Mechanism for the formation of isolated poly(p-xylylene) fibrous structures under shadowing growth.

Because of the low sticking coefficient, conventional parylene deposition is known to achieve the conformal coating on corrugated or patterned surfaces. However, recently, it has been shown that in contrary to the conformal coating, extremely nonconformal and isolated fibrous parylene structures can be formed on surfaces if it is deposited at an oblique angle using a directional flux. We demonstrate that directional flux can create a high local vapor pressure facing the flux, while the reflection of monomers because of a small sticking coefficient would generate a background vapor pressure. The parylene oblique angle deposition is a combination of the shadowing growth and a much slower conformal coating process, which together give rise to the isolated fibrous structure.

Biaxially textured Al film growth on CaF2 nanostructures toward a method of preparing single-crystalline Si film on glass substrates.

We report the room temperature growth of biaxially textured Al films and further demonstrate the use of these Al films in preparing single-crystalline Si layers on glass substrates. The formation of the biaxial texture in Al film relies on the existence of the CaF(2) buffer layer prepared using oblique angle physical vapor deposition, which consists of single-crystalline nanorods with caps that are in the form of inverted nanopyramids. The single-crystalline Si film was obtained upon crystallization of the amorphous Si film deposited through physical evaporation on the biaxially textured Al film. This method of preparing single-crystalline Si film on glass substrate is potentially attractive for being employed in silicon technology and in fabrication of low-cost electronic devices.

Size control of Cu nanorods through oxygen-mediated growth and low temperature sintering.

Control of the size of Cu nanorods vapor-deposited at an oblique angle (approximately 85 degrees) by oxygen-mediated growth was investigated using scanning electron microscopy (SEM) and x-ray diffraction (XRD). It was observed that exposure of Cu nanorods to the oxygen ambient periodically resulted in a reduction in the diameter of the nanorods as well as an increase in the areal density of the nanorods. This oxygen-induced modification to the nanorod growth is attributed to the higher energy barrier for Cu adatom migration on the oxide surface at room temperature; this reduces the rod diameter. At a low annealing temperature of approximately 300 degrees C, the SEM images show that the nanorods have densified and formed a continuous film structure, which is consistent with the sintering phenomenon. The XRD and SEM analyses show that the coalescent/grain growth rate for Cu nanorods with smaller diameters is enhanced due to the size effect. This low temperature sintering characteristic of the Cu nanorod array has great potential for being utilized in wafer bonding for three-dimensional integration of devices.