Wei-Shan Lee

Bio: Wei-Shan Lee is an academic researcher from Academia Sinica. The author has contributed to research in topics: Nanocrystalline material & Band gap. The author has an hindex of 1, co-authored 1 publications receiving 35 citations. Previous affiliations of Wei-Shan Lee include National Taiwan University.

Cesium doped and undoped ZnO nanocrystalline thin films: a comparative study of structural and micro‐Raman investigation of optical phonons

Abstract: Undoped and cesium-doped zinc oxide (ZnO) thin films have been deposited on sapphire substrate (0001) using the sol–gel method. Films were preheated at 300 °C for 10 min and annealed at 600 and 800 °C for 1 h. The grown thin films were confirmed to be of wurtzite structure using X-ray diffraction. Surface morphology of the films was analyzed using scanning electron microscopy. The photoluminescence (PL) spectra of ZnO showed a strong ultraviolet (UV) emission band located at 3.263 eV and a very weak visible emission associated with deep-level defects. Cesium incorporation induced a blue shift of the optical band gap and quenching of the near-band-edge PL for nanocrystalline thin film at room temperatures because of the band-filling effect of free carriers. A shift of about 10–15 cm−1 is observed for the first-order longitudinal-optical (LO) phonon Raman peak of the nanocrystals when compared to the LO phonon peak of bulk ZnO. The UV resonant Raman excitation at RT shows multiphonon LO modes up to fifth order. Copyright © 2010 John Wiley & Sons, Ltd.

The one phonon raman spectrum in microcrystalline silicon

Abstract: The red shift and the broadening of the Raman signal from microcrystalline silicon films is described in terms of a relaxation in the q-vector selection rule for the excitation of the Raman active optical phonons. The relationship between width and shift calculated from the known dispersion relation in c-Si is in good agreement with available data. An increase in the decay rate of the optical phonons predicted on the basis of the same model is confirmed experimentally.

Fabrication of p-CuO/n-ZnO heterojunction diode via sol-gel spin coating technique

Abstract: We report a facile all-solution approach for the growth of nanostructured p-CuO and n-ZnO thin films. The influence of annealing temperature on the physical properties of CuO and ZnO thin films was examined. XRD and Raman spectra depict the structural and phase purity of solution grown CuO and ZnO films. The electrical as well as the optical properties of thin films were also studied. The average optical transmission of CuO and ZnO thin films in the visible spectral region was found to be above 80 and 95% respectively. Band gap energy variations on annealing temperature were investigated for CuO as well as ZnO films. Surface morphology analyzed by FESEM shows that the films are very smooth. All solution grown p-n heterojunction using p-CuO and n-ZnO films was fabricated in the structure ITO/n-ZnO/p-CuO/Au which showed rectification behavior with a turn on voltage of 2.5 V and an ideality factor of 3.15.

Synthesis of novel triarylamine-based dendrimers with N4,N6-dibutyl-1,3,5-triazine-4,6-diamine probe for electron/energy transfers in H-bonded donor–acceptor–donor triads and as efficient Cu2+ sensors

Abstract: Two novel highly soluble triarylamine dendrimers TPAD1 and TPAD2 with N4,N6-dibutyl-1,3,5-triazine-4,6-diamine probe were synthesized via normal synthetic routes Both dendrimers (TPAD1 and TPAD2) form H-bonded donor–acceptor–donor (D–A–D) supramolecular triads TPAD1-PBI-TPAD1 and TPAD2-PBI-TPAD2 with 3,4,9,10-perylene tetra carboxylic diimide derivative (PBI) The presence of multiple H-bonds in the solution state was elucidated by 1H NMR titrations and IR spectral studies J-aggregations and electron/energy transfers provided by both dendrimers were verified by UV–Vis and photoluminescence (PL) titrations with PBI and the particle sizes of supramolecular triads were calculated by X-ray diffraction (XRD) analysis Similarly, both dendrimers also showed sensitivities towards Cu2+ in comparison with 19 interfering metal ions, which were evidenced via UV–Vis and PL titraions in both single and dual metal systems The maximum detection limit of Cu2+ ions was determined to be 20 ppm from PL titrations for both dendrimers, and the 1 : 2 stoichiometry of the complexes formed by both dendrimers (TPAD1-Cu2+ and TPAD2-Cu2+) were calculated by Job plots based on UV–Vis absorption titrations More importantly, the binding mechanism of the 1,3,5-triazine-4,6-diamine probe of both dendrimers was well characterized by 1H and 13C NMR titrations ([D8]THF : D2O = 2 : 1 in vol) and supported by the fluorescence reversibility by adding metal ions and PMDTA sequentially