Thin films of barium titanate (BaTiO3) have been grown on Pt(111)/Si(100) substrates by radio frequency (RF) magnetron sputtering at a substrate temperature of 560-580 degrees C in a mixture of Ar/O-2 atmosphere. Analysis of X-ray diffraction data shows that these films have a single-phase perovskite structure and are tetragonal BaTiO3 with a (211) orientation. The full width at half maximum (FWHM) of the (211) omega-rocking curve is similar to 0.54 degrees. The growth direction of the BaTiO3 (211) lattice planes with respect to the Pt(lll) and Si(100) substrate planes during the sputtering process is characterised in detail by X-ray diffraction theta-2 theta scans for various chi-angles.