrared camera into a conveyor belt furnace, conduct a customer correction of a factory calibrated IR camera, and evaluate the spatial surface temperature distribution of an object of interest. The example objects are industrial silicon solar cells.

In Situ Surface Temperature Measurement in a Conveyor Belt Furnace via Inline Infrared Thermography

Freshly excised human breast cancer tumors are characterized with terahertz spectroscopy and imaging following fresh tissue handling protocols. Tissue positioning is taken into consideration to enable effective characterization while providing analysis in a timely manner for future intraoperative applications.

Terahertz Imaging and Characterization Protocol for Freshly Excised Breast Cancer Tumors

Here, we present a protocol for measuring brown adipose tissue activity after a meal in humans and laboratory animals.

Infrared Thermography for the Detection of Changes in Brown Adipose Tissue Activity

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution.

Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM

Learn the Frequency Domain Thermoreflectance technique for thermal property measurements using laser-based methods. This approach enables nondestructive microscale characterization of grain boundaries and thermal connectivity.

The Frequency Domain Thermoreflectance Technique for Thermal Property Measurements

Explore More Videos