UC San Diego

Nanotechnology has seen great development in the past two decades, and numerous nano-devices with superior electrical/mechanical/optical performance have emerged in wide applications such as electronics, biomedicine, solar energy, and aerospace. Nanofabrication, and in particular 3-D nanostructure fabrication, has been intensively studied for the creation of novel devices, the scaling of existing systems, and the improvement in utilities and reliabilities. However, there are quite a few challenges in nanofabrication, such as the spontaneous attractions among nanostructures.

Spontaneous attractions have often caused adhesion or stiction that affects a wide range of nanoscale devices, particularly nano/microelectromechanical systems. Previous explorations of the attraction mechanisms have suggested a wide range of origins but none of them is universally applicable to most nanostructures. Here a simple capacitive force model based on the nanoscale electrostatic interaction is proposed to quantitatively study this universally observed phenomenon. Our model is experimentally verified using arrays of vertical silicon nanowire pairs with varied spacing, diameter, and size differences. This work illustrates a new understanding of spontaneous attraction that will impact the design, fabrication and reliable operation of nanoscale devices and systems.

By taking advantage of the nanoscale electrostatic attraction, low voltage nano-electro-mechanical (NEM) switches are built with innovative grayscale electron-beam lithography. The main benefit of this new fabrication technique is that the essential air gaps for movable components (nano-cantilevers or nano-beams) can be generated in a straightforward one-step lithography process, without any growth or etching to traditional sacrificial layers such as dielectrics. The structural dimensions of the nano-switches, as well as switch-on (pull-in) voltages are both readily controllable. The fabrication and performance for both single-cantilever nano-switches and doubly-clamped NEM devices are demonstrated.

Nano-metrology such as Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) is extremely useful in the characterization of various nanostructures, and has been widely applied in our research. At the end of this thesis, one particular example using ambient condition AFM characterization of synthetic individual DNA molecule with site-specific decoration of proteins will be discussed.