Publication Date:
2016-01-14
Description:
Undoped n-type BaSi 2 films were grown on Si(111) by molecular beam epitaxy, and the valence band (VB) offset at the interface between the BaSi 2 and its native oxide was measured by hard x-ray photoelectron spectroscopy (HAXPES) at room temperature. HAXPES enabled us to investigate the electronic states of the buried BaSi 2 layer non-destructively thanks to its large analysis depth. We performed the depth-analysis by varying the take-off angle (TOA) of photoelectrons as 15°, 30°, and 90° with respect to the sample surface and succeeded to obtain the VB spectra of the BaSi 2 and the native oxide separately. The VB maximum was located at −1.0 eV from the Fermi energy for the BaSi 2 and −4.9 eV for the native oxide. We found that the band bending did not occur near the native oxide/BaSi 2 interface. This result was clarified by the fact that the core-level emission peaks did not shift regardless of TOA (i.e., analysis depth). Thus, the barrier height of the native oxide for the minority-carriers in the undoped n-BaSi 2 (holes) was determined to be 3.9 eV. No band bending in the BaSi 2 close to the interface also suggests that the large minority-carrier lifetime in undoped n-BaSi 2 films capped with native oxide is attributed not to the band bending in the BaSi 2 , which pushes away photogenerated minority carriers from the defective surface region, but to the decrease of defective states by the native oxide.
Print ISSN:
0021-8979
Electronic ISSN:
1089-7550
Topics:
Physics
