This 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.
