Exploiting the superior properties of nanomaterials at macroscopic scale is a key issue of nanoscience. Different from the integration strategy, "additive synthesis" of macroscopic structures from nanomaterial templates may be a promising choice. In this paper, we report the epitaxial growth of aligned, continuous, and catalyst-free carbon nanofiber thin films from carbon nanotube films. The fabrication process includes thickening of continuous carbon nanotube films by gas-phase pyrolytic carbon deposition and further graphitization of the carbon layer by high-temperature treatment. As-fabricated nanofibers in the film have an "annual ring" cross-section, with a carbon nanotube core and a graphitic periphery, indicating the templated growth mechanism. The absence of a distinct interface between the carbon nanotube template and the graphitic periphery further implies the epitaxial growth mechanism of the fiber. The mechanically robust thin film with tunable fiber diameters from tens of nanometers to several micrometers possesses low density, high electrical conductivity, and high thermal conductivity. Further extension of this fabrication method to enhance carbon nanotube yarns is also demonstrated, resulting in yarns with ∼4-fold increased tensile strength and ∼10-fold increased Young's modulus. The aligned and continuous features of the films together with their outstanding physical and chemical properties would certainly promote the large-scale applications of carbon nanofibers.
van der Waals crystals exhibit excellent
material performance when
exfoliated to few-atomic-layer thickness. In contrast, the van der
Waals thin films more than 10 nm thick are believed to show bulk properties,
in which outstanding material performance is rarely found. Here we
report the largest anomalous Hall conductivity observed so far in
a 170 nm van der Waals ferromagnetic 1T-CrTe2 flake, which reaches 67,000 Ω–1 cm–1. Such a colossal anomalous Hall conductivity in 1T-CrTe2 is dominated by the extrinsic skew scattering
process rather than the intrinsic Berry phase effect, as evidenced
by the linear relation between the anomalous Hall conductivity and
the longitudinal conductivity. Defying the dilemma of mutually exclusive
large anomalous Hall angle and high electric conductivity for most
ferromagnets, 1T-CrTe2 achieves both in
a thin film sample. Considering the shared physics of the anomalous
Hall effect and the spin Hall effect, our finding offers a guideline
for searching large spin Hall materials of high conductivity which
may overcome the bottleneck of overheating in spintronics devices.
Integrated circuits (ICs) and optoelectronic chips are the foundation stones of the modern information society. The IC industry has been driven by the so-called "Moore's law" in the past 60 years, and now has entered the post Moore's law era. In this paper, we review the recent progress of ICs and optoelectronic chips. The research status, technical challenges and development trend of devices, chips and integrated technologies of typical IC and optoelectronic chips are focused on. The main contents include the development law of IC and optoelectronic chip technology, the IC design and processing technology, emerging memory and chip architecture, brain-like chip structure and its mechanism, heterogeneous integration, quantum chip technology, silicon photonics chip technology, integrated microwave photonic chip, and optoelectronic hybrid integrated chip.
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