Electronic band gap reduction and intense luminescence in Co and Mn ion-implanted SiO2

Abstract

Cobalt and manganese ions are implanted into SiO 2 over a wide range of concentrations. For low concentrations, the Co atoms occupy interstitial locations, coordinated with oxygen, while metallic Co clusters form at higher implantation concentrations. For all concentrations studied here, Mn ions remain in interstitial locations and do not cluster. Using resonant x-ray emission spectroscopy and Anderson impurity model calculations, we determine the strength of the covalent interaction between the interstitial ions and the SiO 2 valence band, finding it comparable to Mn and Co monoxides. Further, we find an increasing reduction in the SiO 2 electronic band gap for increasing implantation concentration, due primarily to the introduction of Mn-and Co-derived conduction band states. We also observe a strong increase in a band of x-ray stimulated luminescence at 2.75 eV after implantation, attributed to oxygen deficient centers formed during implantation.

Octahedral conversion of a-SiO2 host matrix by pulsed ion implantation

“…XES Si L 2,3 of ion‐implanted a‐SiO 2 (the upper panel) compared with those of quartz and stishovite (the lower panel) .…”

“…The main idea of our study is to report about the influence of pulsed ion implantation on the local symmetry of constituent atoms in a‐SiO 2 host matrix without and with thermal annealing. The XPS data are combined for analysis with soft X‐ray emission spectroscopy (XES) measurements of ion‐implanted a‐SiO 2 and with specially performed density functional theory (DFT) calculations of Si L 2,3 XES. The performed full electronic structure analysis allows to fix the local octahedral conversion of SiO units in a‐SiO 2 after single and double ion implantations.…”

Final-State Projection Method in Charge-Transfer Multiplet Calculations: An Analysis of Ti L-Edge Absorption Spectra

“…10,30,31 Covalent mixing of the metal valence is simulated using a valence bond configuration interaction (VBCI) description as implemented by Thole et al 32 using the exact diagonalization method. 33 A two configuration model is used by adding a ligand-to-metal charge transfer configuration d n+1 L to a d n configuration in the ground state, where L denotes a ligand hole. The corresponding charge transfer energy Δ is defined as the difference between the center of masses of the two multiplet sets Δ = E(d n+1 L )-E(d n ).…”

Structure‐Induced Switching of the Band Gap, Charge Order, and Correlation Strength in Ternary Vanadium Oxide Bronzes

“…The measured RIXS spectra and V L-edgea bsorption spectra are shown in Figure 8, along with singlei mpurity Anderson model (SIAM) calculations. [52,53] It can be seen that the calculatedX AS spectra requireamixture of V 4 + and V 5 + to match the experiment in all cases,l eading to ac ombination of CT and d-d excitation features in the RIXS spectra,w hich similarly match the experiment. The relative prominence of these states is similari nd-Sr Table 3.…”

“…However it is clear that the V sites must have a mixed oxidation state, leading to the presence of V 4+ states and the observation of d–d transitions in the RIXS process. The measured RIXS spectra and V L ‐edge absorption spectra are shown in Figure , along with single impurity Anderson model (SIAM) calculations …”