Huntsville, AL, United States
Huntsville, AL, United States

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Budak S.,Alabama A&M University | Muntele C.,Cygnus Scientific Services | Heidary K.,Alabama A&M University | Johnson R.B.,Alabama A&M University | Ila D.,Fayetteville State University
Journal of Intelligent Material Systems and Structures | Year: 2013

We have fabricated the thermoelectric generator devices from 100 alternating layers of SiO2/SiO2+CoSb superlattice thin films using the ion beam-assisted deposition. Rutherford backscattering spectrometry was used for quantitative elemental analysis of Si, Co, and Sb in the multilayer films. The thin films were then modified by 5-MeV Si ion bombardments using the Alabama A&M University Pelletron ion beam accelerator. Quantum dots and/or clusters were produced in the nanolayered superlattice films to decrease the cross-plane thermal conductivity, increase the cross-plane Seebeck coefficient, and the cross-plane electrical conductivity. We have characterized the thermoelectric generator devices before and after Si ion bombardments using the thermoelectric, optical, and surface characterization techniques. The optical absorption amplitude decreased when the first fluence of 1 × 1012 ions/cm2 was introduced from the value of 2.8 to about 1.9 at 200 nm. The figure of merit reached the maximum value of about 0.005 at the fluence of 1 × 1013 ions/cm2. © The Author(s) 2012.


Budak S.,Alabama A&M University | Guner S.,Fatih University | Minamisawa R.A.,Jülich Research Center | Muntele C.I.,Cygnus Scientific Services | Ila D.,Fayetteville State University
Applied Surface Science | Year: 2014

We prepared multilayers of superlattice thin film system with 50 periodic alternating nano-layers of semiconducting half-Heusler β-Zn 4Sb3 and skutterudite CeFe2Co 2Sb12 compound thin films using ion beam assisted deposition (IBAD) with Au layers deposited on both sides as metal contacts. The deposited multilayer thin films have alternating layers about 5 nm thick. The total thickness of the multilayer system is 275 nm. The superlattices were then bombarded by 5 MeV Si ion at six different fluences to form nano-cluster structures. The film thicknesses and composition were monitored by Rutherford backscattering spectrometry (RBS) before and after MeV ion bombardment. We have measured the thermoelectric efficiency, Figure of Merit ZT, of the fabricated device by measuring the cross plane thermal conductivity by the 3rd harmonic (3ω) method, the cross plane Seebeck coefficient, and the electrical conductivity using the van der Pauw method before and after the MeV ion bombardments. We reached the remarkable thermoelectric Figure of Merit results at optimal fluences. © 2014 Elsevier B.V.


Budak S.,Alabama A&M University | Heidary K.,Alabama A&M University | Johnson R.B.,Alabama A&M University | Colon T.,Alabama A&M University | And 2 more authors.
Applied Surface Science | Year: 2014

The performance of thermoelectric materials and devices is characterized by a dimensionless figure of merit, ZT = S2σT/K, where, S and σ denote, respectively, the Seebeck coefficient and electrical conductivity, T is the absolute temperature in Kelvin and K represents the thermal conductivity. The figure of merit may be improved by means of raising either S or σ or by lowering K. In our laboratory, we have fabricated and characterized the performance of a large variety of thermoelectric generators (TEG). Two TEG groups comprised of 50 and 100 alternating layers of Si/Si + Ge multi-nanolayered superlattice films have been fabricated and thoroughly characterized. Ion beam assisted deposition (IBAD) was utilized to assemble the alternating sandwiched layers, resulting in total thickness of 300 nm and 317 nm for 50 and 100 layer devices, respectively. Rutherford Backscattering Spectroscopy (RBS) was employed in order to monitor the precise quantity of Si and Ge utilized in the construction of specific multilayer thin films. The material layers were subsequently impregnated with quantum dots and/or quantum clusters, in order to concurrently reduce the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and raise the cross plane electrical conductivity. The quantum dots/clusters were implanted via the 5 MeV Si ion bombardment which was performed using a Pelletron high energy ion beam accelerator. We have achieved remarkable results for the thermoelectric and optical properties of the Si/Si + Ge multilayer thin film TEG systems. We have demonstrated that with optimal setting of the 5 MeV Si ion beam bombardment fluences, one can fabricate TEG systems with figures of merits substantially higher than the values previously reported. © 2014 Elsevier B.V.


Budak S.,Alabama A&M University | Guner S.,Fatih University | Muntele C.,Cygnus Scientific Services | Ila D.,Fayetteville State University
Journal of Electronic Materials | Year: 2015

The ternary chalcogenides AgBiTe2 and AgSbTe2 belong to the family of semiconductors with disordered NaCl cubic structure in which Ag and Sb occupy metal sublattices. Both compounds are very interesting due to their thermoelectric properties. We have grown single-layer AgBiTe and AgSbTe thin films on silicon (Si) and fused silica (Suprasil) substrates using electron beam deposition. High-energy (MeV) Si-ion bombardment was performed on the thin-film samples at five different fluences between 5 × 1013 ions/cm2 and 7 × 1015 ions/cm2. We have measured the thermoelectric efficiency (figure of merit, ZT) of the fabricated thermoelectric devices by measuring the cross-plane thermal conductivity using the third-harmonic (3ω) method, the cross-plane Seebeck coefficient, and the in-plane electrical conductivity using the van der Pauw method before and after MeV Si-ion bombardment. Rutherford backscattering spectrometry and the Rutherford Universal Manipulation Program (RUMP) simulation package were used to analyze the elemental composition and thickness of the deposited materials on the substrates. The RUMP simulation gave thicknesses for the AgBiTe and AgSbTe thin films of 270 nm and 188 nm, respectively. The figure of merit for AgBiTe started to decrease from the value of 0.37 for the virgin sample after bombardment. We saw similar decreasing behavior for the AgSbTe thin-film system. The figure of merit for AgSbTe started to decrease from the value of 0.88 for the virgin sample after bombardment. MeV Si-ion bombardment caused changes in the thermoelectric properties of the thin films. © 2014, The Minerals, Metals & Materials Society.


Budak S.,Alabama A&M University | Baker M.,Alabama A&M University | Lassiter J.,Alabama A&M University | Smith C.,4 Sight Inc | And 2 more authors.
Journal of Electronic Materials | Year: 2015

We have prepared multi-nanolayer superlattice thin-film systems comprising 36 alternating layers of SiO2 and SiO2+Cu nanolayers, of total thickness approximately 300 nm, by magnetron direct current–radio frequency sputtering. To modify their thermoelectric and optical properties, the films were placed in a furnace for annealing at temperatures between 500°C and 700°C, in air, for 1 h, to form quantum nano-dots and/or quantum clusters. Atomic force microscopy was used to analyze the surface of the thin-film systems. The thermoelectric and optical properties of the systems were characterized by study of ultraviolet–visible–near infrared absorption, fluorescence, and Raman spectroscopy, and by measurement of Seebeck coefficients. Seebeck coefficients increased from −70 μV/K to −100 μV/K when the temperature was increased from 0°C to 700°C. Optical absorption spectra showed that formation of nano-dots and/or nano-clustering also occurred as the temperature was increased. Thermal annealing affected the optical and thermal properties of the multi-nanolayer thermoelectric thin-film systems in the positive direction. © 2014, The Minerals, Metals & Materials Society.


Budak S.,Alabama A&M University | Gulduren E.,University of Alabama in Huntsville | Allen B.,Alabama A&M University | Cole J.,Alabama A&M University | And 6 more authors.
Solid-State Electronics | Year: 2014

We prepared thermoelectric generator devices from 100 alternating layers of SiO2/SiO2 + Ge superlattice thin films using Magnetron DC/RF Sputtering. Rutherford Backscattering Spectrometry (RBS) and RUMP simulation software package were used to determine the proportions of Si and Ge in the grown multilayer films and the thickness of the grown multi-layer films. 5 MeV Si ion bombardments were performed using the AAMU-Pelletron ion beam accelerator, to form quantum clusters in the multi-layer superlattice thin films, in order to tailor the thermoelectrical and optical properties. We characterized the fabricated thermoelectric devices using cross-plane Seebeck coefficient, van der Pauw resistivity, mobility, density (carrier concentration), Hall Effect coefficient, Raman, Fluorescence, Photoluminescence, Atomic Force Microscopy (AFM) and Impedance analyzing measurements. Some suitable high energy ion fluences and thermal annealings caused some remarkable thermoelectrical and optical changes in the fabricated multilayer thin film systems. © 2014 Elsevier Ltd. All rights reserved.


Budak S.,Alabama A&M University | Parker R.,NASA | Smith C.,Alabama A&M University | Muntele C.,Cygnus Scientific Services | And 3 more authors.
Journal of Intelligent Material Systems and Structures | Year: 2013

Thermoelectric generators convert heat to electricity. Effective thermoelectric materials and devices have a low thermal conductivity and a high electrical conductivity. The performance of thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and K is the thermal conductivity. We have prepared 100 alternating layers of SiO2/SiO2+ Ge superlattice thin films using ion beam-assisted deposition for the thermoelectric generator device application. The 5 MeV Si ion bombardments were performed using the Center for Irradiation Materials' Pelletron ion beam accelerator to form quantum dots and/or quantum clusters in the multinanolayer superlattice thin films to decrease the cross-plane thermal conductivity and increase the cross-plane Seebeck coefficient and cross-plane electrical conductivity. The thermoelectric and transport properties have been characterized for SiO2/SiO2+ Ge superlattice thin films. © The Author(s) 2013.

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