Thermal Conductivity Measurements of Thin Aluminum Layers Using Steady State Joule Heating and Electrical Resistance Thermometry in Suspended Bridges

2003 ◽  
Author(s):  
J. Reifenberg ◽  
R. England Voss ◽  
P. Rao ◽  
W. Schmitt ◽  
Y. Yang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Joule Heating ◽  
Electrical Resistance ◽  
Room Temperature ◽  
Aluminum Film ◽  
Thin Metallic Film ◽  
Thin Aluminum ◽  
Film Layer ◽  
Resistance Thermometry

Thin metallic film layers are extensively used as the constituents of the micro-devices. The reliability of these devices, therefore, strongly depends on the thermal behavior of such film layers. Aluminum thin film layers are of particular interest in this respect. The lateral thermal conductivity of the aluminum film layers is measured, using the steady state electrical Joule heating and electrical resistance thermometry technique. Aluminum suspended microbridges of identical thicknesses (500 nm) and variable widths (16 to 18 μm) and/or lengths (200 to 500 μm) are fabricated, using conventional microfabrication processes. The lateral thermal conductivity of the 500 nm thick Aluminum film layer was found to be k = 174 ± 13 Wm−1 K−1, at room temperature (300 K).

Thermal Conductivity of Porous Silicon Layers for MEMS

1999 ◽  
Author(s):  
Uma Srinivasan ◽  
Peter Breh ◽  
Mehdi Asheghi ◽  
Maxat Touzelbaev ◽  
Kenneth E. Goodson
Keyword(s):  
Thermal Conductivity ◽  
Porous Silicon ◽  
Electrical Resistance ◽  
Room Temperature ◽  
Single Crystal Silicon ◽  
Silicon Layer ◽  
Boundary Scattering ◽  
Conductivity Data ◽  
Crystal Silicon ◽  
Resistance Thermometry

Abstract Porous silicon is a promising material for MEMS because of its unique electrical, thermal, optical, and absorptive properties. This work measures the thermal conductivity of a silicon layer with 40 percent porosity at temperatures between 20 and 300 K using Joule heating and electrical-resistance thermometry. The room-temperature thermal conductivity is 0.43 Wm−1K−1, which is almost three orders of magnitude less than the value for single-crystal silicon. The data are interpreted using a new model based on electron microscopy, which shows a sponge-like morphology with embedded crystalline regions. The model separately treats the contributions of the sponge-like material, in which the solid regions are assumed to be amorphous silicon, and the larger crystallites, in which the conductivity is reduced by boundary scattering. The present work is particularly useful for MEMS based on silicon with porosity below 50 percent, for which no thermal conductivity data were previously available.

Thermal Conductivity of Single-Crystal Silicon Microbridges Measured by Electrical Resistance Thermometry and Time-Domain Thermoreflectance

2012 ◽  
Author(s):  
Timothy S. English ◽  
Leslie M. Phinney ◽  
Patrick E. Hopkins ◽  
Justin R. Serrano
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Time Domain ◽  
Electrical Resistance ◽  
Microelectromechanical Systems ◽  
Single Crystal Silicon ◽  
Operating Conditions ◽  
Equation Modeling ◽  
Crystal Silicon ◽  
Resistance Thermometry

Accurate thermal conductivity values are essential to the modeling, design, and thermal management of microelectromechanical systems (MEMS) and devices. However, the experimental technique best suited to measure thermal conductivity, as well as thermal conductivity itself, varies with the device materials, fabrication conditions, geometry, and operating conditions. In this study, the thermal conductivity of boron doped single-crystal silicon-on-insulator (SOI) microbridges is measured over the temperature range from 77 to 350 K. The microbridges are 4.6 mm long, 125 μm tall, and two widths, 50 or 85 μm. Measurements on the 85 μm wide microbridges are made using both steady-state electrical resistance thermometry and optical time-domain thermoreflectance. A thermal conductivity of ∼ 77 W/mK is measured for both microbridge widths at room temperature, where both experimental techniques agree. However, a discrepancy at lower temperatures is attributed to differences in the interaction volumes and in turn, material properties, probed by each technique. This finding is qualitatively explained through Boltzmann transport equation modeling under the relaxation time approximation.

Bond Pad Effects on Steady State Thermal Conductivity Measurement Using Suspended Micromachined Test Structures

2007 ◽  
Author(s):  
Leslie M. Phinney ◽  
Edward S. Piekos ◽  
Jaron D. Kuppers
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Joule Heating ◽  
Conductivity Measurement ◽  
Test Element ◽  
Heating Effects ◽  
Temperature Boundary ◽  
Bond Pads ◽  
State Resistance ◽  
Heat Sink Temperature

This study examines the effects of bond pads on the measurement of thermal conductivity for micromachined polycrystalline silicon using suspended test structures and a steady state resistance method. Bond pad heating can invalidate the assumption of constant temperature boundary conditions used for data analysis. Bond pad temperatures above the heat sink temperature arise from conduction out of the bridge test element and Joule heating in the bond pad. Simulations results determined correction factors for the electrical resistance offset, Joule heating effects in the beam, and Joule heating in the bond pads. Fillets at the base of the beam reduce the effect of bond pad heating until they become too large.

Thermal Characterization of Cu∕CoFe Multilayer for Giant Magnetoresistive Head Applications

2005 ◽  
Vol 128 (2) ◽  
pp. 113-120 ◽  
Author(s):  
Y. Yang ◽  
R. M. White ◽  
M. Asheghi
Keyword(s):  
Electrical Resistance ◽  
Multilayer Structure ◽  
Giant Magnetoresistance ◽  
Room Temperature ◽  
Thermal Characterization ◽  
Disk Drive ◽  
Multilayer Structures ◽  
Large Decrease ◽  
Resistance Thermometry

Giant magnetoresistance (GMR) head technology is one of the latest advancements in the hard disk drive (HDD) storage industry. The GMR head multilayer structure consists of alternating layers of extremely thin metallic ferromagnetic and nonmagnetic films. A large decrease in the electrical resistivity from antiparallel to parallel alignment of the film magnetizations is observed, known as the GMR effect. The present work characterizes the in-plane electrical and thermal conductivities of Cu∕CoFe GMR multilayer structures in the temperature range of 50K to 340K using Joule-heating and electrical resistance thermometry on suspended bridges. The thermal conductivity of the GMR layer monotonically increases from 25Wm−1K−1 (at 55K) to nearly 50Wm−1K−1 (at room temperature). We also report a GMR ratio of 17% and a large magnetothermal resistance effect (GMTR) of 25% in the Cu∕CoFe multilayer structure.

Transient and Steady-State Experimental Comparison Study of Effective Thermal Conductivity of Al2O3∕Water Nanofluids

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Calvin H. Li ◽  
Wesley Williams ◽  
Jacopo Buongiorno ◽  
Lin-Wen Hu ◽  
G. P. Peterson
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Steady State ◽  
Effective Thermal Conductivity ◽  
Room Temperature ◽  
Transient Hot Wire ◽  
Hot Wire ◽  
Transient Hot Wire Method ◽  
Wire Method ◽  
Reported Data

Nanofluids are being studied for their potential to enhance heat transfer, which could have a significant impact on energy generation and storage systems. However, only limited experimental data on metal and metal-oxide based nanofluids, showing enhancement of the thermal conductivity, are currently available. Moreover, the majority of the data currently available have been obtained using transient methods. Some controversy exists as to the validity of the measured enhancement and the possibility that this enhancement may be an artifact of the experimental methodology. In the current investigation, Al2O3∕water nanofluids with normal diameters of 47nm at different volume fractions (0.5%, 2%, 4%, and 6%) have been investigated, using two different methodologies: a transient hot-wire method and a steady-state cut-bar method. The comparison of the measured data obtained using these two different experimental systems at room temperature was conducted and the experimental data at higher temperatures were obtained with steady-state cut-bar method and compared with previously reported data obtained using a transient hot-wire method. The arguments that the methodology is the cause of the observed enhancement of nanofluids effective thermal conductivity are evaluated and resolved. It is clear from the results that at room temperature, both the steady-state cut-bar and transient hot-wire methods result in nearly identical values for the effective thermal conductivity of the nanofluids tested, while at higher temperatures, the onset of natural convection results in larger measured effective thermal conductivities for the hot-wire method than those obtained using the steady-state cut-bar method. The experimental data at room temperature were also compared with previously reported data at room temperature and current available theoretical models, and the deviations of experimental data from the predicted values are presented and discussed.

Joule Heating and Thermal Conductivity Determination of Nanoscale Metallic Thin Films and Interconnects

2005 ◽  
Author(s):  
Siva P. Gurrum ◽  
William P. King ◽  
Yogendra K. Joshi ◽  
Koneru Ramakrishna
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Free Path ◽  
Joule Heating ◽  
High Performance ◽  
Effective Conductivity ◽  
Mean Free Path ◽  
Current Crowding ◽  
Metal Line ◽  
Thin Metallic Film

Evolution of high performance microprocessors has resulted in a steady decrease in on-chip feature sizes. Increasing requirements on maximum current density are expected to increase interconnect temperature drastically due to Joule heating. As interconnect dimensions approach the electron mean free path range, effective conductivity reduces due to size effects. Thermal characterization of sub-micron interconnects and thin films is thus highly important. This work investigates current crowding and the associated Joule heating near a constriction in a thin metallic film and proposes a novel technique to determine thermal conductivity of thin metallic films and interconnects in the sub-100 nm range. Scanning Joule Expansion Microscopy (SJEM) measures the thermal expansion of the structure whose thickness is comparable to the mean free path of electrons. Numerical solution of heat conduction equation in the frequency space is used to obtain a fit for effective thermal conductivity. A thermal conductivity of ~ 80.0 W/mK provides a best fit to the data. This is about one-third the bulk thermal conductivity of gold, which is 318 W/mK at room temperature. Using Wiedemann-Franz Law a thermal conductivity of 92.0 W/mK is obtained after measuring the electrical resistivity of the metal line. This is close to that obtained through numerical fit.

Studies on Water in the Hydration Chamber of a Modified Electron Microscope

1970 ◽  
Vol 28 ◽  
pp. 544-545
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Electron Microscope ◽  
Steady State ◽  
Room Temperature ◽  
Small Mass ◽  
Equilibrium Pressure ◽  
Biological Objects ◽  
Mechanical Pump ◽  
Differential Pumping

Use of the electron microscope to examine wet objects is possible due to the small mass thickness of the equilibrium pressure of water vapor at room temperature. Previous attempts to examine hydrated biological objects and water itself used a chamber consisting of two small apertures sealed by two thin films. Extensive work in our laboratory showed that such films have an 80% failure rate when wet. Using the principle of differential pumping of the microscope column, we can use open apertures in place of thin film windows.Fig. 1 shows the modified Siemens la specimen chamber with the connections to the water supply and the auxiliary pumping station. A mechanical pump is connected to the vapor supply via a 100μ aperture to maintain steady-state conditions.

High thermal conductivity of pure dense SiC ceramics prepared via HTPVT

2019 ◽  
Vol 12 (03) ◽  
pp. 1950032 ◽  
Author(s):  
Yuchen Deng ◽  
Yaming Zhang ◽  
Nanlong Zhang ◽  
Qiang Zhi ◽  
Bo Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Silicon Carbide ◽  
Grain Size ◽  
Phase Composition ◽  
Room Temperature ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Growth Substrate ◽  
Sic Ceramics ◽  
Evolution Of Microstructure

Pure dense silicon carbide (SiC) ceramics were obtained via the high-temperature physical vapor transport (HTPVT) method using graphite paper as the growth substrate. The phase composition, the evolution of microstructure, the thermal diffusivity and thermal conductivity at RT to 200∘C were investigated. The obtained samples had a relative density of higher than 98.7% and a large grain size of 1[Formula: see text]mm, the samples also had a room-temperature thermal conductivity of [Formula: see text] and with the temperature increased to 200∘C, the thermal conductivity still maintained at [Formula: see text].

scholarly journals Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aastha Vasdev ◽  
Moinak Dutta ◽  
Shivam Mishra ◽  
Veerpal Kaur ◽  
Harleen Kaur ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Direct Evidence ◽  
Temperature Dependent ◽  
Force Microscopy ◽  
Ferroelectric Domains ◽  
Pdf Analysis ◽  
Ferroelectric Transition Temperature

AbstractA remarkable decrease in the lattice thermal conductivity and enhancement of thermoelectric figure of merit were recently observed in rock-salt cubic SnTe, when doped with germanium (Ge). Primarily, based on theoretical analysis, the decrease in lattice thermal conductivity was attributed to local ferroelectric fluctuations induced softening of the optical phonons which may strongly scatter the heat carrying acoustic phonons. Although the previous structural analysis indicated that the local ferroelectric transition temperature would be near room temperature in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te , a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te using piezoeresponse force microscopy(PFM) and switching spectroscopy over a range of temperatures near the room temperature. From temperature dependent (250–300 K) synchrotron X-ray pair distribution function (PDF) analysis, we show the presence of local off-centering distortion of Ge along the rhombohedral direction in global cubic $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te . The length scale of the $${\text {Ge}}^{2+}$$ Ge 2 + off-centering is 0.25–0.10 Å near the room temperatures (250–300 K). This local emphatic behaviour of cation is the cause for the observed local ferroelectric instability, thereby low lattice thermal conductivity in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te .

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