Measurement of the density of states in a Si nanowall exhibiting the quantum size effect

We developed a slimming process of Si nanowall aiming at the Si nanowall solar cell whose band gap is tuned by the quantum size effect. The width of Si nanowall was successfully reduced to 3 nm by using thermal oxidation. The density of states (DOS) in Si nanowall was measured by ultraviolet photoelectron spectroscopy. The 3-nm width Si nanowall showed DOS with stepwise shape which is completely different from that of bulk Si. This change in the DOS is probably due to the quantum size effect.