Fabrication of nanoscale alumina on NiAl(1Â 0Â 0) with a scanning tunneling microscope

► Nanoscale alumina was fabricated on NiAl(1 0 0) surface with a STM tip. ► Varied powers (bias × current) give two distinct modes of oxidation. ► In the high-power mode alumina forms on the surface near the tip. ► In the low-power mode alumina grows along direction [0 0 1] or [0 1 0] of NiAl(1 0 0). ► The grown alumina strips have minimal width about 3 nm.