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Abstract: ZnO films prepared by the thermal oxidation of the ZnS films through thermal evaporation are reported. The as-deposited ZnS films have transformed to ZnO films completely at 400°C. The 400–700°C annealed films with a preferential c-axis (002) orientation have a hexagonal wurtzite structure. The band gap of ZnO films shifts towards longer wavelength with the increase of the annealing temperature. The relationship between the band gap energy of ZnO films and the grain size is discussed. The shift of the band gap energy can be ascribed to the quantum confinement effect in nanocrystal ZnO films. The photoluminescence spectra of ZnO films show a dominant ultraviolet emission and no deep level or trap state defect emission in the green region. It confirms the absence of interstitial zinc or oxygen vacancies in ZnO films. These results indicate that ZnO film prepared by this simple thermal oxidation method is a promising candidate for optoelectronic devices and UV laser. [Copyright &y& Elsevier]

In this study, four Ta 2 O 5 -based mixture coatings, including Ta 2 O 5 -TiO 2 , Ta 2 O 5 -HfO 2 , Ta 2 O 5 -Al 2 O 3 , and Ta 2 O 5 -SiO 2 , are deposited via plasma-ion-assisted electron-beam co-evaporation and compared with a Ta 2 O 5 monolayer coating. The chemical compositions, microstructures, and optical and femtosecond laser-induced damage threshold (LIDT) properties of the coatings are investigated. For different doping materials, when the refractive indices of the mixture coatings are close, the femtosecond LIDTs exhibit a considerable difference. The experimental results indicate that the Ta 2 O 5 -HfO 2 mixture coating exhibits a larger optical bandgap and higher femtosecond LIDT than other coatings. The 1-on-1 LIDT of the Ta 2 O 5 -HfO 2 mixture coating is approximately 1032.3 mJ/cm2 (170 fs), which is 25% higher than that of the Ta 2 O 5 monolayer coating. We believe the Ta 2 O 5 -HfO 2 mixture will be useful for various multilayer coatings such as chirped mirrors and other mirrors in femtosecond laser applications. • The effect of doping materials on Ta 2 O 5 -X mixtures is systematically studied. • Ta 2 O 5 -X mixtures with similar refractive indices show different optical bandgaps. • The optical bandgap affects the femtosecond laser-induced damage threshold. • The Ta 2 O 5 –HfO 2 mixture coating exhibits excellent performance. [ABSTRACT FROM AUTHOR]

HfO 2 monolayer coatings are grown by plasma-enhanced atomic layer deposition (PEALD), and the effects of the thermal annealing atmosphere and temperature on the surface morphology, crystal structure, chemical composition, optical absorption, and laser-induced damage threshold (LIDT) of the HfO 2 monolayer coatings are investigated. The experimental results show that annealing in an oxygen atmosphere is more beneficial to the decomposition of impurity compounds (carbonates and amines) and the elimination of oxygen deficiency in HfO 2 coating than in a nitrogen atmosphere. Compared to the as-deposited coating, the HfO 2 coating annealed under an oxygen atmosphere and specific temperature has lower C and N impurity contents, a better stoichiometric ratio, and thus lower absorption and higher LIDT. The highest LIDT (at 355 nm) of 6.3 J/cm2 is obtained at an annealing temperature of 700 ℃, which is approximately three times that of the as-deposited coating. We believe that this experimental result can help improve the LIDT of PEALD-grown oxide coatings or other oxide coatings containing similar impurities. • The effect of annealing on the properties of PEALD HfO 2 coatings is investigated. • The carbonates and amines in the HfO 2 coating decompose during annealing. • The oxygen-annealed HfO 2 coating has lower absorption and higher LIDT. • The oxygen-annealed HfO 2 coating shows different damage morphology. [ABSTRACT FROM AUTHOR]

Nonstoichiometric titanium dioxide nanostructured thin film (TNF) has attracted a range of interest in the green energy field. In this paper, we introduce the glancing angle deposition (GLAD) technique to produce the amorphous TNFs with discrete nanoscale columnar structures. In order to improve the crystallinity and/or gain the Ti 3+ doped states, amorphous TNFs were annealed at 400 °C in air or H 2 . XRD, SEM, AFM, XPS and PL were used to characterize the crystallization structure morphology, chemical state, PL properties of the TNFs with different annealing conditions. Photocatalytic activities of the samples were reflected by decolorization experiments of methylene blue (MB) solution irradiated by the simulated sunlight light of AM 1.5 G. The photocatalytic activity of amorphous TNF is higher than that of conventional TiO 2 thin film, indicating the prominent properties of nanostructures. Compared with annealing in air, the photocatalytic activity of TiO 2-x nanostructures annealed in hydrogen is further increased and higher. The results demonstrated that Ti 3+ and oxygen vacancies were beneficial and played the dominant role for the enhancement of photocatalytic activity. [ABSTRACT FROM AUTHOR]

Abstract: TiO2 films deposited by electron beam evaporation with glancing angle deposition (GLAD) technique were reported. The influence of flux angle on the surface morphology and the microstructure was investigated by scanning electron microscopy. The GLAD TiO2 films are anisotropy with highly orientated nanostructure of the slanted columns. With the increase of flux angle, refractive index and packing density decrease. This is caused by the shadowing effect dominating film growth. The anisotropic structure of TiO2 films results in optical birefringence, which reaches its maximum at the flux angle α =65°. The maximum birefringence of GLAD TiO2 films is higher than that of common bulk materials. It is suggested that glancing angle deposition may offer an effective method to obtain tailorable refractive index and birefringence in a large continuous range. [Copyright &y& Elsevier]

The laser-induced damage threshold (LIDT) of HfO 2 /SiO 2 anti-reflection (AR) films for ultraviolet (UV) lasers was improved via low-temperature plasma-enhanced atomic layer deposition (PEALD). Focused on the chemical composition, optical absorption, surface scattering, and laser-resistance, the impact of precursor exposure time on PEALD SiO 2 film properties and growth temperature on PEALD SiO 2 and HfO 2 film properties were investigated respectively. When irradiated by UV laser, PEALD SiO 2 film exhibits a higher LIDT than the PEALD HfO 2 film, which is consistent with their less impurity content and lower absorption. A bilayer structure HfO 2 /SiO 2 AR film for 355 nm laser was designed and experimentally demonstrated via PEALD growth at a temperature of 150 °C. The prepared PEALD AR film shows a reflectance <0.2% at 355 nm as designed and better laser-damage resistance with a LIDT of 24.4 J/cm2 (355 nm, 7.8 ns) than the conventional e-beam deposition method. Image 1 • The HfO 2 /SiO 2 anti-reflection film for UV laser was presented via low-temperature PEALD. • The presented PEALD AR film shows better laser-damage resistance than conventional e-beam deposition method. • The impact of precursor exposure time on PEALD film properties were investigated. • The XPS measurement shows the impurity content of PEALD HfO 2 film is high, leading to a large absorption and low LIDT. [ABSTRACT FROM AUTHOR]

To further improve the quality of the cuboid DKDP crystal, the effect of thermal annealing at 160 °C were evaluated. After thermal annealing, the symmetry of the HRXRD of the X-cut sample is much better, indicating that the uniformity of the cuboid crystal is improved. The transmittance of annealed THG-oriented sample is obviously higher than the as-grown THG-oriented sample from 400 to 300 nm. At 355 nm, the transmittance of the THG-oriented sample increases from 80.4% to 87.9% after thermal annealing. Besides, thermal annealing is also beneficial to the weak absorption properties at 355 nm of the X-cut cuboid DKDP crystal. The average weak absorption of the X-cut sample is decreased from 26.6 ppm to 12.3 ppm, and the standard deviation of the X-cut sample is decreased from 17.0 ppm to 4.8 ppm after thermal annealing. The LID performance of the THG-oriented sample is improved through thermal annealing, and the fluences corresponding to 50% probability of LID is increased from 13.4 to 14.8 J/cm2 (@3ns, 355 nm). Also, the density of the defect with low LID threshold decreases by two-thirds. The above results indicate that thermal annealing is an effective means to further improve the quality of the cuboid DKDP crystal. • Through thermal annealing, the symmetry of the HRXRD of the cuboid DKDP is much better. • At 355 nm, the transmittance of the cuboid DKDP increases from 80.4% to 87.9%. • The average weak absorption of the cuboid DKDP is decreased from 26.6 ppm to 12.3 ppm. • The fluences corresponding to 50% probability of LID of the cuboid DKDP is increased from 13.4 to 14.8 J/cm2 (@3ns, 355 nm). • Also, the density of the defect with low LID threshold decreases by two-thirds. [ABSTRACT FROM AUTHOR]