In order to investigate function of carrier behavior on gas-sensing properties, tin oxide-based films with different carrier concentration and mobility were obtained, by magnetron sputtering from the powder target, which was followed by further oxygen-management though the annealing treatment. The microstructure, surface morphology, electrical properties and gas sensitivity were characterized by XRD, Raman spectrum, photoluminescence spectrum, atomic force microscope, the hall effect system and electrochemical workstation, respectively. The results showed that all SnO₂-based films had a tetragonal rutile phase with (101) preferred orientation. The introduction of fluorine and regulation of oxygen vacancies tuned carrier concentration from 10¹⁵/cm³ to 10²¹/cm³ and mobility from 10² cm²/V·s to 10⁻¹ cm²/V·s. The decreasing carrier concentration as well as increasing mobility had a positively important function to improve the sensitivity of SnO₂-based films. The air-annealed SnO₂ film with lowest carrier concentration had a maximum sensitivity of R = 5.0, while vacuum-annealed SnO₂:F film with the highest carrier concentration being the minimum sensitivity. This puts forward a novel reference for the design and application of SnO₂-based gas sensing films.

Tin-based perovskite material is the best choice to replace heavy metal element lead during the last several years. Cs₂SnI₆ with Sn⁴⁺ is a fascinating optoelectronic material, which is a more air-stable composite cesium tin halide peroxide variant from CsSnI₃. However, the optoelectronic performance between N and P type of Cs₂SnI₆ varies considerably. Herein, we synthesized uniform Cs₂SnI₆ by modified two-step method, which thermal evaporated CsI firstly, and followed annealing in the SnI₄ and I₂ vapor at 150 °C resulted in uniform Cs₂SnI₆ films. SnF₄ is used as a dopant source to improve the optoelectronic properties of Cs₂SnI₆ films. Results indicate that good crystallinity was obtained for all films and the doped films underwent a crystalline plane meritocracy transition. The doped films had a flat, non-porous morphology with large grains. The high transmittance of the doped films in the infrared region led to the avoidance of self-generated thermal decomposition. With the help of F⁻, the films became more conductive and had higher carrier mobility. DFT calculations showed that doping with F reduced the surface energy of (004), resulted in a preferred orientation transition in the crystal of Cs₂SnI₆. Fluorine doped double layer perovskite materials would have a broader application prospect.

Fluorine dopant inhibited the oxidation process in CsSnI_3−xF_x films with high carrier concentration, low resistivity and wide light absorption.

Research on the preparation and performance of graphene composite materials has become a hotspot due to the excellent electrical and mechanical properties of graphene. Among such composite materials, zinc oxide/graphene (ZnO/graphene) composite films are an active research topic. Therefore, in this study, we used the vacuum thermal evaporation technique at different evaporation voltages to fabricate an amorphous ZnO/graphene composite film on a flexible polyethylene terephthalate (PET). The amorphous ZnO/graphene composite film inherited the great transparency of the graphene within the visible spectrum. Moreover, its electrical properties were better than those of pure ZnO but less than those of graphene, which is not consistent with the original theoretical research (wherein the performance of the composite films was better than that of ZnO film and slightly lower than that of graphene). For example, the bulk free charge carrier concentrations of the composite films (0.13, 1.36, and 0.47 × 10¹⁸ cm⁻³ corresponding to composite films with thicknesses of 40, 75, and 160 nm) were remarkably lower than that of the bare graphene (964 × 10¹⁸ cm⁻³) and better than that of the ZnO (0.10 × 10¹⁸ cm⁻³). The underlying mechanism for the abnormal electrical performance was further demonstrated by X-ray photoelectron spectroscopy (XPS) detection and first-principles calculations. The analysis found that chemical bonds were formed between the oxide (O) of amorphous ZnO and the carbon (C) of graphene and that the transfer of the π electrons was restricted by C=O and C-O-C bonds. Given the above, this study further clarifies the mechanism affecting the photoelectric properties of amorphous composite films.