Writing with atoms: Oxygen adatoms on the MoO2/Mo(110) surface

Writing at the nanoscale using the desorption of oxygen adatoms from the oxygen-rich MoO2+x/Mo(110) surface is demonstrated by scanning tunnelling microscopy (STM). High-temperature oxidation of the Mo(110) surface results in a strained, bulk-like MoO2(010) ultra-thin film with an O-Mo-O trilayer structure. Due to the lattice mismatch between the Mo(110) and the MoO2(010), the latter consists of well-ordered molybdenum oxide nanorows separated by 2.5 nm. The MoO2(010)/Mo(110) structure is confirmed by STM data and density functional theory calculations. Further oxidation results in the oxygen-rich MoO2+x/Mo(110) surface, which exhibits perfectly aligned double rows of oxygen adatoms, imaged by STM as bright protrusions. These adatoms can be removed from the surface by scanning (or pulsing) at positive sample biases greater than 1.5 V. Tip movement along the surface can be used for controlled lithography (or writing) at the nanoscale, with a minimum feature size of just 3 nm. By moving the STM tip in a predetermined fashion, information can be written and read by applying specific biases between the surface and the tip.