Excitons

Böer, Karl W.; Pohl, Udo W.

doi:10.1007/978-3-031-18286-0_14

Cited by 6 publications

(5 citation statements)

References 164 publications

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“…For the data shown in Figure 4A, V g was calculated as ∼1.25 V. From two samples collected with the same potential step size, the average bandgap was V g = 1.2 ± 0.1 V. This value agrees well with the literature spectroscopic value for the silicon bandgap, E g = 1.12 eV. 44 Furthermore, in Figure 4B, eq 5 was used to calculate the corresponding DOS derived from Figure 4A. Lastly, the line shape of both Figure 4A,B can be compared with the well-known calculated band structure for bulk silicon, and the calculation was reproduced here in Figure 4C for reference 45−47 Non-idealities were sometimes observed during data collection.…”

Section: ■ Results and Discussionsupporting

confidence: 84%

“…Moreover, the electrochemical bandgap derived from the capacitance−potential plot was extrapolated as V g = 0.7 V, consistent with the literature value for the spectroscopic bandgap of E g = 0.664 eV. 44 The experimentally determined DOS values at the band edge for both silicon and germanium surfaces occured within the same order of magnitude as those expected for the VB and CB edges.…”

Section: ■ Results and Discussionsupporting

confidence: 84%

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Electrochemical Impedance of Well-Passivated Semiconductors Reveals Bandgaps, Fermi Levels, and Interfacial Density of States

Hallock,

Rose

2024

J. Am. Chem. Soc.

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For well-passivated semiconductor materials, the density of states (DOS) at the band edge determines the concentration of electrons (or holes) available to participate in photo/electrochemical redox and chemical reactions. Electrochemical impedance enables the characterization of photo-electrode DOS in a functional, in situ, electrochemical environment. However, the in situ electrochemical approach remains underutilized for band structure characterization of inorganic semiconductors. In this work, we demonstrate that the DOS of the well-passivated, highly ordered semiconductors silicon and germanium is directly probed by electrochemical impedance spectroscopy (EIS). More specifically, EIS measurements of the chemical capacitance in contact with electrolyte enable direct analysis of the DOS properties. From the capacitance−potential plot, the following parameters can be extracted: Fermi level, valence band maximum, conduction band minimum, and a quantitative value of the number of states at each potential. This study aims to establish the groundwork for future EIS investigations of electronically modified semiconductor interfaces with covalently bound organic molecules, organometallic catalysts, or more complex biorelated functionalizations.

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Section: ■ Results and Discussionsupporting

confidence: 84%

Section: ■ Results and Discussionsupporting

confidence: 84%

Electrochemical Impedance of Well-Passivated Semiconductors Reveals Bandgaps, Fermi Levels, and Interfacial Density of States

Hallock,

Rose

2024

J. Am. Chem. Soc.

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“…Similarly, the drain current density I D improves by 52 ± 20% at Δ ε = 0.48 ± 0.05%, with an enhancement rate of 109 ± 33 per % of biaxial strain. This trend is consistent with the mobility change, as I D is proportional to μ with fixed carrier concentration in the linear regime . Finally, there is only a small shift in the threshold voltage V th with strain, reaching a value of Δ V th = 9.1 ± 6.1 V at Δ ε = 0.48 ± 0.05%.…”

Section: Resultssupporting

confidence: 83%

Enhancing Carrier Mobility in Monolayer MoS₂ Transistors with Process-Induced Strain

Zhang,

Zhao,

Huang

et al. 2024

ACS Nano

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Two-dimensional electronic materials are a promising candidate for beyond-silicon electronics due to their favorable size scaling of electronic performance. However, a major challenge is the heterogeneous integration of 2D materials with CMOS processes while maintaining their excellent properties. In particular, there is a knowledge gap in how thin film deposition and processes interact with 2D materials to alter their strain and doping, both of which have a drastic impact on device properties. In this study, we demonstrate how to utilize processinduced strain, a common technique extensively applied in the semiconductor industry, to enhance the carrier mobility in 2D material transistors. We systematically varied the tensile strain in monolayer MoS 2 transistors by iteratively depositing thin layers of high-stress MgO x stressor. At each thickness, we combined Raman spectroscopy and transport measurements to unravel and correlate the changes in strain and doping within each transistor with their performance. The transistors displayed uniform strain distributions across their channels for tensile strains of up to 0.48 ± 0.05%, at 150 nm of stressor thickness. At higher thicknesses, mechanical instability occurred, leading to nonuniform strains. The transport characteristics systematically varied with strain, with enhancement in electron mobility at a rate of 130 ± 40% per % strain and enhancement of the channel saturation current density of 52 ± 20%. This work showcases how established CMOS technologies can be leveraged to tailor the transport in 2D transistors, accelerating the integration of 2D electronics into a future computing infrastructure.

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“…The “ 2 ” superscript indicates irreducible representations that belong to superpositional point groups in which the base identity operation ( E ) has a character of “2” (including all A n and B n terms) rather than “1”; this notation is required to account for the degeneracies of all converging and diverging states. Part A is reproduced with permission from ref , Copyright 1987, Springer; part B was derived therefrom by the present author.…”

Section: Band Structure Analysismentioning

confidence: 99%

Semiconductor Band Structure, Symmetry, and Molecular Interface Hybridization for the Chemist

Rose

2024

J. Am. Chem. Soc.

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Merging molecular bonding concepts with semiconductor-and materials-based concepts of band structure is challenging due to the mutually exclusive historical development and notations used in those respective fields: symmetry adapted linear combinations (SALCs) and Mulliken terms for molecules, versus k space and Bloch sums for materials. This lack of commonality brings the issue of hybridization (aka electronic coupling) between molecules and materials to the forefront in many aspects of modern chemical research�including nanocrystal properties, solar energy conversion, and molecular computing. It is thus critical to establish a holistic approach to hybridizing orbital (molecule) and plane-wave (semiconductor/material) systems to better describe symmetry-based molecule|material bonding and the corresponding symmetry-adapted molecular orbital (MO) diagrams. Such a unified approach would enable the construction of testable hypotheses about the role of symmetry and electronic structure in determining the extent of electronic coupling between molecular orbitals and semiconductor band structure. This Perspective provides an analysis and compendium of "translations" between the physics and chemistry language of group theory. In this vein, this approach describes the symmetries�and corresponding point groups�that occur in k space along the available descent in symmetry pathways (k space vectors). As a result, chemists may arrive at a more intuitive understanding of the band symmetries of semiconductors, as well as insights into the corresponding algebraic formulations. This analysis can ultimately generate MO diagrams for hybrid molecule|material systems. Lastly, an Outlook provides some context to the application of this analysis to modern problems at the interface of molecular and materials chemistry.To make sense of the marvelous electronic properties of the solid state, chemists must learn the language of solidstate physics, band structures. An attempt is made here to demystify that language, drawing explicit parallels to wellknown concepts in theoretical chemistry."

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Excitons

Cited by 6 publications

References 164 publications

Electrochemical Impedance of Well-Passivated Semiconductors Reveals Bandgaps, Fermi Levels, and Interfacial Density of States

Electrochemical Impedance of Well-Passivated Semiconductors Reveals Bandgaps, Fermi Levels, and Interfacial Density of States

Enhancing Carrier Mobility in Monolayer MoS₂ Transistors with Process-Induced Strain

Semiconductor Band Structure, Symmetry, and Molecular Interface Hybridization for the Chemist

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Excitons

Cited by 6 publications

References 164 publications

Electrochemical Impedance of Well-Passivated Semiconductors Reveals Bandgaps, Fermi Levels, and Interfacial Density of States

Electrochemical Impedance of Well-Passivated Semiconductors Reveals Bandgaps, Fermi Levels, and Interfacial Density of States

Enhancing Carrier Mobility in Monolayer MoS2 Transistors with Process-Induced Strain

Semiconductor Band Structure, Symmetry, and Molecular Interface Hybridization for the Chemist

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Product

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Enhancing Carrier Mobility in Monolayer MoS₂ Transistors with Process-Induced Strain