GLANCING ANGLE DEPOSITION
Our main nanofabrication technqiue is glancing angle deposition (GLAD) method. GLAD is a physical vapor deposition technique with a large deposition angle, i.e., the substrate normal and incident vapor form a large angle, in general, > 75°. It is compatible for large scale microfabrication processes, i.e., can be used for large scale production. In particular, for GLAD, the substrate is rotated in the polar and azimuthal directions by two stepper motors programmed by a computer, The main mechanisms that control the growth are the shadowing effect and surface diffusion. GLAD is simple to implement, and any thin film physical vapor deposition system can be readily adapted to a GLAD system. In fact, the most intriguing aspect of GLAD is that the structures of the nanorods can be well-designed by programming the substrate rotations. The GLAD technique offers several strategic advantages compared to other nanofabrication techniques. For example:
- The size, separation, and density of the nanorods are controlled by the vapor incident angle. Therefore, the porosity of the nanostructure is a function of deposition angle.
- The shape, alignment, and orientation of the nanorods can be easily changed by programming the rotation procedures.
- Three-dimensional nanorod structures can also be sculptured by programming the rotation of the two motors.
- The shadowing growth mechanism results in self-alignment, where the templates can be used to mediate the size, order and orientation of nanorods.
- By varying the incident angle continuously during the deposition, one can seal the top of the nanostructure by putting on a blanket of continuous film.
- There is virtually no constraint on the materials that can be used. As long as the material can be evaporated, it is possible to form vertically aligned nanorod structures.
- Multilayered nanostructures are achievable using a multilayer deposition system.
- As a physical vapor deposition method, GLAD can be integrated with other microelectronic fabrication techniques to develop chip-level products.
GLAD is a versatile nanofabrication technique for the design of nanostructured substrates in which all the substrate structural parameters can be controlled by simple computer programming.
OTHER NANOFABRICATION TECHNIQUE
We also use other nanofabrication technqiues such as nanosphere lithography, electron beam lithography, chemical synthesis of nanoparticles, etc, in our research.
