Local Anodic Oxidation Nanolithography on Silicon: Chemical Routes to Functional Nanostructures pp. 175-193
Authors: (Thomas Baumgaertel, Harald Graaf, Chemnitz University of Technology, Chemnitz, Germany)
Abstract: The structuring of silicon surfaces in the nanometer regime is one of the demands that have to be fulfilled in order to advance the design and aspired miniaturisation in semiconductor technologies. Besides further development of conventional optical lithography techniques into the ultraviolet regime, alternative lithography techniques are in the focus of recent research to achieve lateral structures in the nanometer scale. These structuring technologies are mostly based on direct writing, for example electron beam lithography, imprint lithography and scanning probe based lithography (SPL). Among the SPL techniques there is a widespread multitude of different methods for the structuring of various surfaces. The scope ranges from moving single atoms (via scanning tunnelling microscopy) to the deformation of soft materials via contact atomic force microscopy (AFM) to drawing structures with ink (Dip-Pen lithography). Another approach, which has received a broad attention in the scientific community, is the local anodic oxidation (LAO). Here a voltage is applied between SPM tip and sample surface which leads to an electrochemical oxidation reaction under certain environmental conditions (generally the presence of an oxygen-containing electrolyte). In the case of a silicon sample, the silicon is oxidized locally at the tip apex leading to the formation of silicon oxide structures. The chemically different oxide can afterwards be altered through the attachment of molecules or nanoparticles in order to give the structures a defined functionality. Yet the underlying mechanisms and phenomena are not fully understood. Systematic chemistry on surfaces and confined geometries is still a very challenging topic since it is rather difficult to access directly by measurement. This chapter will introduce the basics of the LAO technique and provide an overview over the research in that field both regarding the understanding of the process itself as well as possible applications to generated functionalized structures.
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