Kelvin probe microscopy to image and characterise erasable electrostatic lithography

We present low-temperature Kelvin probe microscopy (KPM) images of charge patterns drawn on GaAs using erasable electrostatic lithography (EEL). EEL is a new technology to fabricate high quality quantum devices with high productivity. A low-temperature scanning probe biased negatively draws charge on a GaAs surface which locally depletes electrons from a subsurface 2D electron system to define the quantum device. From KPM images, the amplitude and radius of charge spots were measured as a function of EEL tip bias. A potential barrier is found between the tip and surface, and a small plateau in amplitude is seen where the 2D electron system becomes depleted. KPM images made after illumination show that there is no charge spreading which suggests that the erasure mechanism is thermal activation.