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  • 1.
    Gooran, Sasan
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Yang, Li
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Basics of tone reproduction2015In: Handbook of Digital Imaging / [ed] Michael Kriss, Wiley , 2015Chapter in book (Refereed)
    Abstract [en]

     There is no doubt that printing has been one of the most important technological inventions for

    human civilization. Books, magazines, news papers, and so on have been printed for different

    purposes such as distributing knowledge, thoughts, and news and commercializing products.

    Tone reproduction for images has been one of the challenging parts of the printing technology

    because the printing devices are restricted to a few color inks, whereas the original image

    may consist of millions of color tones. In this chapter, the basics of the tone reproduction

    are introduced. We begin with a brief history of halftoning and a short introduction of digitalization.

    It is followed by the description on visual acuity of human visual system and its

    relationship with the screen resolution. Then the basic and general concepts of tone reproduction,

    such as screen frequency, print resolution, screen angle and Moiré pattern, and dot gain

    are described and illustrated. Dot gain is only briefl y described and illustrated in this chapter as

    it is thoroughly discussed in Physical Evaluation of the Quality of Color Halftone . Finally,

    technologies for color reproduction and color halftoning are discussed.

  • 2.
    Gooran, Sasan
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Yang, Li
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Frequency Modulated Halftoning and Dot Gain2004In: Proceedings of the Technical Association of the Graphic Arts, TAGA, Technical Association of the Graphic Arts , 2004Conference paper (Other academic)
  • 3.
    Yang, Li
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    A unified model of optical and physical dot gain in print color reproduction2004In: Journal of Imaging Science And Technology, ISSN 8750-9237, Vol. 48, no 4, p. 347-353Article in journal (Refereed)
    Abstract [en]

    A unified model coping with both physical and optical dot gains on print color tone reproduction is proposed. The physical dot gain, is approximated by a quadratic function of nominal dot percentages. The function, for each color, is characterized by a single parameter depending on printing technologies as well as ink-paper interactions, and has a symmetric form around where the nominal dot percentage is 50%. The parameter can be derived from the best fit for the model to measured data, such as spectral reflectance values or CIEXYZ tristimulus values. Applications to a color laser printer (on office copy paper) reproduces the experimental dot gain curves fairly well. Dependence on physical dot percentage, a summation of the nominal dot percentage and the corresponding physical dot gain, results in the optical dot gain and in turn the overall dot gain asymmetric forms, plotted against the nominal dot percentages. Furthermore, theoretical analysis reveals fundamental differences between physical and optical dot gains. Therefore, effects of optical dot gain can not be accurately represented by any physical extension in printing practices.

  • 4.
    Yang, Li
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Characterization of inks and ink application for ink-jet printing: model and simulation2003In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 20, no 7, p. 1149-1154Article in journal (Refereed)
    Abstract [en]

    Ink-jet printing quality is determined primarily by, among other factors, the printing engine and its inks. The printing engine controls the process of ink application and the scheme of ink mixing for the generation of secondary and tertiary colors. The inks selectively absorb different wavelengths from the illumination and result in the visible color output. Therefore characterizations of the output print in terms of ink distribution and volume, the scheme of ink mixing, light absorption, and light scattering are of essential importance in controlling and understanding the quality of the color reproduction. I present a method to characterize the ink volume and the properties of the ink by means of spectral reflectance measurements and simulations. The simulations are based on the Kubelka-Munk theory, whose applicability to ink-jet printing is also discussed. (C) 2003 Optical Society of America.

  • 5.
    Yang, Li
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Qualifying the arguments used in the derivation of the revised Kubelka-Munk theory: reply2007In: JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION, ISSN 1084-7529, Vol. 24, no 2, p. 557-560Other (Other academic)
    Abstract [en]

    The fundamental assumptions made in the revised Kubelka-Munk (KM) model of light propagation in scattering and absorptive media, recently proposed [J. Opt. Soc. Am. A 21, 1942 (2004), 22, 866 (2005)], are critically reviewed and analyzed. The authors argue that the model, now questioned by Edstrom [J. Opt. Soc. Am. A 24, 548 (2007)] is well founded on physical grounds and consistent with the original KM model, which has been the cornerstone of light propagation studies and utilized for more than half a century. (c) 2007 Optical Society of America

  • 6.
    Yang, Li
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Spectral model of halftone on a fluorescent substrate2005In: Journal of Imaging Science And Technology, ISSN 8750-9237, Vol. 49, no 2, p. 179-184Article in journal (Refereed)
    Abstract [en]

    The color rendition of a halftone image depends on, among other things, physical and optical dot gains and fluorescence of substrates. A unified model describing spectral reflectance of a print is proposed with consideration of these effects. In this model the effects of either physical or optical dot gain are characterized by a single parameter, while those of fluorescence by two sets of spectral parameters, one for fluorescence of bare paper and one for fluorescence of a print solid. This model is tested and further illustrated with applications to images generated by a laser color printer on ordinary office papers. © 2005, IS&T - The Society for Imaging Science and Technology.

  • 7.
    Yang, Li
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Fogden, Andrew
    Institute for Surface Chemistry, Stockholm.
    Pauler, Nils
    Mid Sweden University.
    Saevborg, Oerjan
    Stora Enso Research Center.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Studying ink penetration with microscopic and spectroscopic techniques2006In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 50, no 4, p. 327-332Article in journal (Refereed)
    Abstract [en]

    Distribution of ink jet ink in paper substrates and the consequences of ink penetration for printing color reproduction have been studied by combining microscopic image processing with spectroscopic analysis. The study focused on the effects of the composition of uncoated paper, for five laboratory papers plus two commercial products, all consisting of similar pulps but with different combinations of additives. In particular, it was observed that hydrophobizing internal size agents significantly reduced ink penetration, while their effect on paper optical properties was negligible. This observation thus made it possible to study experimentally the pure effects of ink penetration. Pairwise comparisons of prints on such laboratory papers with identical optical properties revealed remarkable impacts of ink penetration on optical density, causing color saturation reduction and color shift. These experimental observations confirmed the theoretical predictions.

  • 8.
    Yang, Li
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Fogden, Andrew
    Pauler, Nils
    Sävborg, Örjan
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    A novel method for studying ink penetration of a print2005In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 4, p. 423-429Article in journal (Refereed)
    Abstract [en]

    A method combining microscopy with image analysis for studying ink penetration of ink-jet prints has been proposed. Prints on paper substrates of various material compositions have been microtomed, imaged with optical microscopy, and analyzed with image processing. The penetration depth and distribution of the ink-jet dye in the paper, which depend on the material compositions of the substrates and printed ink volumes, are then obtained by means of statistical analysis. The study focuses on uncoated fine papers, including five types of hand-sheets and two commercial papers. It is observed that ink penetration can be significantly reduced by adding internal sizing (hydrophobizing) chemicals in the hand-sheet making, while it is relatively less affected by addition of filler and fluorescent whitening agent (FWA). Ink volume obviously influences the depth of its penetration, with depth increasing linearly for higher ink volumes but displaying a disproportionately shallow penetration for smaller applied volumes.

  • 9.
    Yang, Li
    et al.
    Karlstad University.
    Gooran, Sasan
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Eriksen, Magnus
    Johansson, Tobias
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Color Based Maximal GCR for Electrophotography2006In: IS&T Int. Conf. on Digital Printing Technologies (NIP22), The Society for Imaging Science and Technology , 2006, p. 394-397Conference paper (Other academic)
    Abstract [en]

    The underline idea of grey component replacement (GCR) is to replace a mixture of primary colors (cyan, magenta, and yellow) by a black. Current algorithms of GCR are mainly based on the concept of equal-tone-value-reduction or mixing equal amount (tone value) of primary colors generating gray, which in turn can be represented by the same amount of black. As the colors used are usually non-ideal, such a replacement can result in remarkable color deviation.    

    We proposed an algorithm of maximal GCR based on color matching, i.e. the black is introduced in a way that preserves the color (before and after GCR). In the algorithm, the primary with smallest tonal value is set to be zero (tone value) while the other two are reduced according to the color matching calculations. To achieve a real color matching of print, dot gain effects have been considered in the calculation. The proposed algorithm has been tested successfully for FM halftoning using an electrophotographic printer.   

  • 10.
    Yang, Li
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Simulation of optical dot gain in multichromatic tone production2001In: Journal of Imaging Science And Technology, ISSN 8750-9237, Vol. 45, no 2, p. 198-204Article in journal (Refereed)
    Abstract [en]

    Optical dot gain (light scattering or Yule-Nielsen effect) is an important effect influencing the quality of tone reproductions. Based on probability descriptions on the light scattering, a framework is established for describing this effect on the reflectance and color appearance of a chromatic halftone image. General expressions for the reflectance and CIEXYZ tristimulus values have been derived. Simulations for images printed with 2 inks have been carried out by applying Gaussian type of point spread function (PSF). Dependence of the optical dot gain on the optical properties of substrate and inks, the dot geometry etc., have been studied in detail.

  • 11.
    Yang, Li
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Gooran, Sasan
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Yule-Nielsen Effect and Ink-penetration in Multi-chromatic Tone Reproduction2000In: IS & T's NIP16: International Conference on Digital Printing Technologies, 2000, p. 363-366Conference paper (Other academic)
    Abstract [en]

    A framework describing influences of ink penetration and Yule-Nielsen effect on the reflectance and tristimulus values of a halftone sample has been proposed. General expressions of the reflectance values and CIEXYZ tristimulus values have been derived. Simulations for images printed with two inks have been carried out by applying Gaussian type of point spread function (PSF). Dependence of Yule-Nielsen effect on the optical properties of substrate, inks, the dot geometry, ink penetration etc., have been discussed.

  • 12.
    Yang, Li
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Evaluation of the effects of ink penetration in ink jet printing: Experiments and simulation2004In: Journal of Imaging Science And Technology, ISSN 8750-9237, Vol. 48, no 3, p. 260-264Article in journal (Refereed)
  • 13.
    Yang, Li
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Revised Kubelka-Munk theory. I. Theory and application2004In: Journal of the Optical Society of America A: Optics and Image Science, and Vision, ISSN 1084-7529, Vol. 21, no 10, p. 1933-1941Article in journal (Refereed)
    Abstract [en]

    Using a statistical analysis of light propagation in media, we propose a revision to Kubelka-Munk (K-M) theory by taking into account the effect of scattering on the path length of light propagation (path variation). This leads to new relationships between the K-M scattering S and absorbing K coefficients and the intrinsic scattering s and absorbing a coefficients of a material that indicate that the S and K coefficients depend nonlinearly on both a and s. The additivity law that bridges K-M S and K coefficients of a composite medium, such as dye-dispersed paper (dyed paper) and those of its material components (dye and paper), is also revised. It is further shown that experimental findings on dyed paper that the original K-M theory failed to explain can be clearly understood and accommodated by the new K-M theoretical framework (two-flux approach). Numerical simulations with the revised theory on model ink, paper, and dyed paper have been carried out.

  • 14.
    Yang, Li
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Revised Kubelka-Munk theory. II. Unified framework for homogeneous and inhomogeneous optical media2004In: Journal of the Optical Society of America A: Optics and Image Science, and Vision, ISSN 1084-7529, Vol. 21, no 10, p. 1942-1952Article in journal (Refereed)
    Abstract [en]

    We extend the applicability of the recently revised Kubelka-Munk (K-M) theory to inhomogeneous optical media by treating inhomogeneous ink penetration of the substrate. We propose a method for describing light propagation in either homogeneous or inhomogeneous layers using series representations for the K-M scattering and absorption coefficients as well as for intensities of the upward and downward light streams. The conventional and matrix expressions for spectral reflectance and transmittance values of optically homogeneous media in the K-M theory are shown to be special cases of the present framework. Three types of ink distribution - homogeneous, linear, and exponential - have been studied. Simulations of spectral reflectance predict a depression of reflectance peaks and reduction of absorption bands characteristic of hue shifts and significant reduction of saturation and, in turn, color gamut.

  • 15.
    Yang, Li
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Lenz, Reiner
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Light scattering and ink penetration effects on tone reproduction2001In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 18, no 2, p. 360-366Article in journal (Refereed)
    Abstract [en]

    Light scattering, or the so-called Yule-Nielsen effect, and ink penetration into the substrate paper play important roles in tone reproduction. We develop a framework in which the influences of both of these effects on the reflectance and tristimulus values of a halftone sample are investigated. The properties of the paper and the ink and their bilateral interaction can be parameterized by the reflectance R-p(0) of the substrate paper, the transmittance T-i of the ink layer, the parameter gamma describing the ink penetration, and (p) over bar describing the Yule-Nielsen effect. We derive explicit expressions that relate the reflectance of the ink dots (R-i), the paper (R-p) and the halftone image (R) as functions of these parameters, We also describe the optical dot gain as a function of these parameters. We further demonstrate that ink penetration leads to a decrease in optical dot gain and that scattering in the paper results in the printed image's being viewed as more saturated in color. (C) 2001 Optical Society of America. OCIS codes: 100.7810, 290.7050.

  • 16.
    Yang, Li Li
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Synthesis and Characterization of ZnO Nanostructures2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    One-dimensional ZnO nanostructures have great potential applications in the fields of optoelectronic and sensor devices.  Therefore, it is very important to realize the controllable growth of one-dimensional ZnO nanostructures and investigate their properties. The main points for this thesis are not only to successfully realize the controllable growth of ZnO nanorods (ZNRs), ZnO nanotubes (ZNTs) and ZnMgO/ZnO heterostructures, but also investigate the structure and optical properties in detail by means of scanning electron microscope (SEM), transmission electron microscope (TEM), resonant Raman spectroscopy (RRS), photoluminescence (PL), time resolved PL (TRPL), X-ray photoelectron spectroscopy (XPS) and Secondary ion mass spectrometry (SIMS).

    For ZNRs, on one hand, ZNRs have been successfully synthesized by a two-step chemical bath deposition method on Si substrates. The diameter of ZNRs can be well controlled from 150 nm to 40 nm through adjusting the diameter and density of the ZnO nanoparticles pretreated on the Si substrates. The experimental results indicated that both diameter and density of ZnO nanoparticles on the substrates determined the diameter of ZNRs. But when the density is higher than the critical value of 2.3×108cm-2, the density will become the dominant factor to determine the diameter of ZNRs.

    One the other hand, the surface recombination of ZNRs has been investigated in detail. Raman, RRS and PL results help us reveal that the surface defects play a significant role in the as-grown sample. It is the first time to the best of our knowledge that the Raman measurements can be used to monitor the change of surface defects and deep level defects in the CBD grown ZNRs. Then we utilized TRPL technique, for the first time, to investigate the CBD grown ZNRs with different diameters. The results show that the decay time of the excitons in ZNRs strongly depends on the diameter. The altered decay time is mainly due to the surface recombination process. A thermal treatment under 500°C can strongly suppress the surface recombination channel. A simple carrier and exciton diffusion equation is also used to determine the surface recombination velocity, which results in a value between 1.5 and 4.5 nm/ps. Subsequently, we utilized XPS technique to investigate the surface composition of as-grown and annealed ZNRs so that we can identify the surface recombination centers. The experimental results indicated that the OH and H bonds play the dominant role in facilitating surface recombination but specific chemisorbed oxygen also likely affect the surface recombination. Finally, on the basis of results above, we explored an effective way, i.e. sealing the beaker during the growth process, to effectively suppress the surface recombination of ZNRs and the suppression effect is even better than a 500oC post-thermal treatment.

    For ZNTs, the structural and optical properties have been studied in detail. ZNTs have been successfully evolved from ZNRs by a simple chemical etching process. Both temperature-dependent PL and TRPL results not only further testify the coexistence of spatially indirect and direct transitions due to the surface band bending, but also reveal that less nonradiative contribution to the emission process in ZNTs finally causes their strong enhancement of luminescence intensity.

    For ZnMgO/ZnO heterostructures, the Zn0.94Mg0.06O/ZnO heterostructures have been deposited on 2 inch sapphire wafer by metal organic chemical vapor deposition (MOCVD) equipment. PL mapping demonstrates that Mg distribution in the entire wafer is quite uniform with average concentration of ~6%. The annealing effects on the Mg diffusion behaviors in Zn0.94Mg0.06O/ZnO heterostructures have been investigated by SIMS in detail. All the SIMS depth profiles of Mg element have been fitted by three Gaussian distribution functions. The Mg diffusion coefficient in the as-grown Zn0.94Mg0.06O layer deposited at 700 oC is two orders of magnitude lower than that of annealing samples, which clearly testifies that the deposited temperature of 700 oC is much more beneficial to grow ZnMgO/ZnO heterostructures or quantum wells.

    This thesis not only provides the effective way to fabricate ZNRs, ZNTs and ZnMgO/ZnO heterostructures, but also obtains some beneficial results in aspects of their optical properties, which builds theoretical and experimental foundation for much better understanding fundamental physics and broader applications of low-dimensional ZnO and related structures.

    List of papers
    1. Size-controlled growth of well-aligned ZnO nanorod arrays with two-step chemical bath deposition method
    Open this publication in new window or tab >>Size-controlled growth of well-aligned ZnO nanorod arrays with two-step chemical bath deposition method
    2009 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 469, no 1-2, p. 623-629Article in journal (Refereed) Published
    Abstract [en]

    Well-aligned ZnO nanorod arrays (ZNAs) with different sizes in diameter were fabricated on Si substrates by two-step chemical bath deposition method (CBD), i.e. substrate pre-treatment with spin coating to form ZnO nanoparticles layer and CBD growth. The effects of substrate pre-treatments, pH, angel (θ) between substrate and beaker bottom and growth time (t) on the structure of ZNAs were investigated in detail by X-ray diffraction (XRD), field emission scan electronic microscope (SEM) and photoluminescence (PL). The results show that substrate pre-treatment, pH, θ and t indeed have great influence on the growth of ZNAs, and their influence mechanisms have been, respectively, explained in detail. The introduction of a ZnO nanoparticle layer on the substrate not only helps to decrease the diameter but also has a strong impact on the orientation of ZNAs. Under the growth condition of pH 6, θ = 70° and t = 2 h, the well-aligned ZnO nanorod arrays with 50 nm diameter was obtained on the pre-treated Si substrates. And only a strong UV peak at 385 nm appears in room temperature PL spectrum for this sample, which indicates that as-synthesized ZnO nanorods have a perfect crystallization and low density of deep level defects.

    Keywords
    ZnO nanorods, Chemical bath deposition, Optical properties
    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:liu:diva-15532 (URN)10.1016/j.jallcom.2008.08.002 (DOI)
    Note
    Original Publication:LiLi Yang, Qingxiang Zhao and Magnus Willander, Size-controlled growth of well-aligned ZnO nanorod arrays with two-step chemical bath deposition method, 2009, Journal of Alloys and Compounds, (469), 1-2, 623-629.http://dx.doi.org/10.1016/j.jallcom.2008.08.002Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com/Available from: 2009-03-27 Created: 2008-11-14 Last updated: 2017-12-14Bibliographically approved
    2. Effective way to control the size of well-aligned ZnO nanorod arrays with two-step chemical bath deposition
    Open this publication in new window or tab >>Effective way to control the size of well-aligned ZnO nanorod arrays with two-step chemical bath deposition
    2009 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 311, no 4, p. 1046-1050Article in journal (Refereed) Published
    Abstract [en]

    The diameter of well-aligned ZnO nanorod arrays (ZNAs) grown on Si substrates has been well controlled from 150nm to 40nm by two-step chemical bath deposition method (CBD), i.e. substrate pretreatment with spin coating to form ZnO nanoparticles seed layer and CBD growth. The effects of ZnO nanoparticles density and diameter on size and alignment of ZNAs were investigated in detail by atomic force microscope (AFM), X-ray diffraction (XRD), scan electronic microscope (SEM), transmission electron microscope (TEM) and photoluminescence (PL). The results indicate that both diameter and density of ZnO nanoparticles which were pre-coated on the substrates will influence the size and alignment of ZNAs, but the density will play a key role to determine the diameter of ZNAs when the density is higher than the value of 2.3×108cm-2. Moreover, only a strong UV peak at 385 nm appears in room temperature PL spectrum for these samples, which indicates that  as-synthesized ZnO nanorods have a perfect crystallization and low density of deep level defects.

    Keywords
    ZnO nanorods arrays, CBD, Size-controlled growth
    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:liu:diva-15533 (URN)10.1016/j.jcrysgro.2008.12.028 (DOI)
    Note
    Original Publication: Li-Li Yang, Qingxiang Zhao, Magnus Willander and J.H. Yang, Effective way to control the size of well-aligned ZnO nanorod arrays with two-step chemical bath deposition, 2009, Journal of Crystal Growth, (311), 4, 1046-1050. http://dx.doi.org/10.1016/j.jcrysgro.2008.12.028 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2008-11-14 Created: 2008-11-14 Last updated: 2017-12-14
    3. Annealing effects on optical properties of low temperature grown ZnO nanorod arrays
    Open this publication in new window or tab >>Annealing effects on optical properties of low temperature grown ZnO nanorod arrays
    Show others...
    2009 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 105, no 5, p. 053503-Article in journal (Refereed) Published
    Abstract [en]

    Vertically well-aligned ZnO nanorods on Si substrates were prepared by a two-step chemical bath deposition method. The structure and optical properties of the grown ZnO nanorods were investigated by Raman and photoluminescence spectroscopy. The results showed that after an annealing treatment at around 500 degrees C in air atmosphere, the crystal structure and optical properties became much better due to the decrease in surface defects. The resonant Raman measurements excited by 351.1 nm not only revealed that the surface defects play a significant role in the as-grown sample, which was supported by low temperature time-resolved photoluminescence measurements, but also suggested that the strong intensity increase in some Raman scatterings was due to both outgoing resonant Raman scattering effect and deep level defect scattering contribution for ZnO nanorods annealed from 500 to 700 degrees C.

    Keywords
    annealing, crystal structure, deep levels, II-VI semiconductors, liquid phase deposition, nanostructured materials, nanotechnology, photoluminescence, Raman spectra, time resolved spectra, wide band gap semiconductors, zinc compounds
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-17508 (URN)10.1063/1.3073993 (DOI)
    Note
    Original Publication:Lili Yang, Qingxiang Zhao, Magnus Willander and Ivan Gueorguiev Ivanov , Annealing effects on optical properties of low temperature grown ZnO nanorod arrays, 2009, JOURNAL OF APPLIED PHYSICS, (105), 5, 053503.http://dx.doi.org/10.1063/1.3073993Copyright: American Institute of Physicshttp://www.aip.org/Available from: 2009-04-07 Created: 2009-03-27 Last updated: 2017-12-13Bibliographically approved
    4. Surface recombination in ZnO nanorods grown by chemical bath deposition
    Open this publication in new window or tab >>Surface recombination in ZnO nanorods grown by chemical bath deposition
    Show others...
    2008 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 104, no 7, p. 073526-Article in journal (Refereed) Published
    Abstract [en]

    Verticallywell-aligned ZnO nanorods on Si substrates were prepared by atwo-step chemical bath deposition (CBD) method. The optical properties ofthe grown ZnO nanorods were investigated by time resolved photoluminescencespectroscopy. It was found that the effective decay time ofthe near bandgap recombination in the CBD grown ZnO nanorodsstrongly depends on the diameter of the ZnO nanorods. Typically,the decay curves obtained from these ZnO nanorods show acombination of two exponential decays. The experimental results show thatthe fast exponential decay is related to the surface recombinationand the slow decay is related to the “bulk” decay.The measured decay time of the effective surface recombination decreaseswith decreasing diameter, while the bulk decay time remains unchanged.The results also show that an annealing treatment around 500 °Csignificantly reduces the surface recombination rate. A simple carrier andexciton diffusion equation is also used to determine the surfacerecombination velocity, which results in a value between 1.5 and4.5 nm/ps.

    Keywords
    Annealing, excitons, II-VI semiconductors, nanostructured materials, nanotechnology, photoluminescence, semiconductor growth, surface recombination, time resolved spectra, wide band gap semiconductors, zinc compounds
    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:liu:diva-15425 (URN)10.1063/1.2991151 (DOI)
    Note

    Original publication: Q. X. Zhao, L. L. Yang, M. Willander, B. E. Sernelius and P. O. Holtz, Surface recombination in ZnO nanorods grown by chemical bath deposition, 2008, Journal of Applied Physics, (104), 073526.http://dx.doi.org/10.1063/1.2991151. Copyright: Institute of Physics and IOP Publishing Limited, http://www.iop.org/EJ/journal/PM

    Available from: 2008-11-06 Created: 2008-11-06 Last updated: 2017-12-14Bibliographically approved
    5. Origin of the surface recombination centers in ZnO nanorods arrays by X-ray photoelectron spectroscopy
    Open this publication in new window or tab >>Origin of the surface recombination centers in ZnO nanorods arrays by X-ray photoelectron spectroscopy
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    2010 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 256, no 11, p. 3592-3597Article in journal (Refereed) Published
    Abstract [en]

    The surface composition of as-grown and annealed ZnO nanorods arrays (ZNAs) grown by a two-step chemical bath deposition method has been investigated by X-ray photoelectron spectroscopy (XPS). XPS confirms the presence of OH bonds and specific chemisorbed oxygen on the surface of ZNAs, as well as H bonds on (1 0 (1) over bar 0) surfaces which has been first time observed in the XPS spectra. The experimental results indicated that the OH and H bonds play the dominant role in facilitating surface recombination but specific chemisorbed oxygen also likely affect the surface recombination. Annealing can largely remove the OH and H bonds and transform the composition of the other chemisorbed oxygen at the surface to more closely resemble that of high temperature grown ZNAs, all of which suppresses surface recombination according to time-resolved photoluminescence measurements.

    Place, publisher, year, edition, pages
    Amsterdam, Netherlands: Elsevier, 2010
    Keywords
    ZnO nanorods, Optical properties, Surface recombination, X-ray photoelectron spectroscopy
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-54620 (URN)10.1016/j.apsusc.2009.12.160 (DOI)000275515100042 ()
    Note

    Original Publication: Li-Li Yang, Qingxiang Zhao, Magnus Willander, Xianjie Liu, Mats Fahlman and J H Yang, Origin of the surface recombination centers in ZnO nanorods arrays by X-ray photoelectron spectroscopy, 2010, APPLIED SURFACE SCIENCE, (256), 11, 3592-3597. http://dx.doi.org/10.1016/j.apsusc.2009.12.160 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/

    Available from: 2010-03-26 Created: 2010-03-26 Last updated: 2017-12-12
    6. Effective Suppression of Surface Recombination in ZnO Nanorods Arrays during the Growth Process
    Open this publication in new window or tab >>Effective Suppression of Surface Recombination in ZnO Nanorods Arrays during the Growth Process
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    2010 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 10, no 4, p. 1904-1910Article in journal (Refereed) Published
    Abstract [en]

    ZnO nanorods arrays are respectively prepared under different vapor pressures with opening (OZN) or sealing (SZN) of the beaker. The results from time-resolved photoluminescence measurements indicate that sealing the beaker during the growth process can effectively suppress the surface recombination of ZnO nanorods, and the suppression effect is even better than a 500 degrees C post-thermal treatment or OZN samples. The results from X-ray photoelectron spectroscopy measurements reveal that the main reason for this phenomenon is that the surfaces of the SZN samples are attached by groups related to NH3 instead of the main surface recombination centers such as OH and groups in the OZN samples. The ammonia surface treatment on both OZN and SZN samples further testifies that the absorption of the groups related to NH3 does not contribute to the surface recombination on the ZnO nanorods.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2010
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-54866 (URN)10.1021/cg100017b (DOI)000276234500068 ()
    Note

    This document is the Accepted Manuscript version of a Published Work that appeared in final form in CRYSTAL GROWTH and DESIGN, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: Li-Li Yang, Qingxiang Zhao, Magnus Willander, Xianjie Liu, Mats Fahlman and J H Yang, Effective Suppression of Surface Recombination in ZnO Nanorods Arrays during the Growth Process, 2010, CRYSTAL GROWTH and DESIGN, (10), 4, 1904-1910. http://dx.doi.org/10.1021/cg100017b Copyright: The American Chemical Society http://pubs.acs.org/

    Available from: 2010-04-16 Created: 2010-04-16 Last updated: 2017-12-12Bibliographically approved
    7. Indirect optical transition due to surface band bending in ZnO nanotubes
    Open this publication in new window or tab >>Indirect optical transition due to surface band bending in ZnO nanotubes
    Show others...
    2010 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 10Article in journal (Refereed) Published
    Abstract [en]

    ZnO nanotubes (ZNTs) have been successfully evolved from ZnO nanorods (ZNRs) by a simple chemical etching process. Two peaks located at 382 nm and 384 nm in the UV emission region has been observed in the room temperature photoluminescence (PL) spectrum of ZNTs since the surface band bending in ZNTs induces the coexistence of indirect and direct transitions in their emission process. In addition, a strong enhancement of total luminescence intensity at room temperature in ZNTs has also be observed in comparison with that of ZNRs. Both temperature-dependent PL and time-resolved PL results not only further testify the coexistence of indirect and direct transitions due to the surface band bending, but also reveal that less nonradiative contribution to the emission process in ZNTs finally causes their stronger luminescence intensity.

    Place, publisher, year, edition, pages
    American Institute, 2010
    Keywords
    Zinc Oxide, Nanotube, Surface band bending, Indirect transition, Temperature-dependent photoluminescence
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-60853 (URN)10.1063/1.3511345 (DOI)000285005000053 ()
    Note
    Original Publication: Li Li Yang, Qingxiang Zhao, Muhammad Qadir Israr, Jamil Rana Sadaf, Magnus Willander, Galia Pozina and J. H. Yang, Indirect optical transition due to surface band bending in ZnO nanotubes, 2010, Journal of Applied Physics, (108), 10, 103513. http://dx.doi.org/10.1063/1.3511345 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2010-10-28 Created: 2010-10-28 Last updated: 2017-12-12
    8. Mg diffusion in Zn0.94Mg0.06O/ZnO heterostructures grown by MOCVD
    Open this publication in new window or tab >>Mg diffusion in Zn0.94Mg0.06O/ZnO heterostructures grown by MOCVD
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Zn0.94Mg0.06O/ZnO heterostructures were grown on 2 inch sapphire wafer by MOCVD equipment. Photoluminescence mapping demonstrated that Mg uniformly distributed on the entire wafer with average concentration of ~6%. The annealing effects on the Mg diffusion behaviors were investigated by secondary ion mass spectrometry (SIMS). All Mg SIMS depth profiles were fitted by three Gaussian distribution functions. The Mg diffusion coefficient in the as-grown Zn0.94Mg0.06O layer deposited at 700 oC was two order of magnitude lower than that of annealed samples, which indicated that the deposition temperature of 700 oC is much more beneficial to grow ZnMgO/ZnO heterostructures or quantum wells.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-60854 (URN)
    Available from: 2010-10-28 Created: 2010-10-28 Last updated: 2014-01-15
  • 17.
    Yang, Li
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Lundström, Niclas
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Physical dot gain of offset: Understanding and determination2007In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, no 3, p. 388-393Article in journal (Refereed)
    Abstract [en]

    This report consists of two parts. In the first, a methodology for estimating physical dot gain from scanned images of test patches is proposed. Mathematical relationships bridging the image intensities with the physical dot coverage have been worked out, taking into consideration of light scattering inside the paper substrate and the light reflection at air-paper and air-ink interfaces. In the second part, the possible causes for the physical dot gain in the light of ink-transfer and ink-setting are discussed. The physical dot gain obtained reveals significant differences in the light tones compared to the middle and dark tones. This indicates differences in ink-transfer and ink-setting between the prints consisting of well isolated dots in the light tones and those of overlapping dots in the middle and dark tones. A tentative explanation based on process-competition between press, ink spreading, and free ink-splitting, is given.

  • 18.
    Yang, Li
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Theory of light propagation incorporating scattering and absorption in turbid media2005In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, no 7, p. 792-794Article in journal (Refereed)
    Abstract [en]

    A general theoretical approach to the description of light propagating through turbid media is proposed. The theory is a modification of the two-flux model of Kubelka-Munk (KM), extending its applicability to media systems containing an absorptive component. The modified KM model takes into account the influence of internal scattering on the total path length and accommodates a wide range of absorption influences. Experimental results obtained for dyed-paper systems illuminated by diffuse light are demonstrated to be qualitatively and quantitatively reproduced by the theory. © 2005 Optical Society of America.

1 - 18 of 18
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