LAYER-BY-LAYER HETEROEPITAXIAL GROWTH-PROCESS OF A BAO LAYER ON SRTIO3(001) AS INVESTIGATED BY MOLECULAR-DYNAMICS

Layer-by-layer heteroepitaxial growth processes of a BaO layer on SrTi O3(001) were simulated in order to predict an appropriate buffer layer for a YBa(2)Cu(3)O(7-)x(YBCO)/SrTiO3(001) heterojunction by using our crystal growth molecular dynamics (MD) simulation code. The SrTiO3(00 1) terminated by a TiO2 atomic plane was employed as the substrate in the present simulations. BaO molecules were continuously deposited on the SrTiO3(001) one by one, and finally a two-dimensional and epitaxia l growth of a BaO layer was observed at 700 K. Moreover, the construct ed BaO layer was atomically hat and smooth without defects, retaining a NaCl-type structure and (001) oriented configuration. However, the s tress of the BaO/SrTiO3(001) heterojunction gradually increased and fi nally reached to approximately 1.2 GPa during the epitaxial growth pro cess. it is expected that the large stress disturbs the subsequent fab rication of the uniform YBCO/SrTiO3(001) heterojunction. We also simul ated the epitaxial growth process of a BaO layer on a I:single SrO lay er/SrTiO3(001)]. An atomically flat and smooth BaO layer without defec ts was also obtained at 700 K. Surprisingly, the stress of the BaO/[si ngle SrO layer/SrTiO3(001)] heterojunction was almost 0.0 GPa after ep itaxial growth. We have already suggested that [BaO layers/single SrO layer] are suitable buffer layers for the YBCO/SrTiO3(001) heterojunct ion on the basis of regular MD simulations [M. Kubo et al., Phys. Rev. B 56, 13535 (1997)]. From the present crystal growth simulations, we confirmed that the above atomically uniform and smooth BaO/SrO/SrTiO3( 001) can be fabricated and almost no heterointerface stress was induce d after the epitaxial growth. Moreover, the effect of substrate temper ature on the heteroepitaxial growth process of the BaO layer on the Sr O/SrTiO3(001) was discussed. (C) 1998 American Institute of Physics. [ S0021-9606(98)70444-1].