Raman and Photoluminescence Spectroscopic Detection of Surface-Bound Li+O2− Defect Sites in Li-Doped ZnO Nanocrystals Derived from Molecular Precursors

Kirste, Ronny; Aksu, Yılmaz; Wagner, Markus R.; Khachadorian, Sevak; Jana, Surajit; Drieß, Matthias; Thomsen, C.; Hoffmann, A.

doi:10.1002/cphc.201000852

Cited by 22 publications

(6 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This line was reported in a multitude of different ZnO samples such as substrates, 3-6 homoepitaxial 7-9 and heteroepitaxial films, [10][11][12][13] microcrystals and nanocrystals, [14][15][16][17][18] nanowires, 19 and quantum wells. 20 In nanomaterials the Y 0 line is only observed in structures with sufficiently large dimensions.…”

Section: Introductionmentioning

confidence: 88%

Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

et al. 2011

View full text Add to dashboard Cite

ZnO single crystals, epilayers, and nanostructures often exhibit a variety of narrow emission lines in the spectral range between 3.33 and 3.35 eV which are commonly attributed to deeply bound excitons (Y lines). In this work, we present a comprehensive study of the properties of the deeply bound excitons with particular focus on the Y 0 transition at 3.333 eV. The electronic and optical properties of these centers are compared to those of the shallow impurity related exciton binding centers (I lines). In contrast to the shallow donors in ZnO, the deeply bound exciton complexes exhibit a large discrepancy between the thermal activation energy and localization energy of the excitons and cannot be described by an effective mass approach. The different properties between the shallow and deeply bound excitons are also reflected by an exceptionally small coupling of the deep centers to the lattice phonons and a small splitting between their two electron satellite transitions. Based on a multitude of different experimental results including magnetophotoluminescence, magnetoabsorption, excitation spectroscopy (PLE), time resolved photoluminescence (TRPL), and uniaxial pressure measurements, a qualitative defect model is developed which explains all Y lines as radiative recombinations of excitons bound to extended structural defect complexes. These defect complexes introduce additional donor states in ZnO. Furthermore, the spatially localized character of the defect centers is visualized in contrast to the homogeneous distribution of shallow impurity centers by monochromatic cathodoluminescence imaging. A possible relation between the defect bound excitons and the green luminescence band in ZnO is discussed. The optical properties of the defect transitions are compared to similar luminescence lines related to defect and dislocation bound excitons in other II-VI and III-V semiconductors.

show abstract

Section: Introductionmentioning

confidence: 88%

Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

et al. 2011

View full text Add to dashboard Cite

show abstract

“…The strainsensitive E 2 (high), observed at 439.4 cm -1 in both samples, is characteristic of a small compressive strain. 47,48 The identical position of this mode in the Li doped and undoped nanorods proves that no additional lattice strain is induced by the Li doping. In addition to the ZnO modes, the Li doped samples show Raman modes at 95.…”

Section: Li-zno Nanorods Via Non-classical Crystallizationmentioning

confidence: 75%

Li-doped ZnO nanorods with single-crystal quality – non-classical crystallization and self-assembly into mesoporous materials

et al. 2014

Self Cite

View full text Add to dashboard Cite

The benefits and promise of nanoscale dimensions for the properties of (ceramic) semiconductors are widely known. 1-D nanostructures in particular have proven to be of extraordinary relevance due to their applicability in future electronic and optoelectronic devices. Key to successful technological implementation of semiconductor nanostructures is the control of their electronic properties via doping. Despite its tremendous importance, precise chemical doping of defined nano-objects has been addressed rarely so far. Frequent problems are the creation of secondary defects and related undesired property changes by incorporation of hetero-elements, and the difficulty in ensuring a uniform and precise positioning of the dopant in the nanocrystal lattice. Here, we present the synthesis of Li-doped zinc oxide nanorods, which possess excellent (single-crystal) quality. The method is based on a novel non-classical crystallization mechanism, comprising an unusually oriented disassembly step. Afterwards, the nanorods are incorporated into mesoporous layers using colloidal self-assembly. Proof-of-principle gas sensing measurements with these novel materials demonstrate the beneficial role of Li-doping, indicating not only better conductivity but also the occurrence of catalytic effects.

show abstract

“…[10,11] Furthermore, the relocation of lithium ions in ZnO lattices was observed in recent studies and the ratio between Li Zn (i.e., Li in the Zn sites) and Li i · (i.e., Li in the interstitial sites) is temperature and process dependent. [11] The intrinsic mobility of Li doping usually leads to the complexity of defect states in ZnO, including those at the surface, [12] which then influence electron-hole separation under photon excitation, such as UV irradiation. [12][13][14] Thus, an understanding of the surface-defect states is relevant to many properties of ZnO materials, including photocatalytic activity and selectivity.…”

Section: Introductionmentioning

confidence: 99%

“…[11] The intrinsic mobility of Li doping usually leads to the complexity of defect states in ZnO, including those at the surface, [12] which then influence electron-hole separation under photon excitation, such as UV irradiation. [12][13][14] Thus, an understanding of the surface-defect states is relevant to many properties of ZnO materials, including photocatalytic activity and selectivity. [14][15][16][17] The photocatalytic degradation of pollutants in the gas or liquid phases is an efficient process for environmental remediation and water decontamination.…”

Section: Introductionmentioning

confidence: 99%

Photocatalytic Activity and Selectivity of ZnO Materials in the Decomposition of Organic Compounds

Lin¹,

Cojocaru²,

Chou³

et al. 2013

ChemCatChem

View full text Add to dashboard Cite

ZnO and Li‐doped ZnO photocatalysts were prepared by using a solvothermal method, aided by a supercritical drying technique. The structure and morphology of the photocatalysts were investigated by using SEM, X‐ray diffraction (XRD), UV/Vis and Raman spectroscopy. The photocatalytic activity and selectivity were investigated in the aqueous‐phase photodegradation of methylene blue and phenol as model reactions. Herein, it is reported for the first time that Li doping can lead to significant deactivation of the photocatalytic activity (i.e., decreased oxidization capability) of ZnO materials. The distribution of intermediate products (i.e., selectivity) was also significantly modified in the decomposition of phenol catalyzed by Li‐doped ZnO compared to that catalyzed by ZnO. Photoluminescence (PL) and soft X‐ray absorption spectroscopy (XAS) studies suggested that dopant‐induced surface‐defect states acted as electron–hole combination centers and changed the adsorbate/surface binding, thus causing the deactivation of photocatalytic activity and altering the photocatalytic selectivity in Li‐doped ZnO materials.

show abstract

Raman and Photoluminescence Spectroscopic Detection of Surface-Bound Li+O2− Defect Sites in Li-Doped ZnO Nanocrystals Derived from Molecular Precursors

Cited by 22 publications

References 36 publications

Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

Li-doped ZnO nanorods with single-crystal quality – non-classical crystallization and self-assembly into mesoporous materials

Photocatalytic Activity and Selectivity of ZnO Materials in the Decomposition of Organic Compounds

Contact Info

Product

Resources

About