C‐axis oriented YBa2Cu3O7−x(YBCO) thin films were deposited by an ozone‐assisted reactive coevaporation method and characterized byinsitulow‐energy ion scattering spectroscopy (LEISS). We successfully evaluated compositional information in depth by an angle‐resolved LEISS method and a depth profiling LEISS method. These LEISS analyses indicated that the second outermost layer of the YBCO surface consisted of Ba atoms. This result confirmed that YBCO surfaces were terminated by Cu(1)‐O chains. ©1995 American Institute of Physics.