Resonance Tunneling Diode Structures on CdTe Nanowires Made by Conductive AFM

Variation of band gap across the nanowire length would be an exceptionally attractive property for the fabrication of on-nanowire devices such as resonance tunneling diodes (RTD). Band gap variation can be achieved by selective thinning of semiconductor wires by scanning probe lithography (SPL) technique. The external bias applied to a conductive AFM tip during scanning of CdTe nanowires was chosen so as to exceed the threshold of electric field-assisted evaporation of CdTe, estimated to be 5.5 V. Relatively high external voltages of 10−11 V cause fast and complete disintegration of a nanowire portion under the tip. In this way the nanowire can be cut to a desired length. Selection of a voltage between 5.5 and 10 V allows one to control the speed of CdTe evaporation. Thus, one can modulate the thickness of the semiconductor with angstrom scale precision along the nanowire length. Smaller diameter of the nanowire results in increase of quantum confinement in selected areas. The double barrier quantum well valence band profile necessary for the manufacturing of RTD Esaki diodes was demonstrated.