Analysis and Characterization of Thermoelectric Microrefrigerators

2000 ◽  
Author(s):  
Y. Sungtaek Ju
Keyword(s):  
Thin Film ◽  
Quantum Wells ◽  
Phonon Scattering ◽  
Film Growth ◽  
Electrical Contact ◽  
Electrical Contact Resistance ◽  
Onsager Relation ◽  
Thermal Interface Resistance ◽  
Complete Discussion ◽  
The Impact

Abstract Advances in film growth techniques have sparked a renewed interest in thermoelectric (TE) devices. A previous study suggested that a drastic improvement in the figure of merit can be achieved for superlattices and quantum wells by exploiting phonon scattering/reflection at interfaces [1] or carrier pocket engineering [2]. Thin-film devices are also of great significance because of their capability to handle considerably higher heat flux than conventional bulk modules [3]. Microrefrigerators consist of a single or multiple thin-film thermoelement(s). The use of thin films introduces the full complexity of solid-solid interfaces into any complete discussion of these refrigerators. Many investigators noted that the electrical contact resistance has adverse effects on TE cooling. Less attention has been paid to thermal interface resistance and the boundary Seebeck effects. While previous studies [4] have indicated that the interface effects are related to each other via boundary forms of the Wiedemann-Franz-Lorenz law and the Kelvin-Onsager relation, the impact of their mutual interactions on thermoelectric cooling has remained relatively unexplored.

Practical electrical contact resistance measurement method for bulk thermoelectric devices

2013 ◽  
Vol 1490 ◽  
pp. 153-159 ◽  
Author(s):  
Rahul P. Gupta ◽  
Robin McCarty ◽  
Jim Bierschenk ◽  
Jeff Sharp
Keyword(s):  
Contact Resistance ◽  
Thermoelectric Materials ◽  
Measurement Method ◽  
Electrical Contact ◽  
Device Performance ◽  
Metal Contacts ◽  
Electrical Contact Resistance ◽  
Industry Standard ◽  
Manufacturing Techniques ◽  
The Impact

ABSTRACTAs thermoelectric (TE) element length decreases, the impact of contact resistance on TE device performance grows more significant. In fact, for a TE device containing 100-μm tall Bi2Te3TE elements, the figure of merit ratio (ZTDevice/ZTMaterial) drops from 0.9 to 0.5 as the contact resistivity increases from 5 x 10-07 to 5 x 10-06 Ω-cm2. To understand the effects of contact resistance on bulk TE device performance, a reliable experimental measurement method is needed. There are many popular methods to extract contact resistance such as Transmission Line Measurements (TLM) and Kelvin Cross Bridge Resistor method (KCBR), but they are only well-suited for measuring metal contacts on thin films and do not necessarily translate to measuring contact resistance on bulk thermoelectric materials. The authors present a new measurement technique that precisely measures contact resistance (on the order of 5 x 10-07 Ω-cm2) on bulk thermoelectric materials by processing stacks of bulk, metal-coated TE wafers using TE industry standard processes. One advantage of this technique is that it exploits realistic TE device manufacturing techniques and results in an almost device-like structure, therefore representing a realistic value for electrical contact resistance in a bulk TE device. Contact resistance measurements for metal contacts to n- and p-type Bi2Te3 alloys are presented and an estimate of the accuracy of the measurements is discussed.

Boundary Effects in Thin-Film Thermoelectrics

1998 ◽  
Vol 545 ◽  
Author(s):  
M. Bartkowiak ◽  
G. D. Mahan
Keyword(s):  
Thin Film ◽  
Contact Resistance ◽  
Figure Of Merit ◽  
Electrical Contact ◽  
Kapitza Resistance ◽  
Electrical Contact Resistance ◽  
Thermoelectric Effects ◽  
Contact Electrical Resistance ◽  
New Type ◽  
Boundary Form

AbstractEquations describing the resistances to the transport of heat and electricity through boundaries of thin-film thermoelectrics are derived. We show that these boundary resistances obey a boundary form of the Wiedemann-Franz law and cause a new type of thermal instability for short thermoelectric devices. We consider boundary thermal resistances both for phonons (Kapitza resistance) and for electrons, the contact electrical resistance at the junctions, and the boundary thermoelectric effects. It is shown that the Kapitza resistance causes reduction of the effective thermal conductivity of the system only if the electron and phonon subsystems are out of equilibrium. In this case, the thermoelectric figure of merit Z can be increased by reducing the thickness of the film. The electrical contact resistance at the junctions is shown to degrade the performance of the device. However, according to the boundary Wiedemann-Franz law, electrical contact resistance is accompanied by a thermal boundary resistance for the electron subsystem, which can cause an additional enhancement of Z. In some cases, this can lead to a device with ZT as high as 3 at room temperatures.

Molecular Dynamics Simulation of Ni/Cu Epitaxial Thin Film Growth

2011 ◽  
Vol 320 ◽  
pp. 373-376
Author(s):  
Zhi Qiang Liu ◽  
Jie Li ◽  
Nai Gen Zhou ◽  
Jian Ning Wei
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Substrate Temperature ◽  
Growth Pattern ◽  
Film Growth ◽  
Three Dimensional ◽  
Thin Film Growth ◽  
Dynamics Simulation ◽  
Lower Temperature ◽  
The Impact

In this paper, the growth process of Ni deposited on the Cu() surface at 300K and 700K was simulated by molecular dynamics. The impact of the substrate temperature on the growth pattern and structure of thin film was investigated. The simulation results show that, at the higher substrate temperature, the surface of thin film is smoother and the growth pattern of thin film is two-dimensional layer, however, at the lower temperature, the growth mode of thin film is three-dimensional island.

Microstructural characterization of YBa2Cu3O7-x thin films formed by metalorganic CVD

1991 ◽  
Vol 49 ◽  
pp. 1080-1081
Author(s):  
P. Lu ◽  
W. Huang ◽  
C.S. Chern ◽  
Y.Q. Li ◽  
J. Zhao ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Film Growth ◽  
Chemical Vapor ◽  
Microstructural Characterization ◽  
Ion Milling ◽  
Conventional Grinding

The YBa2Cu3O7-x thin films formed by metalorganic chemical vapor deposition(MOCVD) have been reported to have excellent superconducting properties including a sharp zero resistance transition temperature (Tc) of 89 K and a high critical current density of 2.3x106 A/cm2 or higher. The origin of the high critical current in the thin film compared to bulk materials is attributed to its structural properties such as orientation, grain boundaries and defects on the scale of the coherent length. In this report, we present microstructural aspects of the thin films deposited on the (100) LaAlO3 substrate, which process the highest critical current density.Details of the thin film growth process have been reported elsewhere. The thin films were examined in both planar and cross-section view by electron microscopy. TEM sample preparation was carried out using conventional grinding, dimpling and ion milling techniques. Special care was taken to avoid exposure of the thin films to water during the preparation processes.

Quantitative Image Analysis of Fractal-like Thin Films of Organic Semiconductors

2018 ◽  
Author(s):  
Weikun Zhu ◽  
Erfan Mohammadi ◽  
Ying Diao
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Image Analysis ◽  
Fractal Dimension ◽  
Organic Semiconductors ◽  
Film Growth ◽  
Electronic Device ◽  
Significant Control ◽  
Semiconductor Thin Films ◽  
Two Parameters

Morphology modulation offers significant control over organic electronic device performance. However, morphology quantification has been rarely carried out via image analysis. In this work, we designed a MATLAB program to evaluate two key parameters describing morphology of small molecule semiconductor thin films: fractal dimension and film coverage. We then employ this program in a case study of meniscus-guided coating of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C<sub>8</sub>-BTBT) under various conditions to analyze a diverse and complex morphology set. The evolution of morphology in terms of fractal dimension and film coverage was studied as a function of coating speed. We discovered that combined fractal dimension and film coverage can quantitatively capture the key characteristics of C<sub>8</sub>-BTBT thin film morphology; change of these two parameters further inform morphology transition. Furthermore, fractal dimension could potentially shed light on thin film growth mechanisms.

scholarly journals Thin film growth of heavy fermion chiral magnet YbNi3Al9

2021 ◽  
Vol 118 (10) ◽  
pp. 102402
Author(s):  
Hiroaki Shishido ◽  
Akira Okumura ◽  
Tatsuya Saimyoji ◽  
Shota Nakamura ◽  
Shigeo Ohara ◽  
...  
Keyword(s):  
Thin Film ◽  
Heavy Fermion ◽  
Film Growth ◽  
Thin Film Growth
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