Bulletin of the American Physical Society
2006 59th Annual Gaseous Electronics Conference
Tuesday–Friday, October 10–13, 2006; Columbus, Ohio
Session PR1: Plasma Applications for Nanotechnology |
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Chair: Toshiake Makabe, Keio University Room: Holiday Inn Salon CD |
Thursday, October 12, 2006 8:00AM - 8:30AM |
PR1.00001: Ultimate Top-down Etching Processes Using Advanced Neutral Beam for Future Nano-scale Devices Invited Speaker: For the past 30 years, plasma etching technology has led efforts to shrink the pattern size of ultra-large-scale integrated (ULSI) devices. However, inherent problems in the plasma processes, such as charge build-up and UV photon radiation, limit the etching performance for nanoscale devices. To overcome these problems and fabricate sub-10-nm devices in practice, neutral beam etching has been proposed. In this invited talk, I introduce the ultimate etching processes in the neutral beam sources and discuss the fusion of top-down and bottom-up processing for future nanoscale devices. Neutral beams can perform atomically damage-free etching and surface modification of inorganic and organic materials. This technique is a promising candidate for a practical fabrication technology for future nano-devices. [Preview Abstract] |
Thursday, October 12, 2006 8:30AM - 8:45AM |
PR1.00002: Deposition of vertically oriented single-walled carbon nanotubes in highly collisional atmospheric pressure plasma Kuma Ohnishi, Tomohiro Nozaki, Ken Okazaki, Joachim Heberlein, Uwe Kortshagen We succeeded synthesis of vertically aligned single-walled carbon nanotubes (SWNTs) in atmospheric pressure radio frequency discharge (APRFD). This is because ion bombardment to the substrate, which causes cohesion or diffusion of catalyst nano-particles as well as growing SWNTs, can be minimized in highly collisional plasma sheath at atmospheric pressure. In this process (Carbon source; CH$_{4}$, Wafer temperature; 700$^{\circ}$C), it is essential for growth of SWNTs to supply radicals produced by plasma. Higher power supply causes higher growth rate. However, maximum power input was limited to 80 W because of the stability of the plasma. The higher substrate temperature up to 700$^{\circ}$C means better yield (G band / D band) of SWNTs, and causes faster growth rate.The catalyst particles maintained their activities at least 20 minutes and the initial growth rate of SWNTs was about 4.0 $\mu $/min at the condition of 60 W. The catalysts lost their activities, not because of the damage caused by plasma but because of the thermal sintering which was caused by high temperature like 700$^{\circ}$C. [Preview Abstract] |
Thursday, October 12, 2006 8:45AM - 9:00AM |
PR1.00003: Measurement of plasma density and electron energy distribution function in a filamented capacitively coupled silane-argon plasma Ameya Bapat, Uwe Kortshagen A capacitively coupled, filamented argon-silane plasma is studied. This discharge has been shown to produce highly monodisperse, facetted, cube shaped silicon nanocrystals which were previously successfully used in novel single nanoparticle vertical Schottky barrier transistors. The striated filament has a diameter of about 3 mm and rotates erratically in the 5 cm inner diameter discharge tube at a frequency of about 150 Hz. The plasma is run at a pressure of $\sim $2 Torr in 5{\%} silane diluted in helium and argon. RF power up to 200 W is applied at 13.56 MHz. A capacitive probe (Braithwaite et al., Plasma Sources Sci. Technol., vol. 5, 677 (1996)) is used to measure the ion density within the filament and the background plasma. Emission and absorption spectroscopy combined with a model based on a Boltzmann solver and a collisional-radiative model for argon-silane are used to determine the electron energy distribution function. We expect that a better understanding of the plasma process will help to understand the formation of silcon nanocrystals with the unique cubic shape. [Preview Abstract] |
Thursday, October 12, 2006 9:00AM - 9:15AM |
PR1.00004: Application of microplasma to synthesis of silicon nanoparticles Kenji Sasaki, Tomohisa Ogino, Daisuke Asahi, Tomohiro Nozaki, Ken Okazaki We developed microplasma to synthesize nanocrystalline silicon particles (nc-Si). Gas residence time in micro plasma reactor is of the order of $\mu $s, while time required for particle nucleation by three-body collision? is about ms. Thus it is possible to separate crystal nucleation and growth in a single reactor. This process is very important for synthesis nc-Si. Microplasma was formed in a capillary tube of diameter 470 $\mu $m which is connected to the VHF power source. We used Ar/SiCl$_{4}$ mixtures for nc-Si source for safety. H$_{2}$ was added to convert exhausted Cl to HCl. Electron density of micro plasma (N$_{e})$ was estimated by Stark broadening of H$_{\beta }$, and found that N$_{e}$ is 1-3*10$^{15}$ cm$^{-3}$. Rotation temperature was measured to be approximately 1500 K. Intensity ratio of Si(288 nm)/Ar(750 nm) increased linearly with increasing initial concentration of SiCl$_{4}$. If the residence time was 30 $\mu $s, particle nucleation seemed to start in the discharge region, and particles keep growing involving impurity elements such as N or Cl. On the other hand, when residence time was set to shorter than 10 $\mu $s, the amount of impurities can be minimized. Under this condition, Raman spectra showed crystalline silicon peak around 520 cm$^{-1}$. TEM image also indicated the size of synthesized nc-Si to be in the range of 4-20 nm. [Preview Abstract] |
Thursday, October 12, 2006 9:15AM - 9:30AM |
PR1.00005: Synthesis of highly monodisperse Ge crystals in a capacitively coupled flow through reactor for photovoltaic applications Ryan Gresback, Uwe Kortshagen Germanium nanocrystals are interesting candidates for quantum dot-based solar cells. While the band gap of bulk Ge is $\sim $0.7 eV, the energy gap can be increased due to quantum confinement to $\sim $ 2eV for Ge particles of $\sim $3 nm in size. With a single material, Ge nanocrystals of sizes from 3 -15 nm would thus allow to span the entire range of band gaps that is of interest for photovoltaic devices. Moreover, compared to many other quantum dot materials that are currently studied for photovoltaic applications, Ge is perceived as non-toxic and environmentally benign. Ge nanocrystals are synthesized in a tubular, capacitively coupled flow through reactor. Germanium tetrachloride is used as a precursor. It is introduced into the plasma by a flow of argon and hydrogen. At typical pressures of 2 Torr and 40 W of RF power at 13.56 MHz, Ge crystals are generated and reside in the plasma for several tens of milliseconds. The size of the nanocrystals can be controlled in a range from 3-20 nm through the residence time. Particles are highly monodisperse. Organically passivated Ge nanocrystals self-assemble into monolayers when cast from colloidal solutions. [Preview Abstract] |
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