2-DIMENSIONAL LASER MOLECULAR-BEAM EPITAXY AND CARRIER MODULATION OF INFINITE-LAYER BACUO2 FILMS

BaCuO2 thin films were fabricated on SrTiO3 substrates by laser MBE to elucidate the conditions for two-dimensional heteroepitaxial growth o f the infinite-layer structure. The fine streak pattern and intensity oscillations observed by in situ reflection high-energy electron diffr action (RHEED) verified that tetragonal BaCuO2 (001) was grown in a tw o-dimensional unit cell-by-cell mode. Effective carrier injection into the BaCuO2 films was investigated in two different modes, i.e. homoge neous and molecular-layer dopings. In the former mode, 1 mol% of Ba wa s substituted to form a (Na-0.01, Ba-0.99)CuO2 film. In the latter, Ba CuO2 and (Na-0.01, Ba-0.99)CuO2 molecular layers were alternately depo sited to form carrier modulated multilayered films. Both homogeneous B aCuO2 and (Na-0.01, films were semiconductive, whereas the carrier mod ulated multilayered films turned out to be metallic without showing an y indication of superconductivity at 4 K and above.