The IBM/TENN/TULANE/LLNL/LBL Beamline 8.0 at the advanced light source combining a 5.0 cm, 89 period undulator with a high-throughput, high-resolution spherical grating monochromator, provides a powerful excitation source over a spectral range of 70-1200 eV for surface physics and material science research. The beamline progress and the first experimental results obtained with a fluorescence end station on graphite and titanium oxides are presented here. The dispersive features in K emission spectra of graphite excited near threshold, and found a clear relationship between them and graphite band structure are observed. The monochromator is operated at a resolving power of roughly 2000, while the spectrometer has a resolving power of 400 for these fluorescence experiments. Q
When epitaxial graphene layers are formed on SiC͑0001͒, the first carbon layer ͑known as the "buffer layer"͒, while relatively easy to synthesize, does not have the desirable electrical properties of graphene. The conductivity is poor due to a disruption of the graphene bands by covalent bonding to the SiC substrate. Here we show that it is possible to restore the graphene bands by inserting a thin oxide layer between the buffer layer and SiC substrate using a low temperature, complementary metal-oxide semiconductor-compatible process that does not damage the graphene layer.
Sophisticated microelectromechanical systems for device and sensor applications have flourished in the past decade. These devices exploit piezoelectric, capacitive, and piezoresistive effects, and coupling between them. However, high-performance piezoresistivity (as defined by on/off ratio) has primarily been observed in macroscopic single crystals. In this Letter, we show for the first time that rare-earth monochalcogenides in thin film form can modulate a current by more than 1000 times due to a pressure-induced insulator to metal transition. Furthermore, films as thin as 8 nm show a piezoresistive response. The combination of high performance and scalability make these promising candidates for nanoscale applications, such as the recently proposed piezoelectronic transistor (PET). The PET would mechanically couple a piezoelectric thin film with a piezoresistive switching layer, potentially scaling to higher speeds and lower powers than today's complementary metal-oxide-semiconductor technology.
A process has been described which can produce a midgap tungsten gate compatible with the current and future complementary metal–oxide–semiconductor technology. The tungsten was deposited directly onto a 3.0 nm SiO2 gate dielectric without measurable degradation of any of its electrical properties. The tungsten deposition process yields no reactive or corrosive by-products that affect the gate dielectric integrity. The tungsten film is found to be pure within the limits of several analytical techniques and the resistivity of the tungsten films was found to be within a factor of 2 of the bulk value.
The Si/SiO2 interface in 100-nm-thick chemical vapor deposition (CVD) tungsten gate metal–oxide–semiconductor (MOS) structures exhibits high interface state densities (Dit0>5×1011/cm2 eV) after conventional forming gas anneals over varying temperatures and times. In this letter, we show this is a consequence of the low diffusivity and solubility of molecular hydrogen in tungsten and the high temperature CVD process. We have discovered that atomic hydrogen is more effective in passivating tungsten gate MOS interfaces because of its higher diffusivity in tungsten. Atomic hydrogen can be produced (1) by the reaction of aluminum with water vapor when aluminum is evaporated on the top of tungsten, (2) by hydrogen implantation, and (3) by hydrogen plasma. These techniques can passivate the Si/SiO2 interface effectively in MOS structures (Dit0<5×1010/cm2 eV) with 100-nm thick CVD tungsten gates.
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