Converting dimensions: A facile and high-yield route for getting sub-100 nm silicon nanowires

To get circular and regular sub-100 nm Si nanowires (NWs), we introduced a metal-assisted chemical etching (MCE)-based method employing a rapid thermal annealing (RTA) and vacuum deposition processes. A deposited two dimensional ultra-thin Ag layer on silicon as a substrate turns into zero dimensional self-organized nanoparticles (NPs) through RTA process. And these NPs act as catalyst and make nanoholes onto a Si substrate under the first MCE process. After sputtering porous Ag and Au layer on caved Si substrate, the second MCE process is conducted. Finally, one dimensional Si NWs with cylindrical structure are synthesized and their diameters are coincident to those of Ag and Au NPs because the region of Si covered with porous Ag and Au layer is vertically etched and the non-covered, nanoholes, remain. By changing the thickness of ultra-thin Ag film on Si substrate, the diameter of Si NWs formed after second MCE could be controlled.