Study on magneto-transport properties of semiconductor/magnetic-material heterostructures by ballistic electron emission microscopy

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The aim of this study is to explore the spin-dependent electron tunneling in semiconductor/magnetic-material nano-structures by using ballistic electron emission microscopy and spectroscopy (BEEM/BEES). The major results obtained are as follows.1.We have developed low temperature BEEM/BEES measurement systems, which make it possible that the whole the measurement procedures from sample preparation to LT-MEEM/BEES measurements under ultrahigh vacuum.2.On preparation of novel surface semiconductor/magnetic materials nano-structures(1)We have investigated Fe deposition on GaAs(001) surface with various surface reconstructions, and find that 4x6 reconstructed surfaces give most reliable Shottky contact.(2)In order to clarify the properties of MnAs and CrAs crystallized in zincblende structures, which is expected to have half-metallic band structures based on first principle calculation, surface structure model of GaAs(001) covered with sub-monolayer MnAs was presented based on STM observat … More ions and LEED IV analysis.(3)In order to prepare iron silicide related semiconductor/magnetic materials surface nanostructures, Fe deposition on Si surface was investigated. It was found that Ag-terminated Si(111)√<3>x√<3>-Ag surface allow us to prepare Fe_3Si nano-dot having 10-20 nm in diameter.3.BEES observations of GaAs(001)/Fe Schottky contacts with different Fe layer thickness reveal that electron attenuation length in Fe layers is to be ranging from 1.52 to 2.74 nm depending on electron energy, which is fairly longer than previous reports.4.Careful examination of GaAs(001)c(4x4) surfaces by RHEED rocking curve and LEED IV analysis reveals that GaAs(00l)c(4x4) is not single structure, and have at least two similar but different structures. Furthermore it was demonstrated that phase transition between them can be taken place even at substrate temperatures as low as 300℃ and that confusing behaviors of low temperature MBE growth on GaAs(001)c(4x4) surfaces seems to be well accounted base on its multi-structure nature of c(4x4) surfaces. Less