NER: Nanoscale Molecular Spintronic Materials and Devices

该提案是为了响应纳米科学与工程倡议，计划征求NSF 01-157，在NER类别中提交的。 建议的重点是（a）。（B）有机/无机界面及其对自旋输运的影响。尽管自旋相关效应在各种金属和传统半导体中得到了广泛的研究，但在有机半导体中用于纳米器件应用的研究却很少。 使用有机半导体，特别是用于自旋电子学的π共轭半导体有两个主要优点。 首先，这些材料中的自旋弛豫时间相对较长，通常在室温下为微秒量级。 这是由制造这些半导体的轻原子和π电子波函数的小超精细相互作用引起的。 第二个优点是，载流子注入到有机半导体中的主要机制是通过隧穿，这保留了自旋状态，使得铁磁自旋对准器和半导体之间的电导失配的严重问题不那么麻烦。 此外，有机材料提供宽范围的功函数值，使得隧道势垒可以相对容易地被设计用于自旋相关的低隧穿电阻，这对于高密度信息存储和存储器应用是必不可少的。我们的可行性研究包括两种类型的纳米器件。 第一种类型是使用π共轭材料作为间隔物的平面自旋阀器件。 目的是探索具有高磁电阻的低隧道势垒自旋阀。 第二类是有机自旋发光器件，其中电致发光发射将由外部磁场调制。 预期发射光效率和磁场灵敏度的改善。 这两类器件涉及到新材料制造、精细光刻和新材料加工，具有高度的非平凡性和高风险性。PI和co-PI（Shi和Vardney）在磁性隧道结材料和纳米器件制造、聚合物合成、有机晶体生长、磁输运、光学和磁光学方面具有专业知识。 因此，两名研究生和两名本科生参加这个项目将在一个相当跨学科的领域得到良好的训练。

This proposal was submitted in response to the Nanoscale Science and Engineering Initiative, Program Solicitation NSF 01-157, in the NER category. The proposal focuses on (a). the fabrication of planar spin-valve and light-emitting devices using ferromagnetic eletrodes and pi-conjugated materials; (b) the study of organic/inorganic interfaces and the effect of the interfaces on spin-transport. Although spin-dependent effects have been widely studied in a variety of metals and conventional semiconductors, very little has been done in organic semiconductors for nanoscale device applications. There are two main advantages for using organic semiconductors, in particular pi-conjugated semiconductors for spin-electronics. Firstly, the spin relaxation time in these materials is relatively long, typically of the order of a microsecond at room temperature. This is caused by the light atoms from which these semiconductors are made and the small hyperfine interaction of the pi-electron wave function. The second advantage is that the main mechanism for carrier injection into organic semiconductors is by tunneling, which preserves spin states, so that the acute problem of conductance mismatch between the ferromagnetic spin aligner and the semiconductor is less troublesome. In addition, organic materials offer a wide range of work function values so that the tunnel barrier can be relatively easily engineered for spin-dependent low tunneling resistance, which is essential for high-density information storage and memory applications. Our feasibility study consists of two types of nanoscale devices. The first type is the planar spin-valve devices using pi-conjugated materials as a spacer. The objective is to explore low tunnel barrier spin-valves with high magnetoresistance. The second type is the organic spin light-emitting devices, where the electroluminescence emission will be modulated by an external magnetic field. The improved emitted light efficiency and magnetic field sensitivity are anticipated. These two types of devices involve with new material fabrication, fine lithography, and new material processing, which are highly non-trivial and of high risk. The PI and co-PI (Shi and Vardney) have expertise in magnetic tunnel junction materials and nanoscale device fabrication, polymer synthesis, organic crystal growth, magneto-transport, optics, and magneto-optics. Thus the two graduate students and two undergraduate students participating in this project will be well-trained in a rather interdisciplinary field.