Band gap maps beyond the delocalization limit: correlation between optical band gaps and plasmon energies at the nanoscale

Zhan, Wei; Aarholt, Thomas; Kuznetsov, A. Yu.; Prytz, Øystein

doi:10.1038/s41598-017-18949-9

Cited by 22 publications

(13 citation statements)

References 27 publications

(42 reference statements)

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“…Egerton [30], for 60 keV incident electrons, EELS spatial resolutions in measuring band gaps of ZnO (~3.3 eV) and ZnCr 2 O 4 (~3.8 eV) are about 5.4 nm and 4.9 nm, respectively, which is highly suitable to characterize the band gap of the ZnCr 2 O 4 particles in this work. The band gap extraction procedures used here were the same as those described previously [28,31,32]. In brief, a power-law model was employed to remove the background from the ZLP.…”

Section: Experimental Methodsmentioning

confidence: 99%

ZnCr2O4 Inclusions in ZnO Matrix Investigated by Probe-Corrected STEM-EELS

et al. 2019

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The ZnCr2O4/ZnO materials system has a wide range of potential applications, for example, as a photocatalytic material for waste-water treatment and gas sensing. In this study, probe-corrected high-resolution scanning transmission electron microscopy and geometric phase analysis were utilized to study the dislocation structure and strain distribution at the interface between zinc oxide (ZnO) and embedded zinc chromium oxide (ZnCr2O4) particles. Ball-milled and dry-pressed ZnO and chromium oxide (α-Cr2O3) powder formed ZnCr2O4 inclusions in ZnO with size ~400 nm, where the interface properties depended on the interface orientation. In particular, sharp interfaces were observed for ZnO [2113]/ZnCr2O4 [110] orientations, while ZnO [1210]/ZnCr2O4 [112] orientations revealed an interface over several atomic layers, with a high density of dislocations. Further, monochromated electron energy-loss spectroscopy was employed to map the optical band gap of ZnCr2O4 nanoparticles in the ZnO matrix and their interface, where the average band gap of ZnCr2O4 nanoparticles was measured to be 3.84 ± 0.03 eV, in contrast to 3.22 ± 0.01 eV for the ZnO matrix.

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Section: Experimental Methodsmentioning

confidence: 99%

ZnCr2O4 Inclusions in ZnO Matrix Investigated by Probe-Corrected STEM-EELS

et al. 2019

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“…In undoped samples, EELS is often used for studying the volume plasmon generated by the valence band. n is then the density of valence electrons, and in ZnO the plasmon occurs as a broad peak centered at 18.9 eV [47]. However, in heavily doped samples with a significant amount of charge carriers in the conduction band, the conduction band can set up its own plasmon oscillation [48][49][50][51].…”

Section: Plasmon Analysismentioning

confidence: 99%

Direct observation of conduction band plasmons and the related Burstein-Moss shift in highly doped semiconductors: A STEM-EELS study of Ga-doped ZnO

et al. 2018

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The combination of high optical transparency and low electrical resistivity has made transparent conductive oxides (TCOs) a key technology in many optoelectronic applications. Furthermore, the study of TCOs yields insight into many fundamental parameters of semiconductors. For example, the high charge carrier concentration results in an apparent shift in the band gap, the so-called Burstein-Moss shift, in addition to plasmonic resonances in the near infrared regime. While both effects are related to the carrier concentration and band structure, their lateral distribution and interaction with boundary conditions such as interfaces and surfaces are difficult to assess, and a direct observation of the local distribution has remained elusive. Here we employ electron energy-loss spectroscopy in scanning transmission electron microscopy (STEM-EELS) for direct observation of spatially resolved plasmonic resonances and Burstein-Moss shift in gallium doped zinc oxide (GZO), one of the most widely used TCOs. A 25 nm thick GZO film with a carrier concentration of 7 × 10 20 cm −3 has been grown epitaxially on a nominally undoped ZnO film. The GZO film shows a renormalized Burstein-Moss shift of ∼0.5 eV, in accordance with that expected from Hall effect measurements. The plasma resonance of the conduction band electrons is located at 0.82 eV in the bulk GZO, and with a substantial increase in intensity towards the sample surface, where a surface plasmon energy of 0.54 eV is observed. Hence we have directly measured differences in optical properties between the two films, the local variation across the GZO film has been studied, and we are also directly observing the difference between bulk and surface properties of GZO.

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“…Although most reported studies deal with noble metal nanostructures with characteristic resonances around the visible range, the analyses may extend over any other system showing collective electron oscillation, from the UV to the IR, providing valuable insights on size and environmental effects, coupling and hybrid modes, etc. The already mentioned technique capabilities allow for exploring different approaches for the study of photonic systems, such as the simultaneous band gap and plasmon map acquisition in ZnO/Zn 1−x CdxO heterostructures [ 67 ]. The methodology can also be successfully applied to the study of other light-matter quasiparticles, such as plasmon-exciton polaritons (plexitons) originating from hybrid systems combining layered semiconductors coupled to metal nanoparticles acting as nanoantennas, probing the plasmon–exciton hybridization, while revealing the plasmon-like charge and field distribution of the plexito [ 68 ].…”

Section: Spectroscopy In Stemmentioning

confidence: 99%

STEM Tools for Semiconductor Characterization: Beyond High-Resolution Imaging

Mata

Molina

2022

Nanomaterials

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The smart engineering of novel semiconductor devices relies on the development of optimized functional materials suitable for the design of improved systems with advanced capabilities aside from better efficiencies. Thereby, the characterization of those materials at the highest level attainable is crucial for leading a proper understanding of their working principle. Due to the striking effect of atomic features on the behavior of semiconductor quantum- and nanostructures, scanning transmission electron microscopy (STEM) tools have been broadly employed for their characterization. Indeed, STEM provides a manifold characterization tool achieving insights on, not only the atomic structure and chemical composition of the analyzed materials, but also probing internal electric fields, plasmonic oscillations, light emission, band gap determination, electric field measurements, and many other properties. The emergence of new detectors and novel instrumental designs allowing the simultaneous collection of several signals render the perfect playground for the development of highly customized experiments specifically designed for the required analyses. This paper presents some of the most useful STEM techniques and several strategies and methodologies applied to address the specific analysis on semiconductors. STEM imaging, spectroscopies, 4D-STEM (in particular DPC), and in situ STEM are summarized, showing their potential use for the characterization of semiconductor nanostructured materials through recent reported studies.

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Band gap maps beyond the delocalization limit: correlation between optical band gaps and plasmon energies at the nanoscale

Cited by 22 publications

References 27 publications

ZnCr2O4 Inclusions in ZnO Matrix Investigated by Probe-Corrected STEM-EELS

ZnCr2O4 Inclusions in ZnO Matrix Investigated by Probe-Corrected STEM-EELS

Direct observation of conduction band plasmons and the related Burstein-Moss shift in highly doped semiconductors: A STEM-EELS study of Ga-doped ZnO

STEM Tools for Semiconductor Characterization: Beyond High-Resolution Imaging

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