scholarly journals Experimental Control and Statistical Analysis of Thermal Conductivity in ZnO–Benzene Multilayer Thin Films

2020 ◽  
Vol 124 (45) ◽  
pp. 24731-24739
Author(s):  
Fabian Krahl ◽  
Ashutosh Giri ◽  
Md Shafkat Bin Hoque ◽  
Linda Sederholm ◽  
Patrick E. Hopkins ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Statistical Analysis ◽  
Multilayer Thin Films ◽  
Experimental Control

Anderson Localization of Phonons in Random Multilayer Thin Films

2012 ◽  
Vol 1404 ◽  
Author(s):  
Anthony Frachioni ◽  
Bruce White
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Anderson Localization ◽  
Lattice Thermal Conductivity ◽  
Waste Heat ◽  
Mean Free Path ◽  
The United States ◽  
Energy Scavenging ◽  
Multilayer Thin Films

ABSTRACT1020 Joules of energy are generated by the United States each year; 60% of this energy is lost to waste heat [1]. Thermoelectric based energy scavenging has tremendous potential for the recovery of significant quantities of this waste heat. However, utilization of thermoelectric devices is limited due to relatively low energy conversion efficiency and the utilization of relatively scarce materials. This work focuses on generating sustainable and efficient thermoelectric materials through modifications to the lattice vibrations of materials with excellent thermoelectric electronic properties (Seebeck coefficients larger than 500 μV/K). In particular, Anderson localization of phonons in random multilayer thin films has been explored as a means for reducing lattice thermal conductivity to values approaching that of aerogels (∼10 mW/m-K). Silicon has been a sample of choice due to its high crust abundance and Seebeck coefficient. Reverse non-equilibrium molecular dynamics simulations have been utilized to determine the thermal conductivity of structures of interest. Simulations with pure Lennard-Jones argon solids have been performed to establish a methodology and to characterize the effect of different kinds of disorder prior to the examination of silicon. The simulation results indicate that mass disorder confined to randomly selected planes to be an effective way in which to reduce lattice thermal conductivity with the lattice thermal conductivity decreasing by a factor of thirty (to 4 mW/m-K) in the argon case and a factor of over ten thousand (to 15 mW/m-K) for silicon. Based on models in which the charge carrier mean free path is limited by scattering from the planes with mass disorder, the mobility of silicon is expected to reach values of 10 cm2/V-s. At this mobility the thermoelectric figure of merit, ZT, (utilizing the Wiedeman-Franz law to calculate the electronic thermal conductivity) varies between 4.5 and 11 as the mass ratio of the disordered planes is varied from 4 to 10 in 20% of the lattice planes. These results indicate that the pursuit of nanostructured thermoelectric materials in the form of random multilayers may provide a path to efficient and sustainable thermoelectric materials.

Enhanced Phonon Scattering in Oxide Superlattices to Improve Laser Induced Thermoelectric Voltages

2007 ◽  
Vol 1053 ◽  
Author(s):  
Hanns-Ulrich Habermeier ◽  
Peng Xiang Zhang ◽  
Hui Zhang
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Layered Structure ◽  
Phonon Scattering ◽  
Single Layer ◽  
Multilayer Thin Films ◽  
Maximum Enhancement ◽  
Seebeck Coefficients ◽  
Thermoelectric Voltage ◽  
First Time

AbstractOptimizing the figure of merit for thermoelectric applications, ZT = S2σ2T/κ is currently at the core of materials oriented research in thermoelectricity. Here, one promising approach is to reduce ther thermal conductivity without sacrificing the electrical conductivity. Constructing superlattices of structurally compatible materials is one way to accomplish this goal. We report an enhanced laser induced thermoelectric voltage (LITV) effect observed in (YBa2Cu3O7/La1-xPbxMnO3)n multilayer thin films for the first time. Two groups of multilayer thin films grown on vicinal cut LaAlO3 substrates were prepared by pulsed laser deposition technique. The first group were grown on different substrates vicinal cut at different angles, and were used for checking the mechanism of the induced voltages. The second group samples were made at different period number n and for studying the number dependence of the peak values of LITV. The substrate angle dependence proved that this is a thermoelectric effect [1]. It was found that the LITV signals were enhanced significantly for these multilayer thin films comparing with the single layer ones. It is natural that the conductivity is going to be anisotropic due to the layered structure, and the same holds for the Seebeck coefficients. The enlarged Seebeck anisotropy will lead to higher induced voltages. Another possible reason is the reduced thermal conductivity in the layered structure. The maximum enhancement of LITV signals takes place at period number of 7, which seems in agreement with the prediction of minimum thermal conductivity in superlattices by Simkin and Mahan.

scholarly journals On the Steady-State Temperature Rise During Laser Heating of Multilayer Thin Films in Optical Pump–Probe Techniques

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Jeffrey L. Braun ◽  
Chester J. Szwejkowski ◽  
Ashutosh Giri ◽  
Patrick E. Hopkins
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Steady State ◽  
Temperature Rise ◽  
Laser Heating ◽  
Thermal Parameters ◽  
Heat Diffusion ◽  
Multilayer Thin Films ◽  
Steady State Temperature

In this study, we calculate the steady-state temperature rise that results from laser heating of multilayer thin films using the heat diffusion equation. For time- and frequency-domain thermoreflectance (TDTR and FDTR) that rely on modulated laser sources, we decouple the modulated and steady-state temperature profiles to understand the conditions needed to achieve a single temperature approximation throughout the experimental volume, allowing for the estimation of spatially invariant thermal parameters within this volume. We consider low thermal conductivity materials, including amorphous silicon dioxide (a-SiO2), polymers, and disordered C60, to demonstrate that often-used analytical expressions fail to capture this temperature rise under realistic experimental conditions, such as when a thin-film metal transducer is used or when pump and probe spot sizes are significantly different. To validate these findings and demonstrate a practical approach to simultaneously calculate the steady-state temperature and extract thermal parameters in TDTR, we present an iterative algorithm for obtaining the steady-state temperature rise and measure the thermal conductivity and thermal boundary conductance of a-SiO2 with a 65-nm gold thin film transducer. Furthermore, we discuss methods of heat dissipation to include the use of conductive substrates as well as the use of bidirectional heat flow geometries. Finally, we quantify the influence of the optical penetration depth (OPD) on the steady-state temperature rise to reveal that only when the OPD approaches the characteristic length of the temperature decay does it alter the temperature profile relative to the surface heating condition.

Thermal transport through thin films: Mirage technique measurements on aluminum/titanium multilayers

2000 ◽  
Vol 15 (3) ◽  
pp. 764-771 ◽  
Author(s):  
E. J. Gonzalez ◽  
J. E. Bonevich ◽  
G. R. Stafford ◽  
G. White ◽  
D. Josell
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Thermal Transport ◽  
Multilayer Films ◽  
Multilayer Thin Films ◽  
Bilayer Thickness ◽  
Cu Films ◽  
Si Substrates ◽  
Electrical Conductances

Thermal transport properties of multilayer thin films both normal and parallel to the layers were measured. Al/Ti multilayer films 3 μm thick, with individual layers systematically varied from 2.5 to 40 nm, were studied on Si substrates. Layers of Al and Ti were nominally equal in thickness, with actual composition determined for each specimen using energy dispersive spectroscopy. The thermal diffusivity both in the plane and normal to the plane of the films (thermal conductivity divided by specific heat per volume) was found to decrease significantly with decreasing bilayer thickness. Pure Ti and Al films as well as Cu films from 0.1 to 5 μm thick were also studied. In-plane electrical conductances of the Al/Ti multilayers were also measured.

The Effects of Van Der Waals Bonding Strength on the In-Plane Lattice Thermal Conductivities of Multilayer Thin Films

2012 ◽  
Author(s):  
Weiyu Chen ◽  
Zhonghua Ni ◽  
Juekuan Yang ◽  
Yan Zhang ◽  
Deyu Li ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Bonding Strength ◽  
Van Der Waals ◽  
Interface Roughness ◽  
Multilayer Thin Films ◽  
Continuous Increase ◽  
Non Equilibrium Molecular Dynamics ◽  
The Impact ◽  
Thermal Conductivities

A non-equilibrium molecular dynamics (NEMD) simulation model is established to investigate the impact of vdW strength on thermal transport along the in-plane direction in argon bi-layer films (BLFs) and silicon BLFs. Simulation results indicate that higher strength leads to a higher in-plane thermal conductivity. However, interface roughness also increases with the continuous increase of the van der Waals (vdW) strength and leads to the reduction of thermal conductivities. The bonding strength does play an important role in manipulating thermal conductivity of multilayer thin films.

Influence of upper layer on measuring thermal conductivity of multilayer thin films using differential 3-ω method

2008 ◽  
Vol 517 (2) ◽  
pp. 933-936 ◽  
Author(s):  
Sangwoo Shin ◽  
Han Na Cho ◽  
Beom Seok Kim ◽  
Hyung Hee Cho
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Multilayer Thin Films

Characterization of reactive phase formation in sputter-deposited Ni/Al multilayer thin films using TEM

1996 ◽  
Vol 54 ◽  
pp. 1000-1001
Author(s):  
G. Lucadamo ◽  
K. Barmak ◽  
C. Michaelsen
Keyword(s):  
Thin Films ◽  
Phase Formation ◽  
Dark Field ◽  
Nickel Layer ◽  
Multilayer Thin Films ◽  
Cross Sectional ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Sputter Deposited ◽  
Constant Heating

The subject of reactive phase formation in multilayer thin films of varying periodicity has stimulated much research over the past few years. Recent studies have sought to understand the reactions that occur during the annealing of Ni/Al multilayers. Dark field imaging from transmission electron microscopy (TEM) studies in conjunction with in situ x-ray diffraction measurements, and calorimetry experiments (isothermal and constant heating rate), have yielded new insights into the sequence of phases that occur during annealing and the evolution of their microstructure.In this paper we report on reactive phase formation in sputter-deposited lNi:3Al multilayer thin films with a periodicity A (the combined thickness of an aluminum and nickel layer) from 2.5 to 320 nm. A cross-sectional TEM micrograph of an as-deposited film with a periodicity of 10 nm is shown in figure 1. This image shows diffraction contrast from the Ni grains and occasionally from the Al grains in their respective layers.

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