1,720,962 research outputs found
Thin film thermoelectric materials and generators deposited by chemical vapour processes
No full textAt present, a huge expansion of the Internet of Things (IoT) market is taking place, with issues stemming from potential power methods for integrated wireless sensor networks, which operate in the range of 1μW- 10mW. Common power methods, such as batteries, are impractical due to the sheer number of IoT nodes that are projected to be in operation. This has caused a shift to alternative energy harvesting methods to be explored. One that has shown great promise is thermoelectric power generation realised by thin-film thermoelectric generators. These devices directly convert heat into usable electrical energy and are comprised of an array of n-type and p-type semiconductors wired electrically in series and thermally in parallel. Enclosed within this thesis is an exploration of alternative thin film thermoelectric materials, which alleviate the need for scarce and expensive materials. The thin films in this work were deposited via chemical vapour processes, due to superior conformity, coverage and stoichiometry when compared to industrially established physical vapour processes (i.e sputtering, thermal evaporation, and electrodeposition). The successful deposition of binary and ternary thin films has been reported with the negation of the use of multiple sources which often require calibration, which is unfavourable for supply chains. The use of chemical vapour processes has also led to the formation of nanostructured films which display improved material properties, beneficial for thermoelectric applications. Exploration of the thermoelectric performance of highly stoichiometric GeTe thin films deposited by low-pressure chemical vapour deposition (LPCVD) using a novel single source precursor (SSP) is conducted. The potential of tuning thermoelectric performance will also be presented through the alteration of deposition conditions which suggests the potential to control crystallite size and majority carrier concentration. A competitive power factor of 40 μW/cm·K2 at 629 K was achieved, attributed to a high electrical conductivity driven by the formation of Ge vacancies. A prototype device was also fabricated with an encouraging specific power generation density of 175.4 μW/cm2K2. A range of binary and ternary WS2xSe2−2x (0 ≤ x ≤ 1) films were deposited via LPCVD using a range of SSPs containing different configurations of S and Se. The successful deposition of stoichiometric binary films and ternary films with a stable composition is encouraging, along with evidence of Janus binding which has been suggested to exhibit outstanding thermoelectric performance. Interestingly the films all displayed semi-metallic p-type conduction, this is unexpected for WS2 which generally favours n type conduction. This behaviour is believed to be linked to the formation of S vacancies acting as trapping centres for electrons. The deposited WS2 films achieved a power factor of 6 μW/mK2 at 553 K. Improved performance was also noted with a simple annealing process which enhanced the room temperature power factor from 1.9 to 3.9 μW/mK2. Al-doped ZnO (AZO) thin films were deposited via plasma-enhanced atomic layer deposition (PE-ALD) using an in-situ O2 plasma treatment. The thin films were deposited with a 4% Al doping concentration. The deposition process displayed the ability to grow AZO nanopillars perpendicular to the substrate, which is supported by SEM, AFM and XRD measurements. The formation of this led to the lowest reported cross plane thermal conductivity for AZO thin films, with a cross-plane thermal conductivity of 0.16 W/mK. The deposited thin films also yielded an encouraging power factor of 2.94 μW/cmK2 at 563 K. Furthermore, the fabrication and testing of a prototype thin film μ-TEG, without the use of scarce and expensive materials is reported. The device achieved a specific power generation density of 88.1 nW/cm2K2, with a peak power output of 1.08 nW with an applied temperature difference of 16.9◦C
Dataset in support of the Southampton doctoral thesis 'Flexible Thermoelectric Energy Generators for E-textiles'
No full textThe dataset collected in the research thesis of "Flexible Thermoelectric Energy Generators for E-textiles". Contains SEM images, EDX elemental analysis and XRD crystal lattice characterisations. Additionally, the dataset contains hall probe and thermoelectric data and device power outputs and thermal images of devices at different thermal gradients. Data used in the dataset contributed to the publication:
“Screen-printed Bismuth telluride nanostructured composites for flexible thermoelectric
applications” A. Amin, R. Huang, D. W. Newbrook, V. Sethi, S. P. Beeby and I. S. Nandhakumar, J.
Phys. Energy, , DOI:10.1088/2515-7655/ac572e.
</span
Dataset in support of the Southampton doctoral thesis 'Thin film thermoelectric materials and generators deposited by chemical vapour processes'
No full textThis dataset includes various data relating to the characterisation of various deposited thermoelectric thin films (i.e. GeTe, WS2xSe2-2x, and AZO). Thin films were characterised by SEM, EDX, XRD, XPS, Raman, AFM, Hall and Seebeck measurements. Further details of the dataset can be found in the README files attached.</span
Low pressure CVD of GeE (E = Te, Se, S) thin films from alkylgermanium chalcogenolate precursors and effect of the deposition temperature on the thermoelectric performance of GeTe
No full textThe homologous series [GenBu3(EnBu)] (E = Te, Se, S; (1), (3) and (4)) and [GenBu2(TenBu)2] (2) have been synthesized as mobile oils in excellent yield (72-93%) and evaluated as single-source precursors for the low-pressure chemical vapor deposition (LPCVD) of GeE thin films on silica. Compositional and structural characterizations of the deposits have been performed by grazing-incidence X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, and Raman spectroscopy, confirming the phase purity and stoichiometry. Electrical characterization via variable-temperature Hall effect measurements is also reported. Given the strong interest in GeTe and its alloys for thermoelectric applications, variable-temperature Seebeck data were also investigated for a series of p-type GeTe films. The data show that it is possible to tune the thermoelectric response through intrinsic Ge vacancy regulation by varying the deposition temperature, with the highest power factor (40 μW/K2cm@629 K) and effective ZT values observed for the films deposited at higher temperatures.</p
Screen-printed bismuth telluride nanostructured composites for flexible thermoelectric applications
No full textWe herein report the results of a facile two-step surfactant assisted reflux synthesis of bismuth telluride (Bi2Te3) nanowires (NWs). The as-synthesised NWs had diameters ranging from 70 to 110 nm with a length varying between 0.4 and 3 µm and a preferential lattice orientation of (0 1 5) as determined by grazing incidence x-ray diffraction. We demonstrate for the first time that a solvent/binder paste formulation of N-methyl-2-pyrrolidone/polyvinylidene fluoride (PVDF) is suitable for screen-printing the Bi2Te3 NWs with the potential for the fabrication of flexible thermoelectric (TE) materials. The wt% of PVDF in the composite films was varied from 10% to 20% to identify the optimal composition with a view to achieving maximum film flexibility whilst retaining the best TE performance. The films were screen-printed onto Kapton substrates and subjected to a post-printing annealing process to improve TE performance. The annealed and screen printed Bi2Te3/PVDF NW composites yielded a maximum Seebeck coefficient −192 µV K−1 with a power factor of 34 µW m−1K−2 at 225 K. The flexible screen printed composite films were flexible and found to be intact even after 2000 bending cycles
Tungsten(VI) selenide tetrachloride, WSeCl<sub>4</sub> - synthesis, properties, coordination complexes and application of [WSeCl<sub>4</sub>(SenBu<sub>2</sub>)] for CVD growth of WSe<sub>2</sub> thin films
No full textWSeCl4 was obtained in good yield by heating WCl6 and Sb2Se3in vacuo. Green crystals grown by sublimation were shown by single crystal X-ray structure analysis to contain square pyramidal monomers with apical WSe, and powder X-ray diffraction (PXRD) analysis confirmed this to be the only form present in the bulk sample. Density functional theory (DFT) calculations using the B3LYP-D3 functional replicated the structure, identified the key bonding orbitals, and were used to aid assignment of the IR spectrum of WSeCl4. Reaction of WSeCl4 with ligands L gave [WSeCl4(L)] (L = MeCN, DMF, thf, py, OPPh3, 2,2′-bipy, SeMe2, SenBu2), whilst the dimers [(WSeCl4)2(μ-L-L)] were formed with L-L = Ph2P(O)CH2P(O)Ph2, 1,4-dioxane and 4,4′-bipyridyl. The complexes were characterised by microanalysis, IR and 1H NMR spectroscopy, and single crystal X-ray structures determined for [WSeCl4(L)] (L = OPPh3, MeCN, DMF) and [(WSeCl4)2(μ-L-L)] (L-L = 1,4-dioxane, 4,4′-bipyridyl). All except the 2,2′-bipy complex, which is probably seven-coordinate, contain six-coordinate tungsten with the neutral donor trans to WSe. Alkylphosphines, including PMe3 and PEt3, decompose WSeCl4 upon contact, forming phosphine selenides (SePR3). In contrast, the selenoether complexes [WSeCl4(SeMe2)] and [WSeCl4(SenBu2)] were isolated and characterised. The crystal structure of the minor W(vi) by-product, [(WSeCl4)2(μ-SeMe2)], was determined and using SMe2, a few crystals of the W(v) species, [{WCl3(SMe2)}2(μ-Se)(μ-Se2)], were obtained and structurally characterised. The isolated W(vi) complexes are compared with those of WOCl4 and WSCl4 and the combination of experimental and computational data are consistent with WSeCl4 being a weaker Lewis acid and its complexes significantly less stable than those of the lighter analogues, especially in solution. Low pressure chemical vapour deposition (LPCVD) using [WSeCl4(SenBu2)] in the range 660-700 °C (0.1 mmHg) produced highly reflective thin films, which were identified to be WSe2 by grazing incidence X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. XRD analysis of the thinner films revealed them to be highly oriented in the <00l> direction. This journal is</p
Datatset for the journal article 'Tungsten dichalcogenide WS2xSe2-2x films via single source precursor low-pressure CVD and their (thermo-)electric properties'
No full textData in support of the journal article published in Journal of Materials Chemistry A
This dataset contains:
The raw data of figure 3 to 8.
The figures are as follows:
Figure 3. Grazing incidence X-ray diffraction patterns of the as-deposited WS2xSe2-2x films from (1)-(4).
Figure 4. Raman spectral scan presented over a range of 50-450 cm-1, of the as-deposited WS2xSe2-2x. films.
Figure 5. Elemental XPS scans of (a) W 4f, (b) Se 3d and (c) S 2p for all as-deposited WS2xSe2-2x films deposited from precursors (1)–(4). (d) Composition of all the as-deposited films deposited from precursors (1)–(4).
Figure 6. (a) Temperature-dependent electrical conductivity, (b) Arrhenius plot for WS2xSe2-2x films deposited from precursors (1)-(4). (c) Electrical conductivity and (d) Hall measurements against the chalcogenide content of the films.
Figure 7. (a) Carrier concentration and (b) carrier mobility of the as-deposited binary films, WS2 (red) and WSe2 (orange). Compared with the films annealed at 500oC in the respective chalcogenide atmospheres.
Figure 8. Temperature-dependent (a) Seebeck, and (b) power factor measurements for the WS2xSe2-2x films deposited from precursors (1)-(4).</span
Ultralow thermal conductivity and improved thermoelectric properties of Al-doped ZnO by In Situ O<sub>2</sub> plasma treatment
No full textThe thriving of Internet-of-Things and integrated wireless sensor networks has brought an unprecedented demand for sustainable micro-Watt-scale power supplies. Development of high-performing micro-thermoelectric generator (μ-TEG) that can convert waste thermal energy into electricity and provide sustainable micro-Watt-scale power is therefore extremely timely and important. Herein, a significant advance in the development of earth-abundant, nontoxic thermoelectric materials of aluminium-doped zinc oxide (AZO) is presented. Through nanostructure engineering using a novel in situ O2 plasma treatment, AZO films are demonstrated with ultralow thermal conductivity of 0.16 W m-1 K-1 which is the lowest reported in the literature. This nanostructured film yields a power factor of 294 μW m-1K-2 at 563 K and has resulted in a state-of-the-art ZT of 0.11 at room temperature and 0.72 at 563 K for AZO thin films. Furthermore, the fabrication and testing of a prototype lateral μ-TEG are reported based on the AZO thin film which achieves a power output of 1.08 nW with an applied temperature difference of 16.9 °C
Dataset in support of the journal article 'Ultra-low thermal conductivity and improved thermoelectric properties of Al-doped ZnO by in-situ O2 plasma treatment'
No full textThe thriving of Internet-of-Things and integrated wireless sensor networks has brought an unprecedented demand for sustainable micro-Watt-scale power supplies. Development of high-performing micro-thermoelectric generator (μ-TEG) that can convert waste thermal energy into electricity and provide sustainable micro-Watt-scale power is therefore extremely timely and important. Herein, a significant advance in the development of earth-abundant, nontoxic thermoelectric materials of aluminium-doped zinc oxide (AZO) is presented. Through nanostructure engineering using a novel in situ O2 plasma treatment, AZO films are demonstrated with ultralow thermal conductivity of 0.16 W m-1 K-1 which is the lowest reported in the literature. This nanostructured film yields a power factor of 294 μW m-1K-2 at 563 K and has resulted in a state-of-the-art ZT of 0.11 at room temperature and 0.72 at 563 K for AZO thin films. Furthermore, the fabrication and testing of a prototype lateral μ-TEG are reported based on the AZO thin film which achieves a power output of 1.08 nW with an applied temperature difference of 16.9 °C. </span
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