Min Jung Song

Direct deposition of patterned nanocrystalline CVD diamond using an electrostatic self-assembly method with nanodiamond particles

Micron-sized and precise patterns of nanocrystalline CVD diamond were fabricated successfully on substrates using dispersed nanodiamond particles, charge connection by electrostatic self-assembly, and photolithography processes. Nanodiamond particles which had been dispersed using an attritional milling system were attached electrostatically on substrates as nuclei for diamond growth. In this milling process, poly sodium 4-styrene sulfonate (PSS) was added as an anionic dispersion agent to produce the PSS/nanodiamond conjugates. Ultra dispersed nanodiamond particles with a ζ-potential and average particle size of - 60.5 mV and ∼ 15 nm, respectively, were obtained after this milling process. These PSS/nanodiamond conjugates were attached electrostatically to a cationic polyethyleneimine (PEI) coated surface on to which a photoresist had been patterned in an aqueous solution of the PSS/nanodiamond conjugated suspension. A selectively seeded area was formed successfully using the above process. A hot filament chemical vapor deposition system was used to synthesize the nanocrystalline CVD diamond on the seeded area. Micron-sized, thin and precise nanocrystalline CVD diamond patterns with a high nucleation density (3.8 ± 0.4 × 10(11) cm(-2)) and smooth surface were consequently fabricated.

Effect of nitrogen doping on the performance of Ge2Sb2Te5 films in chemical mechanical polishing

The effects of nitrogen doping on Ge2Sb2Te5 (GST) films for chemical mechanical polishing (CMP) and their performance were investigated. Nitrogen doping was controlled using a rapid thermal annealing system with nitrogen gas flow rates that varied from 0 to 20 sccm at 300 °C. The material removal rate, surface characteristics and crystal structure of the nitrogen doped GST films after CMP were examined by X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy. XRD patterns revealed that the intensities of crystalline diffraction peaks decreased with increasing nitrogen flow rate. With increasing flow rate, the material removal rate and surface roughness of GST films reduced owing to nitrogen doping effects. Current–voltage (I–V) characteristics of the nitrogen doped GST films after CMP showed changes in the threshold voltage owing to changes in crystallization and surface roughness. Further, Nitrogen doped GST films in CMP showed a strong correlation with material removal rate, surface roughness, and crystallization.