Thermoelectric materials are solid-state energy converters whose combination of thermal, electrical, and semiconducting properties allows them to be used to convert waste heat into electricity or electrical power directly into cooling and heating. These materials can be competitive with fluid-based systems, such as two-phase air-conditioning compressors or heat pumps, or used in smaller-scale applications such as in automobile seats, night-vision systems, and electrical-enclosure cooling. More widespread use of thermoelectrics requires not only improving the intrinsic energy-conversion efficiency of the materials but also implementing recent advancements in system architecture. These principles are illustrated with several proven and potential applications of thermoelectrics.

http://engin1000.pbworks.com/f/TE_rev.pdf

Cooling, heating, generating power, and recovering waste heat with thermoelectric systems.

The dimensionless thermoelectric figure of merit (ZT) in bismuth antimony telluride (BiSbTe) bulk alloys has remained around 1 for more than 50 years. We show that a peak ZT of 1.4 at 100°C can be achieved in a p-type nanocrystalline BiSbTe bulk alloy. These nanocrystalline bulk materials were made by hot pressing nanopowders that were ball-milled from crystalline ingots under inert conditions. Electrical transport measurements, coupled with microstructure studies and modeling, show that the ZT improvement is the result of low thermal conductivity caused by the increased phonon scattering by grain boundaries and defects. More importantly, ZT is about 1.2 at room temperature and 0.8 at 250°C, which makes these materials useful for cooling and power generation. Cooling devices that use these materials have produced high-temperature differences of 86°, 106°, and 119°C with hot-side temperatures set at 50°, 100°, and 150°C, respectively. This discovery sets the stage for use of a new nanocomposite approach in developing high-performance low-cost bulk thermoelectric materials.

/pdf/high-thermoelectric-performance-of-nanostructured-bismuth-4evuadx0tz.pdf

High-Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys

http://absimage.aps.org/image/MAR08/MWS_MAR08-2007-001627.pdf

High Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys.

Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

/pdf/prospects-of-colloidal-nanocrystals-for-electronic-and-3dxpyhl3r7.pdf

Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

Approximately 90 per cent of the world's power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30-40 per cent efficiency, such that roughly 15 terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT > 1, since the parameters of ZT are generally interdependent. While nanostructured thermoelectric materials can increase ZT > 1 (refs 2-4), the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here we report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20-300 nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50 nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.

Enhanced thermoelectric performance of rough silicon nanowires

We experimentally demonstrate the integration of 128 waveguide-coupled diamond spin qubits with aluminum nitride photonics. This large-scale, tunable, efficient and optically coherent multi-qubit platform sets the stage for high-rate entanglement distribution in a large quantum network.

A 128-Channel Diamond Quantum Memory Array Integrated in a Microphotonic Chip

We show the design, fabrication, and integration of a 128-channel aluminum nitride photonic chip with tunable diamond quantum micro-chiplets containing silicon vacancy and germanium vacancy color centers, enabling a chip-integrated architecture towards multiplexed photon-mediated entanglement.

Design and Fabrication of a 128-Channel Array of Quantum Memories in Hybrid Photonic Circuits

The development of micro- and nanofabrication, their applications, and their dependent industries has progressed to a point where a bifurcation of technology development will likely occur. On the one hand, the semiconductor industry (at least in the USA) has decided to develop EUV and SCALPEL to meet its future needs. Even if the semiconductor industry is successful in this (which is by no means certain) such tools will not be useful in most other segments of industry and research that will employ nanolithography. As examples, MEMS, integrated optics, biological research, magnetic information storage, quantum-effect research, and multiple applications not yet envisioned will not employ the lithography tools of the semiconductor industry, either because they are too expensive, insufficiently flexible, or lacking in accuracy and spatial-phase coherence. Of course, direct-write electron-beam lithography can meet many of these non-semiconductor-industry needs, but in other cases a technique of higher throughput or broader process-latitude is necessary. Our experience at MIT in applying low-cost proximity x-ray nanolithography to a wide variety of applications leads us to conclude that this technology can provide an alternative path of a bifurcation. A new projection lithography technique, zone-plate-array lithography (ZPAL), does not require a mask, can operate from UV to EUV to x-rays, and has the potential to reach the limits of the lithographic process.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400182259

Soft X-Rays for Deep Sub-100 Nm Lithography, with and Without Masks

The role of lithography in the future of nanoscale science and engineering is to put high-density spatial information into nanoscale assemblies. Because information content determines the functionality of such assemblies, lithography will be a key enabler. Conventional lithographic techniques generally lack the flexibility, low cost and the resolution that research in nanoscale science and engineering requires. Although no single lithographic technique is likely to be a panacea, it is important to seek novel approaches that meet the needs of researchers, and open a path to directly manipulating nanoparticles and macromolecules. We review the various forms of lithography and focus special attention on maskless zone-plate-array lithography, assessing its impact, advantages and extendibility to the limits of the lithographic process. 

Nanoscale assemblies will require control at the macromolecular level, and this has begun with research on templated self assembly. Going beyond that to the control and utilization of the information content of nanoparticles and molecules will require innovations whose origin is uncertain at this point.

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/6002/1/Enabling-nanoscale-science-and-engineering-via-highly-flexible-low-cost/10.1117/12.632117.pdf

Enabling nanoscale science and engineering via highly flexible low-cost maskless lithography

We report a new fabrication process of planar photonic crystal nanocavities from bulk diamond. Experimental devices have quality factors Q > 1 × 104 with resonances matched to the negatively charged nitrogen vacancy zero phonon line, allowing for an enhanced spin-photon interface.

Michael Walsh

Papers

A 128-Channel Diamond Quantum Memory Array Integrated in a Microphotonic Chip

Design and Fabrication of a 128-Channel Array of Quantum Memories in Hybrid Photonic Circuits

Soft X-Rays for Deep Sub-100 Nm Lithography, with and Without Masks

Enabling nanoscale science and engineering via highly flexible low-cost maskless lithography

Photonic crystal cavities in bulk diamond for efficient spin-photon interfaces