Despite superior compatibility to mass-production, magnetic tunnel junction (MTJ) with MgO barrier prepared by oxidation process (MgO x ) has shown unacceptable magnetotransport properties for proper operation of spintronics devices because poor crystalline MgO x cannot properly provide a template for crystallization of amorphous CoFeB layers, thus lack of pseudo-epitaxy in overall. We report novel stack structure for MgO x -based MTJ to assure acceptable magnetotransport properties: insertion of preferred-grain-growth-promotion (PGGP) seed layer and bi-layered ferromagnetic pinned layer (bi-PL) to induce preferred grain growth in MgO x and crystallization of CoFeB layers at higher temperature annealing. Microstructure analysis confirms highly crystalline MgO x in pseudo-epitaxy with fully crystallized CoFeB via PGGP by high temperature annealing, attributed to enhanced thermal stability of bi-PL. Tunneling magnetoresistance (TMR) 132.6% at resistance-area product (RA) 1.2 mm 2 and 253% at 5.9 mm 2 from novel MTJ stack successfully satisfy specifications for spintronics devices.

Surface structures of Ni adsorbed on the Mo(110) surface have been studied using reflection high energy electron diffraction (RHEED). The surface phase diagram of Ni on the Mo(110) surface for annealing temperature vs Ni coverage has been completed. Both a two-dimensional layer and three-dimensional islands were observed in a thickness region of more than 1 ML (1 ML = 2.0 Å) and at annealing temperatures between 650°C and 850°C showing the Nishiyama-Wassermann orientation relationship on the Mo(110) substrate. The structure of the two-dimensional layer has a unit mesh of the distorted Ni(111) plane which is expanded by 0.9% in the [011]Ni direction and by 3% in the [112]Ni direction. The three-dimensional islands observed in the coverage of less than 15 ML have an atomic arrangement with a nearly six-fold symmetric structure of the distorted Ni(111) layer which is expanded uniformly by 3%. Both the layer and islands are commensurate with the Mo(110) lattice to form long-range-ordered structures.

We report here the measurements of the valence spectra, the C 1s and the Si 2p core-level spectra of C 60 molecules adsorbed on a Si(111)-(7ϫ7) surface, using photoelectron spectroscopy. In the valence spectra, the highest occupied molecular orbital ͑HOMO͒ of a C 60 splits into two peaks at a coverage lower than 0.25 ML. The binding energies of the split peaks are 1.8 and 2.4 eV. Taking into account the polarization-dependence of the valence spectra and the binding energy of the C 1s core-level spectra, it is found that the 2.4-eV peak observed in the valence spectra is the covalent bonding state between a C 60 molecule and the Si substrate, and that the 1.8-eV peak is the shifted HOMO. The Si 2 p core-level spectra suggest that the bonding site is localized at the interface. We also present the energy-level scheme of the bonding state in terms of the symmetry of the HOMO. ͓S0163-1829͑98͒02443-6͔

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