SPIN ELECTRONICS: Spintronics with Novel Half-Metals: Computational Design

该提案是根据21世纪自旋电子学倡议，项目招标NSF 02-036收到的。该方案的重点是计算设计以异质结、量子阱和由锌-闪锌矿结构的半金属化合物组成的量子点形式的新型量子结构，并将磁性和非磁性掺杂半导体作为自旋电子学的新材料。这些半金属化合物具有的独特特征是：(A)每种化合物的半金属性质在每个晶格常数的范围内都保持不变，(B)大磁矩（= 1 uB）， (C)高居里温度（= 400oK）， (D)由于半金属是化学计量化合物，因此与稀释磁掺杂半导体相比，本然散射更少（相干性更强）。它们激发了制造新型量子结构的独特机会。这项提议的结果将包括(1)自旋电子应用的量子结构的技术信息，(2)关于界面，表面对所提议的量子结构的磁性和电子性质的影响的特定科学知识，以及(3)作为抗表面活性剂生长半金属量子点的元素的选择。特别与(1)相关的是，pi将提供：(a)涉及铬和锰化合物与磁性和非磁性掺杂半导体的量子结构的组成，并表现出半金属行为作为新的自旋电子材料，(b)有前途的量子结构的磁性和电子特性，(c)制造自旋极化肖特基势垒的可能性，以及(d)在异质结和量子阱中进行弹道自旋输运的条件。对于(2)，这些信息将引导他们理解：(i)在掺杂各种半导体的半金属化合物的异质结和量子阱中是否形成自旋极化肖特基势垒，以及界面是否影响相应的半金属特性和磁矩？（ii）异质结金属自旋通道形成的肖特基势垒对其半导体自旋通道的影响是什么？（iii）在量子阱中形成的子带是否表现出电导的阶梯式特征？（iv）由半金属化合物制成的量子点的磁性如何取决于量子点的大小，以及阳离子端与阴离子端表面？最后，与(3)相关的结果将为促进锌-闪锌矿结构的半金属量子点的生长提供指导。

0225007FongThis proposal was received in response to the Spin Electronics for the 21st century Initiative, Program Solicitation NSF 02-036. The proposal focuses on the computational design of novel quantum structures in the forms of heterojunctions, quantum wells, and quantum dots composed of half-metallic compounds in zinc-blende structure with both magnetically and nonmagnetically doped semiconductors as new materials for spintronics. The unique features possessed by these half-metals compounds are: (A) the half metallic properties of each compound are preserved for a range of each lattice constant, (B) large magnetic moments (= 1 uB), (C) high Curie temperature (= 400oK), and (D) less intrinsic scattering (greater coherence) than for dilute magnetically doped semiconductors due to the fact that the half metals are stoichiometric compounds. They inspire a singular opportunity for making novel quantum structures. The outcome of this proposal will include (1) the technological information of quantum structures for spintronic applications, (2) specific scientific knowledge about the effects of interfaces, surfaces on the magnetic and electronic properties of the proposed quantum structures, and (3) the selections of elements serving as antisurfactants to grow half-metallic quantum dots. Specifically relevant to (1), The PIs will provide: (a) the compositions of quantum structures involving chromium and manganese compounds with magnetic and nonmagnetic doped semiconductors and exhibiting half-metallic behaviors as new spintronic materials, (b) the magnetic and electronic properties of the promising quantum structures, (c) the possibility of making spin polarized Schottky barriers, and (d) the conditions for ballistic spin transport in heterojunctions, and quantum wells. For (2), the information will lead them to understand: (i) Whether spin polarized Schottky barriers are being formed in heterojunctions and quantum wells made of half metal compounds with various doped semiconductors, and do the interfaces affect the corresponding half-metallic character and magnetic moment? (ii) What are the effects of the Schottky barrier formed by the metallic spin channel of a heterojunction on its semiconducting spin channel? (iii) Do subbands formed in a quantum well exhibit the stepwise feature in the conductance? (iv) How do the magnetic properties of a quantum dot made of a half-metal compound depend on the sizes of the dots, and on cation- versus anion-terminated surface? Finally, the results relevant to (3) will provide guidelines for facilitating the growth of quantum dots composed of half-metals with the zinc-blende structure.