There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Emerging challenges and materials for thermal management of electronics

Optical transparency, tunable conducting properties and easy processability make metal oxides key materials for advanced optoelectronic devices. This Review discusses recent advances in the synthesis of these materials and their use in applications. Metal oxides (MOs) are the most abundant materials in the Earth's crust and are ingredients in traditional ceramics. MO semiconductors are strikingly different from conventional inorganic semiconductors such as silicon and III–V compounds with respect to materials design concepts, electronic structure, charge transport mechanisms, defect states, thin-film processing and optoelectronic properties, thereby enabling both conventional and completely new functions. Recently, remarkable advances in MO semiconductors for electronics have been achieved, including the discovery and characterization of new transparent conducting oxides, realization of p-type along with traditional n-type MO semiconductors for transistors, p–n junctions and complementary circuits, formulations for printing MO electronics and, most importantly, commercialization of amorphous oxide semiconductors for flat panel displays. This Review surveys the uniqueness and universality of MOs versus other unconventional electronic materials in terms of materials chemistry and physics, electronic characteristics, thin-film fabrication strategies and selected applications in thin-film transistors, solar cells, diodes and memories.

Metal oxides for optoelectronic applications

Semiconductor nanowires (NWs) have been studied extensively for over two decades for their novel electronic, photonic, thermal, electrochemical and mechanical properties. This comprehensive review article summarizes major advances in the synthesis, characterization, and application of these materials in the past decade. Developments in the understanding of the fundamental principles of "bottom-up" growth mechanisms are presented, with an emphasis on rational control of the morphology, stoichiometry, and crystal structure of the materials. This is followed by a discussion of the application of nanowires in i) electronic, ii) sensor, iii) photonic, iv) thermoelectric, v) photovoltaic, vi) photoelectrochemical, vii) battery, viii) mechanical, and ix) biological applications. Throughout the discussion, a detailed explanation of the unique properties associated with the one-dimensional nanowire geometry will be presented, and the benefits of these properties for the various applications will be highlighted. The review concludes with a brief perspective on future research directions, and remaining barriers which must be overcome for the successful commercial application of these technologies.

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25th Anniversary Article: Semiconductor Nanowires – Synthesis, Characterization, and Applications

Silicon nanowires have received considerable attention as transistor components because they represent a facile route toward sub-100-nm single-crystalline Si features. Herein we demonstrate the direct vertical integration of Si nanowire arrays into surrounding gate field effect transistors without the need for postgrowth nanowire assembly processes. The device fabrication allows Si nanowire channel diameters to be readily reduced to the 5-nm regime. These first-generation vertically integrated nanowire field effect transistors (VINFETs) exhibit electronic properties that are comparable to other horizontal nanowire field effect transistors (FETs) and may, with further optimization, compete with advanced solid-state nanoelectronic devices.

/pdf/silicon-vertically-integrated-nanowire-field-effect-2un7bo9af6.pdf

Silicon Vertically Integrated Nanowire Field Effect Transistors

Harnessing the potential of single crystal inorganic nanowires for practical advanced nanoscale applications requires not only reproducible synthesis of highly regular one-dimensional (1D) nanowire arrays directly on device platforms but also elegant device integration which retains structural integrity of the nanowires while significantly reducing or eliminating complex critical processing steps. Here we demonstrate a unique, direct, and bottom-up integration of a semiconductor 1D nanowire, using zinc oxide (ZnO) as an example, to obtain a vertical surround-gate field-effect transistor (VSG-FET). The vertical device structure and bottom-up integration reduce process complexity, compared to conventional top-down approaches. More significantly, scaling of the vertical channel length is lithographically independent and decoupled from the device packing density. A bottom electrical contact to the nanowire is uniquely provided by a heavily doped underlying lattice-match substrate. Based on the nanowire-integrated platform, both n- and p-channel VSG-FETs are fabricated. The vertical device architecture has the potential for use in tera-level ultrahigh-density nanoscale memory and logic devices.

Single Crystal Nanowire Vertical Surround-Gate Field-Effect Transistor

Using a nanowire-based templating approach, lithography-free fabrication of three-dimensional circular optical nanostructures with a minimum physical size of 20 nm is demonstrated. Regular circular gratings with alternating transparent and opaque annular zones and having discrete nanometer length scale separations can be easily achieved. These columnar optical nanostructures could potentially be used for direct integration with other optical components.

Three-dimensional columnar optical nanostructures fabricated by using lithography-free templating approach

Inorganic single crystal nanowires and nanowalls which exhibit rich growth morphogenesis are shown. More specifically, these were grown on lattice-matched substrates, which facilitate their specific growth directions with respect to the substrates' planes. Structural and optical characterizations suggest high single crystallinity of these nanostructures and possible applications in nano-optoelectronics are discussed.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Epitaxial single-crystalline inorganic nanowires and nanowalls: growth morphogenesis and applications in nano-optoelectronics

Our team tested spinal cord fusion (SCF) using the neuroprotective agent polyethylene glycol (PEG) in different animal (mice, rats, and beagles) models with complete spinal cord transection. To further explore the application of SCF for the treatment of paraplegic patients, we developed a new clinical procedure for SCF called vascular pedicle hemisected spinal cord transplantation (vSCT) and tested this procedure in eight paraplegic participants.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/cns.13853

Partial restoration of spinal cord neural continuity via vascular pedicle hemisected spinal cord transplantation using spinal cord fusion technique

Background Spinal cord injury (SCI) can cause paralysis and serious chronic morbidity, and there is no effective treatment. Based on our previous experimental results of spinal cord fusion (SCF) in mice, rats, beagles, and monkeys, we developed a surgical protocol of SCF for paraplegic human patients. We designed a novel surgical procedure of SCF, called sural nerve transplantation (SNT), for human patients with lower thoracic SCI and distal cord dysfunction. Methods We conducted a clinical trial (ChiCTR2000030788) and performed SNT in 12 fully paraplegic patients due to SCI between T1 and T12. We assessed pre- and postoperative central nerve pain, motor function, sensory function, and autonomic nerve function. Conduction of action potentials across the sural nerve transplant was evaluated. Neural continuity was also examined by diffusion tensor imaging (DTI). Results Among the 12 paraplegic patients enrolled in this clinical trial, seven patients demonstrated improved autonomic nerve functions. Seven patients had clinically significant relief of their symptoms of cord central pain. One patient, however, developed postoperative cord central pain (VAS: 4). Five patients had varying degrees of recovered sensory and/or motor functions below the single neurologic level 1 month after surgery. One patient showed recovery of electrophysiologic, motor-evoked potentials 6 months after the operation. At 6 months after surgery, DTI indicated fusion and nerve connections of white cord and sural nerves in seven patients. Conclusion SNT was able to fuse the axonal stumps of white cord and sural nerve and at least partially improve the cord central pain in most patients. Although SNT did not restore the spinal cord continuity in white matter in some patients, SNT could restore spinal cord continuity in the cortico-trunco-reticulo-propriospinal pathway, thereby restoring in part some motor and sensory functions. SNT may therefore be a safe, feasible, and effective method to treat paraplegic patients with SCI. Future clinical trials should be performed to optimize the type/technique of nerve transplantation, reduce surgical damage, and minimize postoperative scar formation and adhesion, to avoid postoperative cord central pain. Clinical Trial Registration [http://www.chictr.org.cn/showproj.aspx?proj=50526], identifier [ChiCTR2000030788].

Yi P. Chen

Papers

Single Crystal Nanowire Vertical Surround-Gate Field-Effect Transistor

Three-dimensional columnar optical nanostructures fabricated by using lithography-free templating approach

Epitaxial single-crystalline inorganic nanowires and nanowalls: growth morphogenesis and applications in nano-optoelectronics

Partial restoration of spinal cord neural continuity via vascular pedicle hemisected spinal cord transplantation using spinal cord fusion technique

Partial Restoration of Spinal Cord Neural Continuity via Sural Nerve Transplantation Using a Technique of Spinal Cord Fusion