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Title: Understanding and eliminating artifact signals from diffusely scattered pump beam in measurements of rough samples by time-domain thermoreflectance (TDTR)

Abstract

Time-domain thermoreflectance (TDTR) is a pump-probe technique frequently applied to measure the thermal transport properties of bulk materials, nanostructures, and interfaces. One of the limitations of TDTR is that it can only be employed to samples with a fairly smooth surface. For rough samples, artifact signals are collected when the pump beam in TDTR measurements is diffusely scattered by the rough surface into the photodetector, rendering the TDTR measurements invalid. In this paper, we systemically studied the factors affecting the artifact signals due to the pump beam leaked into the photodetector and thus established the origin of the artifact signals. We find that signals from the leaked pump beam are modulated by the probe beam due to the phase rotation induced in the photodetector by the illumination of the probe beam. As a result of the modulation, artifact signals due to the leaked pump beam are registered in TDTR measurements as the out-of-phase signals. We then developed a simple approach to eliminate the artifact signals due to the leaked pump beam. We verify our leak-pump correction approach by measuring the thermal conductivity of a rough InN sample, when the signals from the leaked pump beam are significant. We also discussmore » the advantages of our new method over the two-tint approach and its limitations. Our new approach enables measurements of the thermal conductivity of rough samples using TDTR.« less

Authors:
 [1];  [1];  [2]
  1. Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576 (Singapore)
  2. (Singapore)
Publication Date:
OSTI Identifier:
22597985
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 87; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BEAMS; ILLUMINANCE; INDIUM NITRIDES; INTERFACES; NANOSTRUCTURES; PHOTODETECTORS; PROBES; PUMPING; ROTATION; SIGNALS; SURFACES; THERMAL CONDUCTIVITY

Citation Formats

Sun, Bo, Koh, Yee Kan, E-mail: mpekyk@nus.edu.sg, and Centre of Advanced 2D Materials, National University of Singapore, Singapore 117542. Understanding and eliminating artifact signals from diffusely scattered pump beam in measurements of rough samples by time-domain thermoreflectance (TDTR). United States: N. p., 2016. Web. doi:10.1063/1.4952579.
Sun, Bo, Koh, Yee Kan, E-mail: mpekyk@nus.edu.sg, & Centre of Advanced 2D Materials, National University of Singapore, Singapore 117542. Understanding and eliminating artifact signals from diffusely scattered pump beam in measurements of rough samples by time-domain thermoreflectance (TDTR). United States. doi:10.1063/1.4952579.
Sun, Bo, Koh, Yee Kan, E-mail: mpekyk@nus.edu.sg, and Centre of Advanced 2D Materials, National University of Singapore, Singapore 117542. 2016. "Understanding and eliminating artifact signals from diffusely scattered pump beam in measurements of rough samples by time-domain thermoreflectance (TDTR)". United States. doi:10.1063/1.4952579.
@article{osti_22597985,
title = {Understanding and eliminating artifact signals from diffusely scattered pump beam in measurements of rough samples by time-domain thermoreflectance (TDTR)},
author = {Sun, Bo and Koh, Yee Kan, E-mail: mpekyk@nus.edu.sg and Centre of Advanced 2D Materials, National University of Singapore, Singapore 117542},
abstractNote = {Time-domain thermoreflectance (TDTR) is a pump-probe technique frequently applied to measure the thermal transport properties of bulk materials, nanostructures, and interfaces. One of the limitations of TDTR is that it can only be employed to samples with a fairly smooth surface. For rough samples, artifact signals are collected when the pump beam in TDTR measurements is diffusely scattered by the rough surface into the photodetector, rendering the TDTR measurements invalid. In this paper, we systemically studied the factors affecting the artifact signals due to the pump beam leaked into the photodetector and thus established the origin of the artifact signals. We find that signals from the leaked pump beam are modulated by the probe beam due to the phase rotation induced in the photodetector by the illumination of the probe beam. As a result of the modulation, artifact signals due to the leaked pump beam are registered in TDTR measurements as the out-of-phase signals. We then developed a simple approach to eliminate the artifact signals due to the leaked pump beam. We verify our leak-pump correction approach by measuring the thermal conductivity of a rough InN sample, when the signals from the leaked pump beam are significant. We also discuss the advantages of our new method over the two-tint approach and its limitations. Our new approach enables measurements of the thermal conductivity of rough samples using TDTR.},
doi = {10.1063/1.4952579},
journal = {Review of Scientific Instruments},
number = 6,
volume = 87,
place = {United States},
year = 2016,
month = 6
}
  • We report on thermal investigations performed in a time resolved experimental scheme. The time domain thermoreflectance (TDTR) is applied in an unusual geometry where the pump and probe beams are not superimposed but focused and shifted. In this way, the determination of the in-plane thermal diffusivity is achieved from temperature snapshots at different time delays. In the first part, taking into account the specific generation process and the detection inherent to the time domain thermoreflectance approach, an analytical solution for the temperature field is obtained for bulk samples, and compared to experimental data. A comparison with the frequency domain thermoreflectancemore » microscopy is also outlined. In Part II section, the lateral heat diffusion in a layered structure is investigated. The comparison of the heat diffusion spreading in case of a highly conductive layer deposited on an insulator substrate and the reverse situation are carefully studied. Finally, we show how the time dependence is efficient to probe and identify material thermal properties or thermal interfacial resistance.« less
  • The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacementmore » damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 10 15 cm -2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.« less
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