Shuqin Zhang

Bio: Shuqin Zhang is an academic researcher from China Jiliang University. The author has contributed to research in topics: Work function & Photocathode. The author has an hindex of 4, co-authored 20 publications receiving 38 citations. Previous affiliations of Shuqin Zhang include University of Alabama in Huntsville.

Temperature-dependent color-tunable luminescence in CsPbBr3: Dy3+ glass ceramic

Abstract: Available tunability of energy up-conversion in rare-earth (RE) ion doped nanomaterials has drawn great attention recently in the field of high-sensitive optical temperature transducer, but the intrinsically sharp fluorescence thermal-quenching and low energy transfer efficiency certainly limit further development. In this work, CsPbBr3 perovskite quantum dots (PQDs) was prepared by the melt-quenching method, simultaneously doping with Dy3+ in borosilicate glass, aiming to explore the thermochromic property. The novel phenomenon herein is that emerged bimodal emissions come from a luminescent active center of CsPbBr3 and a temperature-passivated RE Dy3+ ion, synergistically contributed to the remarkable relative sensitivities (2.631% K − 1). Interestingly, temperature-depended polychromatic luminescence among the PQDs embedded glass has been fully demonstrated as pumped by 365 nm ultraviolet light. Precise control of luminescent centers and color gamut is expected to design a temperature-sensitive material based on PQDs for promising optical applications.

Time-wavelength optical sampling spectroscopy based on dynamic laser cavity tuning

Abstract: Time-wavelength optical sampling (TWOS) is proposed here as a scheme that leverages the advantages of both wavelength-time mapping and ultrafast optical sampling to achieve real-time spectral measurement with simple configurations and slow photodetectors. As a proof of concept, a TWOS spectrometer based on dynamic optical sampling by laser cavity tuning is developed. Real-time absorption spectroscopy with a 0.3-nm spectral resolution and a 60-nm total spectral range (laser limited) is demonstrated at a 150-Hz updating rate. Theoretical analysis and practical limiting factors are discussed in detail. Potential applications of TWOS include spectroscopy, imaging, metrology, and optical sensing.

Cs and Cs/O adsorption mechanism on GaN nanowires photocathode

Abstract: We have investigated the stability and electronic properties of GaN nanowires photocathode based on first-principle calculations. The most stable adsorption configuration of Cs adatoms on the (001) surface of [001]-oriented GaN nanowires changes accordingly as Cs coverage increases. The work function of Cs-only-covered surface falls off with increasing Cs coverage. For the nanowire surface covered with either excessive or minor Cs coverage, the work function surprisingly increases slightly after O activation; however, for Cs coverage of 0.5 (monolayer) ML and 0.75 ML, O activation process still works for the nanowires photocathode. A downward band bending region is formed after Cs adsorption and will further bend downward after O adsorption only for models with Cs coverage of 0.5 ML and 0.75 ML. The optimized atomic ratio of Cs/O is 3:1. The diversification of the band structures is mainly attributed to the orbital hybridization between Cs-5 s, Cs-5p, O-2p states and Ga-4 s, N-2p states.

Ab initio determination of electron affinity of polar nitride surfaces, clean and under Cs coverage

Abstract: Ab initio simulations were used to determine electron affinity, work function, and ionization energy of AlN, GaN, and InN polar surfaces. The work function depends weakly on the doping in the bulk for the nitrides due to pinning of Fermi level at all polar surfaces. At the metal surface, it is smaller, equal to 3.87, 4.06, and 2.99 eV for AlN, GaN, and InN, respectively, while at the nitrogen side, it is much higher: 9.14, 9.02, and 8.24 eV. It was shown that the electron affinity and ionization potential do not obey the bandgap rule because of the quantum overlap repulsion of the surface and band states: conduction at the metal, and valence at the nitrogen side. The shift is substantial, even more than 1 eV, which may explain the first measured InN identified bandgap of 1.9 eV and the later much lower value of 0.7 eV. Cesium at both polar GaN surfaces does not create bonding states, nevertheless initially decreases electron affinity by charge transfer to surface states reducing electric dipole layer so t...