The direct measurement of the electronic density of states of graphene using metastable induced electron spectroscopy

Chambers, Benjamin A.; Neumann, Christof; Turchanin, Andrey; Gibson, Christopher T.; Andersson, Gunther G.

doi:10.1088/2053-1583/aa62cb

Cited by 15 publications

(13 citation statements)

References 52 publications

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“…The C 1s spectra were characteristic for sp 2 hybridised C and are shown in the supplementary section in Figure S3 . The C 1s spectra were similar to those published for highly oriented pyrolytic graphite (HOPG) [ 24 ]. Further, the Raman spectra were typical for SWCNTs and DWCNTs.…”

Section: Methodssupporting

confidence: 77%

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Measuring the Density of States of the Inner and Outer Wall of Double-Walled Carbon Nanotubes

Chambers

Shearer

et al. 2018

Nanomaterials

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The combination of ultraviolet photoelectron spectroscopy and metastable helium induced electron spectroscopy is used to determine the density of states of the inner and outer coaxial carbon nanotubes. Ultraviolet photoelectron spectroscopy typically measures the density of states across the entire carbon nanotube, while metastable helium induced electron spectroscopy measures the density of states of the outermost layer alone. The use of double-walled carbon nanotubes in electronic devices allows for the outer wall to be functionalised whilst the inner wall remains defect free and the density of states is kept intact for electron transport. Separating the information of the inner and outer walls enables development of double-walled carbon nanotubes to be independent, such that the charge transport of the inner wall is maintained and confirmed whilst the outer wall is modified for functional purposes.

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Section: Methodssupporting

confidence: 77%

“…The second mechanism is Auger de-excitation (AD). The details of the MIES technique has been discussed in a previous paper [ 24 , 26 ].…”

Section: Methodsmentioning

confidence: 99%

Measuring the Density of States of the Inner and Outer Wall of Double-Walled Carbon Nanotubes

Chambers

Shearer

et al. 2018

Nanomaterials

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“…Thus an observation on the closed layer of MoO 3 on BHJ can be achieved. The interaction of metastable He* is based either on the combination of the processed resonant ionization (RI) and Auger neutralization (AN) or based on the Auger de‐excitation (AD) process . RI/AN occur at surfaces with valence electron density close to the Fermi level which typically is given for metal surfaces.…”

Section: Methodsmentioning

confidence: 99%

Dipole Formation at the MoO₃/Conjugated Polymer Interface

Yin

Sibley

Quinton

et al. 2018

Adv Funct Materials

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MoO 3 is known as high work function (WF) transparent metal oxides. It is used as anode buffer layer in organic based solar cells because of its capability to extract electrons and inject holes from the active layer due to its high WF. Here a broad range of techniques is used to determine the energy levels of the bulk heterojunction (BHJ) and MoO 3 to determine that the minimum deposition thickness to achieve a closed layer is 1 nm due to penetration of the evaporated MoO 3 into the BHJ. The investigation shows that upon evaporation of the MoO 3 , a strong dipole is formed at the extended interface between the active layer and the MoO 3 and that the strength of the dipole increases with increasing thickness of the MoO 3 layer and saturates at 2.2 eV at a thickness around 3 nm.

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“…Metastable impact electron spectroscopy (MIES) and UV-light photoelectron spectroscopy (UPS) methods were used to characterize the valence electron structure and WF . Details about both methods can be found in refs and . Here, we summarize the main features of the methods.…”

Section: Methodsmentioning

confidence: 99%

Influence of Moisture on the Energy-Level Alignment at the MoO₃/Organic Interfaces

Yin

Lewis

Andersson

2018

ACS Appl. Mater. Interfaces

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MoO 3 is widely used in polymer-based organic solar cells as an anode buffer layer because of its high workfunction and formation of a strong dipole at the MoO 3 /polymer interface facilitating charge transfer across the MoO 3 /polymer interface. In the present work, we show that exposure of the MoO 3 /polymer interface to moisture attracts water molecules to the interface via diffusion. Because of their own strong dipole, water molecules counter the dipole at the MoO 3 /polymer interface. As a consequence, the charge transfer across the MoO 3 /polymer will reduce and affect the charge transport across the interface. The outcome of this work thus suggests that it is critical to keep the MoO 3 /polymer interface moisture-free, which requires special precautions in device fabrications. The composition of the MoO 3 /P3HT:PC 61 BM interface is analyzed with X-ray photoelectron spectroscopy and the depth profiling technique, neutral impact collision ion scattering spectroscopy. The results show that the concentration of oxygen increases upon exposure but leaves the oxidation state of Mo unchanged. The valence electron spectroscopy technique shows that the dipole across the MoO 3 /P3HT:PC 61 BM interface decreases even for short-time exposure to atmosphere because of the diffusion of water molecules to the interface. The far-ranging consequences for organic electronic devices are discussed.

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The direct measurement of the electronic density of states of graphene using metastable induced electron spectroscopy

Cited by 15 publications

References 52 publications

Measuring the Density of States of the Inner and Outer Wall of Double-Walled Carbon Nanotubes

Measuring the Density of States of the Inner and Outer Wall of Double-Walled Carbon Nanotubes

Dipole Formation at the MoO₃/Conjugated Polymer Interface

Influence of Moisture on the Energy-Level Alignment at the MoO₃/Organic Interfaces

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The direct measurement of the electronic density of states of graphene using metastable induced electron spectroscopy

Cited by 15 publications

References 52 publications

Measuring the Density of States of the Inner and Outer Wall of Double-Walled Carbon Nanotubes

Measuring the Density of States of the Inner and Outer Wall of Double-Walled Carbon Nanotubes

Dipole Formation at the MoO3/Conjugated Polymer Interface

Influence of Moisture on the Energy-Level Alignment at the MoO3/Organic Interfaces

Contact Info

Product

Resources

About

Dipole Formation at the MoO₃/Conjugated Polymer Interface

Influence of Moisture on the Energy-Level Alignment at the MoO₃/Organic Interfaces