Conduction Band Discontinuity in n-type Si/TiO₂ Heterojunction Interfaces

Abstract

The conduction band discontinuity between n-type Si substrates and anatase TiO2 films has been investigated. n-type Si substrates with three different dopant concentrations were used as a substrate for TiO2 thin-films: ND = 1015–16 cm−3 (as n-Si); ND = 1017–18 cm−3 (as n+-Si); ND = 1020–21 cm−3 (as n++-Si). The translation of X-ray photoelectron spectroscopy (XPS) results to an energy band diagram through the valence band offset (VBO) enables us to evaluate the conduction band discontinuities accurately: n-Si/TiO2—−0.22 eV, n+-Si/TiO2—−0.06 eV, and n++-Si/TiO2—+0.07 eV. Temperature–dependent current–voltage (I–V) characteristics were measured to evaluate the Fermi energy level (EF) of the TiO2 thin-films. Light transmittance was measured to evaluate the energy bandgap of the TiO2 thin-films. The band diagram of the n-type Si/TiO2 heterojunction was proposed. Deep-insight analysis of n-type Si/TiO2 was carried out on the basis of measured I–V characteristics.

Structural Design of TiO2/Si Hybrid Photoelectrode and Pt-Free Counter Photoelectrodes for Charge Carrier Separation in Water-Splitting Reactions

“…The energy band alignment in the TiO 2 and n-type Si heterojunction interface was already discussed in a previous work. 31 Figure 8 shows an I-V curve of the TiO 2 and n ++ -Si heterojunction used for TiO 2 /Si HPE preparation. The ohmic characteristic was obtained.…”

“…Here, the ab initio calculation 28,29 with data gathered from the X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) measurements are the most reliable method to analyze it. 30 The conduction band alignment in the TiO 2 and n-type Si heterojunction was investigated in our previous work, 31 where differently doped n-type Si wafers were used as a substrate for TiO 2 , and current-voltage (I-V) characteristics were measured. Moreover, the optical properties, such as the optical transmittance and solar spectrum selectivity of the layers or interlayers, should be analyzed.…”