Imaging and identification of point defects in PtTe2

Zhussupbekov, Kuanysh; Ansari, Lida; McManus, J. Barry; Zhussupbekova, Ainur; Shvets, I. V.; Duesberg, Georg S.; Hurley, Paul K.; Gity, Farzan; Coileáin, Cormac Ó; McEvoy, Niall

doi:10.1038/s41699-020-00196-8

Cited by 35 publications

(38 citation statements)

References 58 publications

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“…Furthermore, a direct correlation with the optical emission is missing. Even though STM is a tool able to identify atomic defects in 2D materials, 56,[93][94][95][96] STM/STS measurements of point defects in monolayer h-BN have not been reported yet.…”

Section: Electronic Structure and Light Emission Related To Point Def...mentioning

confidence: 99%

Band gap measurements of monolayer h-BN and insights into carbon-related point defects

Román¹,

Costa²,

Zobelli³

et al. 2021

2D Mater.

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Being a flexible wide band gap semiconductor, hexagonal boron nitride (h-BN) has great potential for technological applications like efficient deep ultraviolet (DUV) light sources, building block for two-dimensional heterostructures and room temperature single photon emitters in the UV and visible spectral range. To enable such applications, it is mandatory to reach a better understanding of the electronic and optical properties of h-BN and the impact of various structural defects. Despite the large efforts in the last years, aspects such as the electronic band gap value, the exciton binding energy and the effect of point defects remained elusive, particularly when considering a single monolayer.Here, we directly measured the density of states of a single monolayer of h-BN epitaxially grown on highly oriented pyrolytic graphite, by performing low temperature scanning tunneling microscopy (LT-STM) and spectroscopy (STS). The observed h-BN electronic band gap on defect-free regions is (6.8 ± 0.2) eV. Using optical spectroscopy to obtain the h-BN optical band gap, the exciton binding energy is determined as being of (0.7 ± 0.2) eV. In addition, the locally excited cathodoluminescence and photoluminescence show complex spectra that are typically associated to intragap states related to carbon defects. Moreover, in some regions of the monolayer h-BN we identify, using STM, point defects which have intragap electronic levels around 2.0 eV below the Fermi level.

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Section: Electronic Structure and Light Emission Related To Point Def...mentioning

confidence: 99%

Band gap measurements of monolayer h-BN and insights into carbon-related point defects

Román¹,

Costa²,

Zobelli³

et al. 2021

2D Mater.

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“…The topographic STM image of the MnBi 2 Te 4 flat terrace reveals randomly distributed triangular defects with an average density of the order of 3.4 − 5.2% (Fig. 2c and its inset), similar to those at the Te-terminated transition metal dichalcogenides surfaces 53 , as well as bright atomic-size protrusions, although much less abundant.…”

Section: Figure 1dmentioning

confidence: 76%

“…This is consistent with the circular shape of the features, suggesting that they are either incorporated in the surface Te layer or adsorbed on top of it. The bright appearance excludes the possibility of them being Te vacancies, which are usually resolved as depressions at Te-terminated surfaces 53,63 . The small measured apparent height of 0.5 Å at 1 V as well as the difficulty to manipulate it with the STM tip points towards the substitutional character of this defect.…”

Section: Figure 1dmentioning

confidence: 99%

Native point defects and their implications for the Dirac point gap at MnBi$_2$Te$_4$(0001)

Garnica¹,

Otrokov²,

Aguilar³

et al. 2021

Preprint

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The Dirac point gap at the surface of the antiferromagnetic topological insulator MnBi2Te4 is a highly debated issue. While the early photoemission measurements reported on large gaps in agreement with theoretical predictions, other experiments found vanishingly small splitting of the MnBi2Te4 Dirac cone. Here, we study the crystalline and electronic structure of MnBi2Te4(0001) using scanning tunneling microscopy/spectroscopy (STM/S), micro(µ)-laser angle resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations. Our topographic STM images clearly reveal features corresponding to point defects in the surface Te and subsurface Bi layers that we identify with the aid of STM simulations as BiTe antisites (Bi atoms at the Te sites) and MnBi substitutions (Mn atoms at the Bi sites), respectively. X-ray diffraction (XRD) experiments further evidence the presence of cation (Mn-Bi) intermixing. Altogether, this affects the distribution of the Mn atoms, which, inevitably, leads to a deviation of the MnBi2Te4 magnetic structure from that predicted for the ideal crystal structure. Our transport measurements suggest that the degree of this deviation varies from sample to sample. Consistently, the ARPES/STS experiments reveal that the Dirac point gap of the topological surface state is different for different samples/sample cleavages. Our DFT surface electronic structure calculations show that, due to the predominant localization of the topological surface state near the Bi layers, MnBi defects can cause a strong reduction of the MnBi2Te4 Dirac point gap, given the recently proved antiparallel alignment of the MnBi moments with respect to those of the Mn layer. Our results provide a key to puzzle out the MnBi2Te4 Dirac point gap mystery.

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“…Two terraces separated by terrace edge, which run vertically though the center of the image ( V = 1.0 V and I = 80 pA). STS measurements were performed at each of the 50 points along the 15 nm length blue line. , An I ( V ) curve was obtained for each point and differentiated with respect to the voltage. Figure c displays representative d I /d V spectra measured on and away from the step edge.…”

Section: Resultsmentioning

confidence: 99%

“…The primary motivation underpinning this study relates to the formation of defects on the surface, their evolution in time, and their effect on the electronic surface states. , Using ion bombardment, we can reduce the degree of order. This can result in anomalous monolayer planes and A-type bilayer steps coexisting with the B-type bilayer step, which dominate the pristine cleaved Bi(111) surface.…”

Section: Introductionmentioning

confidence: 99%

Surface Modification and Subsequent Fermi Density Enhancement of Bi(111)

et al. 2021

Self Cite

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Defects introduced to the surface of Bi(111) break the translational symmetry and modify the surface states locally. We present a theoretical and experimental study of the 2D defects on the surface of Bi(111) and the states that they induce. Bi crystals cleaved in ultrahigh vacuum (UHV) at low temperature (110 K) and the resulting ion-etched surface are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) as well as spectroscopy (STS) techniques in combination with density functional theory (DFT) calculations. STS measurements of cleaved Bi(111) reveal that a commonly observed bilayer step edge has a lower density of states (DOS) around the Fermi level as compared to the atomic-flat terrace. Following ion bombardment, the Bi(111) surface reveals anomalous behavior at both 110 and 300 K: Surface periodicity is observed by LEED, and a significant increase in the number of bilayer step edges and energetically unfavorable monolayer steps is observed by STM. It is suggested that the newly exposed monolayer steps and the type A bilayer step edges result in an increase to the surface Fermi density as evidenced by UPS measurements and the Kohn–Sham DOS. These states appear to be thermodynamically stable under UHV conditions.

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Imaging and identification of point defects in PtTe2

Cited by 35 publications

References 58 publications

Band gap measurements of monolayer h-BN and insights into carbon-related point defects

Band gap measurements of monolayer h-BN and insights into carbon-related point defects

Native point defects and their implications for the Dirac point gap at MnBi$_2$Te$_4$(0001)

Surface Modification and Subsequent Fermi Density Enhancement of Bi(111)

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