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We present a defect spectroscopy technique to profile the energy and spatial distribution of defects within a material stack from leakage current ( ${J}$ – ${V}$ ), capacitance ( ${C}$ – ${V}$ ), and conductance ( ${G}$ – ${V}$ ) measurements. The technique relies on the concept of sensitivity maps (SMs) that identify the bandgap regions, where defects affect those electrical characteristics. The information provided by SMs are used to reproduce ${J}$ – ${V}$ , ${C}$ – ${V}$ , and ${G}$ – ${V}$ data measured at different temperatures and frequencies by means of physics-based simulations relying on an accurate description of carrier-defect interactions. The proposed defect spectroscopy technique is applied to ZrO2-based metal–insulator–metal structures of different compositions for dynamic random-access memory capacitor applications. The origin of the observed voltage, temperature, and frequency dependencies of the ${I}$ – ${V}$ , ${C}$ – ${V}$ , and ${G}$ – ${V}$ data is understood, and the atomic structure of the relevant stack defects is identified.

Understanding the energy alignment of electronic bands, which originate from ultrathin MoS2 layers and metal electrodes attached to them, is crucial for the design of MoS2-based electronic devices. We have applied internal photoemission spectroscopy (IPE) to analyze this alignment. We demonstrate that IPE can yield the barrier heights in the metal/ two-dimensional semiconductor/insulator stacks when the top metal electrode is sufficiently thin for allowing both the photoexcitation of electrons and their transport towards the insulator. The electron barrier at the interface between Al and monolayer (1ML) of MoS2 is estimated at 0.7 eV, and this value explains the experimentally observed attenuated quantum yield contribution from the aluminum. Based on the relative energies of the low-energy threshold position and the Fermi level of aluminum at the interface with the SiO2 insulator, we provide a simple explanation for the observed current photoinjection at the interface between aluminum and 1ML MoS2.

The article overviews experimental results obtained by applying internal photoemission (IPE) spectroscopy methods to characterize electron states in single- or few-monolayer thick two-dimensional materials and at their interfaces. Several conducting (graphene) and semiconducting (transitional metal dichalcogenides MoS2, WS2, MoSe2, and WSe2) films on top of thermal SiO2 have been analyzed by IPE, which reveals significant sensitivity of interface band offsets and barriers to the details of the material and interface fabrication, indicating violation of the Schottky-Mott rule. This variability is associated with charges and dipoles formed at the interfaces with van der Waals bonding as opposed to the chemically bonded interfaces of three-dimensional semiconductors and metals. Chemical modification of the underlying SiO2 surface is shown to be a significant factor, affecting interface barriers due to violation of the interface electroneutrality. ispartof: JOURNAL OF PHYSICS-CONDENSED MATTER vol:32 issue:41 ispartof: location:England status: published

Excitonic and band-to-band transitions in monolayer WS2 were observed using transient photoconductivity in metal-insulator-silicon structures. Significant improvement in sensitivity was achieved by introducing an Al/WS2 contact scheme. We attribute this improvement to high density of traps in the AlOx interlayer formed at the interface which gives rise to displacement current due to capture of electrons or holes optically generated in WS2. This new method is found to be viable with transferred monolayer films.

For the integration of two-dimensional (2D) transition metal dichalcogenides (TMDC) with high-performance electronic systems, one of the greatest challenges is the realization of doping and comprehension of its mechanisms. Low-temperature atomic layer deposition of aluminum oxide is found to n-dope MoS

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Internal photoemission of electrons (IPE) from large area one monolayer 2H-MoS 2 films synthesized on top of amorphous (a−) SiO 2 or Al 2 O 3 is used to determine the energy of the semiconductor valence band (VB) relative to the reference level of the insulator conduction band (CB). This allows us to compare the VB top energy in MoS 2 to that of the (100)Si substrate crystal at the interface with the same insulator. Despite the CB in a–Al 2 O 3 is found to be ≈1 eV below that in SiO 2 as measured relative to the Si VB edge, the authors observe nearly no shift of the spectral threshold in the case of IPE from the MoS 2 VB. This observation indicates violation of electroneutrality at the MoS 2 /a–Al 2 O 3 interface causing an increase in barrier by ≈1 eV. This conclusion is supported by the much weaker field dependence of the IPE threshold at the MoS 2 /a–Al 2 O 3 interface compared to the MoS 2 /a–SiO 2 one, suggesting the presence of negative charges and/or interface dipoles. Therefore, the commonly accepted electron affinity rule (EAR) appears to be not appropriate to describe the band alignment at 2D/insulator interfaces. ispartof: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE vol:216 issue:8 ispartof: location:FRANCE, Strasbourg status: published

We investigate the electronic structure and defects of Ge x Se 1−x materials at the atomic level, using full-layer-thickness (5nm) amorphous models. In Ge-rich Ge x Se 1−x , the nature of the mobility gap defects is mostly related to miscoordinated Ge. The population/localization of mobility-gap states changes solely under the effect of electric field. Strong covalent bonds introduced by N doping in the material increase its thermal conductivity and crystallization temperature beyond 600C. C/N dopants are found to add/remove mobility-gap states in the doped systems. Our investigation sets guidelines for material design in view of improved electro-thermal device performance.

Density functional theory simulations are used to identify the structural factors that define the material properties of ovonic threshold switches (OTS). They show that the nature of mobility-gap trap states in amorphous Ge-rich Ge50Se50 is related to Ge-Ge bonds, whereas in Se-rich Ge30Se70 the Ge valence-alternating-pairs and Se lone-pairs dominate. To obtain a faithful description of the electronic structure and delocalization of states, it is required to combine hybrid exchange-correlation functionals with large unit-cell models. The extent of localization of electronic states depends on the applied external electric field. Hence, OTS materials undergo structural changes during electrical cycling of the device, with a decrease in the population of less exothermic Ge-Ge bonds in favor of more exothermic Ge-Se. This reduces the amount of charge traps, which translates into coordination changes, an increase in mobility-gap, and subsequently changes in the selector-device electrical parameters. The threshold voltage drift process can be explained by natural evolution of the nonpreferred Ge-Ge bonds (or "chains"/clusters thereof) in Ge-rich GexSe1-x. The effect of extrinsic doping is shown for Si and N, which introduce strong covalent bonds into the system, increase both mobility-gap and crystallization temperature, and decrease the leakage current.

© 2019 Elsevier B.V. Spectral measurements of illumination-induced displacement currents related to trapping of charge carriers optically excited in semiconductor electrodes are shown to deliver information regarding energy onsets of electron transitions at the interface. Presented examples include determination of the conduction band offset at the GaN/Al2O3 interface and determination of charge carrier excitation spectra of two-dimensional (2D)semiconductors MoS2 and WS2 at the interface with insulating SiO2. ispartof: MICROELECTRONIC ENGINEERING vol:215 status: published

Many authors (Haunschild et al., Phys. Status Solidi RRL 5, 199–201 (2012) [1]) reported about areas in Cz-Si with an extremely low lifetime of minority carriers after high temperature stages of solar cell manufacture. In such regions the minority carrier lifetime may be fallen 100 times after annealing, what leads to a considerable drop in the solar cell efficiency. In present work the electrical and structural properties of phosphorus doped Bosch Cz-Si wafers with degrading areas were studied by means of photoluminescence, deep level transient spectroscopy, transmission electron microscopy, electron energy loss spectroscopy and Fourier transform infrared spectroscopy. Based on these data it is concluded that the dominant recombination channel in the degrading areas is related to strained oxygen precipitates. We found electronic states of traps which may cause their formation. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

© 2017 Author(s). Electron band alignment at interfaces of SiO 2 with directly synthesized few-monolayer (ML) thin semiconducting MoS 2 films is characterized by using field-dependent internal photoemission of electrons from the valence band of MoS 2 into the oxide conduction band. We found that reducing the grown MoS 2 film thickness from 3 ML to 1 ML leads to 400 meV downshift of the valence band top edge as referenced to the common energy level of the SiO 2 conduction band bottom. Furthermore, comparison of the MoS 2 layers grown by a H-free process (sputtering of Mo in sulfur vapor) to films synthesized by sulfurization of metallic Mo in H 2 S indicates a significant (500 meV) electron barrier increase in the last case. This effect is tentatively ascribed to the formation of an interface dipole due to the interaction of hydrogen with the oxide surface. ispartof: APL MATERIALS vol:6 issue:2 status: published

For the integration of two-dimensional (2D) transition metal dichalcogenides (TMDC) with high-performance electronic systems, one of the greatest challenges is the realization of doping and compreh...