(Hg1−xRex)Ba2CaCu2Oy(x≈0.1)thin films have been preparedex situonLaAlO3substrates by a two-step process in which anHgO/Re0.1Ba2CaCu2Oymultilayer precursor film is annealed in a quartz tube using an unreacted monoxide pellet containing HgO as an Hg vapor source. By varying the composition of the monoxide pellet, the film orientation can be changed fromc-axis to the predominantlya-axis one. Thea-axis growth of the grains directly on the substrate is confirmed by x-ray diffraction and transmission electron microscopic observation, although the grains are twinned with 90° orientation. Thea-axis films exhibit aTconset andTczero of approximately 110–127 and 55 K, respectively, suggesting substantial influence of weak links at the grain boundaries on their transport properties. ©1998 American Institute of Physics.