Abstract

After oxygen, silicon is the second most abundant element on Earth. It has many useful properties that facilitate its many applications such as electronics and optoelectronic devices. Recent trends of miniaturizing electronic devices have uncovered many novel properties. First, silicon can gradually transform into a direct semiconductor if the size of the silicon is less than 5 nm. ¹ Second, the ratio of the surface to volume increases, and lastly the energy band gap is wider. The measurement of 5 nm is known as Bohr radius of the exciton or the electron–hole pair of silicon. Photogenerated electrons and holes show more obvious quantum confinement effect when their distance is reduced to, or below, the exciton Bohr radius of bulk silicon. Silicon nanostructures with such a quantum confinement effect can be applied in the optoelectronics devices due to their efficient photoluminescence properties.