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1.'5 nanometer carbon nanotube CMOS device 'selected ten major university science and technology progress;
Recently, the "Top Ten Scientific and Technological Progress of Chinese Colleges and Universities in 2017" organized by the Science and Technology Commission of the Ministry of Education was unveiled in Beijing after the review and publicity, formal examination, initial assessment of the department and final project review process in Beijing.
The "5-nanometer carbon nanotube CMOS device" declared by Peking University was selected.
Chip is the foundation and driving force of the information age, and the existing CMOS technology will touch its limit.Carbon nanotube technology is considered as an important option in post-Moore era.
Theoretical studies show that CNT transistors are expected to provide higher performance and lower power consumption, and easier to achieve three-dimensional integration, system-level synthesis advantages will be up to thousands of times, the chip technology may thus be raised to new heights.
Peking University Department of Electronics Professor Peng Lianchao team made significant breakthroughs in the carbon nanotube CMOS device physics and preparation techniques, explore the performance limits and so on, to give up the traditional doping process, by controlling the electrode material to control the polarity of the transistor, inhibit short ditch For the first time, a 5 nanometer gate length high performance carbon nanotube transistor is achieved. Its performance surpasses that of the best silicon-based transistor at present, approaching the physical limit determined by the quantum mechanics principle and is expected to advance the CMOS technology to the technology node below 3 nanometers.
Marked achievements on Scaling carbon nanotube complementary transistors to 5-nm gate lengths, January 20, 2017, published online in Science, 2017, 355: 271-276; included by IBM researchers Of its peers published 24 open and positive citations in the journal Science and Nature and Nanotechnology and was selected as ESI Highly Cited Papers by the major domestic and international academic media such as Nature Index, IEEE Spectrum, Nano Today, Science and Technology Daily, And Xinhua News Agency reported;
"People's Daily" (Overseas Version) Carbon nanotube transistors 'work at three times the speed of Intel's state-of-the-art 14nm commercial silicon material transistors, consuming only a quarter of their energy, meaning that Chinese scientists' Technology catch up with foreign counterparts', 'is a new milestone in the development of China's information technology'.
2. Fudan University designed a new type of light-sensitive semiconductor memory;
Recently, a research team designed a memory based on atomic-grade semiconductors. In addition to its good performance, it can also eliminate stored data with light without the need for power assist. The team believes this new memory System on Panel (System on Panel), has great potential applications.
Phys.org reports that Long-Fei He and related researchers at Fudan University and the Institute of Microelectronics, Chinese Academy of Sciences, recently published a paper on the new type of memory in the new AIP Journal.
Because most of the existing memory technologies are too bulky to integrate on display panels, researchers are constantly looking at new designs and materials in an effort to create storage devices that are equally well-behaved yet ultra-thin.
In this new study, researchers use a two-dimensional (MoS2) over-metallic material to create an atomic-scale semiconductor whose conductivity can be refined Adjust, and then form a memory with the high switching current ratio of the basic components.
In addition, the team also confirmed in tests that this type of memory has fast, large memory space and excellent storage, and researchers estimate that even at high temperatures of 85 ° C (185 ° F) Year, the storage space can still save about 60% of the original, which is still enough for practical application.
In the past, studies have confirmed that molybdenum disulfide has a photoresponsive effect, which means that some properties can be controlled by light. To understand the actual application, the team actually conducted relevant experiments. As a result, they found that when the light shines on the programmed Of the storage device, the stored data is completely erased, but at the same time using the voltage erase information can still be used.
Co-owner Hao Zhu said the team is currently investigating the large-scale integration of such storage components with programmable, programmable optical pulse wavelengths and timing, and researchers believe the future of such storage devices will be in the application of system-integrated panels Play an important role on the technews
3. China made important progress in the study of ultra-fast kinetics of atomic molecules;
Xinhua News Agency, Wuhan, February 2 (Reporter Li Wei) Femtosecond intense laser provides an important measure for detecting the microstructure and electron fast kinetics of matter at the time-space scale of atoms (A second time and the space scale of Aene) , Our country experts made great progress in using the femtosecond laser to probe the molecular structure of the atom and the electron fast kinetics.
Femtosecond intense laser-induced ionization of electron-wave packets or can return to the parent ion and then with the occurrence of re-scattering process, caused by re-scattering of high-order harmonic spectra or photoelectron spectroscopy to detect the molecular structure and rapid evolution of electronic states provide Effective way.At present, the development of space-time high-resolution atomic structure and kinetic detection methods for the research field of widespread concern.
Liu Xiaojun, a researcher at Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, researched by Quan Wei and others, together with Chen Jing, a researcher at Beijing Institute of Applied Physics and Computational Mathematics and associate researcher Wu Yong, proposed a new laser-induced inelastic electron diffraction scheme and adopted This scheme experimentally determined the inelastic scattering differential cross section caused by the electron-inert gas ion collisions.
According to reports, in this program, experts use the femtosecond laser-driven atom-generated electron scattering package instead of the traditional electron beam electron inertia precursor ion structure detection method. Combined with the number of objects in Wuhan pre-built High-resolution electron-ion mass spectrometer devices and measurement methods, they experimentally measured the corresponding photoelectron ion-pair collision ionization process two-dimensional momentum spectra and extracted from the interaction of electrons and the parent ion inelastic scattering differential cross section, The experimental results are in good agreement with the theoretical results of the twisted wave Bonn approximation.
This scheme inherits the advantages of ultrahigh-spatial resolution of traditional electron diffraction methods and has ultra-high temporal resolution capability, which provides an important means for studying the laser-induced ultra-fast kinetic processes of atomic molecules on the femtosecond and even second-order time scales. The research results recently published in the academic journal "Physical Review Letters" on.
4. High energy and other advances in quantum chromodynamics;
Jia Yu, a fellow at the Institute of High Energy Physics, Chinese Academy of Sciences, Feng Feng, a visiting professor at China University of Mining and Technology and a visiting scholar at the Institute of High Energy, and Sang Wenlong, associate professor at Southwest University, for the first time calculated the second leading edge of the strong decay- (NNLO) radiation correction, combined with the latest experimental measurements conducted an in-depth phenomenological discussion.December 20, the relevant paper published in the "Physical Review Letters", the study represents a heavy quarks the important theoretical advances in the study .
Explaining the annihilation decay of heavy quarks has historically played a key role in establishing the gradual and free-form nature of quantum chromodynamics. About 40 years ago, the pseudoscalar singlet strong decay width was below the non-relativistic limit The NLO correction has been done independently by two theorists in Italy and Japan. The contribution of the NLO correction is so important that it is natural for the curiosity of the size of the next-order radiation correction. Due to technical challenges, For a long time, NNLO correction of the strong decay width of ηc has never been known.With the rapid development of quantum field theory high-order perturbation calculation technology in recent years, the people of the summer of 2017 finally usher in the long-awaited breakthrough. After several years of unremitting efforts, Jia Yu overcome numerous technical difficulties, and ultimately with the help of the National Supercomputing Center, Guangzhou Tianhe platform to complete the calculation.In this paper, Jia Yu, for the first time specifically verified from QCD first principle The effective field theory of departure - the non-relativistic QCD (NRQCD) factorization holds for the lead in the second leg of the single-lift process However, correlating the NNLO radiation correction with the known The combination of relativistic corrections found that the most complete NRQCD predictions and experimental measurements of the total width of ηc, in particular, severely diverged from the experimentally measured ηc decay to the two-photon branching ratio, meant that the well-known NRQCD method, despite its theoretical roots Is very sturdy, but for the quark-quark element, the quark-quark quality is not big enough, which leads to very poor convergence of the perturbation unfolding, which makes the validity of the quark quark challenging.On the other hand, the NRQCD method can satisfactorily explain the experimental measurement , The exact prediction of ηb decay to two-photon branching ratio, Br'ηb → γγ '= (4.8 ± 0.7) × 10-5, is yet to be super B factory test.
It is noteworthy that the conclusion of the research is in agreement with the conclusion of Jia Yu and others published in the Physics Review Letters in 2015. That is to say, the NRQCD method is challenged in the application of the method involving 粲 quark conjugation. The NNLO radiation correction of 遍 quark conjugation was calculated, and the variation of γ * ηηc transition shape factor with momentum transfer was studied. The results show that the prediction of the most accurate NRQCD prediction differs greatly from the BaBar experiment when NNLO correction is included.
For the first time, Jia et al. Calculated the NNLO radiation correction for single-decay and over-all generation involving 粲 -quarkson, and found that its contribution is very important. After considering its correction effect, the theoretical prediction seriously agrees with the experimental measurement, In terms of the perturbation of the NRQCD short-range coefficients, the convergence of the perturbations is poor, arguing that the root cause of this problem is that the mass of the quarks is not so large that the strong coupling constants that can be defined are not Small, thus seriously undermining the convergence of perturbation expansion.While the widely used NRQCD factorization method is solidly based on the theory, its validity appears to be a serious challenge for the quark-quark element and still requires further research To find its solution.
Research has been funded by the National Natural Science Foundation of China.
Paper link: 1 2
Theoretical prediction of ηc total width as a function of renormalization energy standard μR. LO, NLO, NNLO corresponding perturbation corresponding to the leading order, sub-leading order, and the second leading theoretical predictions. Is the experimental measurement of the total width of ηc.
NRQCD factorization predicts ηc to two-photon branching ratio as a function of renormalization energy marker μR The blue band diagram in the figure is an experimental measurement of ηc to two-photon branching ratio.
The (normalized) γ * γηc transition shape factor predicted by the NRQCD theory changes with the momentum transfer Q2. The black dots with errors in the figure represent the experimental measurements of BaBar. The dotted, dashed, Under the leadership of the perturbation on the order, second leading, second leading prediction. Chinese Academy of Sciences website
5. The progress of the research on the preparation of native quantum dots in the national nanocenters
As a product of the continuous development and cross-over of two-dimensional material systems and quantum systems, quantum chips have drawn much attention in recent years.Due to their transverse size generally less than 20 nm, quantum chips not only have the intrinsic characteristics of two-dimensional materials, but also have quantum limits Domain and prominent edge effects.
Transition metal disulfides (TMDs) are a class of two-dimensional materials with extraordinary properties and great potential. As the most representative TMDs, molybdenum disulfide (MoS2) and tungsten disulfide (WS2) have been widely studied. Quantum chip preparation is divided into bottom-up and top-down two ways. Bottom-up preparation methods often require harsh reaction conditions and complicated post-processing, top-down preparation of the quantum yield of the normal yield In addition, both methods of preparation face the challenge of how to avoid defects and obtain intrinsic quantum sheets.
Zhang Yong, director of the National Nanoscience Center, co-authored the research team of Liu Xinfeng and Gao Peng of Peking University, and invented a new technology that can produce defect-free intrinsic MoS2 and WS2 quantum chips on a large scale. Assisted ball milling, ultrasonic assisted solvent stripping and other measures to produce the defect-free intrinsic MoS2 and WS2 quantum sheets at very high yields of 25.5 wt% and 20.1 wt%, respectively.After collecting the quantum dot powder, by means of redispersion The quantum dots can be dispersed in high concentration (20mg / mL) in a variety of solvents.When the 0.1wt% quantum dot is loaded on the PMMA film, the optical properties of the quantum dots can be greatly improved, which is higher than that of the films loaded with nanosheets An order of magnitude.The preparation technology has very good universality, provides a train of thought for large-scale production of two-dimensional quantum sheets.
Relevant research results have been published in Nano Letters on the topic of High-yield production of MoS2 and WS2 quantum sheets from their bulk materials, and the preparation method has been applied for a Chinese invention patent. The research was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences's Hundred Talents Program, Start-up funds and other funding.
Papers link
MoS2 and WS2 quantum chip preparation mechanism diagram Chinese Academy of Sciences website