Epitaxial wurzite-structure AIN thin films have been grown on 6H-SiC substrates by ultra-high-vacuum (UHV) low-energy-ion-assisted reactive de magnetron sputtering. The quality of epitaxial AIN films is significantly improved by low-energy ion assistance (E-i = 17-27 eV), during reactive magnetron sputter growth on vicinal (3.5 degrees) 6H-SiC. The ion-assisted growth results in an increased surface mobility, which promotes domain boundary annihilation and epitaxial growth. This results in lateral expansion of column width. Thus, AIN films with domains as large as 40 nm at the interface to 6H-SiC can be realized. At film thickness above 100 nm, the column width expands to 100 nm. The crystal quality of the films is very good with low background impurities (O: 3.5x10 (18)cm(-3)).