A scanning tunnelling microscope operating in air is employed to expose a 50 nm thick electron beam sensitive resist with low energetic electrons. We demonstrate that it is possible to expose the resist under ambient conditions with voltages of similar to 50 V without observable modification of the resist surface after exposure prior to development. A resolution of 150 nm has been achieved. The dose for complete exposure has been determined as 10 mC cm(-2). This is about 1000 times higher than the value for conventional high-voltage electron beam lithography.