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[en] Several techniques in optical spectroscopy make use of similar sets of instruments such as spectrometers lasers, optics, etc. However it has been very challenging endeavor to incorporate as many functionalities into one instrument without compromise of quality of results and at the same time allow easy switching between operating modes. It is therefore worthwhile to develop an instrument that integrates as much functionality as possible and at the same time allow even a common user to switch modes easily. A novel instrument capable of performing various types of microspectroscopy techniques is developed. The instrument is capable of performing Photoluminescence (PL), Raman, Time resolved PL spectroscopy (TRPL) and Photoluminescence excitation spectroscopy (PLE). The instrument makes use of a polarizing beamsplitter (PBS) for Photoluminescence or a diochronic raman beamsplitter, for Raman, to insert the laser excitation onto the instrument optical axis. In using the PBS, the large operational range of beamsplitter coating (400-750nm or 650-1000nm), provides more than 99% insertion efficiency for a large range of laser wavelengths with proper orientation of the incident polarization. The crossed polarized transmitted signal emanating from the sample is detected by the instrument. Due to polarization independence of most signals obtained in PL spectroscopy the crosses polarized geometry is sufficient for observation of such signals. Due to the flexibility of the instrument, it is currently a workhorse in the laboratory. Raman (one of its modes) has been employed by other researchers in failure analysis experiments such as measurements of stress in Silicon devices, and determination of different forms of carbon used in coatings for hard disks. (author)
[en] Highlights: • Electronic properties of Nd-doped PbS is studied. • Nd-doped PbS is converted to an indirect band gap semiconductor. • Nd(4f) state plays an important role in the doping system. - Abstract: The electronic and optical properties of Nd-doped PbS are investigated by the first-principles calculation and experimental method. Our results indicate that introducing of Nd will enlarge the band gap of PbS slightly, and the doped PbS will be converted to an indirect band-gap semiconductor from a direct band-gap semiconductor. The electronic state of this doped PbS system eventually exhibits a good ferromagnetism, in which Nd (4f) states play an important role. The calculated refractive index and extinction coefficient are basically consistent with the experimental values. This study will help us to understand how Nd-doping affects the electronic properties of PbS.
[en] Crystal structure of a new misfit layer compound (PbS)1.14(NbS2)2 has been determined. The structure which is analyzed in terms of a composite crystal consisting of [PbS], [NbS2] and common parts corresponds to an alternated sequence of [PbS] and [NbS2] layers along the c axis. Incommensurability is occurring along the a axis
[en] Some issues on the method used by Zhang et al. [Appl. Spectrosc. 51, 576 (1997)] to correct for the nonlinearity of a HgCdTe detector in Fourier transform spectrometry measurements are discussed in response to comments by Zhang. Other problems that must be taken into consideration before the effects of detector nonlinearity of HgCdTe detectors are fully accounted for in FT spectrometry are highlighted
[en] Lead sulfide nanowires with controllable optoelectronic properties would be promising building blocks for various applications. Here, we report the hot colloidal synthesis of radically branched and zigzag nanowires through self-attachment of star-shaped and octahedral nanocrystals in the presence of multiple surfactants. We obtained high-quality single-crystal nanowires with uniform diameter along the entire length, and the size of the nanowire can be tuned by tailoring the reaction parameters. This slow oriented attachment provides a better understanding of the intricacies of this complex nanocrystal assembly process. Meanwhile, these self-assembled nanowire structures have appealing lateral conformations with narrow side arms or highly faceted edges, where strong quantum confinement can occur. Consequently, the single-crystal nanowire structures exhibit strong photoluminescence in the near-infrared region with a large blue-shift compared to the bulk material.
[en] In a recent paper (Lewis et al 2010 Nanotechnology 21 45502) proposed a previously unidentified gap state within lead sulfide nanocrystals (PbS-NCs) based on analysis of their temperature dependent optical properties. In the following we argue that due to oversights in the analysis of the data presented, inconsistencies arise which question their exclusion of 'dark' excitonic states as the origin of the observed effects. (comment)