Niobium films have been prepared by bias sputtering in a conventional sputter system operated in the triode configuration. Gas analysis of the discharge and of the deposited films as well as resistivity and lattice-parameter measurements provide the basis for the interpretation of the deposition process under ion bombardment. The importance of defining the relative rate of arrival of energetic ion versus neutrals in addition to defining the energy of arriving particles is emphasized. The close relationship of bias sputtering to ion implantation is stressed. A model for bias sputtering is developed which is suited for fine-tuning film composition and structure and thereby the resultant thin-film properties.