Atomic‐level characterization of materials with core‐ and valence‐level photoemission: basic phenomena and future directions

Fadley, C. S.

doi:10.1002/sia.2902

Cited by 43 publications

(34 citation statements)

References 83 publications

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“…Since the escape depth of photo emitted electrons in HRXPS is remarkably low, over grown GaN layer of heterojunction sample has to be thin enough in such a way that the electrons knocked out from both thin overgrown GaN and underlying SL-MoS 2 layers can be easily probed. 31 As the SL-MoS 2 is not formed continuously on the entire Sapphire substrate, the region of interest on GaN/MoS 2 and MoS 2 /Sapphire samples was selectively chosen within the spatial resolution of HRXPS measurements by comparing the intensity of Ga 2p, Mo 3d, and Al 2p core-levels. This allowed us to collect the photoemission signal from solely SL-MoS 2 /Sapphire and GaN/SL-MoS 2 heterostructures for samples A and B, respectively.…”

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confidence: 99%

Determination of band offsets at GaN/single-layer MoS2 heterojunction

Tangi

Mishra

et al. 2016

Applied Physics Letters

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We report the band alignment parameters of the GaN/single-layer (SL) MoS2 heterostructure where the GaN thin layer is grown by molecular beam epitaxy on CVD deposited SL-MoS2/c-sapphire. We confirm that the MoS2 is an SL by measuring the separation and position of room temperature micro-Raman E12g and A1g modes, absorbance, and micro-photoluminescence bandgap studies. This is in good agreement with HRTEM cross-sectional analysis. The determination of band offset parameters at the GaN/SL-MoS2 heterojunction is carried out by high-resolution X-ray photoelectron spectroscopy accompanying with electronic bandgap values of SL-MoS2 and GaN. The valence band and conduction band offset values are, respectively, measured to be 1.86 ± 0.08 and 0.56 ± 0.1 eV with type II band alignment. The determination of these unprecedented band offset parameters opens up a way to integrate 3D group III nitride materials with 2D transition metal dichalcogenide layers for designing and modeling of their heterojunction based electronic and photonic devices.

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confidence: 99%

Determination of band offsets at GaN/single-layer MoS2 heterojunction

Tangi

Mishra

et al. 2016

Applied Physics Letters

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“…In ARPES, the mean depth of electron emission varies as cos(α), with α being the off-normal emission angle. 18 Shirley-type backgrounds were subtracted from the raw spectra to account for inelastic scattering of the photoelectrons. In the following, we refer to the effective photoelectron information depth D z as the depth z down to which 90% of the photoelectrons are emitted.…”

Section: Methodsmentioning

confidence: 99%

Chemical stability of the magnetic oxide EuO directly on silicon observed by hard x-ray photoemission spectroscopy

et al. 2011

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We present a detailed study of the electronic structure and chemical state of high-quality stoichiometric EuO and O-rich Eu 1 O 1+x thin films grown directly on silicon without any buffer layer using hard x-ray photoemission spectroscopy (HAXPES). We determine the EuO oxidation state from a consistent quantitative peak analysis of 4f valence band and 3d core-level spectra. The results prove that nearly ideal, stoichiometric, and homogeneous EuO thin films can be grown on silicon, with a uniform depth distribution of divalent Eu cations. Furthermore, we identify the chemical stability of the EuO/silicon interface from Si 2p core-level photoemission. This work clearly demonstrates the successful integration of high-quality EuO thin films directly on silicon, opening up the pathway for the future incorporation of this functional magnetic oxide into silicon-based spintronic devices.

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“…[29][30][31] In the past, this method has mostly been restricted to chemical reactions on solid surfaces [32][33][34][35][36][37][38][39][40][41][42] because conventional XPS requires ultrahigh vacuum (UHV) conditions, which are not compatible with the high vapor pressure of most liquids and solvents. An exception is the use of dedicated experimental setups with differential pumping stages, which allow for performing XPS at the so-called near ambient pressure (NAP) conditions.…”

Section: Introductionmentioning

confidence: 99%

Perspective: Chemical reactions in ionic liquids monitored through the gas (vacuum)/liquid interface

Maier

Niedermaier

Steinrück

2017

The Journal of Chemical Physics

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This perspective analyzes the potential of X-ray photoelectron spectroscopy under ultrahigh vacuum (UHV) conditions to follow chemical reactions in ionic liquids in situ. Traditionally, only reactions occurring on solid surfaces were investigated by X-ray photoelectron spectroscopy (XPS) in situ. This was due to the high vapor pressures of common liquids or solvents, which are not compatible with the required UHV conditions. It was only recently realized that the situation is very different when studying reactions in Ionic Liquids (ILs), which have an inherently low vapor pressure, and first studies have been performed within the last years. Compared to classical spectroscopy techniques used to monitor chemical reactions, the advantage of XPS is that through the analysis of their core levels all relevant elements can be quantified and their chemical state can be analyzed under well-defined (ultraclean) conditions. In this perspective, we cover six very different reactions which occur in the IL, with the IL, or at an IL/support interface, demonstrating the outstanding potential of in situ XPS to gain insights into liquid phase reactions in the near-surface region.

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Atomic‐level characterization of materials with core‐ and valence‐level photoemission: basic phenomena and future directions

Cited by 43 publications

References 83 publications

Determination of band offsets at GaN/single-layer MoS2 heterojunction

Determination of band offsets at GaN/single-layer MoS2 heterojunction

Chemical stability of the magnetic oxide EuO directly on silicon observed by hard x-ray photoemission spectroscopy

Perspective: Chemical reactions in ionic liquids monitored through the gas (vacuum)/liquid interface

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