Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “LEVELS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Emergence of shallow energy levels in B-doped Q-carbon: A high-temperature superconductor

We report the spectroscopic demonstration of the shallow-level energy states in the recently discovered B-doped Q-carbon Bardeen-Cooper-Schrieffer (BCS) high-temperature superconductor. The Q-carbon is synthesized by ultrafast melting and quenching, allowing for high B-doping concentrations which increase the superconducting transition temperature (Tc) to 36 K (compared to 4 K for B-doped diamond). The increase in Tc is attributed to the increased density of energy states near the Fermi level in B-doped Q-carbon, which give rise to superconducting states via strong electron-phonon coupling below Tc. These shallow-level energy states, however, are challenging to map due to limited spatial and energy resolution. Here, we use ultrahigh energy resolution monochromated electron energy-loss spectroscopy (EELS), to detect and visualize the newly formed shallow-level energy states (vibrational modes) near the Fermi level (ranging 30–100 meV) of the B-doped Q-carbon. In this work, we establish the significance of high-resolution EELS in understanding the superconducting behavior of BCS superconducting C-based materials, which demonstrate a phenomenal enhancement in the presence of shallow-level energy states.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Fine-structure calculations of energy levels, oscillator strengths, and transition probabilities for sulfur-like iron, Fe XI

Energy levels, oscillator strengths, and transition probabilities for transitions among the 14 LS states belonging to configurations of sulfur-like iron, Fe XI, have been calculated. These states are represented by configuration interaction wavefunctions and have configurations 3s{sup 2}3p{sup 4}, 3s3p{sup 5}, 3s{sup 2}3p{sup 3}3d, 3s{sup 2}3p{sup 3}4s, 3s{sup 2}3p{sup 3}4p, and 3s{sup 2}3p{sup 3}4d, which give rise to 123 fine-structure energy levels. Extensive configuration interaction calculations using the CIV3 code have been performed. To assess the importance of relativistic effects, the intermediate coupling scheme by means of the Breit–Pauli Hamiltonian terms, such as the one-body mass correction and Darwin term, and spin–orbit, spin–other-orbit, and spin–spin corrections, are incorporated within the code. These incorporations adjusted the energy levels, therefore the calculated values are close to the available experimental data. Comparisons between the present calculated energy levels as well as oscillator strengths and both experimental and theoretical data have been performed. Our results show good agreement with earlier works, and they might be useful in thermonuclear fusion research and astrophysical applications. -- Highlights: •Accurate atomic data of iron ions are needed for identification of solar corona. •Extensive configuration interaction wavefunctions including 123 fine-structure levels have been calculated. •The relativistic effects by means of the Breit–Pauli Hamiltonian terms are incorporated. •This incorporation adjusts the energy levels, therefore the calculated values are close to experimental values.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

A block-tridiagonal solver with two-level parallelization for finite element-spectral codes

Two-level parallelization is introduced to solve a massive block-tridiagonal matrix system. One-level is used for distributing blocks whose size is as large as the number of block rows due to the spectral basis, and the other level is used for parallelizing in the block row dimension. The reason for the added parallelization dimension is to retard the saturation of the scaling due to communication overhead and inefficiencies in the single-level parallelization only distributing blocks. As a technique for parallelizing the tridiagonal matrix, the combined method of “Partitioned Thomas method” and “Cyclic Odd–Even Reduction” is implemented in an MPI-Fortran90 based finite element-spectral code (TORIC) that calculates the propagation of electromagnetic waves in a tokamak. The two-level parallel solver using thousands of processors shows more than 5 times improved computation speed with the optimized processor grid compared to the single-level parallel solver under the same conditions. Three-dimensional RF field reconstructions in a tokamak are reflected as examples of the physics simulations that have been enabled by this algorithmic advance.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Cosmogenic surface exposure ( 10 Be) dating of raised beaches in Marguerite bay, Antarctic Peninsula: Implications for relative sea-level history

Understanding the dynamics of ice mass loss in polar regions is crucial for deciphering climate change and Glacio Isostatic Adjustment patterns. This study focuses on Marguerite Bay, located in the south-central Antarctic Peninsula. We dated raised beaches to investigate relative sea-level changes using the cosmogenic surface exposure ( 10 Be) method. Previous studies have provided valuable insights into the region's glacial history, but limitations in dating techniques and age estimates necessitate further investigation. By analysing raised shingle beaches in Gaul Cove of Horseshoe Island and the southern coast of Calmette Bay, this research aims to contribute relative sea-level change history for these areas. In Horseshoe Island's Gaul Cove, raised beaches clustered on prominent steps reveal a 15 m relative sea-level change over the last 3.31 ka. Differently, Calmette Bay exhibits a 36 m relative sea-level fall over the last 7.29 ka. Finally, these findings indicate significant and differential glacial-isostatic adjustments in both regions during the middle and late Holocene. Additionally, our data reveal accelerated sea-level fall periods corresponding to Holocene deglaciation and glacial advance events, indicating the shorelines' relative sea-level change sensitivity to climate change.

58 GEOSCIENCES↗
DOE OSTI2012

Assessing methane oxidation under landfill covers and its contribution to the above atmospheric CO{sub 2} levels: The added value of the isotope ({delta}{sup 13}C and {delta}{sup 18}O CO{sub 2}; {delta}{sup 13}C and {delta}D CH{sub 4}) approach

Highlights: Black-Right-Pointing-Pointer Comparison of the isotope and mass balance approaches to evaluate the level of methane oxidation within a landfill. Black-Right-Pointing-Pointer The level of methane oxidation is not homogenous under the landfill cover and is strongly correlated to the methane flux. Black-Right-Pointing-Pointer Isotope tracking of the contribution of the methane oxidation to the CO{sub 2} concentrations in the ambient air. - Abstract: We are presenting here a multi-isotope approach ({delta}{sup 13}C and {delta}{sup 18}O of CO{sub 2}; {delta}{sup 13}C and {delta}D of CH{sub 4}) to assess (i) the level(s) of methane oxidation during waste biodegradation and its migration through a landfill cover in Sonzay (France), and (ii) its contribution to the atmospheric CO{sub 2} levels above the surface. The isotope approach is compared to the more conventional mass balance approach. Results from the two techniques are comparable and show that the CH{sub 4} oxidation under the landfill cover is heterogenous, with low oxidation percentages in samples showing high biogas fluxes, which was expected in clay covers presenting fissures, through which CH{sub 4} is rapidly transported. At shallow depth, more immobile biogas pockets show a higher level of CH{sub 4} oxidation by the methanotrophic bacteria. {delta}{sup 13}C of CO{sub 2} samples taken at different heights (from below the cover up to 8 m above the ground level) were also used to identify and assess the relative contributions of its main sources both under the landfill cover and in the surrounding atmosphere.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

The minimum-uncertainty coherent states for Landau levels

The Glauber minimum-uncertainty coherent states with two variables for Landau levels, based on the representation of Weyl-Heisenberg algebra by two different modes, have been studied about four decades ago. Here, we introduce new two-variable coherent states with minimum uncertainty relationship for Landau levels in three different methods: the infinite unitary representation of su(1, 1) is realized in two different methods, first, by consecutive levels with the same energy gaps and also with the same value for z-angular momentum quantum number, then, by shifting z-angular momentum mode number by two units while the energy level remaining the same. Besides, for su(2), whether by lowest Landau levels or Landau levels with lowest z-angular momentum, just one finite unitary representation is introduced. Having constructed the generalized Klauder-Perelomov coherent states, for any of the three representations, we obtain their Glauber coherency by displacement operator of Weyl-Heisenberg algebra.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Characterization of deep level defects and thermally stimulated depolarization phenomena in La-doped TlInS{sub 2} layered semiconductor

Lanthanum-doped high quality TlInS{sub 2} (TlInS{sub 2}:La) ferroelectric-semiconductor was characterized by photo-induced current transient spectroscopy (PICTS). Different impurity centers are resolved and identified. Analyses of the experimental data were performed in order to determine the characteristic parameters of the extrinsic and intrinsic defects. The energies and capturing cross section of deep traps were obtained by using the heating rate method. The observed changes in the Thermally Stimulated Depolarization Currents (TSDC) near the phase transition points in TlInS{sub 2}:La ferroelectric-semiconductor are interpreted as a result of self-polarization of the crystal due to the internal electric field caused by charged defects. The TSDC spectra show the depolarization peaks, which are attributed to defects of dipolar origin. These peaks provide important information on the defect structure and localized energy states in TlInS{sub 2}:La. Thermal treatments of TlInS{sub 2}:La under an external electric field, which was applied at different temperatures, allowed us to identify a peak in TSDC which was originated from La-dopant. It was established that deep energy level trap BTE43, which are active at low temperature (T ≤ 156 K) and have activation energy 0.29 eV and the capture cross section 2.2 × 10{sup −14} cm{sup 2}, corresponds to the La dopant. According to the PICTS results, the deep level trap center B5 is activated in the temperature region of incommensurate (IC) phases of TlInS{sub 2}:La, having the giant static dielectric constant due to the structural disorders. From the PICTS simulation results for B5, native deep level trap having an activation energy of 0.3 eV and the capture cross section of 1.8 × 10{sup −16} cm{sup 2} were established. A substantial amount of residual space charges is trapped by the deep level localized energy states of B5 in IC-phase. While the external electric field is applied, permanent dipoles, which are originated from the charged B5 deep level defects, are aligned in the direction of the applied electric field and the equilibrium polarization can be reached in a relatively short time. When the polarization field is maintained, while cooling the temperature of sample to a sufficiently low degrees, the relaxation times of the aligned dipoles drastically increases. Practically, frozen internal electric field or electrets states remain inside the TlInS{sub 2}:La when the applied bias field is switched off. The influence of deep level defects on TSDC spectra of TlInS{sub 2}:La has been revealed for the first time.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Subgap time of flight: A spectroscopic study of deep levels in semi-insulating CdTe:Cl

We report on a study of deep levels in semi-insulating CdTe:Cl by means of a time-of-flight spectral approach. By varying the wavelength of a pulsed optical source within the CdTe energy gap, transitions to/from localized levels generate free carriers which are analysed through the induced photocurrent transients. Both acceptor-like centers, related to the A-center, and a midgap level, 0.725 eV from the valence band, have been detected. The midgap level is close to the Fermi level and is possibly a recombination center responsible for the compensation mechanism. When the irradiance is varied, either linear or quadratic dependence of the electron and hole collected charge are observed, depending on the dominant optical transitions. The analysis discloses the potentiality of such a novel approach exploitable in the field of photorefractive materials as well as for deep levels spectroscopy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Identification of the defect dominating high temperature reverse leakage current in vertical GaN power diodes through deep level transient spectroscopy

Deep level defects in wide bandgap semiconductors, whose response times are in the range of power converter switching times, can have a significant effect on converter efficiency. We use Deep Level Transient Spectroscopy (DLTS) to evaluate such defect levels in the n- drift layer of vertical GaN (v-GaN) power diodes with VBD ~ 1500 V. DLTS reveals three energy levels that are at ~0.6 eV (highest density), ~0.27 eV (lowest density) and ~ 45 meV (a dopant level) from the conduction band. Dopant extraction from Capacitance-Voltage measurement test (C-V) at multiple temperatures enables trap density evaluation, and the ~0.6 eV trap has a density of 1.2 × 10 15 cm -3 . Here, the 0.6 eV energy level and its density are similar to a defect that is known to cause current collapse in GaN based surface conducting devices (like HEMTs). Analysis of reverse bias currents over temperature in the v-GaN diodes indicates a predominant role of the same defect in determining reverse leakage current at high temperatures, reducing switching efficiency.

42 ENGINEERING↗
DOE OSTI2023

Sea-level rise in Southwest Greenland as a contributor to Viking abandonment

The first records of Greenland Vikings date to 985 CE. Archaeological evidence yields insight into how Vikings lived, yet drivers of their disappearance in the 15th century remain enigmatic. Research suggests a combination of environmental and socioeconomic factors, and the climatic shift from the Medieval Warm Period (~900 to 1250 CE) to the Little Ice Age (~1250 to 1900 CE) may have forced them to abandon Greenland. Glacial geomorphology and paleoclimate research suggest that the Southern Greenland Ice Sheet readvanced during Viking occupation, peaking in the Little Ice Age. Counterintuitively, the readvance caused sea-level rise near the ice margin due to increased gravitational attraction toward the ice sheet and crustal subsidence. We estimate ice growth in Southwestern Greenland using geomorphological indicators and lake core data from previous literature. We calculate the effect of ice growth on regional sea level by applying our ice history to a geophysical model of sea level with a resolution of ~1 km across Southwestern Greenland and compare the results to archaeological evidence. The results indicate that sea level rose up to ~3.3 m outside the glaciation zone during Viking settlement, producing shoreline retreat of hundreds of meters. Sea-level rise was progressive and encompassed the entire Eastern Settlement. Moreover, pervasive flooding would have forced abandonment of many coastal sites. These processes likely contributed to the suite of vulnerabilities that led to Viking abandonment of Greenland. Sea-level change thus represents an integral, missing element of the Viking story.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2011

Radiative decay probabilities of the (2s{sup 2}2p{sub 1/2}{sup 5}3s{sub 1/2}){sub J=0} level in neonlike ions

The radiative decay rates of the (2s{sup 2}2p{sub 1/2}{sup 5}3s{sub 1/2}){sub J=0} level in neonlike ions have been calculated for nuclear charges ranging from Z=10 to Z=110. The calculations include the magnetic dipole decay to the (2s{sup 2}2p{sub 3/2}{sup 5}3s{sub 1/2}){sub J=1} level, which is shown to be the dominant decay branch in low-Z and very-high-Z ions, as well as the two-electron, one-photon decays to the (2s{sup 2}2p{sub 3/2}{sup 5}3p{sub 1/2}){sub J=1} and (2s{sup 2}2p{sub 3/2}{sup 5}3p{sub 3/2}){sub J=1} levels, which dominate near Z=50. We also take into account a small magnetic quadrupole decay branch to the (2s{sup 2}2p{sub 3/2}{sup 5}3s{sub 1/2}){sub J=2} level and calculate the total radiative lifetime of the (2s{sup 2}2p{sub 1/2}{sup 5}3s{sub 1/2}){sub J=0} level. The resulting values span over 15 orders of magnitude, and much of this range is accessible with modern atomic lifetime measurement techniques. In particular, we calculate a value of 1.6x10{sup 4} s{sup -1} for the radiative decay rate of the (2s{sup 2}2p{sub 1/2}{sup 5}3s{sub 1/2}){sub J=0} level in Fe XVII and show that the corresponding magnetic dipole transition has a measurable spectral intensity for electron densities below about 1x10{sup 13} cm{sup -3}.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Level density rotational enhancement factor

Bethe wrote a pivotal paper providing the formalism for the theory of nuclear level densities. At that time, there were no known deformed nuclei, so Bethe made the assumption that all nuclei are spherical. After deformed nuclei were discovered, theorists predicted that the level density for such nuclei should be substantially enhanced over the level density for neighboring spherical nuclei. Despite these results, two comprehensive level density compilations based on neutron resonances counting at low neutron energy failed to find significant enhancement in level density for deformed nuclei. A recent paper has concluded that the Bethe spin distribution for nuclear levels is not appropriate for deformed nuclei. When a more accurate spin distribution is used in resonance analysis, it is found that an enhancement of approximately the predicted magnitude is observed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Validation of finite-element models using full-field experimental data: Levelling finite-element analysis data through a digital image correlation engine

Full-field data from digital image correlation (DIC) provide rich information for finite-element analysis (FEA) validation. However, there are several inherent inconsistencies between FEA and DIC data that must be rectified before meaningful, quantitative comparisons can be made, including strain formulations, coordinate systems, data locations, strain calculation algorithms, spatial resolutions and data filtering. As such, in this paper, we investigate two full-field validation approaches: (1) the direct interpolation approach, which addresses the first three inconsistencies by interpolating the quantity of interest from one mesh to the other, and (2) the proposed DIC-levelling approach, which addresses all six inconsistencies simultaneously by processing the FEA data through a stereo-DIC simulator to ‘level’ the FEA data to the DIC data in a regularisation sense. Synthetic ‘experimental’ DIC data were generated based on a reference FEA of an exemplar test specimen. The direct interpolation approach was applied, and significant strain errorswere computed, even though therewas no model form error, because the filtering effect of theDIC enginewas neglected. In contrast, the levelling approach provided accurate validation results, with no strain error when no model form error was present. Next, model form error was purposefully introduced via a mismatch of boundary conditions. With the direct interpolation approach, the mismatch in boundary conditions was completely obfuscated, while with the levelling approach, it was clearly observed. Finally, the ‘experimental’ DIC datawere purposefully misaligned slightly fromthe FEA data. Both validation techniques suffered from the misalignment, thus motivating continued efforts to develop a robust alignment process. In conclusion, direct interpolation is insufficient, and the proposed levelling approach is required to ensure that the FEA and the DIC data have the same spatial resolution and data filtering. Only after the FEA data have been ‘levelled’ to the DIC data can meaningful, quantitative error maps be computed.

42 ENGINEERING↗
DOE OSTI2015

Measurements of the populations of metastable and resonance levels in the plasma of an RF capacitive discharge in argon

The behavior of the populations of two metastable and two lower resonance levels of argon atoms in the plasma of an RF capacitive discharge was studied. The populations were measured by two methods: the method of emission self-absorption and the method based on measurements of the intensity ratios of spectral lines. It is shown that the populations of resonance levels increase with increasing power deposited in the discharge, whereas the populations of metastable levels is independent of the RF power. The distribution of the populations over energy levels is not equilibrium under these conditions. The population kinetics of argon atomic levels in the discharge plasma is simulated numerically. The distribution function of plasma electrons recovered from the measured populations of atomic levels and numerical simulations is found to be non-Maxwellian.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Deep electron levels in undoped polycrystalline CdTe annealed in liquid Cd

The method of deep-level transient spectroscopy (DLTS) is used to determine the set of deep electron levels in undoped n-CdTe polycrystals grown by chemical synthesis from vapor phase in highly nonequilibrium conditions and then subjected to annealing in liquid Cd. After annealing, the electron concentration is found to increase from {approx}10{sup 8} to 10{sup 15} cm{sup -3}. Electron traps with deep levels E{sub 1} = 0.84 {+-} 0.03 eV and E{sub 2} = 0.71 {+-} 0.02 eV with total concentration {approx}10{sup 14} cm{sup -3} are dominant in the DLTS spectrum. The role of grain boundaries and intrinsic point defects in formation of deep-level centers and their effect on the value of conductivity after annealing are discussed. A relation between the level E{sub 1} and complexes of intrinsic point defects and relation of the level E{sub 2} to the Cd{sub i} point defect are considered.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Preliminary Safety Design Report for Remote Handled Low-Level Waste Disposal Facility

A new onsite, remote-handled low-level waste disposal facility has been identified as the highest ranked alternative for providing continued, uninterrupted remote-handled low-level waste disposal for remote-handled low-level waste from the Idaho National Laboratory and for nuclear fuel processing activities at the Naval Reactors Facility. Historically, this type of waste has been disposed of at the Radioactive Waste Management Complex. Disposal of remote-handled low-level waste in concrete disposal vaults at the Radioactive Waste Management Complex will continue until the facility is full or until it must be closed in preparation for final remediation of the Subsurface Disposal Area (approximately at the end of Fiscal Year 2017). This preliminary safety design report supports the design of a proposed onsite remote-handled low-level waste disposal facility by providing an initial nuclear facility hazard categorization, by discussing site characteristics that impact accident analysis, by providing the facility and process information necessary to support the hazard analysis, by identifying and evaluating potential hazards for processes associated with onsite handling and disposal of remote-handled low-level waste, and by discussing the need for safety features that will become part of the facility design.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2010

Application for a Permit to Operate a Class III Solid Waste Disposal Site at the Nevada National Security Site Area 5 Asbestiform Low-Level Solid Waste Disposal Site

The Nevada National Security Site (NNSS) is located approximately 105 km (65 mi) northwest of Las Vegas, Nevada. The U.S. Department of Energy National Nuclear Security Administration Nevada Site Office (NNSA/NSO) is the federal lands management authority for the NNSS and National Security Technologies, LLC (NSTec) is the Management and Operations contractor. Access on and off the NNSS is tightly controlled, restricted, and guarded on a 24-hour basis. The NNSS is posted with signs along its entire perimeter. NSTec is the operator of all solid waste disposal sites on the NNSS. The Area 5 Radioactive Waste Management Site (RWMS) is the location of the permitted facility for the Solid Waste Disposal Site (SWDS). The Area 5 RWMS is located near the eastern edge of the NNSS (Figure 1), approximately 26 km (16 mi) north of Mercury, Nevada. The Area 5 RWMS is used for the disposal of low-level waste (LLW) and mixed low-level waste. Many areas surrounding the RWMS have been used in conducting nuclear tests. The site will be used for the disposal of regulated Asbestiform Low-Level Waste (ALLW), small quantities of low-level radioactive hydrocarbon-burdened (LLHB) media and debris, LLW, LLW that contains Polychlorinated Biphenyl (PCB) Bulk Product Waste greater than 50 ppm that leaches at a rate of less than 10 micrograms of PCB per liter of water, and small quantities of LLHB demolition and construction waste (hereafter called permissible waste). Waste containing free liquids, or waste that is regulated as hazardous waste under the Resource Conservation and Recovery Act (RCRA) or state-of-generation hazardous waste regulations, will not be accepted for disposal at the site. Waste regulated under the Toxic Substances Control Act (TSCA) that will be accepted at the disposal site is regulated asbestos-containing materials (RACM) and PCB Bulk Product Waste greater than 50 ppm that leaches at a rate of less than 10 micrograms of PCB per liter of water. The term asbestiform is used throughout this document to describe RACM. The disposal site will be used as a depository of permissible waste generated both on site and off site. All generators designated by NNSA/NSO will be eligible to dispose regulated ALLW at the Asbestiform Low-Level Waste Disposal Site in accordance with the DOE/NV-325, Nevada National Security Site Waste Acceptance Criteria (NNSSWAC, current revision). Approval will be given by NNSA/NSO to generators that have successfully demonstrated through process knowledge (PK) and/or sampling and analysis that the waste is low-level, contains asbestiform material, or contains PCB Bulk Product Waste greater than 50 ppm that leaches at a rate of less than 10 micrograms of PCB per liter of water, or small quantities of LLHB demolition and construction waste and does not contain prohibited waste materials. Each waste stream will be approved through the Radioactive Waste Acceptance Program (RWAP), which ensures that the waste meets acceptance requirements outlined in the NNSSWAC.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Effects of HAT-CN Layer Thickness on Molecular Orientation and Energy-Level Alignment with ZnPc

Efficient energy-level alignment is crucial for achieving high performance in organic electronic devices. Because the electronic structure of an organic semiconductor is significantly influenced by its molecular orientation, comprehensively understanding the molecular orientation and electronic structure of the organic layer is essential. In this study, we investigated the interface between a 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) hole injection layer and a zinc-phthalocyanine (ZnPc) p-type organic semiconductor. To determine the energy-level alignment and molecular orientation, we conducted in situ ultraviolet and X-ray photoelectron spectroscopies, as well as angle-resolved X-ray absorption spectroscopy. We found that the HAT-CN molecules were oriented relatively face-on (40°) in the thin (5 nm) layer, whereas they were oriented relatively edge-on (62°) in the thick (100 nm) layer. By contrast, ZnPc orientation was not significantly altered by the underlying HAT-CN orientation. The highest occupied molecular orbital (HOMO) level of ZnPc was closer to the Fermi level on the 100 nm thick HAT-CN layer than on the 5 nm thick HAT-CN layer because of the higher work function. Consequently, a considerably low energy gap between the lowest unoccupied molecular orbital level of HAT-CN and the HOMO level of ZnPc was formed in the 100 nm thick HAT-CN case. This may improve the hole injection ability of the anode system, which can be utilized in various electronic devices.

42 ENGINEERING↗