Interlayer Band‐to‐Band Tunneling and Negative Differential Resistance in van der Waals BP/InSe Field‐Effect Transistors

Atomically thin layers of van der Waals (vdW) crystals offer an ideal material platform to realize tunnel field‐effect transistors (TFETs) that exploit the tunneling of charge carriers across the forbidden gap of a vdW heterojunction. This type of device requires a precise energy band alignment of the different layers of the junction to optimize the tunnel current. Among 2D vdW materials, black phosphorus (BP) and indium selenide (InSe) have a Brillouin zone‐centered conduction and valence bands, and a type II band offset, both ideally suited for band‐to‐band tunneling. TFETs based on BP/InSe heterojunctions with diverse electrical transport characteristics are demonstrated: forward rectifying, Zener tunneling, and backward rectifying characteristics are realized in BP/InSe junctions with different thickness of the BP layer or by electrostatic gating of the junction. Electrostatic gating yields a large on/off current ratio of up to 10⁸ and negative differential resistance at low applied voltages (V ≈ 0.2 V). These findings illustrate versatile functionalities of TFETs based on BP and InSe, offering opportunities for applications of these 2D materials beyond the device architectures reported in the current literature.     

The Overlapped Electron‐Cloud Model for Electron Transfer in Contact Electrification

Contact electrification (CE) is one of the oldest topics in physics, which has been discussed for more than 2600 years. Recently, an overlapped electron‐cloud (OEC) model was proposed by Wang to explain all types of CE phenomena for general materials in which a deep overlapping of electron clouds belonging to two atoms results in a lowered potential barrier for electron transfer from one to the other by applying a compressive force, which is simply referred to as Wang transition for CE. Here, the degree of electron‐cloud overlap between two atoms is controlled by using tapping mode atomic force microscopy. A temperature difference and electric field are applied between atoms of two surfaces. It is found that electron transfer only occurs when the contact tip and sample interact in the repulsive‐force region, which corresponds to a strong overlap of the electron clouds. Such a fact even preserves if the tip is at a higher temperature than the sample for 120 K. Alternatively, by applying a bias, electron tunneling would occur when the tip is in the attractive‐force region within which normal electron transfer would not occur. These studies solidify the overlapped electron‐cloud model first proposed by Wang. Further, the temperature and bias effects on the CE are explained based on a modified OEC model.     

校区间资源共享的研究与实施——以南京铁道职业技术学院为例

为了将南京铁道学院南京校区与苏州校区独立的内网连成一个局域网,利用VPN的技术优势,应用IPSec协议实现两个内网的安全互连,从而保证了其通信的保密性、实时性和防攻击性.校区间资源共享的研究与实施为学院节省了大量的资金,为两校区的真正融合创造了有利的技术条件.     

基于高性能计算的CAE技术在大型盾构施工仿真中的应用

为加强盾构施工的风险提示及防范措施,在总结近几年研究成果的基础上,建立大规模三维数值模型,对泥水盾构施工的各种复杂施工步骤和环境因素进行拟实和简化模拟.在模拟过程中使用"曙光"超级计算机和ANSYS并行求解器,保证大量计算工况的前、后处理及求解分析.2条长江隧道的盾构施工数值仿真表明,该方法能有效预测盾构推进引起的土层...     

基于最大最小距离和动态隧道的聚类算法

针对K-means聚类算法对初值敏感和易陷入局部最小值的缺陷,提出了一种基于最大最小距离和动态隧道的聚类算法.该算法首先利用最大最小距离法来优选初始聚类中心以避免由于聚类中心过于随机而导致其分布较为集中的情形,以提高划分初始数据集的效率.动态隧道法具有全局寻优能力,利用钻隧过程可跳出局部极小点得到更小值点,再由K-means聚类算法对其迭代优化,如此反复直至得到全局极值.实验结果表明了该算法的可行性和有效性.     

浅谈盾构机在复杂地质条件下穿越高压燃气管道的施工技术

盾构机法施工是我国地下隧洞工程施工中非常普遍的一种工艺方法。本文介绍了盾构机穿越南水北调工程地下垃圾填埋区内高压燃气管道的施工技术。通过地层加固和盾构机参数控制等措施,确保了盾构机安全顺利穿越垃圾填埋区及高压燃气管道,可供其他类似工程参考借鉴。     

IPv4与IPv6相互转换技术研究

IP是互联网基础协议,IPv4协议的缺陷逐步暴露出来,而IPv6具有巨大的优越性,但IPv4协议与IPv6协议不相同,如果两种网络互操作,必须进行相互转换。IPv4与IPv6转换技术主要分为双协议栈技术、隧道技术和翻译技术。     

Massive Dirac Fermion Behavior in a Low Bandgap Graphene Nanoribbon Near a Topological Phase Boundary

Graphene nanoribbons (GNRs) have attracted much interest due to their largely modifiable electronic properties. Manifestation of these properties requires atomically precise GNRs which can be achieved through a bottom–up synthesis approach. This has recently been applied to the synthesis of width-modulated GNRs hosting topological electronic quantum phases, with valence electronic properties that are well captured by the Su–Schrieffer–Heeger (SSH) model describing a 1D chain of interacting dimers. Here, ultralow bandgap GNRs with charge carriers behaving as massive Dirac fermions can be realized when their valence electrons represent an SSH chain close to the topological phase boundary, i.e., when the intra- and interdimer coupling become approximately equal. Such a system has been achieved via on-surface synthesis based on readily available pyrene-based precursors and the resulting GNRs are characterized by scanning probe methods. The pyrene-based GNRs (pGNRs) can be processed under ambient conditions and incorporated as the active material in a field effect transistor. A quasi-metallic transport behavior is observed at room temperature, whereas at low temperature, the pGNRs behave as quantum dots showing single-electron tunneling and Coulomb blockade. This study may enable the realization of devices based on carbon nanomaterials with exotic quantum properties.     

Lateral Heterostructures of Graphene and h-BN with Atomic Lattice Coherence and Tunable Rotational Order

In-plane heterostructures of graphene and hexagonal boron nitride (h-BN) exhibit exceptional properties, which are highly sensitive to the structure of the alternating domains. Nevertheless, achieving accurate control over their structural properties, while keeping a high perfection at the graphene-h-BN boundaries, still remains a challenge. Here, the growth of lateral heterostructures of graphene and h-BN on Rh(110) surfaces is reported. The choice of the 2D material, grown firstly, determines the structural properties of the whole heterostructure layer, allowing to have control over the rotational order of the domains. The atomic-scale observation of the boundaries demonstrates a perfect lateral matching. In-plane heterostructures floating over an oxygen layer have been successfully obtained, enabling to observe intervalley scattering processes in graphene regions. The high tuning capabilities of these heterostructures, along with their good structural quality, even around the boundaries, suggest their usage as test beds for fundamental studies aiming at the development of novel nanomaterials with tailored properties.