A two-dimensional (2D) material known as indium selenide (InSe) is widely considered a promising layered semiconductor with potential applications in electronics and optoelectronics. However, the single phase of InSe is still a challenge due to the close formation energy of InSe and In2Se3. In this study, we demonstrate a novel growth method for 2D InSe with an indium precursor layer by molecular beam epitaxy. Indium pre-deposited on substrate at room temperature followed by growth of InSe at 550°C can overcome the problem of stoichiometry control and can be applied on amorphous substrate with high quality. According to Raman scattering spectra, X-ray diffraction, and high-resolution transmission electron microscopy results, we find that 2D InSe phase can be facile formed under both indium-rich and -poor conditions. The pre-deposited indium precursor effectively induces replacement with subsequent Se and In atoms to form the InSe phase while suppressing the In2Se3 phase. Additionally, this single phase InSe is stable in the atmosphere, exhibiting superior electronic properties even after over 100 days exposure. Recently, this method has been successfully applied to a flexible substrate, such as aluminum foil, resulting in reliable InSe quality. Our results demonstrate an innovative and forward-looking approach to developing 2D InSe material.

Thin‐film heterostructures are effective in enhancing the performance or triggering novel physical phenomena of optoelectronic applications. For example, the epitaxial heterostructures of ultraviolet‐light‐sensitive TiO2 with metallic SrRuO3 can acquire visible‐light functionalities using the hot carrier injection mechanism. Therefore, the TiO2/SrRuO3 heterostructure system has recently attracted increasing interest. Herein, the amorphous‐TiO2/SrRuO3 heterostructure is fabricated and compared to the epitaxial TiO2/SrRuO3. As opposed to the occurrence of the visible‐light photovoltaic effect in the epitaxial TiO2/SrRuO3, the amorphous‐TiO2/SrRuO3 heterostructure herein exhibits different optoelectronic functionality, specifically the photoresistor behavior. The amorphous‐TiO2/SrRuO3 heterostructure achieves a photoresponsivity of 6.56 A W−1 at 1 V. Such a performance is hardly obtained in typical oxide‐based photoresistors. The analyses of the crystalline and electronic structures show that it is due to the defect‐induced high electron doping in the amorphous TiO2 with hot carrier injection mechanism. This study discusses the correlation between the hot carrier injection and band diagram, which provides more degrees of freedom in designing potential optoelectronic devices.

By utilizing the combined analyses of X-ray diffraction and X-ray absorption spectroscopy, a systematic identification on the crystal phases of the polymorphic Hf 1−x Zr x O 2 thin films with various series of preparation conditions was presented. The results of the rigorous quantitative analysis show that the monoclinic phase and the tetragonal phase are mutually exclusive and a high fraction of orthorhombic phase up to 97% can be achieved under a specific process condition. On the basis of the observed correlation between the phase fraction and the in-plane strain, the strain-induced activation energy barrier was proposed to clarify the mechanism of the kinetic phase transition process. The endurance test of the device, exhibiting that the wake-up degree (remnant polarization variation ΔP r /P max ) increases exponentially with increasing the content of tetragonal phase in the pristine state, indicating the transition from tetragonal to orthorhombic as a possible mechanism of the wake-up effect. Our study presented herein points the way to efficiently optimize the strain toward highly pure orthorhombic Hf 1−x Zr x O 2 thin film through precisely controlling the process parameters, which is beneficial for the future development of ferroelectric devices.

Hard X-ray photoelectron spectroscopy (HAXPES) was utilized to investigate the thermal effect on heterojunction interfaces of a commercial CIGSeS-based solar cell, especially for the variations in its electronic properties and diffusion behaviors of the elements. To obtain depth-dependent information near the ZnO/CdS/CIGSeS heterojunction interfaces using a nondestructive method, we deliberately prepared a series of CIGSeS solar cells annealed at different temperatures with wedge-like ZnO window layers from a chemical etching method and collected the photoelectrons emitted from the samples with a lateral scan. A quantitative analysis of the HAXPES results revealed that all elements were upwardly diffused, whereas the cadmium atoms in the CdS buffer layer remained unchanged after the thermal treatment. Thermal annealing resulted in the disappearance of the ordered defect compound (ODC) domain and the band realignment at the ZnO/CdS/CIGSeS interfaces due to elemental interdiffusion. Our results elucidate the dominant mechanism behind the heat-induced degradation of the efficiency of energy conversion.