Superconducting YBCO thin films have been grown in-situ by three ion beam co-deposition sputtering. Both metal and oxide targets of Cu and Y and BaF2 and BaCO3 targets have been investigated. Film composition was determined by RBS and AES analysis. Films grown using BaF2 show flourine contamination, whereas the carbon concentration in films grown using BaCO3 is beneath the Auger detection limit. Superconducting films have been grown on SrTiO3 (Tco=78K) and on Si with SiO2 or Y2O3 buffer layers (Tco=35K).