MoS2 quantum dot, given by laser ablation, have 1% sulfur vacancies quantified by ESR as a functional defect. Very good catalyst, the shortest synthesis time, and room-temperature process are achieved against the top 10 papers of the HER of MoS2.
The atomic structures and the electronic states of active and inactive dopant sites in semiconductor are elucidated successfully by using X-ray absorption near-edge structure (XANES), Auger electron spectroscopy (AES), and photoelectron spectroscopy (PES). To demonstrate the versatility of this method, we investigated Si-doped GaN as a prototype and clarified the atomic structures and chemical states at the active and inactive dopant sites in GaN. From AES and PES, it was found that Sidoped GaN formed two dopant states, which were attributed to Si 3 N 4 and SiN x . From the Si K-edge XANES, the Si 3 N 4 state did not exhibit electronic states in the GaN bandgap, indicating inactive dopant sites in GaN, whereas the SiN x state exhibited bandgap states. Thus, the SiN x state should act as an active dopant site in Si-doped GaN. The simulated XANES spectra well reproduced the electronic state in the GaN bandgap when the Ga atom is replaced by the Si atom, suggesting that the active dopant site may be the Si-substituted Ga sites.
We employed photoelectron spectroscopy (PES) and photoelectron
holography (PEH) to clarify the atomic structures and chemical states
in the active and inactive dopant states of Mg-doped GaN. Due to the
lack of available direct evidence, this has been a controversial issue.
From PES, we found that two chemical states existed in the Mg-doped
GaN: One is an active dopant state, and the other is an inactive state.
We employed PEH to investigate the two observed chemical states, indicating
that the active state could be attributed to a Mg atom substituting
a Ga atom in the Mg-doped GaN structure (MgGa). The inactive
state, on the other hand, was considered to be a disordered structure,
an amorphous structure, defects, and/or MgGa bonding with
a H atom in that structure.
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