|1.Research Institution||Tohoku University|
|2.Research Area||Physical and Engineering Sciences|
|3.Research Field||Atomic- scale Surface and Interface Dynamics|
|4.Term of Project||FY 1997 〜 FY 2001|
|6.Title of Project||Atomic Scale Dynamics of Non-Equilibrium Surface Layers and Synthesis of New Materials|
|Name||Institution,Department||Title of Position|
|Hideo, Ohno||Tohoku University, Research Institute of Electrical Communication||Professor|
|Names||Institution,Department||Title of Position|
|Junichi, Murota||Tohoku University, Research Institute of Electrical Communication||Professor|
|Masaaki, Tanaka||The University of Tokyo, Graduate School of Engineering||Associate Professor|
|Tadashi, Itoh||Osaka University, Graduate School of Engineering||Professor|
9.Summary of Research Results
(1) Integration of Magnetic Materials and Semiconductors: Dynamics of non-equilibrium surface
layers during MBE was investigated by in-situ techniques and modeled by Monte Carlo
simulations. Using low-temperature MBE, new ferromagnetic semiconductors and materials
such as GaMnSb and CrSb and their heterostructures were synthesized. Also established are 1)
the origin of ferromagnetism in semiconductors, 2) electrical spin injection into semiconductors,
and 3) tunnel magnetoresistance and spin-dependent scattering in semiconductor trilayers. By
these, we succeeded in establishing the foundations of semiconductor spintronics.
(2) Integration of Insulators and Semiconductors: Established that the adsorption-reaction processes of hydrogenated gas species on Si and Ge surfaces are described systematically by the Langmur type process. Atomic layer epitaxy, insulating layer formation by carbonization and nitridation, and Si epitaxy on C/P/N terminated Si surfaces are also established. Processes for ultrasmall SiGe heterojunction devices were developed and devices were made.
(3) Integration of Metals and Semiconductors: Metal-semiconductor epitaxial heterostructures using semimetal ErAs, ferromagnetic metal MnAs and III-V compounds (GaAs, AlAs) were realized with an atomic level thickness control. Devices such as resonant tunneling diodes, spin valves, and magnetooptical devices were also made.
(4) Characterization and Control of Atomic Level Dynamics of Non-equilibrium Surface Layers: Electronic excited states as well as vibrational states at interfaces were investigated by local spectroscopy of GaAs, ZnCdSe, and CuCl single quantum dots. Enhancement of the third order nonlinear optical susceptibility was realized in CuCl quantum dots grown on CaF2(111) by MBE.
(5) Materials Design for Non-equilibrium Growth: Based on first-principle calculations, electronic structures and material design of magnetic semiconductors based on II-VI compounds like ZnO and III-V compounds like GaAs were established.
(4)Semiconductor spintronics、(5)Atomic level processing、(6)Local spectroscopy
(7)Material design、(8)First principle calculation、(9)Non-equilibrium surface layer