Effects of high-flux low-energy ion bombardment on the low-temperature growth morphology of TiN(001) epitaxial layers

Ultrahigh vacuum scanning tunneling microscopy (STM) is used to characterize the surface morphology of TiN(001) epitaxial layers grown by de reactive magnetron sputtering at growth temperatures of T-s=650 and T-s=750 degrees C. An auxiliary anode is used to bias the N-2 plasma and produce a large flux of low-energy N-2(+) ions that bombard the Aim surface during growth: the ratio of the N-2(+) flux to the Ti growth flux is approximate to 25. At ion energies E-i near the threshold for the production of bulk defects (E-i=43 eV and T-s=650 degrees C), ion bombardment decreases the amplitude of the roughness, decreases the average distance between growth mounds, and reduces the sharpness of grooves between growth mounds. The critical island radius for second layer nucleation R-c is approximately 12 and 17 nm at growth temperatures of 650 and 750 degrees C respectively; at 650 degrees C, R-c is reduced to approximate to 10 nm by ion bombardment.