a b s t r a c tElectro-chemical mechanical polishing (ECMP), which combines anodic oxidation and soft abrasive polishing, was applied to single-crystal SiC. Ceria (CeO 2 ) slurry was used as an electrolyte for anodic oxidation as well as a polishing medium to remove the oxide layer. As a result of anodic oxidation, the surface hardness decreased from 34.5 GPa to 1.9 GPa, which made it possible to polish the oxidized SiC surface using a very soft abrasive such as CeO 2 . It was found that the material removal rate (MRR) of ECMP for a diamond-abrasive-polished surface was 3.62 μm/h. ECMP using CeO 2 slurry was conducted for 30 min on a diamond-abrasive-polished surface. All the scratches were completely removed and a smooth surface with a root mean square (RMS) roughness of 0.23 nm was obtained.
Preliminary study on anodic-oxidation-assisted polishing (AOAP) of 4H-SiC (0001) using ceria polishing film was demonstrated. In the case of using deionized (DI) water as an electrolyte, rms roughness of 0.16 nm was obtained, which is almost the same as roughness of the surface finished by conventional chemical mechanical polishing (CMP). However, the polishing rate was very low and was 23 nm/h. In contrast, the polishing rate of 0.84 μm/h, which is equal to that of conventional CMP of single-crystal SiC or greater, was obtained when we used 1 wt% of phosphoric acid (H3PO4) as the electrolyte, although the surface roughness increased to rms roughness of 1 nm order. These experimental results indicate that the polishing rate greatly depends on the oxidation rate of anodic oxidation and the balance between the oxidation rate and the removal rate of oxide by abrasive greatly affects the roughness of the processed surface.
We report on a linearly polarized non-classical light emission from a single InGaN/GaN nanocolumn, which is a site-controlled nanostructure allowing for pixel-like large-scale integration. We have developed a shadow mask technique to reduce background emissions arising from nitride deposits around single nanocolumns and defect states of GaN. The signal to background ratio is improved from
to
, which allows for detailed polarization-dependent measurement and photon-correlation measurements. Polarization-dependent measurements show that linearly polarized emissions arise from excitonic recombination involving a heavy-hole-like electronic state, corresponding to the bulk exciton of an in-plane polarized A exciton. The second-order coherence function at time zero g
(2)(0) is 0.52 at 20 K without background correction. This value is explained in terms of a statistical mixture of a single-photon emission with residual weak background emissions, as well as efficient carrier injection from other localized states.
We report on the direct observation of Ag filament growth and a peculiar resistance switching in amorphous GeTe films with a lateral electrode geometry. The Ag filament growth was monitored by in-situ optical microscopy. The resistance switching was studied in three electrode pairs, Ag–Ag, Pt–Ag, and Pt–Ag/Pt (Ag electrode covered with Pt). In all the three electrode pairs, similar dendritic Ag filaments were clearly observed growing along both directions from one electrode to the other, according to the applied bias polarity. However, the SET and RESET processes are quite different. The Ag-Ag pair produces a unipolar clockwise switching. The Pt–Ag pair shows a bipolar counter-clockwise switching, as predicted in the basic electrochemical metallization theory, but the observed switching polarity is exactly opposite to the basic theory prediction. The Pt–Ag/Pt pair produces a unipolar counter-clockwise switching. The peculiar SET/RESET processes are explained on the basis of strong Ag diffusion into GeTe matrix resulting in an asymmetric effective electrode pair. The findings suggest that the SET/RESET processes are controlled by the amount of Ag and the electrode geometry.
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