We demonstrate highly directional etching in silicon 100 nm in diameter with an aspect ratio of 160 with no spiking on the pore walls using magnetic-field-assisted anodization. The relationship between the surface geometry of a silicon electrode and its highly directional etching properties have been investigated. Specifically, we show that the pore shape and pore wall orientation are not determined by the surface pattern but by the etching mechanisms specific to the magnetic-field-assisted anodization. These etching mechanisms enable highly directional and high aspect ratio etching at diameters below 100 nm in scale.

In this paper, we describe the size reduction and phosphorus doping of silicon nanocrystals (SiNCs) fabricated using a very high frequency (VHF) plasma deposition system. The size reduction of SiNCs is achieved by changing the VHF plasma power. The size of SiNCs changes from 10 to 5 nm. We discuss the relationship between VHF plasma power and the size of SiNCs in terms of radicals in the VHF plasma, such as SiH3, SiH2, SiH, and H. On the other hand, we have fabricated phosphorus-doped SiNCs by adding PH3 gas diluted with Ar gas. To confirm where phosphorus atoms are located, electrically detected magnetic resonance (EDMR) measurements are conducted. We have observed a hyperfine interaction between unpaired electrons and phosphorus atoms and enhanced hyperfine splitting owing to a quantum size effect. As a result, we can conclude that phosphorus atoms exist at substitutional sites of SiNCs and they act as donors.

We propose the n-type 3C-SiC with Pt nanoparticles (Pt NPs) as photo-anode for photoelectrochemical hydrogen (H2) generation. We found that band-edge structure of 3C-SiC is suitable for H2 generation, and the property can be optimized by dopant (nitrogen) concentration in 3C-SiC. We also confirmed that Pt NPs enhance photoelectrochemical properties showing 0.2%–0.8% higher Incident Photon-to-Current Efficiency than bare 3C-SiC in visible wavelength despite diminished light absorption. Solar-conversion efficiency increases approximately 6.3 times, and H2 production is improved by 6.5 times with 33% of Faradaic efficiency. Lastly, 3C-SiC surface corrosion is effectively inhibited.

We describe the natural oxidation of silicon nanocrystals (SiNCs) and the method of etching the natural oxide layer of SiNC with hydrogen fluoride (HF) vapor. Electrical measurements are conducted in order to investigate the influence of the natural oxidation of SiNCs. The wet HF etching process, which is currently used in the semiconductor industry, results in the removal of all SiNCs from the substrate. Therefore, we use HF vapor etching, which can remove only the natural oxide layer without the removal of SiNCs from the substrate. Consequently, the HF vapor process is suitable for SiNC devices. From electrical measurements, it is observed that current increases by four orders of magnitude after the HF vapor etching treatment. In addition, it is revealed that we can control the thickness of the oxide layer of SiNCs by changing the HF vapor etching time.

The time evolution of the optical emissions of Ar plasma during silicon nanocrystal (SiNC) fabrication using a pulsed SiH4 supply is studied. The enhancement of Ar emission with a duration longer than the ON time of the pulsed SiH4 supply is observed owing to the formation of SiNCs in the plasma. This enhancement can be explained in terms of the increase in the number of high-energy electrons caused by electron attachments to SiNCs. The size and generation rate of SiNCs clearly correlate with the duration and intensity of the enhanced emission even when the Ar flow rate or the plasma power is changed. On the basis of this relationship, the size and density of SiNCs can be predicted during the fabrication by monitoring the enhanced emission.