We proposed and demonstrated a preparation method of (001) preferentially oriented stress-free AlN piezoelectric thin films. The AlN thin films were deposited by a reactive sputtering technique at substrate temperatures up to 330 degrees C using a dual Kaufman ion-beam source setup. We deposited the AlN on Si (100), Si (111), amorphous SiO2, and a (001) preferentially oriented Ti thin film and compared their crystallographic, optical, and piezoelectric properties. The AlN thin films deposited on the (001) preferentially oriented Ti thin films have the highest crystallographic quality. The stress-free AlN reached a high value of the piezoelectric coefficient d(33) = (7.33 +/- 0.08) pC.N-1. The properties of the AlN thin film prepared at such low temperatures are suitable for numerous microelectromechanical systems, piezoelectric sensors, and actuators monolithically integrated with complementary metal-oxide-semiconductor signal-processing circuits.