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- Krammel, C. M., et al.
(author)
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Probing the local electronic structure of isovalent Bi atoms in InP
- 2020
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In: Physical Review B. - 2469-9969 .- 2469-9950. ; 101:2
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Journal article (peer-reviewed)abstract
- Cross-sectional scanning tunneling microscopy (X-STM) is used to experimentally study the influence of isovalent Bi atoms on the electronic structure of InP. We map the spatial pattern of the Bi impurity state, which originates from Bi atoms down to the sixth layer below the surface, in topographic, filled-state X-STM images on the natural {110} cleavage planes. The Bi impurity state has a highly anisotropic bowtielike structure and extends over several lattice sites. These Bi-induced charge redistributions extend along the < 110 > directions, which define the bowtielike structures we observe. Local tight-binding calculations reproduce the experimentally observed spatial structure of the Bi impurity state. In addition, the influence of the Bi atoms on the electronic structure is investigated in scanning tunneling spectroscopy measurements. These measurements show that Bi induces a resonant state in the valence band, which shifts the band edge toward higher energies. Furthermore, we show that the energetic position of the Bi-induced resonance and its influence on the onset of the valence band edge depend crucially on the position of the Bi atoms relative to the cleavage plane.
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| 2. |
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| 3. |
- Krammel, C. M., et al.
(author)
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Incorporation of Bi atoms in InP studied at the atomic scale by cross-sectional scanning tunneling microscopy
- 2017
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In: Physical Review Materials. - 2475-9953. ; 1:3
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Journal article (peer-reviewed)abstract
- We show the potential of cross-sectional scanning tunneling microscopy to address structural properties of dilute III-V bismides by investigating Bi:InP. Bismuth atoms down to the second monolayer below the {110} InP surfaces, which give rise to three classes of distinct contrast, are identified with the help of density functional theory calculations. Based on this classification, the pair-correlation function is used to quantify the ordering of Bi atoms on the long range. In a complementary short-ranged study, we investigate the Bi ordering at the atomic level. An enhanced tendency for the formation of first-nearest-neighbor Bi pairs is found. In addition, the formation of small Bi clusters is observed whose geometries appear to be related to strong first-nearest-neighbor Bi pairing. We also identify growth related crystal defects, such as In vacancies, P antisites, and Bi antisites.
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| 4. |
- Krammel, C. M., et al.
(author)
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Structural Properties of Bi Containing InP Films Explored by Cross-Sectional Scanning
- 2019
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In: Springer Series in Materials Science. - Singapore : Springer Singapore. - 2196-2812 .- 0933-033X. ; 285, s. 215-229
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Book chapter (other academic/artistic)abstract
- The structural properties of highly mismatched III-V semiconductors with small amounts of Bi are still not well understood at the atomic level. In this chapter, the potential of cross-sectional scanning tunneling microscopy (X-STM) to address these questions is reviewed. Special attention is paid to the X-STM contrast of isovalent impurities in the III-V system, which is discussed on the basis of theoretical STM images of the (110) surface using density functional theory (DFT) calculations. By comparing high-resolution X-STM images with complementary DFT calculations, Bi atoms down to the third monolayer below the InP (110) surface are identified. With this information, the Short-range ordering of Bi is studied, which reveals a strong tendency toward Bi pairing and clustering. In addition, the occurrence of Bi surface segregation at the interfaces of an InP/InP1−xBix/InP quantum well with a Bi concentration of 2.4 % is discussed.
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