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The RF-sputtered β-Ga2O3 films prepared on sapphire substrates were treated by rapid thermal annealing (RTA) with an ultrafast processing time of 30 s. The effects of RTA at different process temperatures from 600 to 800 °C on the β-Ga2O3 films were researched. Meanwhile, the schematic diagram for the RTA-induced lattice expansion of films was proposed. The experimental results showed that the variation of Ga oxidation states and lattice oxygen was demonstrated, revealing a greater value of lattice oxygen at 700 °C. The (-201) orientation of Ga2O3 films is observed at 700 °C and 800 °C, where the (111) orientation additionally appeared at 800 °C. The larger grain size and interplanar distance of 4.71 Å for the (−201) orientation were also obtained at 700 °C, accounting for the high-quality β-Ga2O3 films and their lattice expansion. As a result, this RF-sputtered β-Ga2O3 films via the RTA process not only provide a new reference condition but also suitable for optoelectronic devices requiring control of crystallizing temperature and lattice variation.

Perovskite quantum dots (QDs) have showed excellent optoelectronic properties to extend the application range of novel solid-state lighting, such as perovskite QD based LEDs (QD-LEDs). However, the traditional device structure of perovskite QD-LEDs employed PEDOT:PSS as a hole inject layer (HIL), which impairs stability due to acidic surface characteristics. This study proposes the sputtered NiO films as an HIL to replace acidic PEDOT:PSS. The NiO films with significantly different characteristics were prepared by controlling the sputtering parameters to investigate the devices’ performance of NiO-based CsPbBr3 QD-LEDs. The optimized device showed an excellent performance with maxima luminescence of 20,118 cd/m2 and an external quantum efficiency (EQE) up to 3.63%.

THz-time domain spectroscopy is an effective method of label-free molecular detection, but it is limited by the size of the measured samples. Traditional detection approaches will have to overcome challenges when the analyte are in trace amounts. Here, we propose an enhanced mechanism for terahertz molecular fingerprint sensing, involving an all-dielectric metasurface. Based on incident wave angle scanning under light polarization, the broadband light–matter interaction is effectively enhanced, significantly improving the fingerprint signal of the molecule to be detected. The results demonstrate a new method for trace molecular detection in the terahertz region and large-scale molecular screening.

General hot-plate heating is used to form a crystal structure of films; however, how to achieve a homogeneous and regulated crystal formation will be a crucial challenge in the future. In this study, based on perovskite-series materials, organic methylamine lead trioxide (MAPbI3) films doped with inorganic lead iodide (CsPbI3) quantum dots (QDs) are treated using the rapid thermal annealing (RTA) process in argon gas to break the crystallization barrier. These RTA-treated perovskite quantum dot (PQD) films at various temperatures of 100–160 °C are detected using X-ray diffraction, X-ray spectroscopy, and absorbance measurements to investigate their structural and optical properties as well as their binding states. The experimental results demonstrate that the PQD film annealed at 120 °C has optimized characteristics, revealing better crystallinity and the lowest content of oxygen atoms (31.4%) and C-O-C bonding (20.1%). A too-high RTA temperature, more than 140 °C, causes severe degradation with the existence of PbI2. A proper RTA process, an alternative to normal heating and annealing, can effectively inhibit the occurrence of degradation and even usefully improve the performance of PQD films.

In this study, we develop a facile and feasible synthetic technique for producing denser porous titanium dioxide (TiO2) films. The porous TiO2 films are effectively prepared using a sol–gel process with dimethylformamide (DMF). The TiO2 solution is synthesized by adjusting DMF doses ranging from 0 to 10 wt%, and the as-grown TiO2 films are further annealed at different temperatures from 300 to 500 °C. The TiO2 films exhibit an asymmetry anatase TiO2 phase as annealing temperatures increase, and a denser structure as DMF doses increase. The optical properties of all samples are studied, and the porous TiO2 obtained by 7.5 wt% DMF dose demonstrates a remarkable transmittance and reflectance of 51.87% and 27.55%, respectively, in the visible region from 350 to 850 nm when compared to the pure TiO2 films. The calculated band gap values range from 3.15 to 3.25 eV. Furthermore, the resistivity of 350 °C-annealed porous TiO2 thin film is determined by the Hall effect, revealing an increase from 4.46 to an of average 4.79 ohm · cm after injecting DMF solvent. These findings have the potential to assist a growing number of optoelectronic applications.

In this study, a composite perovskite film composed of lead cesium triiodide (CsPbI3) quantum dots (QDs) and methylammonium lead iodide (CH3NH3PbI3; MAPbI3) was proposed. The CsPbI3 QDs prepared by hot-injecting were used as an anti-solvent in precursors to passivate the surface of this composite perovskite film. The further argon (Ar) plasma treatment improves the surface of the film. The effects of the powers from 100 to 200 W on the composite perovskite film structure, chemical element composition, and optical properties were studied. The experimental results demonstrate that the CsPbI3 QDs passivation boosts the ultraviolet light absorption (350–450 nm) and inhibits the formation of the PbI2 phase. Furthermore, Ar plasma treatment effectively improved CsPbI3 QDs passivation on MAPbI3 film. The powers lower than 140 W cause C=O bonds to dissolve and coordination bonds to form between OA carboxyl moieties and undercoordinated Pb2+ ions. At 160 and 140 W, the obvious crystal phase segregation and a decrease in light absorption are observed, respectively. Meanwhile, the strong bombardment of Ar ions at higher than 160 W causes the severe degradation of MAPbI3 film.

The promising functional tin oxide (SnOx) has attracted tremendous attention due to its transparent and conductive properties. The stoichiometric composition of SnOx can be described as common n-type SnO2 and p-type Sn3O4. In this study, the functional SnOx films were prepared successfully by plasma-enhanced atomic layer deposition (PEALD) at different substrate temperatures from 100 to 400 °C. The experimental results involving optical, structural, chemical, and electrical properties and morphologies are discussed. The SnO2 and oxygen-deficient Sn3O4 phases coexisting in PEALD SnOx films were found. The PEALD SnOx films are composed of intrinsic oxygen vacancies with O-Sn4+ bonds and then transformed into a crystalline SnO2 phase with increased substrate temperature, revealing a direct 3.5–4.0 eV band gap and 1.9–2.1 refractive index. Lower (300 °C) substrate temperatures can cause precursor condensation and desorption, respectively, resulting in reduced film qualities. The proper composition ratio of O to Sn in PEALD SnOx films near an estimated 1.74 suggests the highest mobility of 12.89 cm2 V−1 s−1 at 300 °C.

Annealing can usually inhibit the formation of an unstable brookite mesophase in the crystal structure, enhancing the growth of an anatase titanium dioxide (TiO2) thin film. In this study, after a TiO2 solution was prepared with and without a small amount (1 wt%) of the organic solvent dimethylformamide (DMF), TiO2 films were obtained by dynamic spin-coating and were annealed at temperatures of 300, 500, and 700 °C. The structural and optical properties as well as the surface morphologies of the films were studied. The experimental results show that the TiO2 film annealed at 500 °C exhibits a polycrystalline anatase and brookite multiphase and usefully inhibits the formation of the brookite mesophase when annealed at 700 °C. Moreover, adding the DMF effectively contributes to the formation of the polycrystalline phase at 300 °C. The compactness of the annealed TiO2 film was improved by adding 1 wt% DMF, as shown by topographic images obtained by atomic force microscopy, leading to decreased transmittance and increased absorbance. The band gap (Eg) values of all the samples were also estimated. The variation of Eg was evidenced by the structural change and the redshift of the absorption edge. [ABSTRACT FROM AUTHOR]