Emerging properties of non-crystalline phases of graphene and boron nitride based materials

We review recent developments on the synthesis and properties of two-dimensional materials which, although being mainly of an sp^(2) bonding character, exhibit highly disordered, non-uniform and structurally random morphologies. The emergence of such class of amorphous materials, including amorphous graphene and boron nitride, have shown superior properties compared to their crystalline counterparts when used as interfacial films. In this paper we discuss their structural,vibrational and electronic properties and present a perspective of their use for electronic applications.

Charge Transport in Disordered Graphene-Based Low Dimensional Materials

Two-dimensional graphene,carbon nanotubes,and graphene nanoribbons represent a novel class of low dimensional materials that could serve as building blocks for future carbon-based nanoelectronics.Although these systems share a similar underlying electronic structure,whose exact details depend on confi nement effects,crucial differences emerge when disorder comes into play.In this review,we consider the transport properties of these materials,with particular emphasis on the case of graphene nanoribbons.After summarizing the electronic and transport properties of defect-free systems,we focus on the effects of a model disorder potential(Anderson-type),and illustrate how transport properties are sensitive to the underlying symmetry.We provide analytical expressions for the elastic mean free path of carbon nanotubes and graphene nanoribbons,and discuss the onset of weak and strong localization regimes,which are genuinely dependent on the transport dimensionality.We also consider the effects of edge disorder and roughness for graphene nanoribbons in relation to their armchair or zigzag orientation.

Highly defective graphene： A key prototype of two- dimensional Anderson insulators

Electronic structure and transport properties of highly defective two-dimensional （2D） sp2 graphene are investigated theoretically. Classical molecular dynamics are used to generate large graphene planes containing a considerable amount of defects. Then, a tight-binding Hamiltonian validated by ab initio calculations is constructed in order to compute quantum transport within a real-space order-N Kubo-Greenwood approach. In contrast to pristine graphene, the highly defective sp2 carbon sheets exhibit a high density of states at the charge neutrality point raising challenging questions concerning the electronic transport of associated charge carriers. The analysis of the electronic wavepacket dynamics actually reveals extremely strong multiple scattering effects giving rise to mean free paths as low as 1 nm and localization phenomena. Consequently, highly defective graphene is envisioned as a remarkable prototype of 2D Anderson insulating materials.

Large edge magnetism in oxidized few-layer black phosphorus nanomeshes

The formation and control of a room-temperature magnetic order in two- dimensional （2D） materials is a challenging quest for the advent of innovative magnetic- and spintronic-based technologies. To date, edge magnetism in 2D materials has been experimentally observed in hydrogen （H）-terminated graphene nanoribbons （GNRs） and graphene nanomeshes （GNMs）, but the measured magnetization remains far too small to allow envisioning practical applications. Herein, we report experimental evidences of large room-temperature edge ferromagnetism （FM） obtained from oxygen （O）-terminated zigzag pore edges of few-layer black phosphorus （P） nanomeshes （BPNMs）. The magnetization values per unit area are -100 times larger than those reported for H-terminated GNMs, while the magnetism is absent for H-terminated BPNMs. The magnetization measurements and the first-principles simulations suggest that the origin of such a magnetic order could stem from ferromagnetic spin coupling between edge P with O atoms, resulting in a strong spin localization at the edge valence band, and from uniform oxidation of full pore edges over a large area and interlayer spin interaction. Our findings pave the way for realizing high-efficiency 2D flexible magnetic and spintronic devices without the use of rare magnetic elements.

Quantum Transport Properties of Chemically Functionalized Long Semiconducting Carbon Nanotubes

We present a first-principles study of the electronic transport properties of micrometer long semiconducting carbon nanotubes randomly covered with carbene functional groups. Whereas prior studies suggested that metallic tubes are hardly affected by such addends, we show here that the conductance of semiconducting tubes with standard diameter is, on the contrary, severely damaged. The configurational-averaged conductance as a function of tube diameter, with a coverage of up to one hundred molecules, is extracted. Our results indicate that the search for a conductance-preserving covalent functionalization route remains a challenging issue.

装入CPLD/FPGA的步进电机运动控制器与驱动器

本设计实例进一步拓展了以前将步进电机驱动器集成到CPLD中的设计（参考文献1）。本实例不仅集成了驱动器．而且还集成了一个简单的单轴步进电机运动控制器。根据CPLD大小，可以将多个运动控制器设计到单一设备中。例如，单轴运动控制器采用68％或63％的可用宏单元设计到Xilinx XC95108中。运动控制器以确定的速度与时间曲线顺时针或逆时针旋转步进电机指定的步数。运动开始时，控制器对电机加速，直到其达到巡航速度，然后减速直到停止（图1）。

用CPLD实现步进电机驱动器

本设计实例基于摩托罗拉（现为飞思卡尔）广为使用但已淘汰的SAA1042步进电机驱动器JC，用一片CPLD（复杂可编程逻辑器件）实现了步进电机驱动器．它也可以代替基于SAA1027或UCN5804B设计中的驱动器。本设计只使用了Xilinx XC9536CPLD中的6个宏单元，因此可以在一个小容量CPLD中实现多个步进电机驱动器。CPLD步进电机驱动器需要时钟、方向、步长和复位输入。时钟输入接受逻辑电平脉冲．并在脉冲正沿上有效。