Nano-modification on hydrogen-passivated Si surfaces by a laser-assisted scanning tunneling microscope operating in air

A novel method for nanofabrication, i.e., laser-induced nano-modification on hydrogen (H)-passivated Si surfaces under a tip of a scanning tunneling microscope (STM) is proposed. The theory and mechanism are discussed. Enhanced laser irradiation under a STM tip induces a local temperature rise on the nanometer scale, which causes thermal desorption of hydrogen atoms on an H-passivated Si surface. Oxidation occurs after desorption of hydrogen atoms. A vertical polarized Nd:YAG pulsed laser with a duration of 7 ns was used in our investigation. STM tips were electrochemically (EC) etched from a tungsten wire. A 3 x 3 dot array and a single line were created. The sizes of the dots are from 20 to 30 nm, and the width of the line is less than 30 nm. The dependence of the apparent depth on the laser intensity shows that then is a threshold of the intensity and a saturation value of the apparent depth is reached at high intensity. (C) 2000 Elsevier Science B.V. All rights reserved.