Liu H.F.,CAS Institute of Semiconductors
Solid State Communications | Year: 2012
The energy band structures of nitrogen(N)-doped and carbon(C)-doped SrTiO 3 are calculated based on the first-principles density-functional theory. The substitution of N(C) for O may introduce isolated states above the top of O 2p valence band, but the band gap narrowing driven by mixing of N(C) with O 2p states is very small. Our results are consistent with experimental data of N-doped SrTiO 3, where the absorption of visible light arises from the N 2p states localized above the valence-band maximum of SrTiO 3, rather than the band gap narrowing. © 2012 Elsevier Ltd. All rights reserved.
Bonaccorso F.,University of Cambridge |
Tan P.-H.,CAS Institute of Semiconductors |
Ferrari A.C.,University of Cambridge
ACS Nano | Year: 2013
Technological progress is determined, to a great extent, by developments in material science. Breakthroughs can happen when a new type of material or new combinations of known materials with different dimensionality and functionality are created. Multilayered structures, being planar or concentric, are now emerging as major players at the forefront of research. Raman spectroscopy is a well-established characterization technique for carbon nanomaterials and is being developed for layered materials. In this issue of ACS Nano, Hirschmann et al. investigate triple-wall carbon nanotubes via resonant Raman spectroscopy, showing how a wealth of information can be derived about these complex structures. The next challenge is to tackle hybrid heterostructures, consisting of different planar or concentric materials, arranged "on demand" to achieve targeted properties. © 2013 American Chemical Society.
Zhai F.,Zhejiang Normal University |
Chang K.,CAS Institute of Semiconductors
Physical Review B - Condensed Matter and Materials Physics | Year: 2012
We explore valley filtering in a two-terminal graphene system with a Dirac gap. For such a system with a constant Dirac gap, it is found that the presence of a valley-polarized output current requires both a magnetic barrier and an electric potential. For the magnetic-electric barrier generated by a single ferromagnetic stripe, a remarkable valley polarization can be achieved and is tunable by gate voltages. The generated valley polarization can be detected from the Hall measurement in the outgoing region. © 2012 American Physical Society.
Pei Y.,CAS Institute of Semiconductors
Physica B: Condensed Matter | Year: 2012
The influences of strain to the energetic and electronic properties of graphdiyne are investigated based on first-principles calculations. The elastic parameters of graphdiyne are determined by total energy calculation. Compared to graphyne, graphdiyne is softer because it has less C-C bonds. Moreover, the band gap of graphdiyne is tunable under uniform strain. It monotonously increases with increasing strain value, which originates from the decreased orbital overlap between C atoms when strain increases. © © 2012 Elsevier B.V. All rights reserved.
Qi X.-Q.,CAS Institute of Semiconductors |
Liu J.-M.,University of California at Los Angeles
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2011
In this paper, major photonic microwave generation and modulation methods are described. Their advantages and limitations are identified and compared through the analysis of the key characteristics relevant to practical photonic microwave applications. The focus of this paper is on the photonic microwave based on the nonlinear dynamics of optically injected semiconductor lasers. Both single-beam optically injected semiconductor lasers and dual-beam optically injected semiconductor lasers are considered. In particular, the three dynamic states of stable injection locking, period-one oscillation, and period-two oscillation are considered and demonstrated for photonic microwave generation, modulation, and conversion applications. Several prospects for future research and development in this area are discussed. © 2011 IEEE.