Scanning-tunneling-microscopy modification of nitrogen-passivated GaAs (001) surfaces on a nanometer scale

Using scanning tunneling microscopy (STM), we perform nanometer-scale modifications on nitrogen (N)-passivated GaAs (001) surfaces. After the surface is passivated with nitrogen gas through a heated tungsten filament in an ultrahigh-vacuum chamber, STM modification is performed by increasing the tunnel current. A 200×200 nm2 square groove was successfully fabricated. The smallest grooves are 0.5 nm deep and 5 nm wide when sample bias is -3 V and tunnel current is 5 nA. The threshold current for modification is 5 nA for surfaces with N passivation, but more than 50 nA for surfaces without N passivation.