  The structure and electronic order at the cleaved (001) surfaces of the
newly-discovered pnictide superconductors BaFe$_{2-x}$Co$_{x}$As$_{2}$ with x
ranging from 0 to 0.32 are systematically investigated by scanning tunneling
microscopy. A $\sqrt{2}\times\sqrt{2}$ surface structure is revealed for all
the compounds, and is identified to be Ba layer with half Ba atoms lifted-off
by combination with theoretical simulation. A universal short-range charge
order is observed at this $\sqrt{2}\times\sqrt{2}$ surface associated with an
energy gap of about 30 meV for all the compounds.
