Resonant and bound states of charged defects in two-dimensional semiconductors

Aghajanian, Martik; Schuler, Bruno; Cochrane, Katherine A.; Lee, J. H.; Kastl, Christoph; Neaton, Jeffrey B.; Weber‐Bargioni, Alexander; Mostofi, Arash A.; Lischner, Johannes

doi:10.1103/physrevb.101.081201

Cited by 29 publications

(45 citation statements)

References 41 publications

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“…The negative charge localized at the defect gives rise to a strong upwards band bending, explaining why it appears as a dark extended depression in STM images at positive bias voltage. At negative sample bias, multiple defect states are observed, which we attribute to hydrogenic bound and resonant states of the screened Coulomb potential, as we reported recently [29].…”

Section: Ionsupporting

confidence: 83%

Vibronic response of a spin-1/2 state from a carbon impurity in two-dimensional WS2

Cochrane

Lee

Kastl

et al. 2020

Preprint

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We demonstrate the creation of a spin-1/2 state via the atomically controlled generation of magnetic carbon radical ions (CRIs) in synthetic two-dimensional transition metal dichalcogenides. Hydrogenated carbon impurities located at chalcogen sites introduced by chemical doping are activated with atomic precision by hydrogen depassivation using a scanning probe tip. In its anionic state, the carbon impurity exhibits a magnetic moment of 1 μB resulting from an unpaired electron populating a spin-polarized in-gap orbital. By inelastic tunneling spectroscopy and density functional theory we show that the CRI defect states couple to a small number of vibrational modes, including a local, breathing-type mode. The electron-phonon coupling strength critically depends on the spin state and differs for monolayer and bilayer WS2. These carbon radical ions in TMDs comprise a new class of surface-bound, single-atom spin-qubits that can be selectively introduced, are spatially precise, feature a well-understood vibronic spectrum, and are charge state controlled.

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Section: Ionsupporting

confidence: 83%

Vibronic response of a spin-1/2 state from a carbon impurity in two-dimensional WS2

Cochrane

Lee

Kastl

et al. 2020

Preprint

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“…We can identify several point defects based on the close resemblance of their STM topographic contrast with defects previously identified and characterized extensively in CVD‐grown WS 2 . [ 55–59 ] Such defects include for instance Cr and Mo substituting for W, [ 57 ] or oxygen substituting selenium, both at the top and bottom site. [ 55,56 ] All of these defects are charge neutral and feature a low formation energy.…”

Section: Figurementioning

confidence: 99%

“…[ 57 ] Positively and negatively charged defects that exhibit a bright and dark contrast at positive sample bias (Figure 3a) are more difficult to identify due to the presence of band bending (see Figure S13, Supporting Information) and hydrogenic states that obscure the chemical defect signature. [ 58 ] Negatively charged defects do exist in nominally undoped WSe 2 and WS 2 , which we attribute in part to CH impurities at chalcogen sites. [ 59 ] Positively charged defects on the other hand were exclusive to MOCVD WSe 2 samples and found in small abundance in nominally undoped samples and in very large abundance in Re‐doped samples (see Figure S13, Supporting Information), suggesting that the positively charged defects correspond to ionized Re impurities.…”

Section: Figurementioning

confidence: 99%

Scalable Substitutional Re‐Doping and its Impact on the Optical and Electronic Properties of Tungsten Diselenide

et al. 2020

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Doping is the cornerstone of semiconductor technology, enabling the success of modern digital electronics. 2D transition metal dichalcogenides (TMDCs) are promising material platforms for future electronics applications where its wafer-scale synthesis and controllable doping will be a required prerequisite to drive the next technological revolution. [1-6] Successful realization of wafer-scale, electronic grade, intrinsic 2D TMDCs via common deposition methods is rapidly progressing, however, advances in scalable doping still remain in the "proof-of-concept" stage, delaying the largescale fabrication of logic circuits based on extrinsic 2D semiconductors. [7-12] Moreover, integration of 2D TMDCs with Si complementary metal-oxide-semiconductor at the back-end-of-line (BEOL) is being actively explored for diffusion barriers, liners, and thin-film-transistors to improve the overall integrated circuit performance. [13-16] However, BEOL production lines are Reliable, controlled doping of 2D transition metal dichalcogenides will enable the realization of next-generation electronic, logic-memory, and magnetic devices based on these materials. However, to date, accurate control over dopant concentration and scalability of the process remains a challenge. Here, a systematic study of scalable in situ doping of fully coalesced 2D WSe 2 films with Re atoms via metal-organic chemical vapor deposition is reported. Dopant concentrations are uniformly distributed over the substrate surface, with precisely controlled concentrations down to <0.001% Re achieved by tuning the precursor partial pressure. Moreover, the impact of doping on morphological, chemical, optical, and electronic properties of WSe 2 is elucidated with detailed experimental and theoretical examinations, confirming that the substitutional doping of Re at the W site leads to n-type behavior of WSe 2. Transport characteristics of fabricated back-gated fieldeffect-transistors are directly correlated to the dopant concentration, with degrading device performances for doping concentrations exceeding 1% of Re. The study demonstrates a viable approach to introducing true dopantlevel impurities with high precision, which can be scaled up to batch production for applications beyond digital electronics.

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“…143,144 Preliminary steps for modeling charged defects have recently been reported. 66 Finally, extensions to other 2D materials and vdW multilayer structures 145 as well as to solutions of the Boltzmann equation based on first-principles inputs for the band structure, band velocities, and T -matrix scattering amplitude (cf. App.…”

Section: Discussion and Outlookmentioning

confidence: 99%

“…The semiconducting TMD monolayers are some of the most well-studied 2D materials in terms of electrical, optical, and structural properties. This includes numerous STM/STS studies of their atomic defects, showing that the most common types of defects are monovacancies, 13,54-64 oxygen substitutionals, 14,15,65,66 i.e. an oxygen atom substituting a chalcogenide atom, and antisite defects.…”

Section: Defects In 2d Tmdsmentioning

confidence: 99%

Atomistic T -matrix theory of disordered two-dimensional materials: Bound states, spectral properties, quasiparticle scattering, and transport

Kaasbjerg

2020

Phys. Rev. B

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In this work, we present an atomistic first-principles framework for modeling the low-temperature electronic and transport properties of disordered two-dimensional (2D) materials with randomly distributed point defects (impurities). The method is based on the T -matrix formalism in combination with realistic density-functional theory (DFT) descriptions of the defects and their scattering matrix elements. From the T -matrix approximations to the disorder-averaged Green's function (GF) and the collision integral in the Boltzmann transport equation, the method allows calculations of, e.g., the density of states (DOS) including contributions from bound defect states, the quasiparticle spectrum and the spectral linewidth (scattering rate), and the conductivity/mobility of disordered 2D materials. We demonstrate the method by examining these quantities in monolayers of the archetypal 2D materials graphene and transition metal dichalcogenides (TMDs) contaminated with vacancy defects and substitutional impurity atoms. By comparing the Born and T -matrix approximations, we also demonstrate a strong breakdown of the Born approximation for defects in 2D materials manifested in a pronounced renormalization of, e.g., the scattering rate by the higherorder T -matrix method. As the T -matrix approximation is essentially exact for dilute disorder, i.e., low defect concentrations (c dis 1) or density (n dis A −1 cell where A cell is the unit cell area), our first-principles method provides an excellent framework for modeling the properties of disordered 2D materials with defect concentrations relevant for devices. arXiv:1911.00530v1 [cond-mat.mes-hall] 1 Nov 2019

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Resonant and bound states of charged defects in two-dimensional semiconductors

Cited by 29 publications

References 41 publications

Vibronic response of a spin-1/2 state from a carbon impurity in two-dimensional WS2

Vibronic response of a spin-1/2 state from a carbon impurity in two-dimensional WS2

Scalable Substitutional Re‐Doping and its Impact on the Optical and Electronic Properties of Tungsten Diselenide

Atomistic T -matrix theory of disordered two-dimensional materials: Bound states, spectral properties, quasiparticle scattering, and transport

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