Bottom-up Nanofabrication

Abstract

A bottom-up approach to nanofabrication can be looked upon as a synthesis approach mimicking biological processes in which individual atoms are piled up one at a time on the substrate to form molecules. These molecules arrange themselves on their own into the desired form to yield the required nanostructures. The driving mechanisms for this molecular arrangement are the physical and chemical forces operative at the nanoscale. These mechanisms have been perfected by Mother Nature over a period of several millennia. Of particular interest to nanoelectronics are techniques such as sol-gel synthesis, vapour deposition, atomic layer deposition, molecular self-assembly, DNA-assisted assembly and many others. Sol-gel technique offers a simple process to produce nanoparticles. Two forms of vapour-phase techniques are physical vapour deposition in which the active species is evaporated into the vapour phase and chemical vapour deposition in which, a precursor is used which decomposes into the required species via a chemical reaction. Based on successive, self-restricting reaction cycles, atomic layer deposition provides thickness adjustment at nanometer level along with composition control. Molecular self-assembly exploits the organizational capability of matter to form homogeneous monolayers. Physical and chemical vapour deposition constitute self-assembly from gaseous phase. Artificial DNA nanostructures are used to arrange functional nanomaterials into nanoelectronic circuits.