Optical absorption and electronic transitions in MoO₃ single crystals

Theoretical and Experimental Study of the Electronic Structures of MoO3and MoO2

“…The annealing treatment also led to removal of structure in the Mo 3d region associated with MoO 3 to leave a spectrum dominated by two overlapping spin−orbit doublets, as shown in Figure . The resolution achieved in the current work is much better than in previous experimental work on MoO 2 . ,– ,,,, The complex core line shape is characteristic of narrow band metallic oxides where the width of the conduction band is comparable with the potential generated by the core hole. – – The core hole therefore pulls a localized 4d level out of the conduction band. As discussed in detail elsewhere ,– the components at low binding energy (labeled (s) in Figure ) are due to well-screened final states in which the localized level becomes occupied by an itinerant conduction electron, while the broader components at higher binding energy are associated with unscreened final states, labeled (u) in the figure, where the localized level remains empty.…”

“…Each bilayer interacts with the adjacent bilayer in the [010] direction through a weak noncovalent interaction, which is mainly van der Waals in origin . The onset of strong optical absorption in α-MoO 3 thin films is typically around 3.2 eV. ,, However, polycrystalline or single-crystal material has a distinct yellow coloration, and the lowest absorption edge in single crystals is at 440 nm, corresponding to a lower band gap of 2.8 eV …”

Mobile Polaronic States in α-MoO3: An ab Initio Investigation of the Role of Oxygen Vacancies and Alkali Ions

“…Electronically, the material is an indirect band gap system with measured values ranging between 2.8 and 3.2 eV. 35,36 Figure 1a shows the calculated band structure using GGA+U and HSE06. The two methods produce band gaps that are 2.45 and 3.05 eV, respectively, in which the valence band maximum (VBM) is located at the high symmetry point U and the conduction band minimum (CBM) is located at Γ.…”

“…Structural relaxation within DFT leads to an unrealistic value of the b -axis, even with the use of the van der Waals correction, due to the noncovalent interlayer forces, and thus we adopt the method used previously, fix the b -axis to the experimental value, and perform a series of relaxations on the a - and c -axes. , This gives a value of 3.928 and 3.664 Å for the a - and c -axes, respectively. Electronically, the material is an indirect band gap system with measured values ranging between 2.8 and 3.2 eV. , Figure a shows the calculated band structure using GGA+U and HSE06. The two methods produce band gaps that are 2.45 and 3.05 eV, respectively, in which the valence band maximum (VBM) is located at the high symmetry point U and the conduction band minimum (CBM) is located at Γ.…”

Hybrid co-deposition of mixed-valent molybdenum–germanium oxides (MoxGeyOz): A route to tunable optical transmission

“…Increasing U L to 330 V corresponds to films with an E g of 2.97 (±0.04) eV, leading to a yellow tint associated with the increased Mo:Ge ratio. An E g near 2.8 eV is near the lower bound of those reported for MoO 3 [29,64], and is related to absorption of blue light (λ < 440 eV), leading to a yellow coloration [36,95]. The yellow hue of the films persists, becoming more intense within the transition regime (II) for U L values of 340 to 360, and is correlated to an increase in the amount of Mo 2 O 5 ( Figure 10).…”