The effects of glancing-angle argon ion bombardment on air-contaminated Si(001) surfaces were studied. Bombarding at substrate temperature T-s = 730 degrees C, impingement angle phi = 3 - 15 degrees relative to the surface plane, ion energy E = 1 keV and dose D = 3 x 10(15) ions cm(-2) gave high-quality reflection high energy electron diffraction (RHEED) patterns and contaminant-free surfaces as observed by ion scattering spectroscopy. Atomic force microscopy images showed roughness value less than or equal to 0.5 nm under these conditions, but the roughness increased and RHEED patterns became spotty for higher doses or energies. Secco etching of samples bombarded at T-s = 730 degrees C showed etch pits with a density of 10(6)-10(7) cm(-2) that increased with increasing D and E. Room-temperature bombardment with E = 1 keV, D = 3 x 10(15) ions cm(-2) and phi = 3 degrees, followed by a 730 degrees C anneal, yielded a lowest roughness value of 0.2 nm. Secco etching showed no resolvable pits, indicating a dislocation density <4 x 10(4) cm(-2).