XPS analysis and valence band structure of a low‐dimensional SiO₂/Si system after Si⁺ ion implantation

Abstract

A X-ray photoelectron spectroscopy (XPS) of valence band (VB) and core levels are performed for a SiO 2 /p-Si heterostructure containing a thin oxide layer of d ¼ 20 nm thickness and implanted by Si þ ions. With an implantation energy of 12 keV the maximum density of the implanted Si þ profile is located close to the SiO 2 -Si interface at a depth of 18 nm, but a piling-up of Si is also found immediately beneath the surface up to 2 nm, i.e., within the escape depth of XPS electrons. Thus we may expect a partial phase separation associated with Si aggregation and nanocluster formation imbedded in a nonstoichiometric SiO x matrix. By means of XPS and in comparison to X-ray emission spectroscopy (XES) the related changes of the VB structure are investigated.

A Bioinspired Nanofibrous Titania/Silicon Composite as an Anode Material for Lithium‐Ion Batteries

“…A high‐resolution O 1 s XPS spectrum of the titania‐54.3 %‐silicon composite (Figure b) shows two peaks at 530.0 and 532.4 eV, which are attributed to Ti−O and Si−O, respectively . The high‐resolution spectrum of the Si 2 p region of the sample is shown in Figure c; the peaks located at 99.9 eV are indexed to metallic silicon, and the two other peaks located at 100.9 and 103.0 eV are indexed to silicon oxide (SiO x , x <2; and SiO 2 ) owing to the oxidation of silicon nanoparticles in air . This silicon oxide layer could serve as a buffer layer for volume changes to the silicon nanocrystals upon charge/discharge cycles when the composite is employed as the anode of LIBs .…”

“…Moreover,t he original hierarchical network structures of the cellulose substance are maintained in the sample, whichp rovide enough space to accommodate the seriousv olume change of the anode upon cycling, and facilitate the electrode- [67] The high-resolution spectrumo ft he Si 2p region of the sample is shown in Figure 3c;the peaks located at 99.9 eV are indexed to metallic silicon, and the two other peaks located at 100.9 and 103.0 eV are indexed to silicon oxide (SiO x , x < 2; and SiO 2 )o wing to the oxidation of silicon nanoparticles in air. [23,26,68] This silicon oxide layer could serve as ab uffer layer for volumec hanges to the silicon nanocrystals upon charge/discharge cycles when the composite is employed as the anode of LIBs. [69] For the TiO 2 component in the composite, Ti 2p doublet peaks centered at 458.7 (Ti2p 3/2 )a nd 464.4 eV (Ti2p 1/2 ;F igure 3d)a re observed, and the energy gap between the Ti 2p 3/2 and Ti 2p 1/2 peaks is 5.7 eV,w hich indicates the presenceo ft he normal state of Ti 4 + in the composite.…”

Photoluminescence and cathodoluminescence from nanostructured silicon surface

“…Hence, any transformation of VB spectrum indicates re-arrangement of the energy spectrum of the electronic states for black Si sample. 33 The Si 3 d peak is generally situated $2.4-4.2 eV above the Fermi level and Si 3 s level is about 11.1 eV above the Fermi level. 34 The rearrangement of DOS on black Si can be clearly seen.…”

“…Taking into account the positions of Si 3 s and 3 d peak and O 2 p peak from a low energy survey scan, the peak features at A-B-C appear due to strongly hybridized Si 3d3s-O 2 p electronic states. 33 This so called XPS VB transition layer 35 gives further indication of migration of oxygen and formation of non-stoichiometric oxide layer on black Si forming Si/SiO x (x < 2) interface. ) is for SiO 2 .…”

A nanofibrous polypyrrole/silicon composite derived from cellulose substance as the anode material for lithium-ion batteries

“…The Si(2p) peak observed at 99.5 eV indicates the presence of metallic silicon, while the peak at 103.5 eV is indicative of the formation of SiO x (x < 2) due to the oxidation of the silicon nanocrystals in air. 6,44 In the C(1s) region, the three peaks at 284.5, 285.2 and 286.2 eV are assigned to β and α carbon type and C=N in PPy; 45 and in the N(1s) region, the doublet peaks at 397.6 and 399.4 eV are ascribed to =N− and −NH− of PPy, respectively. 46 As a comparison material for the electrochemical study, pure PPy powder was synthesized by the in-situ chemical polymerization process.…”