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Band bending analysis of charge characteristics at GeO <sub/>2</sub> /Ge interface by x-ray photoemission spectroscopy
摘要： Ge complementary metal oxide semiconductor (CMOS) is promising for scaling beyond the Si CMOS due to its higher carrier mobility than Si. Analogue to classical SiO2/Si system in the Si CMOS technology, various interface/bulk charges including interface traps (Qit), fixed surface state charges (Qf), trapped positive charges (Qpt) and negative charges ((Qnt) in GeO2/Ge system are also crucial both for the device performance and reliability. Because small amounts of charges would cause photoemission peak shift characterized by x-ray photoemission spectroscopy (XPS), it offers a feasible way to evaluate various charge densities by measuring the band bending in Ge substrate from Ge 3d core-level energy shift at GeO2/Ge interface. Moreover, photoemission peak shifts as a function of x-ray irradiation time have been widely accepted for characterization of charge trapping phenomena. Here, we report a band bending analysis at GeO2/Ge interface of featuring vital charge characteristics for diverse device applications by XPS. HF-last cleaned Ge surface was verified to tend to be p-type, irrespective of the bulk conductivity. The n-Ge/GeO2 interfaces exhibit a reduction of upward band bending evolution of Ge substrate, while p-type-Ge/GeO2 interfaces indicate a reduction of downward band bending evolution when comparing the different quality GeO2/Ge interfaces. Based on the requirement of surface charge neutrality, such observation has been attributed to a dominated passivation effect to negatively charged interface traps and the positive fixed surface state charges, respectively. Moreover, a time evolution of Ge 3d and O 1s signals reveals a progressive band bending modification at GeO2/Ge interface, clarifying the thermally-grown GeO2 also contains electron traps (Qnt). Ultimately, the four types of charges relying on the GeO2/Ge quality were modeled to correlate with the observed Ge band bending evolution, which would impact both the device operation and reliability.
关键词： band bending,x-ray photoemission spectroscopy,Ge-based electronics,charge characteristics
更新于2025-09-23 15:22:29
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Charge-state analysis of small barium-oxide clusters by X-ray absorption spectroscopy
摘要： Small barium-oxide clusters BamOn+ are studied by mass spectrometry and X-ray absorption spectroscopy to discuss stability of the clusters and oxidation state of constituent atoms. It is found that clusters with bulk composition, n = m, are stable, which can accommodate one or two excess oxygen atoms additionally as manifested by n = m + 1 and m + 2 species in the mass spectrum. XAS spectra of Ba2O2+ and Ba2O3+ reveal that the oxidation state of barium atoms stays at +2 (the bulk BaO value) even after binding excess oxygen, whereas spectral features originating from oxygen exhibit composition dependence. The present finding suggests that stoichiometric small barium-oxide clusters bind less-negatively-charged oxygen atoms without change in the charge state of barium.
关键词： X-ray absorption spectroscopy,charge state,barium-oxide clusters,oxidation number
更新于2025-09-23 15:22:29
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Resonant inelastic x-ray incarnation of Young’s double-slit experiment
摘要： Young’s archetypal double-slit experiment forms the basis for modern diffraction techniques: The elastic scattering of waves yields an interference pattern that captures the real-space structure. Here, we report on an inelastic incarnation of Young’s experiment and demonstrate that resonant inelastic x-ray scattering (RIXS) measures interference patterns, which reveal the symmetry and character of electronic excited states in the same way as elastic scattering does for the ground state. A prototypical example is provided by the quasi-molecular electronic structure of insulating Ba3CeIr2O9 with structural Ir dimers and strong spin-orbit coupling. The double “slits” in this resonant experiment are the highly localized core levels of the two Ir atoms within a dimer. The clear double-slit-type sinusoidal interference patterns that we observe allow us to characterize the electronic excitations, demonstrating the power of RIXS interferometry to unravel the electronic structure of solids containing, e.g., dimers, trimers, ladders, or other superstructures.
关键词： Resonant inelastic x-ray scattering,quasi-molecular orbitals,electronic excitations,Young's double-slit experiment,spin-orbit coupling,interference patterns
更新于2025-09-23 15:22:29
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Pixel-to-pixel variation on a calibrated PILATUS3-based multi-energy soft x-ray detector
摘要： A multi-energy soft x-ray pin-hole camera based on the PILATUS3 100 K x-ray detector has recently been installed on the Madison Symmetric Torus. This photon-counting detector consists of a two-dimensional array of ～100 000 pixels for which the photon lower-threshold cutoff energy Ec can be independently set for each pixel. This capability allows the measurement of plasma x-ray emissivity in multiple energy ranges with a unique combination of spatial and spectral resolution and the inference of a variety of important plasma properties (e.g., T e, nZ, Z eff). The energy dependence of each pixel is calibrated for the 1.6–6 keV range by scanning individual trimbit settings, while the detector is exposed to ?uorescence emission from Ag, In, Mo, Ti, V, and Zr targets. The resulting data for each line are then ?t to a characteristic "S-curve" which determines the mapping between the 64 possible trimbit settings for each pixel. The statistical variation of this calibration from pixel-to-pixel was explored, and it was found that the discreteness of trimbit settings results in an effective threshold resolution of ?E < 100 eV. A separate calibration was performed for the 4–14 keV range, with a resolution of ?E < 200 eV.
关键词： energy calibration,x-ray detector,photon-counting,multi-energy soft x-ray,plasma x-ray emissivity,PILATUS3
更新于2025-09-23 15:21:21
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CoGe surface oxidation studied using X-ray photoelectron spectroscopy
摘要： Cobalt germanides have been widely studied as semiconductor contact materials, but recent theoretical studies suggest that they may also be excellent catalysts for methane steam reforming with stabilities and activities comparable to more expensive noble metal catalysts. We have sputter deposited CoGe alloy films and characterized their structure and morphology after post-deposition annealing in high vacuum up to 1000 °C. We used X-ray photoelectron spectroscopy to study the initial oxidation of amorphous and crystalline CoGe alloy surfaces under low pressures of O2 and H2O. The oxidation rate in O2 was found to be faster for an amorphous CoGe surface compared to a crystalline surface. We also found that there was little difference in the oxidation rate in H2O for either amorphous or crystalline surfaces. During O2 oxidation, the crystalline surface preferentially forms GeO and the amorphous surface preferentially forms GeO2. We have also observed preferential oxidation of Ge in the CoGe thin films. During temperature programmed desorption studies, we found that GeO desorption begins near 350 °C and that GeO2 decomposes to GeO and desorbs near 700 °C. More studies of CoGe catalysts are warranted, however GeO desorption may be a concern under reaction conditions when the film is subjected to an oxidizing environment.
关键词： Oxidation,Cobalt germanium,Temperature programmed desorption,Atomic force microscopy,X-ray photoelectron spectroscopy,X-ray diffraction
更新于2025-09-23 15:21:21
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Soft X-ray Absorption Spectroscopy Study of Spin Crossover Fe-Compounds: Persistent High Spin Configurations under Soft X-ray Irradiation
摘要： Metal-organic complex exhibiting spin crossover (SCO) behavior has drawn attention for its functionality as a nanoscale spin switch. The spin states in the metal ions can be tuned by external stimuli such as temperature or light. This article demonstrates a soft X-ray–induced excited spin state trapping (SOXEISST) effect in Hofmann-like SCO coordination polymers of FeII(4-methylpyrimidine)2[Au(CN)2]2 and FeII(pyridine)2[Ni(CN)4]. A soft X-ray absorption spectroscopy (XAS) study on these polymers showed that the high spin configuration (HS; S = 2) was prevalent in Fe2+ ions during the measurement even at temperatures much lower than the critical temperatures (>170 K), manifesting HS trapping due to the X-ray irradiation. This is in strong contrast to the normal SCO behavior observed in FeII(1,10-phenanthroline)2(NCS)2, implying that the structure of the ligand chains in the polymers with relatively loose Fe-N coordination might allow a structural adaptation to stabilize the metastable HS state under the soft X-ray irradiation.
关键词： soft X-ray induced excited spin state trapping,X-ray absorption spectroscopy,high spin,spin crossover
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Investigations on electrical properties and correlations to electron and X-ray energies of pyroelectric LiTaO<inf>3</inf> and LiNbO<inf>3</inf>
摘要： The electrical properties of pyroelectric Lithium Tantalate (LiTaO3) and Lithium Niobate (LiNbO3) were investigated and compared to accessible X-ray energies by using the pyroelectric effect to generate X-rays. The capacitances of different crystals of varying sizes were measured and the resulting permittivities were calculated. A vacuum setup enabled a correlation to the maximum X-ray energies at a variable pressure. The presented results provide an overview of fundamental material properties and the effect on the generated difference of potential.
关键词： Lithium Niobate,pyroelectric crystal,vacuum electron source,X-ray spectrum,permittivity,X-ray energy,electron acceleration,electron emission,capacitance,Lithium Tantalate
更新于2025-09-23 15:21:21
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Effect of low-energy ion impact on the structure of hexagonal boron nitride films studied in surface-wave plasma
摘要： A high‐density surface‐wave plasma source is used to deposit hexagonal boron nitride (hBN) films in a gas mixture of He, H2, N2, Ar, and BF3 under a high ion flux condition using low‐energy ion irradiation. The ion energy is controlled between around zero and 100 eV by applying a negative or positive bias voltage to a substrate, while the ion flux is increased by locating a substrate upstream in the diffusive plasma. For ion energies above ～37 eV, the structure of the films depends upon ion energy more than substrate temperature, typical of subplantation processes. As a result, the structural order and crystallinity of sp2‐bonded phase in the films characterized by Fourier transform infrared spectroscopy and X‐ray diffraction are increased with decreasing ion energy, while the mass density of the films characterized by X‐ray reflectivity is retained relatively high with a slight dependence upon ion energy.
关键词： surface‐wave plasma,Fourier transform infrared spectroscopy (FTIR),chemical vapor deposition (CVD),hexagonal boron nitride (hBN),X‐ray diffraction (XRD),X‐ray reflectivity (XRR)
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - High performance x-ray source using point-typed CNT field emitter
摘要： The high performance cold cathode x-ray source was fabricated by using the point-typed CNT field emitter. The cold cathode x-ray source consists of the CNT point emitter, the metal mesh gate electrode, the metal hole focusing lens and the tungsten target anode electrode. To fabricate x-ray source, such components were mounted in a SUS vacuum chamber. The fabricated CNT x-ray source showed a good resolution of x-ray images at a low anode current and at a low anode voltage, and also indicated stable operation. We evaluated x-ray images according to the tube voltage and the tube current, respectively.
关键词： point-typed field emitter,carbon nanotube field emitter,metal mesh gate electrode,x-ray image,cold cathode x-ray source,tungsten anode electrode
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Self-focusing of electrons emitted by rectangular pyroelectric crystals: A study on geometrical conditions for optimized X-ray intensities
摘要： Pyroelectric crystals such as LiTaO3 or LiNbO3 offer the opportunity to produce X-rays with high energy and intensity. These pyroelectric X-ray sources may be used in XRF applications due to particular advantages. This report deals with systematic studies on the behavior of these crystals enabling an optimization of X-ray intensity. Furthermore, the focusing of electrons emitted by rectangular pyroelectric crystals has been studied.
关键词： Lithium Niobate,pyroelectric crystal,vacuum electron source,X-ray intensity,X-ray spectrum,focusing,electron acceleration,electron emission,Lithium Tantalate
更新于2025-09-23 15:21:21