Ruxue Li

Investigation of localized and delocalized excitons in ZnO/ZnS core-shell heterostructured nanowires

Abstract The localized states in ZnO nanowires (NWs) through the growth of ZnS shell have been introduced in this paper. Morphology and optical properties of the ZnO/ZnS core-shell heterostructured NWs after different rapid thermal annealing (RTA) treatments are investigated. Transmission electron microscopy measurements show the gradual disappearing of the jagged boundary between ZnO and ZnS with the increase of RTA temperature, while a decrease of interfacial composition fluctuation and a formation of ZnOS phase can be found after a RTA treatment of 300°C. Temperature-dependent photoluminescence exhibits the features of “S-shape” peak positions and a “valley shape” for the emission width, implying the existence of localized excitons in the core-shell NWs. Moreover, it is noted that the RTA treatments can lower the localized degree which is confirmed by optical measurement. The results indicate that the optical behavior of excitons in ZnO/ZnS core-shell heterostructured NWs can be manipulated by appropriate thermal treatments, which is very important for their practical device applications.

Linear and nonlinear optical characteristics of all-inorganic perovskite CsPbBr3 quantum dots modified by hydrophobic zeolites

All-inorganic perovskite quantum dots (QDs) have been considered as outstanding candidates for high-performance optoelectronic device applications. However, the chemical and optical stabilities restrict their device applications. In this paper, hydrophobic zeolites were proposed to modify CsPbBr3 QDs to prevent water influence while achieving good dispersion. These hybrid luminescent materials possess high internal quantum efficiency (IQE, ∼81%@3.52 W cm-2) and low dissociation levels that give rise to improved optical stability in terms of temperature and time. More interesting, it is found that this nanocomposite is able to maintain its optical limiting performance under intensive laser illumination. This paper discusses the linear and nonlinear optical characteristics of CsPbBr3 QDs, which would be of great importance for both fundamental physics investigation and practical multiphoton applications.

Surface sulfurization of ZnO/ZnS core shell nanowires and shell layers dependent optical properties

With the unique properties and superior performance, ZnO/ZnS core shell nanostructures have been applied in many photoelectric devices. Varied growth methods can synthesize ZnO/ZnS core shell samples, which exhibit different crystal and optical properties, and have the positive or negative effect on performance of related devices. To investigate the growth and properties, ZnO/ZnS core shell nanowires were grown through surface sulfurization. X-ray diffraction and scanning electron microscopy measurements indicated surface sulfurization degree can affect crystal quality. In addition, photoluminescence results exhibited that ZnO/ZnS heterojunction emission properties were dependent on shell layers quality. By increasing the amount of surface powder, it would improve shell layers’ crystal quality. And with optimal surface sulfurization degree, the vacancies and interstitial atoms defects can be restrained, which may improve photo-generated carriers separation efficiency.

Band alignment at a MgO/GaSb heterointerface using x-ray photoelectron spectroscopy measurements

The valence band offset (ΔE V) of a MgO/GaSb heterostructure was determined using x-ray photoelectron spectroscopy measurements. A ΔE V value of 2.84 ± 0.10 eV was calculated by using Ga 3d3/2 and Mg 2p1/2 binding energies as references. Taking the empirical band gaps of 7.83 eV and 0.73 eV for MgO and GaSb thin films into consideration, respectively, we obtained the type-I band alignment of a MgO/GaSb heterostructure with a conduction band offset (ΔE c) of 4.26 ± 0.10 eV, suggesting a nested interface band alignment.