S. Skaberna et al., Fabrication of a quantum point contact by the dynamic plowing technique and wet-chemical etching, ULTRAMICROS, 82(1-4), 2000, pp. 153-157
We have fabricated extremely confined ballistic constrictions using a nanol
ithography technique based on an atomic force microscope. Vector-scan contr
olled dynamic plowing with the vibrating tip enables to plastically indent
a thin resist layer along a prearranged path. Transfer of the resist patter
n into the semiconductor substrate is achieved by a strongly diluted aqueou
s etchant. In this way approximately 30 nm deep gooves were etched in the c
hannel area of a modulation-doped GaAs/GaAlAs field-effect transistor. The
quantum point contacts were defined by a broken line whose 60 nm width repr
esents the length and the sub-100 nm gap determines the width of the constr
iction. At liquid-helium temperature the conductance as a function of gate
voltage shows a stepwise increase in units of 2e(2)/h. Signatures of the co
nductance quantization persist up to 50 K, which indicates a large subband
spacing. (C) 2000 Elsevier Science B.V. All rights reserved.