A substrate is positioned within a deposition chamber. At least two gaseous precursors are fed to the chamber which collectively comprise silicon, an oxidizer comprising oxygen and dopant which become part of the deposited doped silicon dioxide. The feeding is over at least two different time periods and under conditions effective to deposit a doped silicon dioxide layer on the substrate. The time periods and conditions are characterized by some period of time when one of said gaseous precursors comprising said dopant is flowed to the chamber in the substantial absence of flowing any of said oxidizer precursor. In one implementation, the time periods and conditions are effective to at least initially deposit a greater quantity of doped silicon dioxide within at least some gaps on the substrate as compared to any doped silicon dioxide deposited atop substrate structure which define said gaps.