Dynamics of bulk-to-surface electron transitions on Si(001)-(2x1) studied by time-resolved two-photon photoemission spectroscopy

作者：Tanaka S^*; Ichibayashi T; Tanimura K

来源：Physical Review B, 2009, 79(15): 155313.

DOI：10.1103/PhysRevB.79.155313

• absorption coefficients
• carrier lifetime
• conduction bands
• electron-hole recombination
• elemental semiconductors
• excited states
• photoelectron spectra
• silicon
• time resolved spectra
• two-photon spectra

The carrier dynamics on Si(001)-(2x1) have been studied by means of time- and angle-resolved two-photon photoemission spectroscopies at 291 K. Temporal changes in electron populations at the normally unoccupied surface band (D(down)) and at the bulk conduction-band minimum (CBM) have been probed simultaneously to characterize the pathways of bulk-to-surface electron transfer. The decay kinetics of the electron population at the bottom of D(down) and at the CBM, obtained at two different excitation wavelengths, where the bulk absorption coefficient differs significantly, show a strong dependence on wavelength. Analysis shows that the dependence of the population at the CBM is characterized by carrier diffusion away from the surface and by rapid surface recombination, with a surface-recombination velocity of 1.2x10(6) cm/s. The surface-recombination pathway from the CBM to the high-lying state along the Gamma-J dispersive branch of the D(down) band has been directly probed by an angle-resolved technique. Quantitative comparisons of electron flows into the D(down) band and the decay kinetics of the population of the bottom of D(down) reveal an efficient quadratic decay channel of the surface electron-hole recombination.

• 出版日期2009-4