Molybdenum oxide can exhibit pronounced photochromism and thus might act as an excellent photonic material for a number of technical applications. In the early stage of the research, the attention was focused mainly on the (band) structure, photochromic mechanism and the behavior of the oxide. Later, many investigations were carried out on the factors that might influence the photochromic performance. At the same time, the photochromic response has been extended from UV light to visible light. In this review, the progress in all of these areas will be reviewed thoroughly.

Photochromism of molybdenum oxide

Synthesis and properties of thin film polymorphs of molybdenum trioxide

Properties of rf‐sputtered molybdenum oxide films for electrochromic display devices have been investigated. This report mainly concerns the dependence of the properties on the oxygen concentration in the sputtering atmosphere. The oxide films were prepared by rf sputtering from a compressed powder MoO3 target under an operating pressure of 4×10−2 Torr using a mixture of Ar‐0.5–50% O2. Electrical resistivity of the films formed increases with increasing oxygen concentration in the sputtering atmosphere and ranges from 2.5×1010 to ∼1×1012 Ω cm. Spectral transmittance of the films is about 85% in the visible and near‐infrared region. Optical band gap and refractive index of these films are 2.67–2.76 eV and 2.01–2.26, respectively. Electrochemichromic properties of the films were also studied using asymmetric cells, and it was found that a good electrochromic performance was obtained usually by the cells composed of the films with a resistivity of 2.5×1010 Ω cm.

Preparation and electrochromic properties of rf‐sputtered molybdenum oxide films

Molybdenum oxide thin films find diverse applications as catalysts, gas sensors, and electrochromic devices. Such films are produced mainly by reactive sputtering and thermal evaporation but other ...

Molybdenum oxide thin films obtained by the hot-filament metal oxide deposition technique

Heating and annealing effects on the optical properties of slightly blue substoichiometric molybdenum trioxide thin films are reported partially. During heating and annealing, different levels of coloration seem to be generated by simultaneous reduction and proton injection into thin films, which cause the formation of hydrogen molybdenum bronzes of different concentrations. The optical band gap, Eo, of MoO3 thin film when annealed in between 313 and 473 K is decreased to 2.82 eV, and this reduction in Eo has been explained with a view to phonon and polaron species. Moreover, temperature-dependent change in the optical band gap has also been interpreted in terms of band gap slope, B, and the real part of the refractive index, n. Urbach slope, σ, also goes down to 0.67 eV−1 due to annealing treatment. Using the oscillator model, a phonon energy, hνo, of about 0.08 eV was found for the reported MoO3 thin film which is very close to the characteristic phonon energy of MoO3. Over and above, the intensity for the blue absorption band, over the photon energy range 0.4–3.0 eV, also reaches a maximum as MoO3 thin film is annealed at 473 K for 1 h and then decreases by 32% after annealing at the same temperature for 2 h. This phenomenon is due to polaronic band intensity which rises and falls during annealing. Half-width of the blue band, as found by fitting polaron model, is changed only by 3% on annealing the MoO3 thin film at 473 K as compared to its value at room temperature.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400059665

Optical and electrochromic properties of heated and annealed MoO 3 thin films

The growth of defects in vacuum-evaporated MoO3 films has been studied by optical absorption in the present work. The as-grown films were subjected to different kinds of treatment such as thermal annealing, UV and X-ray irradiation, and their optical absorption spectra were recorded between 300 and 1500 nm at room temperature as well as at liquid N2 temperature The films were found to be amorphous from X-ray and electron-microscopic studies. From these studies it is observed that in addition to point defects, defect aggregates similar to the colloidal centres in silver and alkali halides, are present in these films.

Colour centre studies in MoO3 films

Annealing and thickness effects on the electrical resistance of vacuum-deposited tin antimonide alloy films

Defect density variation with deposition rate in snsb thin films from annealing study of electrical resistance

Band gap and intergrain barrier activation energies in Bi90Sb10 thin films

The electric resistivity and Hall effect were studied for the vacuum evaporated and annealed ∠1 at.% Sb‐doped bismuth alloy films of various thickness (350–3500 A) in the temperature range of 77–510 K. Contrary to the behavior of bulk BiSb alloy, where the alloy becomes semiconducting only at about 4 at.% of Sb and above (A.L. Jain, 1959), it is found that thin films of 1% Sb‐doped Bi alloy are semiconducting. Moreover, this semiconducting trend begins at about room temperature unlike in bulk BiSb alloys where it is observed only at temperatures below about 180 K. The present type of behavior has been predicted and observed by some earlier workers (Ivanov et al. 1963, 1964). The intercrystalline barrier activation energies determined for various film thicknesses deposited at different substrate temperatures (257 K, 300 K, 373 K) were found to vary with thickness and substrate temperature, activation energy decreasing with increasing thickness and substrate temperature. These observations have been attribu...

M.S. Jagadeesh

Papers

Colour centre studies in MoO3 films

Annealing and thickness effects on the electrical resistance of vacuum-deposited tin antimonide alloy films

Defect density variation with deposition rate in snsb thin films from annealing study of electrical resistance

Band gap and intergrain barrier activation energies in Bi90Sb10 thin films

Semiconducting behavior in antimony-doped bismuth films