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First Experimental Demonstration and Mechanism of Abnormal Palladium Diffusion Induced by Excess Interstitial Ge
摘要： This letter represents the ?rst direct experimental demonstrations and mechanism proposal regarding abnormal palladium diffusion into germanium (Ge). Our experiments indicated that excess Ge atoms among palladium germanide alloy formation indirectly induce the abnormal out-diffusion of mass palladium atoms into Ge. Consequently, palladium germanide alloy on both n-type and p-type Ge form ohmic-like Schottky junctions. To identify this phenomenon, ?rst-principle calculations and technology computer-aided design simulation were used to evaluate the electrical in?uence of palladium atoms in Ge. We discovered that the activated palladium atoms in Ge induce large midgap bulk-trap states, which contribute to a severe increment of trap-assisted tunneling current at the palladium germanide/Ge junction.
关键词： Schottky junction,First-principles calculations,palladium germanide,technology computer-aided design,germanium,trap-assisted tunneling,fermi-level pinning effect
更新于2025-09-10 09:29:36
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Temperature dependent electrical properties of AlN/Si heterojunction
摘要： AlN is an integral part of many Si based electronic, optoelectronic, and electromechanical devices. The transport of charge carriers and their recombination at the AlN (0002)/Si (111) interface become crucial for the performance and reliability of such devices. In this work, we have studied the temperature dependent current-voltage (I-V-T) characteristics of AlN/Si heterojunctions to gain a deeper understanding. The analysis of the I-V-T characteristics interestingly suggested a temperature dependent turn-on voltage in the forward bias of the Schottky barrier. Also, the Schottky barrier itself was found to be temperature dependent as expected. We have qualitatively explained the temperature dependence of the turn-on voltage in terms of trap states at the AlN/Si heterojunction.
关键词： electrical properties,temperature dependent,AlN/Si heterojunction,Schottky barrier,trap states
更新于2025-09-10 09:29:36
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Border trap evaluation for SiO <sub/>2</sub> /GeO <sub/>2</sub> /Ge gate stacks using deep-level transient spectroscopy
摘要： A border trap (BT) evaluation method was established for SiO2/GeO2/Ge gate stacks by using deep-level transient spectroscopy with a lock-in integrator. Ge metal-oxide-semiconductor capacitors (MOSCAPs) with SiO2/GeO2/Ge gate stacks were fabricated by using different methods. The interface trap (IT) and BT signals were successfully separated based on their different dependences on the intensity of injection pulses. By using p-type MOSCAPs, BTs at the position of 0.4 nm from the GeO2/Ge interface were measured. The energy of these BTs was centralized at the position near to the valence band edge of Ge, and their density (Nbt) was in the range of 1017–1018 cm?3. By using n-type MOSCAPs, BTs at the position range of 2.8–3.4 nm from the GeO2/Ge interface were measured, of which Nbt varied little in the depth direction. The energy of these BTs was distributed in a relatively wide range near to the conduction band edge of Ge, and their Nbt was approximately one order of magnitude higher than those measured by p-MOSCAPs. This high Nbt value might originate from the states of the valence alternation pair with energy close to 1 eV above the conduction band edge of Ge. We also found that Al post metallization annealing can passivate both ITs and BTs near to the valence band edge of Ge but not those near to the conduction band edge.
关键词： deep-level transient spectroscopy,valence band edge,conduction band edge,interface trap,border trap,Ge metal-oxide-semiconductor capacitors
更新于2025-09-09 09:28:46
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Measurements of the effective electron density in an electron beam ion trap using extreme ultraviolet spectra and optical imaging
摘要： In an electron beam ion trap (EBIT), the ions are not con?ned to the electron beam, but rather oscillate in and out of the beam. As a result, the ions do not continuously experience the full density of the electron beam. To determine the effective electron density, ne,eff, experienced by the ions, the electron beam size, the nominal electron density ne, and the ion distribution around the beam, i.e., the so-called ion cloud, must be measured. We use imaging techniques in the extreme ultraviolet (EUV) and optical to determine these. The electron beam width is measured using 3d → 3p emission from Fe xii and xiii between 185 and 205 ?. These transitions are fast and the EUV emission occurs only within the electron beam. The measured spatial emission pro?le and variable electron current yield a nominal electron density range of ne ～ 1011–1013 cm?3. We determine the size of the ion cloud using optical emission from metastable levels of ions with radiative lifetimes longer than the ion orbital periods. The resulting emission maps out the spatial distribution of the ion cloud. We ?nd a typical electron beam radius of ～60 μm and an ion cloud radius of ～300 μm. These yield a spatially averaged effective electron density, ne,eff, experienced by the ions in EBIT spanning ～ 5 × 109–5 × 1011 cm?3.
关键词： optical imaging,effective electron density,extreme ultraviolet spectra,electron beam ion trap,Fe xiv,Fe xiii,Fe xii
更新于2025-09-09 09:28:46
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Rationalizing and Controlling the Surface Structure and Electronic Passivation of Cesium Lead Halide Nanocrystals
摘要： Colloidal lead halide perovskite nanocrystals (NCs) have recently emerged as versatile photonic sources. Their processing and luminescent properties are challenged by the lability of their surfaces, i.e. the interface of the NC core and the ligand shell. On the example of CsPbBr3 NCs, we model the nanocrystal surface structure and its effect on the emergence of trap states using density functional theory. We rationalize the typical observation of a degraded luminescence upon aging or the luminescence recovery upon post-synthesis surface treatments. The conclusions are corroborated by the elemental analysis. We then propose a strategy for healing the surface trap states and for improving the colloidal stability by the combined treatment with didodecyldimethyl ammonium bromide and lead bromide and validate this approach experimentally. This simple procedure results in robust colloids, which are both highly pure and exhibit high photoluminescence quantum yields of up to 95-98%, retained even after 3-4 rounds of washing.
关键词： trap states,didodecyldimethyl ammonium bromide,luminescence recovery,photoluminescence quantum yields,lead bromide,CsPbBr3 NCs,density functional theory,Colloidal lead halide perovskite nanocrystals,surface structure
更新于2025-09-09 09:28:46
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Electronic Traps and Phase Segregation in Lead Mixed-Halide Perovskite
摘要： An understanding of the factors driving halide segregation in lead mixed-halide perovskites is required for their implementation in tandem solar cells with existing silicon technology. Here we report that the halide segregation dynamics observed in the photoluminescence from CH3NH3Pb(Br0.5I0.5)3 is strongly influenced by the atmospheric environment, and that encapsulation of films with a layer of poly(methyl methacrylate) allows for halide segregation dynamics to be fully reversible and repeatable. We further establish an empirical model directly linking the amount of halide segregation observed in the photoluminescence to the fraction of charge-carriers recombining through trap-mediated channels, and the photon flux absorbed. From such quantitative analysis we show that under pulsed illumination, the frequency of the modulation alone has no influence on the segregation dynamics. Additionally, we extrapolate that working CH3NH3Pb(Br0.5I0.5)3 perovskite cells would require a reduction of the trap-related charge-carrier recombination rate to (cid:46) 105 s?1 in order for halide segregation to be sufficiently suppressed.
关键词： photoluminescence,lead mixed-halide perovskites,halide segregation,charge-carrier dynamics,trap-mediated recombination
更新于2025-09-09 09:28:46
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Closing the gap between camera trap software development and the user community
摘要： Like many technological advances in the modern era, camera traps present both an exciting opportunity and a host of unforeseen challenges. One critical challenge is processing the large numbers of images/videos from camera traps efficiently and accurately such that resultant data can be analysed, stored and shared with others. Recognising this need, several biologist teams have developed software to meet their own project requirements, but no one package has been developed to meet the diverse array of requirements of the global research community. We combined an online user survey (N = 67) and literature review to create a list of 42 desired features in five categories. We tested six freely available specialist camera trap software and three nonspecialist image viewer software packages against these criteria. Users were most interested in data processing efficiency and automation features (37 of 84 requests). Seven user‐requested features were not available in any of the software we tested. Thirty‐two unique requests indicated the importance of software flexibility, contrasting with growing calls for standardization in the literature. We suggest involving the global user community, current software developers and computer scientists in an inclusive, planned approach to addressing arguably the greatest challenge facing camera trap‐based research today.
关键词： wildlife research,biodiversity monitoring,camera trap,conservation technology,data processing software
更新于2025-09-09 09:28:46
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Switching excitonic recombination and carrier trapping in cesium lead halide perovskites by air
摘要： All-inorganic cesium lead halide perovskites have been emerging as the promising semiconductor materials for next-generation optoelectronics. However, the fundamental question of how the environmental atmosphere affects their photophysical properties, which is closely related to the practical applications, remains elusive. Here, we report the dynamic switching between radiative exciton recombination and non-radiative carrier trapping in CsPbBr3 by controlling the atmospheric conditions. Specifically, we show that the photoluminescence (PL) intensity from the CsPbBr3 crystals can be boosted by ~ 60 times by changing the surrounding from vacuum to air. Based on the comprehensive optical characterization, near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) as well as density functional theory (DFT) calculations, we unravel that the physisorption of oxygen molecules, which repairs the trap states by passivating the PL-quenching bromine vacancies, is accountable for the enhanced PL in air. These results are helpful for better understanding the optical properties of all-inorganic perovskites.
关键词： trap states,bromine vacancies,oxygen physisorption,photoluminescence,all-inorganic cesium lead halide perovskites
更新于2025-09-09 09:28:46
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Fabrication of Ge MOS with low interface trap density by ALD of Al <sub/>2</sub> O <sub/>3</sub> on epitaxially grown Ge
摘要： Effects of initial surface conditions on interface characteristics of Al2O3/GeOx/Ge gate stacks are studied. As a clean surface condition prior to atomic layer deposition (ALD), a non-terminated Ge surface is realized by the insertion of an epitaxial Ge layer are grown on a Ge substrates in a MBE chamber which is directly connected to an ALD chamber. For these structures, the fixed charge density (Qf) and interface trap density (Dit) are evaluated from the C-V characteristics and conductance method. Qf reduction of about 17% and 90% are achieved by insertion of the epi-Ge layer and additional GeOx formation using plasma post-oxidation, respectively. A 90% reduction of Dit is also confirmed. These results indicate the importance of the initial Ge surface conditions before ALD and the Al2O3/GeOx/Ge gate stacks are very promising for high mobility Ge based CMOS applications.
关键词： interface,epitaxy,CV,trap,Al2O3,Ge
更新于2025-09-09 09:28:46
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The Warm Electron Beam Ion Trap (WEBIT): An instrument for ground calibration of space-borne x-ray spectrometers
摘要： The warm electron beam ion trap (WEBIT) at Lawrence Livermore National Laboratory is being developed as a pre-launch, ground calibration source for space-borne, high-throughput, high-resolution x-ray spectrometers, such as the x-ray imaging and spectroscopy mission Resolve quantum calorimeter. Historically, calibration sources for calorimeter spectrometers have relied on characteristic line emission from x-ray tubes, fluorescing metals, and radioactive sources. The WEBIT, by contrast, relies on emission from x-ray transitions in highly charged ions, for example, hydrogen-like and helium-like ions, whose energies are well known and whose line shapes are relatively simple. The WEBIT can create astrophysically relevant ions whose x-ray emission falls in the 0.3-12 keV science bandpass of Resolve and has a portable design advantageous for a calibration source. The WEBIT will be used to help calibrate Resolve’s instrumental line shape and gain scale as a function of various operational parameters during both detector subsystem level testing and instrumental level testing.
关键词： calibration source,highly charged ions,x-ray spectrometers,electron beam ion trap,WEBIT
更新于2025-09-09 09:28:46