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Instrumentation developments in electron energy-loss spectroscopy in the scanning transmission electron microscope one decade ago paved the way for combining milli-electron volt energy resolution in spectroscopy with Ångström-sized electron probes, unlocking unexplored realms for solid state physics at the nanometer scale. The fundamental understanding of the scattering processes involved has made it possible to separate atomically localized signals, providing insight into vibrations at the atomic scale. In this Letter, we outline the experimental, conceptual, and theoretical advances in this field and also make comparisons with tip-based optical techniques before discussing future perspectives of this exciting method. Optimization of dark-field signal collection will play a fundamental role in making this technique more widely applicable to a range of material problems. The benefits of adding momentum-resolution will also be discussed, and a powerful acquisition scheme will be proposed. [ABSTRACT FROM AUTHOR]

This work investigates the interplay between interfacial spin–orbit coupling (SOC) and magnon excitation-induced spin memory loss in epitaxial L10-FePt/MgO/L10-FePt magnetic tunnel junctions, which is crucial for advancing spintronic technologies. By employing systematic temperature-dependent transport measurements and inelastic electron tunneling spectroscopy, our study reveals that interfacial SOC at the Pt-terminated FePt/MgO interface significantly enhances magnon excitation during electron tunneling. This process results in a pronounced loss of spin memory in the spin-polarized current, diminishing the tunnel magnetoresistance ratio. Our findings provide critical insights into the mechanisms of spin memory loss, offering directions for optimizing spintronic device performance in the context of pronounced SOC environments. [ABSTRACT FROM AUTHOR]

There is a widespread interest in time-resolved electron spectroscopies such as ultrafast electron diffraction, ultrafast electron microscopy, and ultrafast electron energy loss spectroscopy. These techniques require pulsed electron beams with both high current and brightness. LaB6 is commonly used as a thermionic emitter because of its low work function and high electron yield. However, its use as a pulsed photocathode has not been widely explored. Here, we present measurements of the electron yield from a LaB6 filament exposed to 392 nm UV ultrafast laser pulses under a wide range of filament temperatures. We find that sample heating strongly enhances photoelectron yield, an effect known as thermionically enhanced photoemission. However, it also creates potentially undesirable, continuous thermionic background. We conclude that the ideal optimal operating conditions strongly depend on the type of measurement and require defining and quantifying an appropriate figure of merit. [ABSTRACT FROM AUTHOR]

Electron emission spectroscopy was performed on metalorganic chemical vapor deposition grown p-n−-n+ junctions with p-thicknesses ranging from 50 to 300 nm, doped with [Mg] = 3.5 × 1019 cm−3. By measuring the decreasing emitted electron intensity from a cesiated p-GaN surface with increasing p-thickness, we were able to extract the minority carrier diffusion length of electron in p-type GaN, Le = 26 ± 3 nm. The measured value is in good agreement with literature reported values. The extrapolated electron current at the n− region–p-GaN interface is in reasonable agreement with the simulated electron current at the interface. [ABSTRACT FROM AUTHOR]

In this work, the impact of plasma treatment on Si wafers with native oxide on top was systematically investigated using spectroscopic ellipsometry. A general applicable three-layer optical model structure for ellipsometry data fitting was developed and employed on samples treated with the N2, O2, and N2/O2 mixture plasma. Oxide-growth, amorphization of crystalline Si, and the formation of a transition layer between the SiO2 and the amorphous Si were detected. The estimated thicknesses of produced layers were confirmed by complementary methods, which allow precise ultra-thin layers thicknesses detection, namely, angle-resolved x-ray photoelectron spectroscopy and transmission electron microscopy. The depth-resolved chemical composition and the direct thickness measurements of the produced amorphous structure revealed pronounced elemental gradients and the absence of sharp interfaces. Nitrogen gas used in the plasma process was found to be implanted mainly at the interface of the SiO2/transition layer in the form of Si3N4. However, it was verified that it is feasible to employ one general ellipsometry model consisting of SiO2/transition layer/amorphous Si on crystalline Si for all plasma species due to comparably low Si3N4 concentrations as well as its refractive index n and absorption k similarity to SiO2. Spectroscopic ellipsometry is nondestructive and can be efficiently applied to analyze whole wafers without any sample preparation. It can be concluded that the present approach to ellipsometry model development and verification is well suited for plasma-activated direct wafer bonding processes. [ABSTRACT FROM AUTHOR]

Surface graphitization as a result of Joule heating by a field-emission (FE) current is revealed for needlelike diamond nanotips. The apex temperature and electrical resistance of the diamond needles during FE were measured by electron spectroscopy. Transmission electron microscopy indicated that the diamond structure in the near-surface layer was transformed into well-ordered graphene layers after FE with currents of up to 30 μA. The resulting structure can be viewed as a multi-walled carbon nanotube (MWCNT) having a diamond core. Thus, the observed FE behavior exhibited by the graphitized diamond needles is qualitatively similar to that of MWCNTs. On the other hand, due to its outstanding thermal conductivity, the diamond core ensures an efficient Joule heat dissipation, which provides better emission stability and higher currents, up to at least 225 μA. It makes these graphitized diamond needles promising candidates for high-brightness point electron sources required for various applications, e.g., in electron microscopy or scanning electron lithography. [ABSTRACT FROM AUTHOR]

Using electron emission spectroscopy, measurement and analysis were conducted on the energy distribution of vacuum emitted electrons from an electrically driven InGaN/GaN commercial blue c-plane (peak wavelengths λ ≈ 465 nm) light emitting diode (LED) with 60 nm of p-GaN on top of the active region. The signal-to-noise ratio of semiconductor peaks is improved on the thin p-GaN LED compared to previously published data on thicker p-GaN samples and is attributed to reduced loss of electrons en route to emission into vacuum during transit through the p-GaN. This further proves that hot electrons are generated in the bulk region and not by light or other hot electron generation mechanisms at the surface. Using square root of the light output power as a proxy for the active region carrier density, n, the hot electron integrated peak intensity is shown to be proportional to n3 and, thus, is directly attributed to a 3-body Auger process. Since there are significant Auger recombination currents even at low injection current densities, it is expected that Auger recombination current will dominate over radiation recombination and Shockley–Read–Hall (SRH) currents at higher current densities. This identifies Auger recombination as the dominant cause of efficiency droop. [ABSTRACT FROM AUTHOR]

p-doped gallium nitride (GaN) regrowth by epitaxial lateral overgrowth using a SiO2 mask is studied. A comparison between SiO2 and Al2O3 masked p-GaN by cathodoluminescence spectroscopy and scanning electron microscopy indicates that donor-type impurities are related to the SiO2 mask. A domain peak of 3.25 eV induced by shallow-donor and acceptor transitions and the dark contrast of obtuse triangles have been detected in SiO2 masked p-type GaN. Secondary ion mass spectroscopy is simultaneously employed for the analysis of SiO2 and Al2O3 masked p-GaN and identifies that the source of donor-type impurities is from Si atoms. Furthermore, the experimental results of cross-sectional microstructures at different regrowth times have been investigated. It is found that the donor-type impurities tend to cluster in semi-polar 11 2 ¯ 2 facets before the coalescence at the bottom of adjacent triangular stripes starts. The explanation for the non-uniform distribution of impurities is that semi-polar 11 2 ¯ 2 facets exhibit more dangling bond densities than the (0001) plane, and the SiO2 mask exposed to the vapor phase would likely introduce more impurities before the coalescence of GaN stripes. [ABSTRACT FROM AUTHOR]

Antiferromagnet (AFM)/ferromagnet (FM) systems such as IrMn/CoFeB/MgO enable spin–orbit-torque- (SOT-) induced switching of perpendicular magnetization in the absence of an external magnetic field. However, the low thermal stability, weak perpendicular magnetic anisotropy (PMA), and indistinctive SOT of these AFM/FM heterostructures pose challenges to the practical application. Here, through the insertion of a thin W layer between the IrMn and CoFeB layers, we show that much larger effective PMA fields are obtained with annealing stability to 300 °C, which is guaranteed by the prevention of Mn diffusion via W insertion as shown in spherical aberration corrected transmission electron microscopy and atomic-resolution electron energy-loss spectroscopy measurement results. Furthermore, the spin–orbit torque is effectively tuned by changing the W layer thickness via modulation of the interfacial spin–orbit coupling at IrMn/W/CoFeB interfaces, which was reported to degrade the interface spin transparency for the spin currents. Finally, field-free magnetization switching was achieved with comparable exchange bias fields to samples without W insertion. This work demonstrates an effective strategy for improving the performance of the thermally robust AFM-based SOT device. [ABSTRACT FROM AUTHOR]

We report on the direct measurement of hot electrons generated in the active region of blue light-emitting diodes grown by ammonia molecular beam epitaxy by electron emission spectroscopy. The external quantum efficiency of these devices is <1% and does not droop; thus, the efficiency losses from the intrinsic, interband, electron–electron–hole, or electron–hole–hole Auger should not be a significant source of hot carriers. The detection of hot electrons in this case suggests that an alternate hot electron generating process is occurring within these devices, likely a trap-assisted Auger recombination process. [ABSTRACT FROM AUTHOR]

Despite exhibiting their attractive properties and performances, the interlayer interaction in two-dimensional van der Waals epitaxy heterostructures is not well understood. Here, we demonstrate the growth of two dimensional vertically stacked multilayer β-In2Se3/monolayer WS2 heterostructures via the chemical vapor deposition method. Despite a large lattice misfit (29.9%), the vertically stacked β-In2Se3/WS2 heterostructures exhibit van der Waals epitaxy with well-aligned lattice orientation of WS2(100)[001]//In2Se3(100)[001], forming a periodic superlattice. Interestingly, a reversible phase transformation of epitaxial β-In2Se3 has been observed by temperature-dependent Raman spectroscopy and electron diffraction conducted from liquid N2 to room temperature. Notably, the phase transformation of epitaxial β-In2Se3 can only be observed when its layer number is larger than 4 and the transformation temperature increases with the increase in the layer number, indicating a layer number dependent phase transformation of epitaxial β-In2Se3. These results indicate that the confinement effect exists between monolayer WS2 and epitaxial β-In2Se3, strongly constraining the lattice change of adjacent few layers of β-In2Se3. [ABSTRACT FROM AUTHOR]

We report on the artificial manipulation of interfacial magnetism in the superlattices (SLs) of ([La0.7Sr0.3MnO3]30/[BaTiO3]25)n (1 ≤ n ≤ 10) fabricated by pulsed laser deposition. The thicker 30 uc-La0.7Sr0.3MnO3 and 25 uc-BaTiO3 layers are designed as a single period of SLs in order to eliminate the interaction between two adjacent interfaces that could contribute to a polar phase transition and the corresponding magnetism. We use aberration-corrected scanning transmission electron microscopy and electron energy-loss spectroscopy to demonstrate that epitaxial-strain-driven lattice distortion renders the emergence of divalent Mn at the La0.7Sr0.3MnO3/BaTiO3 interfaces. The saturated magnetization decreases and the magnetic easy axis becomes more in-plane inclined as the interfacial strain of the SLs increases. [ABSTRACT FROM AUTHOR]

We studied deep levels in quartz-free hydride-vapor-phase epitaxy (QF-HVPE)-grown homoepitaxial n-type GaN layers within which three electron and eight hole traps were detected. The dominant electron and hole traps observed in the QF-HVPE-grown GaN layers were E3 (EC − 0.60 eV) and H1 (EV + 0.87 eV), respectively. We found that the E3 trap density of QF-HVPE-grown GaN (∼1014 cm−3) was comparable with that of MOVPE-grown GaN layers, whereas the H1 trap density of QF-HVPE-grown GaN (∼1014 cm−3) was much smaller than that of an MOVPE-grown GaN layer with a low-residual-carbon growth condition. A detailed analysis of the QF-HVPE-grown GaN layers revealed that the H1 trap density is almost equal to the carbon impurity concentration and other impurities that compensate the Si donors besides the carbon impurity were hardly detected in the QF-HVPE-grown GaN layers. [ABSTRACT FROM AUTHOR]

The presence and potential ordering of oxygen vacancies play an important role in determining the electronic, ionic, and thermal transport properties of many transition metal oxide materials. Controlling the concentration of oxygen vacancies, as well as the structures of ordered oxygen vacancy domains, has been the subject of many experimental and theoretical studies. In epitaxial thin films, the concentration of oxygen vacancies and the type of ordering depend on the structure of the substrate as well as the lattice mismatch between the thin films and the substrate. However, the role of temperature or structural phase transitions in either the substrate or the epitaxial thin films in the oxygen vacancy ordering has remained largely unexplored. In particular, atomic-resolution imaging and spectroscopy analysis of oxygen vacancy ordering in thin films at temperatures below 300 K have not yet been reported. Here, we use aberration-corrected scanning transmission electron microscopy combined with in-situ cooling experiments to characterize the atomic/electronic structures of oxygen-deficient La0.5Sr0.5CoO3−δ thin films grown on SrTiO3 across its antiferrodistortive phase transition at 105 K. We demonstrate that atomic-resolution imaging and electron energy-loss spectroscopy can be used to examine variations in the local density of states as a function of sample temperature. [ABSTRACT FROM AUTHOR]

In this study, a graphene/n-type diamond heterojunction was fabricated by a wet-transfer process on hydrogen-terminated heavily phosphorus-doped diamond. Ultraviolet photoelectron spectroscopy (UPS) and field-emission electron spectroscopy were conducted to study the band structure of the graphene/n-type diamond heterojunction and its field emission mechanism. UPS suggests that an internal barrier is formed in the diamond by upward band bending near the graphene–diamond interface. The work function of graphene is estimated to be 3.72 eV. Field emission occurs from the Fermi level of graphene at low voltages, and then electron emission from the valence band of diamond starts at increased voltages. The results indicate that electron emission limited by surface termination changes to graphene-oriented emission following the formation of the heterojunction. [ABSTRACT FROM AUTHOR]

We report a transmission electron microscopy (TEM) study of the impacts of phosphorus and boron passivation processes at 4H-SiC/SiO2 interfaces. The chemical and electronic structures at these interfaces have been analyzed using high-resolution TEM and spatially resolved electron energy-loss spectroscopy (EELS), uncovering a range of phenomena caused by the presence of B and P within their respective boro- and phosphosilicate glass (BSG/PSG) layers. The phosphorus passivation process was observed to induce roughness at the SiC/PSG interface on the order of 100s of nm. Within the PSG layer, phosphorus was found to segregate into nanometer-scale P-rich clusters, contradicting previous reports that it is distributed uniformly throughout the PSG. Similar to N in nitric oxide annealed devices, boron was determined to accumulate in a thin layer (sub-3 nm in thickness) at the SiC/BSG interface, with a much narrower distribution than previously reported. EELS measurements indicated boron incorporates in a trigonal bonding configuration, supporting the assertion that it softens the oxide and causes significant stress reduction at the interface with 4H-SiC. These results supply further insight into the sources of mobility enhancement in PSG and BSG-gated devices that could be extended into additional improvement in the channel response of SiC MOSFETs. [ABSTRACT FROM AUTHOR]

The chemical and electronic structures of industrial chalcopyrite photovoltaic absorbers after KF post-deposition treatment (KF-PDT) are investigated using electron spectroscopies to probe the occupied and unoccupied electronic states. In contrast to a variety of recent publications on the impact of KF-PDT, this study focuses on industrial Cu(In,Ga)(S,Se)2 absorbers that also contain sulfur at the surface. We find that the KF-PDT removes surface adsorbates and oxides and also observe a change in the S/Se ratio. Furthermore, the KF-PDT leads to a Cu reduction at the surface but to a much lower degree than the strongly Cu-depleted or even Cu-free surfaces reported for (non-industrial) sulfur-free Cu(In,Ga)Se2 absorbers. The valence band maximum at the surface is found at a lower energy compared to the untreated absorber, and the conduction band minimum is found at a higher energy, overall revealing a widening of the bandgap in the surface region. [ABSTRACT FROM AUTHOR]

We demonstrate that inserting a mercaptan-terminated organophosphonic acid monolayer at a Cu-HfO2 interface can alter the metal work function by -0.1 eV ΔΦ≤ -0.4eV. The electron spectroscopy measurements of valence band structure reveal that molecular length-induced changes in ΔΦ can exceed contributions from Cu-S and P-O-Hf bonding dipoles at the Cu-organophosphonate-HfO2 interfaces. The invariance of the organophosphonate monolayer thickness with molecular length indicates that the observed values of ΔΦ are due to differences in molecular configuration and monolayer morphology. These findings suggest that molecular length could be a knob for tuning the electronic properties of inorganic interfaces modified with a nanomolecular layer for applications. [ABSTRACT FROM AUTHOR]

Topical observations of colossal permittivity (CP) with low dielectric loss in donor-acceptor cations co-doped rutile TiO2 have opened up several possibilities in microelectronics and energy-storage devices. Yet, the precise origin of the CP behavior, knowledge of which is essential to empower the device integration suitably, is highly disputed in the literature. From spectromicroscopic approach besides dielectric measurements, we explore that microscopic electronic inhomogeneities along with the nano-scale phase boundaries and the low temperature polaronic relaxation are mostly responsible for such a dielectric behavior, rather than electron-pinned defect-dipoles/grain-boundary effects as usually proposed. Donor-acceptor co-doping results in a controlled carrier-hopping inevitably influencing the dielectric loss while invariably upholding the CP value. [ABSTRACT FROM AUTHOR]

Topical observations of colossal permittivity (CP) with low dielectric loss in donor-acceptor cations co-doped rutile TiO2 have opened up several possibilities in microelectronics and energy-storage devices. Yet, the precise origin of the CP behavior, knowledge of which is essential to empower the device integration suitably, is highly disputed in the literature. From spectromicroscopic approach besides dielectric measurements, we explore that microscopic electronic inhomogeneities along with the nano-scale phase boundaries and the low temperature polaronic relaxation are mostly responsible for such a dielectric behavior, rather than electron-pinned defect-dipoles/grain-boundary effects as usually proposed. Donor-acceptor co-doping results in a controlled carrier-hopping inevitably influencing the dielectric loss while invariably upholding the CP value. [ABSTRACT FROM AUTHOR]

The continuous development of silicon devices has been supported by fundamental understanding of the two interfaces that predict the device properties: high-dielectric oxide (high-k)/SiO2 and SiO2/Si. In the absence of metal electrode fabrication, it is challenging to use spectroscopic approaches to deduce the electric dipoles in these interfaces for the prediction of electrical characteristics such as the leakage current and threshold voltage. Here, we propose a method to analyze the permanent dipole at the high-k/SiO2 interface by surface-charge-switched electron spectroscopy (SuCSES). An electron flood gun was used to switch the electrical polarity at the insulating surface to extract the interface-dipole contribution from the macroscopic dielectric polarization in the high-k/SiO2/Si stack structure. TaO3 - nanosheet (TaNS) crystallites, which are a family of high-k tantalate materials deposited on the SiO2/Si substrates, were annealed to prepare a nanoscale model interface. The properties of this interface were examined as a function of annealing temperature across the crystalline-toamorphous transition. Macroscopic dielectric polarization of the TaNS/SiO2/Si gate stack was found to exhibit a gradual decay that depended upon the quantum tunneling processes of induced carriers at the SiO2/Si interface. Additionally, the dipole at the high-k/thin-SiO2 interface abruptly changed by ∼0.4 eV before and after annealing at 400 °C, which may be the result of a decrease in conductionband offsets at the high-k/Si interface. Thus, SuCSES can aid in determining the inherent valenceband offsets in dielectric interfaces by using X-ray photoelectron spectroscopy with high accuracy and precision. Furthermore, SuCSES can determine whether dielectric polarization, including the interfacial dipole, affects the experimental value of the band offsets. [ABSTRACT FROM AUTHOR]

We show that introducing organophosphonate nanomolecular monolayers (NMLs) at Au-HfO2 interfaces shift the effective work function by 0.2?eV?≥?ΔΦeff?≥?-0.6?eV, due to NML body and bonding dipoles. Electron spectroscopy of NML-Au, NML-HfO2, and Au-NML-HfO2 structures indicate that the Au-NML bond strength is the major factor. Au-NML covalent bonding yields ΔΦeff?~?-?0.2?eV, while weak bonding yields ΔΦeff?~?0.6?eV. In contrast, NMLs on HfO2 decrease Φeff by ~0.4?eV due to competing contributions from NML-HfO2 bonding strength and NML orientation. These findings are relevant for nanomolecularly tailoring the electronic properties of metal-ceramic interfaces for applications. [ABSTRACT FROM AUTHOR]

We show the operation of a Cu/Al2O3/Cu/n-Si hot-electron transistor for the straightforward determination of a metal/semiconductor energy barrier height even at temperatures below carrier-freeze out in the semiconductor. The hot-electron spectroscopy measurements return a fairly temperature independent value for the Cu/n-Si barrier of 0.6660.04 eV at temperatures below 180 K, in substantial accordance with mainstream methods based on complex fittings of either current-voltage (I-V) and capacitance-voltage (C-V) measurements. The Cu/n-Si hot-electron transistors exhibit an OFF current of ~2×10-13 A, an ON/OFF ratio of ~105, and an equivalent subthreshold swing of ~96 mV/dec at low temperatures, which are suitable values for potential high frequency devices. [ABSTRACT FROM AUTHOR]

Using spin-polarized single- and two-electron spectroscopy, we probe exchange and spin-orbit interaction in a double layer of Fe and Au on W(110) and measure the spin asymmetry of the Bloch spectral density function of the sample. In a 5 ML iron film, the spin-orbit contribution to the measured asymmetry of the (e,2e) spectra was not detectable, whereas a deposition of about 1 ML of gold introduced a substantial spin-orbit component in the measured asymmetry. At the same time, this double layer still exhibits ferromagnetic properties: (i) the spectral density function asymmetry demonstrate imbalance of spin-up and spin-down electron densities in the valence band and (ii) the Stoner excitation asymmetry has almost the same value as in a pure Fe film. [ABSTRACT FROM AUTHOR]

Studies of the structural and electronic properties of graphene in its pristine state are hindered by hydrocarbon contamination on the surfaces. Also, in many applications, contamination reduces the performance of graphene. Contamination is introduced during sample preparation and is adsorbed also directly from air. Here, we report on the development of a simple dry-cleaning method for producing large atomically clean areas in free-standing graphene. The cleanness of graphene is proven using aberration-corrected high-resolution transmission electron microscopy and electron spectroscopy. [ABSTRACT FROM AUTHOR]

We present results for electron coincidence spectroscopy using two time-of-flight (ToF) spectrometers. Excited by electron impact, the energy and momentum distribution of electron pairs emitted from the Cu(111) surface are resolved and a spectral feature related to the Shockley surface state is identified. By combining the two ToF spectrometers with a high-order harmonic generation light source, we demonstrate double photoemission spectroscopy in the laboratory that required synchrotron radiation in the past. Utilizing this setup, we report results for (c,2e) on NiO(001) on Ag(001) excited with light at 30 eV photon energy. [ABSTRACT FROM AUTHOR]

We evaluated the perpendicular magnetic anisotropy (PMA) features of a hybrid [CoO/Pd]2/[Co/Pd]7 multilayer (ML) matrix under annealing in which the [CoO/Pd]2 bottom layer was inserted. Annealing allowed for the diffusion of oxygen atoms existing in the inserted [CoO/Pd]2 layer, leading to an atomic structural reconfiguration event. The hybrid matrix was crucial to result in a higher effective anisotropy energy (3.40 Merg/cc) than an ordinary [Co/Pd]7 ML matrix (1.25 Merg/cc) under annealing at 450 °C. X-ray photoelectron spectroscopy confirmed the presence of Co-O bonding states and annealing dependent oxygen atom diffusion. The possible nature of the enhanced PMA features is discussed. [ABSTRACT FROM AUTHOR]

Intensity asymmetry of the elastically scattered spin-polarized electrons from W(110) surface at 22 eV primary energy and at 25° angles of incidence and detection ((00) diffraction beam) was measured as a function of the azimuthal angle. Experimental results are compared with the calculations based on the relativistic multiple scattering formalism. The comparison showed fairly good agreement. These support the general theoretical approach and the input data chosen for the calculations. The information gained from our work is important for the interpretation of results of various spin-polarized electron spectroscopies as well as for design and construction of multi-layered structures with spin-active interfaces. [ABSTRACT FROM AUTHOR]

The resistance switching characteristics of resistive random access memory (ReRAM) based on amorphous GeSe thin films have been demonstrated by using Al/Ag2Se/GeSe/Pt structure. The Ag2Se layer that serves as the metal ionic source of GeSe switching medium was formed by a very simple wet-deposition process in AgNO3 solution. The X-ray diffraction and Auger electron spectroscopy analysis revealed the existence of the Ag2Se layer. As a result, an extremely low-voltage set/reset operation of less than 0.2 V, a high on-off resistance ratio larger than 103, good endurance characteristics, and excellent long-term reliability were achieved by the proposed Ag2Se/GeSe bilayered ReRAMs using the wet-deposition process. [ABSTRACT FROM AUTHOR]

Electrically activated doping of boron (B) atoms into the Si-nanocrystals (Si-NCs) embedded silicon oxide film is achieved by co-sputtering technique following with the annealing treatment. The evolution of the size, the shape, and the density of Si-NCs with the doping of B atoms is investigated. The observation of x-ray photoelectron spectroscopy of Si 2p and B 1s and the decrease in lattice spacing of Si (111) plane suggest that B atoms are doped into Si-NCs. The activated doping is confirmed by the Fano effect of the micro-Raman spectra for Si-NCs and the drastic decrease of the sheet resistance. [ABSTRACT FROM AUTHOR]

We report both the growth of carbon nanotube forests and electrical conduction on W, Ti, and TiN substrates coated with an ultra-thin Al2O3 support layer. Varying the Al2O3 thickness, a good electrical contact and high nanotube density is possible for a 0.5 nm Al2O3 layer as such an ultra-thin film allows tunnelling. X-ray photoelectron spectroscopy shows that, when using these non-continuous Al2O3 films, Fe catalyst diffuses into the conducting substrates, eventually causing growth to stop. Forests grown on ultra-thin Al2O3 are potentially useful for applications as interconnects, supercapacitors, and heat spreaders. [ABSTRACT FROM AUTHOR]

The electrical performance of SiC-based devices is strongly affected by the border traps of high-k dielectrics and carbon (C) interstitials in SiC. The abrupt HfO2/ SiC junction exhibits frequency dispersion in capacitance-voltage (C-V) curves. The thin SiO2 (7.5 nm) sample that is without excess C clusters exhibits ideal C-V characteristics. With the increase of SiO2 thickness, excess C in SiC substrates is detected by using both auger electron spectroscopy and x-ray photoelectron spectroscopy. The thick SiO2 (15.5 nm) sample contains enormous excess C inside SiC close to SiO2 interface, and excess C changes the substrates to n+-like behavior. [ABSTRACT FROM AUTHOR]

Electron energy-loss spectroscopy (EELS) studies in scanning transmission electron microscopy are widely used to investigate the location and bonding of atoms in condensed matter. However, the interpretation of EELS data is complicated by multiple elastic and thermal diffuse scattering of the probing electrons. Here, we present a method for removing these effects from recorded EELS spectrum images, producing visually interpretable elemental maps and enabling direct comparison of the spectral data with established first-principles energy-loss fine structure calculations. [ABSTRACT FROM AUTHOR]

Using a laser plasma accelerator, experiments with a 80 TW and 30 fs laser pulse demonstrated quasi-monoenergetic electron spectra with maximum energy over 0.4 GeV. This is achieved using a supersonic He gas jet and a sharp density ramp generated by a high intensity laser crossing pre-pulse focused 3 ns before the main laser pulse. By adjusting this crossing pre-pulse position inside the gas jet, among the laser shots with electron injection, more than 40% can produce quasi-monoenergetic spectra. This could become a relatively straight forward technique to control laser wakefield electron beams parameters. [ABSTRACT FROM AUTHOR]

The present work reports on the experimental investigation of electronic structure and transport properties of the proposed topological insulator PtLuSb. The electronic structure was investigated by means of polarization dependent hard x-ray photoelectron spectroscopy. The valence band spectra exhibit a linear behavior close to the Fermi energy, as is typical for massless electrons. The transport properties are similar to that of a gapless semiconductor with low carrier concentration. This compound also exhibits an exceptionally high Hall mobility. At low temperatures, the magnetoresistance changes linearly with the applied magnetic field, whereas it exhibits a quadratic nature at high temperatures. A tentative relation between linear magnetoresistance and high mobility is discussed. [ABSTRACT FROM AUTHOR]

We report that graphene grown by molecular beam epitaxy from solid carbon (CMBE) on (0001) SiC in the presence of unintentional oxygen exhibits a small bandgap on the order of tens of meV. The presence of bandgaps is confirmed by temperature dependent Hall effect and resistivity measurements. X-ray photoelectron spectroscopy (XPS) measurements suggest that oxygen incorporates into the SiC substrate in the form of O-Si-C and not into the graphene as graphene oxide or some other species. The effect is independent of the carrier type of the graphene. Temperature dependent transport measurements show the presence of hopping conduction in the resistivity and a concurrent disappearance of the Hall voltage. Interactions between the graphene layers and the oxidized substrate are believed to be responsible for the bandgap. [ABSTRACT FROM AUTHOR]

The nitrogen-doped Ge2Sb2Te5 (GST) programmable metallization cell is investigated to address the low switching voltage and need for a high resistance ratio, which are critical issues for the filed-programmable gate array (FPGA) configuration. Nitrogen doping of GST yields Ge-N covalent bonds, as confirmed by x-ray photoelectron spectroscopy and Raman spectroscopy; this increases the resistivity of GST. Consequently, an excellent resistance ratio (∼107) with appropriate operating voltage and stable retention properties more than for 104 s at 85 °C are achieved. The results indicate that the film is a suitable alternative candidate for the logic switch in static-random-access-memory-based FPGA technology. [ABSTRACT FROM AUTHOR]

First principles calculations of the optical properties of the intermetallic compounds AuAl2, AuIn2, and AuGa2 have been performed. Analysis of the dielectric functions showed that AuAl2 is unique because a bulk plasmon is seen in the optical region and contributes to the purple color of this material. An experimental electron energy-loss spectrum showed excellent agreement with the theoretical prediction and confirmed the presence of the bulk plasmon. [ABSTRACT FROM AUTHOR]

The photocurrent and incident photon conversion efficiency of In0.20Ga0.80N increased about 2 times after a simple electrochemical surface treatment. X-ray photoelectron spectroscopy and photoluminescence analysis suggested that In-rich InGaN region on the surface of the In0.20Ga0.80N electrode was removed by using the electrochemical surface treatment. The enhancement of the photocurrent was attributed to the removal of In-rich InGaN phases caused by indium segregations on the surface of the electrode, which played a major role as surface recombination centers of photo-generated electron-hole pairs. [ABSTRACT FROM AUTHOR]

Combining nanoscale imaging with local electron spectroscopy and diffraction has provided direct information on folding and stacking defects of graphene flakes produced by unrolled multi-walled carbon nanotubes. Structural data obtained by nanoarea electron diffraction complemented with systematic electron energy loss spectroscopy measurements of the surface plasmon losses of single flakes show the presence of flat bilayer regions coexisting with folded areas where the topology of buckled graphene resembles that of warped carbon nanostructures. [ABSTRACT FROM AUTHOR]

The correlation between atomic structure and the electrical properties of thermally grown SiO2/4H-SiC(0001) interfaces was investigated by synchrotron x-ray photoelectron spectroscopy together with electrical measurements of SiC-MOS capacitors. We found that the oxide interface was dominated by Si-O bonds and that there existed no distinct C-rich layer beneath the SiC substrate despite literature. In contrast, intermediate oxide states in Si core-level spectra attributable to atomic scale roughness and imperfection just at the oxide interface increased as thermal oxidation progressed. Electrical characterization of corresponding SiC-MOS capacitors also indicated an accumulation of both negative fixed charges and interface defects, which correlates well with the structural change in the oxide interface and provides insight into the electrical degradation of thermally grown SiC-MOS devices. [ABSTRACT FROM AUTHOR]

We demonstrate a two-dimensional imaging technique that uses a tomographic image reconstruction algorithm of object projections measured with a single photodetector. By imposing a spatially varying amplitude modulation on the illumination beam, the lateral projections of the object are encoded in the electronic spectrum of the signal from a single-element photodetector. [ABSTRACT FROM AUTHOR]

We report room temperature ferromagnetism in partially hydrogenated epitaxial graphene grown on 4H[Single_Bond]SiC(0001). The presence of ferromagnetism was confirmed by superconducting quantum interference devices measurements. Synchrotron-based near-edge x-ray absorption fine structure and high resolution electron energy loss spectroscopy measurements have been used to investigate the hydrogenation mechanism on the epitaxial graphene and the origin of room temperature ferromagnetism. The partial hydrogenation induces the formation of unpaired electrons in graphene, which together with the remnant delocalized π bonding network, can explain the observed ferromagnetism in partially hydrogenated epitaxial graphene. [ABSTRACT FROM AUTHOR]

The understanding of the mechanisms of helium bubble formation and evolution in materials requires the quantitative determination of several key quantities such as the helium density in the bubbles. Helium nanobubbles of about 16 nm in diameter were created in silicon by helium implantation at high fluence and subsequent annealing. Individual nanobubbles were analyzed by spatially resolved Electron Energy-loss Spectroscopy (EELS). We report on the in situ probing of helium desorption from the nanobubbles under electron irradiation. This opens new perspectives for a more accurate determination of the helium density through spatially resolved EELS. [ABSTRACT FROM AUTHOR]

We use secondary electron spectroscopy to probe the excited states of graphene adsorbed on a Ni(111) surface. A fine structure directly related to the empty bands above the vacuum level of the sample is resolved in the spectra excited by electrons. Ion-induced spectra reveal a high energy feature that is consistent with electron promotion from valence to conduction band states, from which electrons emerge into vacuum. [ABSTRACT FROM AUTHOR]

In this letter, we show a method to extract valuable information about electronic traps from inelastic electron tunneling spectroscopy (IETS) obtained on a metal-oxide-semiconductor gate stack with ultrathin gate dielectrics. The trap information extracted from the IETS spectrum includes its location, spatial distribution, and energy distribution. [ABSTRACT FROM AUTHOR]

Temperature dependent Hall measurements were applied to demonstrate, semiconducting n-type high-quality In2O3(001) and (111) thin films with nondegenerate unintentionally doped (UID) electron concentrations on the order of 1017 cm-3 at room temperature, which is below those of bulk single crystals. The freeze-out of the electron concentration in all samples suggests a shallow UID donor with ionization energy in the 17 meV range. Postgrowth annealing in oxygen allowed to further decrease the UID electron concentration with simultaneous mobility increase, suggesting oxygen vacancies to be the shallow UID donors. Hall mobilities above 200 cm2/V s at room temperature and 1000 cm2/V s at low temperatures exceed those of bulk single crystals and demonstrate high material quality and purity. [ABSTRACT FROM AUTHOR]

We report the enhancement of hole current density in the hole transport part of an inverted top-emission organic light emitted diode by applying an organic insertion layer of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN). Poor hole transporting performance of Al/4,4′-bis(N-phenyl-1-naphthylamino)biphenyl (NPB)/indium tin oxide is greatly improved by the HAT-CN insertion between Al and NPB layer. The highest occupied molecular orbital level onset of the NPB bends toward Fermi level at the HAT-CN/NPB interface. This extra charge generation layer made of pure organic molecules substantially enhances hole injection from Al anode as revealed by the results of ultraviolet photoelectron spectroscopy and J-V measurement data. [ABSTRACT FROM AUTHOR]