分子器件的研究进展

分子器件作为下一代电子器件近年来得到了迅速的发展．文章回顾了分子器件的发展历程和研究现状，并重点对分子导线、分子开关、分子整流器和分子晶体管等器件进行了介绍。     

分子器件

本文对分子器件的概念和研究目标作了描述，并对分子导线、分子开关、分子整流器、分子存储器、分子计算机当前的研究状况和存在问题作了简单介绍．     

D-B-A分子整流特性的端基效应

利用密度泛函理论和非平衡格林函数方法,研究了基于同一D-B-A分子在改变端基后形成的4个不同的分子器件的电子输运特性及整流效果.研究表明:端基的改变,能明显影响分子器件的整流效果,这是因为端基能影响分子与电极的耦合程度,从而改变了分子轨道的离域性,进而影响分子的电子输运特性及整流效果.更有趣的是,由于分子轨道HOMO和LUMO随偏压极性不同的非对称移动,导致整流器的整流方向与Aviram和Ratner分子整流器相反. 关键词： 分子整流器 端基 密度泛函理论 非平衡格林函数     

分子整流器整流特性的键桥调控效应

利用密度泛函理论和非平衡格林函数方法,研究了基于同一分子在不同空间构型下形成的三个不同分子器件的电子输运特性及整流效果. 研究表明:旋转中间苯环(键桥——π桥),能明显改变整流效果,这是因为改变了分子轨道的离域性,这一发现说明通过改变键桥的空间取向能有效地调控分子整流器的整流性质,这对于设计新型分子整流器有重要意义. 关键词： 分子整流器 键桥 密度泛函理论 非平衡格林函数     

中国科技大学制成新型单分子整流器

日前，中国科学技术大学微尺度物质科学国家实验室在富勒烯单分子研究中又获重要进展．他们成功得将富勒烯单分子中的一个碳原子用氮原子取代，并利用单电子隧穿效应，研制成仅由一个分子组成的新型单分子整流器．该分子器件有着和传统单分子整流器不同的工作原理，在重复性和可控性方面有着明显的优势。     

分子电子学

 一、什么是分子电子学分子电子学(molecularelectronics),是指用有机功能材料的分子构筑电子线路的各种元器件,如分子开关、分子整流器、分子晶体管等,并测量和解析这些分子尺度元器件的电特性或光特性的一门学科。20世纪是无机半导体的世纪,21世纪将是有机分子电子学的世纪。科学家们根据摩尔定律预测,无机半导体集成电路的发展,将在2020年左右达到极限。随着人类进入信息时代,电子技术要求器件和系统向“更小”“更快”“更冷”的方向发展。     

基于石墨烯电极的齐聚苯乙炔分子器件的整流特性

以齐聚苯乙炔分子为研究对象,采用密度泛函理论与非平衡格林函数相结合的第一性原理方法,对基于石墨烯电极的齐聚苯乙炔分子器件整流特性进行了研究,系统地分析了官能团对分子器件整流特性的影响.通过研究发现,官能团对齐聚苯乙炔分子器件整流特性影响显著,当添加失电子官能团氨基(NH_2)时出现正向整流,添加得电子官能团硝基(NO_2)时出现反向整流,当同时添加氨基和硝基官能团时,会出现正反向整流交替现象,研究结果表明通过添加不同类型的官能团能有效控制分子整流器的整流特性.     

超分子有机薄膜

利用超分子有机薄膜技术能制成新的传感分子电子器件、光学器件和生物分子器件等，受到跨学科高技术研究领域的重视。本文描述了超分子有机薄膜的制备方法以及在各应用领域的研究状况。重点介绍了我们研究组在近20年工作中，利用LB膜技术，在光电器件、气体传感技术和光学非线性，特别是在生物传感技术方面的研究成果。按照生物体系提供的信息，模拟合成功能分子，建造有组织的分子组装体，以便用来研究依赖于分子排列的生物物理化学效应。     

分子电子器件简介

分子电子３器件是新近发展起来的研究领域之一，从化学分子结构的观点简单说明了用于分子电子器件的功能材料的特征，对这些功能分子进行有序组装的技术，以及分子电子元件的功能，并列举了几个简单的器件模型。     

分子整流器的共振隧道效应

讨论了分子整流相关的Ｌａｎｇｍｕｉｒ－Ｂｌｏｄｇｅｔｔ膜的共振隧道效应和单分子、双分子整流器等分子整流概念。这种整流器的整流机制不同于Ａｖｉｒａｍ－Ｒａｔｎｅｒ提出的原始分子整流器模型，也不同于普通半导体的ｐ－ｎ结的整流理论。在这种新概念中，只有整流分子的成键轨道对整流有贡献，而反键轨道在外加偏压时不参与载流子传输。     

Self-assembled and electrochemically deposited mono/multilayers for molecular electronics applications

For the development of molecular electronics, it is desirable to investigate characteristics of organic molecules with electronic device functionalities. In near future, such molecular devices could be integrated with silicon to prepare hybrid nanoelectronic devices. In this paper, we review work done in our laboratory on study of characteristics of some functional molecules. For these studies molecular mono and multilayers have been deposited on silicon surface by self-assembly and electrochemical deposition techniques. Both commercially available and specially designed and synthesized molecules have been utilized for these investigations. We demonstrate dielectric layers, memory, switching, rectifier and negative differential resistance devices based on molecular mono and multilayers.     

Rectifying behavior in Coulomb blockades: charging rectifiers

We introduce examples of tunneling and diffusive, Coulomb-regulated rectifiers based on the Coulomb blockade formalism in discrete and continuum systems, respectively. Nonlinearity of the interacting dynamics profoundly enhances the inherent asymmetry of the devices by reducing the Hilbert space of accessible states. The discrete charging rectifier is structurally similar to hybrid molecular electronic rectifiers, while the continuum-charging rectifier is based on a model of ionic flow through a pore (ion channel) with an artificial branch. The devices are formally related to ratchet systems with spatial periodicity replaced by a winding number: the current.     

Molecular scale electronic devices using single molecules and molecular monolayers

Molecular electronic devices that utilize single molecules or molecular monolayers as active electronic components represent a promising approach in the ongoing miniaturization and integration of electronic devices. Rapid advances in technology have enabled us to engineer molecular electronic devices with diverse functionalities. Significant progress has been made in understanding charge transport in molecular systems at the single-molecule level, and concomitantly, new device concepts have emerged. This review article focuses on experimental aspects of electronic devices made with single molecules or molecular monolayers, with a primary focus on the characterization and manipulation of charge transport.     

A microfluidic rectifier: anisotropic flow resistance at low Reynolds numbers

It is one of the basic concepts of Newtonian fluid dynamics that at low Reynolds number (Re) the Navier-Stokes equation is linear and flows are reversible. In microfluidic devices, where Re is essentially always low, this implies that flow resistance in microchannels is isotropic. Here we present a microfluidic rectifier: a microscopic channel of a special shape whose flow resistance is strongly anisotropic, differing by up to a factor of 2 for opposite flow directions. Its nonlinear operation at arbitrary small Re is due to non-Newtonian elastic properties of the working fluid, which is a 0.01% aqueous solution of a high molecular weight polymer. The rectifier works as a dynamic valve and may find applications in microfluidic pumps and other integrated devices.     

Controlling charge current through a DNA based molecular transistor

Molecular electronics is complementary to silicon-based electronics and may induce electronic functions which are difficult to obtain with conventional technology. We have considered a DNA based molecular transistor and study its transport properties. The appropriate DNA sequence as a central chain in molecular transistor and the functional interval for applied voltages is obtained. I–V characteristic diagram shows the rectifier behavior as well as the negative differential resistance phenomenon of DNA transistor. We have observed the nearly periodic behavior in the current flowing through DNA. It is reported that there is a critical gate voltage for each applied bias which above it, the electrical current is always positive.     

Rectification effect for spin- and charge-currents in a shuttled molecule transistor

We have investigated the spin-dependent electronic transports through a shuttled molecule, a molecule self-excitedly oscillating due to suffering an external electric field. When the shuttled molecule is coupled asymmetrically to a ferromagnetic and a normal metal leads, a pronounced dual rectification effect is predicted for both spin- and charge-currents in the Coulomb blockade regime. As compared to the conventional rectifier based on a static quantum dot, the proposed rectifier based on a movable individual molecule has higher rectification efficiency.     

Overview of CMOS image sensor use in molecular diagnostics

CMOS sensors comprise an important tool in bioscientific applications. This review focuses on CMOS sensor-based molecular diagnostics of DNA, protein, and metabolic molecules. Herein, gene sequencing, DNA–DNA hybridization, single nucleotide polymorphisms (SNP), protein interactions, peptide interactions, antigen–antibody (Ag–Ab) interactions, as well as glucose and cholesterol monitoring using CMOS sensors are discussed along with existing experimental outcomes. CMOS sensor based electrochemical, optical, impedance, dual, continuous, and label-free analysis and their related integration techniques are explained. Moreover, we describe the utilization of a CMOS chip in microarray fabrication, assay platform development, and transducer incorporation for molecular diagnostics. Furthermore, CMOS sensor-based point-of-care (POC) applications, other biological analyses, and the role of nanoparticles in biomolecular sensing are discussed. Future directions include information about the novel integration of CMOS sensor-based molecular diagnostic devices with a central focus towards enhancement of POC approaches. This review is helpful in creating highly sensitive, cheaper, and user-friendly biomedical devices with modern dimensions.     

NEMS/MEMS tools for nanoelectronics development

Present information technologies use semiconductor devices and magnetic/optical discs, however, they are all foreseen to face fundamental limitations within a decade. Therefore, superseding devices are required for the next paradigm of high performance information technologies. This paper describes prospects for single molecule devices suitable for future information processing technologies. Possible four milestones for realizing the Peta (P: 10¹⁵)/Exa (E: 10¹⁸)––floating operations per second (FLOPS) personal molecular supercomputer are proposed. Current status and necessary technologies of the first milestone are described, and necessary technologies for the next three milestones are also discussed.     

Electronic properties of organic monolayers and molecular devices

We review some of our recent experimental results on charge transport in organic nanostructures such as self-assembled monolayer and monolayers of organic semiconductors. We describe a molecular rectifying junction made from a sequential self-assembly on silicon. These devices exhibit a marked current-voltage rectification behavior due to resonant transport between the Si conduction band and the π molecule highest occupied molecular orbital of the π molecule. We discuss the role of metal Fermi level pinning in the current-voltage behavior of these molecular junctions. We also discuss some recent insights on the inelastic electron tunneling behavior of Si/alkyl chain/metal junctions.