Formation of size- and position-controlled nanometer size Pt dots on GaAs and InP substrates by pulsed electrochemical deposition

Attempts were made to form regular arrays of size- and position-controlled Pt-dots on GaAs and InP by combining an ir? situ electrochemical process wi th the electron beam (EB) lithography. This utilizes the precipitation of P t nano-particles at the initial stage of electrodeposition. First, electroc hemical conditions were optimized in the mode of self-assembled dot array f ormation on unpatterned substrates. Minimum in-plane dot diameters of 22 nm and 26 nm on GaAs and InP. respectively, were obtained under the optimal p ulsed mode. Then, Pt dots were selectively formed on patterned substrates w ith open circular windows formed by EB lithography, thereby realizing dot-p osition control. The Pt dot was round to have been deposited at the center of each open window, and the in-plane diameter of the dot could be controll ed by the number, width and period of the pulse-waveform applied to substra tes. A minimum diameter of 20 nm was realized in windows with a diameter of 100 nm, using a single pulse. Current-voltage (I-V) measurements using an atomic force microscopy (AFM) system with a conductive probe indicated that each Pt dot/n-GaAs contact possessed a high Schottky barrier height of abo ut 1 eV.