Removing material using atomic force microscopy with single- and multiple-tip sources

Atomic force microscopy (AFM) has been an effective material removing tool for fabricating various nanostructures because of its sub-nanometer precision and simplicity in operation. AFM material removing techniques have evolved from a solely mechanical process to one in which the tip can be loaded by additional energy sources, such as thermal, electric, or chemical, to enhance its fabrication abilities. In this paper, these material removing techniques are reviewed with an emphasis on their capabilities and recent progress. The recent hardware and software developments are first presented to provide a general view on the current status of the technology to be assessed. Following an overview of the feasibility and effectiveness of using mechanical scratching for removing various types of soft and hard materials, the processes of a wide range of approaches using multiple tip sources are then assessed with a focus on their principles, versatilities, and potentials for future applications.