We fabricated highly dense Si nano-columnar structures accompanied with Si nanocrystals on W-coated quartz and characterized their local electrical transport in the thickness direction in a non-contact mode by using a Rh-coated Si cantilever with pulse bias application, in which Vmax, Vmin, and the duty ratio were set at +3.0V, -14V, and 50%, respectively. By applying a pulse bias to the bottom W electrode with respect to a grounded top electrode made of ∼10-nm-thick Au on a sample surface, non-uniform current images in correlation with surface morphologies reflecting electron emission were obtained. The change in the surface potential of the highly dense Si nano-columnar structures accompanied with Si nanocrystals, which were measured at room temperature by using an AFM/Kelvin probe technique, indicated electron injection into and extraction from Si nanocrystals, depending on the tip bias polarity. This result is attributable to efficient electron emission under pulsed bias application due to electron charging from the top electrode to the Si nanocrystals in a positively biased duration at the bottom electrode and subsequent quasi-ballistic transport through Si nanocrystals in a negatively biased duration.

We have fabricated highly-dense Si nano-columnar structures accompanied with Si nanocrystals on W-coated quartz, and characterized their local electrical transport in the thickness direction using atomic force microscopy (AFM) with a conductive cantilever. By applying DC negative bias to the bottom W electrode with respect to a grounded top electrode made of 10-nm-thick Au on the sample surface, current images reflecting highly-localized conduction were obtained in both contact and non-contact modes. This result is attributable to electron emission due to quasi-ballistic transport through Si nanocrystals via nanocolumnar structure.

Electron-cyclotron-resonance plasma-excited molecular beam epitaxial (ECR-MBE) growth of GaN using hydrogen-nitrogen mixed gas plasma was investigated. The growth rate of GaN was drastically increased by addition of hydrogen to nitrogen plasma. The transition of reflection high energy electron diffraction (RHEED) patterns, from streaked patterns created without the presence of hydrogen to spotted patterns in the presence of hydrogen, indicated that the effective V/III ratio was increased by the addition of hydrogen. NHx radical families were detected in hydrogen-nitrogen mixed gas plasma by quadrupole mass spectroscopy and optical emission spectroscopy. These radicals were considered to be responsible for the observed increase in growth rate. Transmission electron microscope observation showed that the surface morphology of GaN without hydrogen was relatively flat and that with hydrogen was columnar with {1 0 ~1 1} facets. It seems likely that the columnar structure of the GaN layers grown with hydrogen were strongly related to initial island growth.