Optical absorption measurements of electron quantum confinement in Si(111)-2 × 1 surface chains

Optical experiments on the Si(111)-2x1 surface show that the absorption peak due to dangling-bond transitions exhibits a blueshift upon oxygen exposure. The effect is interpreted as due to quantum confinement of surface electrons in pi-bonded chains of atoms, whose length decreases with oxygen uptake (a particle in a box effect, the box being one dimensional). This conclusion is supported by numerical simulation of the optical spectra.