Science China Information Sciences最新文献

Over the past 70 years, the semiconductor industry has undergone transformative changes, largely driven by the miniaturization of devices and the integration of innovative structures and materials. Two-dimensional (2D) materials like transition metal dichalcogenides (TMDs) and graphene are pivotal in overcoming the limitations of silicon-based technologies, offering innovative approaches in transistor design and functionality, enabling atomic-thin channel transistors and monolithic 3D integration. We review the important progress in the application of 2D materials in future information technology, focusing in particular on microelectronics and optoelectronics. We comprehensively summarize the key advancements across material production, characterization metrology, electronic devices, optoelectronic devices, and heterogeneous integration on silicon. A strategic roadmap and key challenges for the transition of 2D materials from basic research to industrial development are outlined. To facilitate such a transition, key technologies and tools dedicated to 2D materials must be developed to meet industrial standards, and the employment of AI in material growth, characterizations, and circuit design will be essential. It is time for academia to actively engage with industry to drive the next 10 years of 2D material research.

This paper is concerned with event-triggered H_∞ control of sampled-data systems. Its novelties lie in three aspects: (i) A novel accumulated-state-error-based event-triggered scheme is introduced by comparing the integral of the state error from t_k to t with the system state sampled at t_k. This condition works well due to the fact that the so-called Zeno behaviour does not occur. (ii) A novel Lyapunov functional is constructed to establish a criterion to ensure some certain H_∞ performance of the closed-loop system. This Lyapunov functional is dependent on the integral of the state error involved in the event-triggered scheme. (iii) Under the event-triggered sampling scheme, suitable state-feedback controllers can be designed rather than be given a priori. Moreover, a self-triggered implementation of the proposed event-triggered sampling scheme is presented as well. Finally, a batch reactor model and an inverted pendulum system are given to demonstrate the effectiveness of the proposed method.

This paper explores covert broadcast communication in a challenging situation in which the transmitter, Alice, faces uncertainty regarding the position of the passive adversary, Willie. In this situation, controlling the signal exposure becomes difficult. Specifically, this paper focuses on the cases where Alice can delimit the suspicious areas where Willie may be located. The suspicious areas can have arbitrary number and shapes. Under the Rician fading model, the analytical expression of Willie’s detection performance is derived. Then, the transmit power, the beamforming direction, and the number of channel uses are jointly designed to minimize the optimal Willie’s detection performance among all the possible positions of Willie, on the premise of satisfying receivers’ quality-of-service requirements. To tackle the formulated knotty problem with an infinite number of irregular and discontinuous Willie’s possible positions, the continuous nature of the antenna pattern is exploited to convert the original problem into the one with a finite number of possible positions, by sampling the suspicious areas. Then, different algorithms are developed to address the resultant non-convex optimization problem for single-antenna Willie and multi-antenna Willie, respectively. Numerical results demonstrate significant performance gains of the proposed scheme over the widely-adopted maximum ratio transmission scheme, which indicates that simply adjusting the main lobe towards the receiver is indeed far away from optimum and shows the importance of leveraging Alice’s limited knowledge of Willie’s position.

Two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductor materials exhibit extraordinary electrical properties, holding promise for the realization of next-generation complementary metal-oxide-semiconductor (CMOS) devices at ultimate scaling. However, constrained by effective device doping strategies, the hole mobility and device performance of tungsten diselenide (WSe₂) p-type transistors, especially monolayer chemical vapor deposition (CVD)-grown WSe₂, have not met expectations. In this paper, an effective performance enhancement of monolayer WSe₂ p-type transistor was achieved through a molecular doping strategy. Synthesizing monolayer WSe₂ directly on SiO₂ back-gated substrates and leveraging energy band alignment design, 4-nitrobenzenediazonium tetrafluoroborate (4-NBD) molecular dopant with a concentration of 10 mM was utilized to modulate the Fermi level position of monolayer WSe₂ for hole doping. The devices demonstrated a more than 98% increase in hole mobility, reaching up to 97 cm² · V⁻¹ · s⁻¹ while maintaining the current on/off ratio of 10⁸. Monolayer p-type WSe₂ transistors with 1 µm channel length exhibit a high drive current surpassing 176 µA · µm⁻¹, exceeding previous CVD-WSe₂ devices with similar channel length. This straightforward and effective approach to improving the electrical performance of WSe₂ transistors paves the way for advanced logic technologies based on transition metal dichalcogenide semiconductors.

Extremely large-scale antenna array (ELAA) at millimeter wave (mmWave) and Terahertz (THz) band has been considered a key technology for combating high attenuation in high-frequency bands in future 6G communications. Uniform circular arrays (UCAs) have attracted much attention because of their ability to provide flat beamforming gain at all angles. To realize efficient beamforming, beam training is widely used to acquire channel state information. However, with a large antenna number, the beam training overhead in ELAA systems becomes overwhelming. Moreover, with a large bandwidth, the beam defocus effect severely degrades beam training accuracy. To address these issues, this paper proposes a frequency-dependent focusing (FDF)-based beam training scheme to realize effective beam training in near-field wideband ELAA systems with UCA. Specifically, we first analyze the FDF property of UCA, where signals at different subcarriers can simultaneously focus on different distances. Then, by exploiting the FDF property to search different distances using different subcarriers simultaneously, we design a hierarchical codebook and propose an FDF-based beam training scheme. To reveal the effectiveness of the proposed scheme, we compare its necessary beam training overhead with that of existing schemes. Finally, the simulation results demonstrate that the proposed scheme can achieve accurate beam training in near-field wideband UCA systems with a low beam training overhead.

This work demonstrates a high-precision in-plane two-axis GMR angle sensor is prepared by post-annealing. The pinning direction of the GMR strips is modulated by annealing two times to achieve orthogonal sensitive directions of the two sensors. The sensitivity of a full-bridge sensor is 6.59 mV/V/mT, with the sensing direction along the Y-axis and the sensitivity of a half-bridge GMR sensor is 1.68 mV/V/mT with the sensing direction along the X-axis. A simulation of the two-axis sensor output with the field has been performed, which proves the correctness of the P2 direction measured by the angle test. The detectivity of the full-bridge sensor is 22 nT/(Hz)^0.5 at 10 Hz and it is 88 nT/(Hz)^0.5 at 10 Hz for half-bridge sensor. The orthogonality error of the two-axis sensor for the geomagnetic angle detection is lower than 0.04. The sensor in this study demonstrates higher detectivity than some commercial GMR sensors, such as YAS532 produced by Yamaha and HSCDTD008A produced by ALPS. This work proposes an efficient and simple method for producing two-axis GMR angle sensors, which can be a promising solution for mass production.

Hardware components can cause different impairments, including power amplifier (PA) non-linearities, which inevitably impact the system performance of satellite communications (SATCOM). In this work, we consider a multi-beam SATCOM downlink system and investigate the distortion-aware beamforming scheme with the characteristics of PA non-linearities. Notably, we aim to maximize the resource efficiency (RE), defined as the weighted sum of energy efficiency (EE) with spectral efficiency (SE), to obtain a flexible EE-SE tradeoff while accounting for the characteristics of PA distortion and the total power constraints. Given that the optimization objective is a sum of ratios and the high non-convexity involved in constraints, we propose an efficient approach that exploits the quadratic transformation, the Lagrange multiplier method, and the gradient ascent approach to handle this issue. Simulation results demonstrate the effectiveness of the distortion-aware beamforming approach in achieving the EE-SE tradeoff and exhibit a substantial RE performance gain over the conventional approach with ideal linear PAs assumed at the satellite transmitters.

Exploration targeting outer planets and even the edge of the solar system is an emerging direction for the deep-space exploration in the next decades. To address this challenge, a novel two-layer Lagrange-based relay network topology is proposed in this study. Specifically, we utilize the Sun-Mars and Sun-Saturn Lagrange points (LPs) L4 and L5 to build a two-layer backbone relay network, which ensures continuous and high-efficiency communication capability for the exploration of the solar system. Furthermore, we utilize the planetary gravity assist and design the transfer trajectory of backbone relays with the help of planetary celestial body motion equations and Kepler’s laws. Moreover, we conduct link budget analysis for multihop relay transmission under Gamma-Gamma distribution, shadowed Rician fading, and additive white Gaussian noise channels in several typical exploration scenarios and validate that the LP relays can effectively support future deep-space exploration missions.

NOMA assisted NGMA has been envisioned in the recently published IMT-2030 Framework. This perspective has outlined three important features of NOMA assisted NGMA, namely multi-domain utilization, multi-mode compatibility, and multi-dimensional optimality, where important directions for future research into the design of NOMA assisted NGMA have also been discussed.

Two-dimensional (2D) materials are at the forefront of innovation, heralding a new era for next-generation electronics and optoelectronics. These materials are distinguished by their unique structural characteristics: they have no hanging bonds on their surface, exhibit weakened electrostatic shielding in the Z-direction, and boast atomic thickness in their monolayers. These features have led to groundbreaking discoveries in electrical, optical, and magnetic properties, paving the way for advancements in low-power electronics, valleytronics, infrared detectors, and memory devices. Despite these promising developments, Si-based technologies continue to dominate the landscape of next-generation electronics and optoelectronics, as well as heterogeneous integration. In response to this ongoing evolution, the National Natural Science Foundation of China (NSFC) initiated a major program in 2021 dubbed “Si-compatible two-dimensional semiconductor materials and devices”. This study reviews the progress made under the NSFC Program, spotlighting its main achievements and outlining key future research directions. Additionally, it sheds light on the challenges that researchers in the 2D domain face, particularly in developing Si-compatible 2D technologies.