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Peter J. Cumpson Jose F. Portoles Naoko Sano 《Surface and interface analysis : SIA》2013,45(2):601-604
Traditionally polymer depth profiling by X‐ray photoelectron spectroscopy (XPS) has been dominated by the damage introduced by the ion beam rather than the X‐rays. With the introduction of polyatomic and especially argon gas cluster ion‐beam (GCIB) sources for XPS instruments, this is no longer the case, and either source of damage may be important (or dominate) under particular conditions. Importantly, while ion‐beam damage is a near‐surface effect, X‐ray damage may extend micrometres into the bulk of the sample, so that the accumulation of X‐ray damage during long depth profiles may be very significant. We have observed craters of similar dimensions to the X‐ray spot well within the perimeter of sputter craters, indicating that X‐rays can assist GCIB sputtering very significantly. We have measured experimentally sputter craters in 13 different polymers. The results show that X‐ray exposure can introduce much more topography than might previously have been expected, through both thermal and direct X‐ray degradation. This can increase the depth of a crater by a remarkable factor, up to three in the case of poly‐L‐lactic acid and polychlorotrifluorothylene under reasonably normal XPS conditions. This may be a major source of the loss of depth resolution in sputter depth profiles of polymers. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Ashley A. Ellsworth Christopher N. Young William F. Stickle Amy V. Walker 《Surface and interface analysis : SIA》2017,49(10):991-999
X‐ray photoelectron spectroscopy is used to study a wide variety of material systems as a function of depth (“depth profiling”). Historically, Ar+ has been the primary ion of choice, but even at low kinetic energies, Ar+ ion beams can damage materials by creating, for example, nonstoichiometric oxides. Here, we show that the depth profiles of inorganic oxides can be greatly improved using Ar giant gas cluster beams. For NbOx thin films, we demonstrate that using Arx+ (x = 1000‐2500) gas cluster beams with kinetic energies per projectile atom from 5 to 20 eV, there is significantly less preferential oxygen sputtering than 500 eV Ar+ sputtering leading to improvements in the measured steady state O/Nb ratio. However, there is significant sputter‐induced sample roughness. Depending on the experimental conditions, the surface roughness is up to 20× that of the initial NbOx surface. In general, higher kinetic energies per rojectile atom (E/n) lead to higher sputter yields (Y/n) and less sputter‐induced roughness and consequently better quality depth profiles. We demonstrate that the best‐quality depth profiles are obtained by increasing the sample temperature; the chemical damage and the crater rms roughness is reduced. The best experimental conditions for depth profiling were found to be using a 20 keV Ar2500+ primary ion beam at a sample temperature of 44°C. At this temperature, there is no, or very little, reduction of the niobium oxide layer and the crater rms roughness is close to that of the original surface. 相似文献
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Electronic Structure of
TiAl-2M(M=V,Nb,Ta,Cr,Mo,W,Mn) Alloy 总被引：1，自引：0，他引：1
1INTRODUCTIONTitaniumaluminidesbasedonY-TiAlarereceivingconsiderableattentionaspo-tentialcandidatesformaterialsinhightemperatureaerospaceapplication.Theirlowdensity,hightemperaturescreepresistance,highoxidationresistanceandstrengthmakesthemexcellentpotentialenginematerials.Howevertheirlowductilityandlowfracturetoughnessatroom'temperaturesaremajorhindrancestotheirpracticaluti-lization.TheTiAlalloymayhaveanelongationabout2%t'},furtherimprovementisnecessarybeforethesematerialscouldbeusedin… 相似文献
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Kaveenga Rasika Koswattage Chathudina Janitha Liyanage G. D. Kaveendra Virajith Maduwantha 《Surface and interface analysis : SIA》2022,54(5):561-566
L-cysteine is one of the most versatile biomolecules with a unique metal-binding ability. L-cysteine has an outstanding role in the bioelectronics field as a linker between proteins of biomolecules and metal electrodes of the inorganic metals through multiple functional groups. The interface electronic structures between L-cysteine with metals deserve further investigation for applications in bioelectronics. However, the interface electronic structures of L-cysteine and metals have not been well understood. We have previously reported the existence of a new state between the highest occupied molecular orbital (HOMO) of L-cysteine and the Fermi level of the metals for L-cysteine/Au(111), L-cysteine/Ag(111), and L-cysteine/Cu(111) using photoemission spectroscopy and attributed the formation of the new state to an interaction of the d band with HOMO of L-cysteine. In this study, the electronic structure at the interfaces of L-cysteine on a Palladium (Pd) surface is investigated by ultraviolet photoemission spectroscopy (UPS) using synchrotron radiation including work function, secondary electron cutoff (SECO), and HOMO onset; the position of an interface state, charge injection barrier, and ionization energy are estimated. It is observed that thin-film spectra of L-cysteine on Pd surfaces in the valance top region are different from the L-cysteine thick films, and this can be attributed to an interaction between a sulfur-originated state of L-cysteine HOMO with Pd d orbitals. Also, a 0.6-eV SECO shift is estimated due to the charge transferring between L-cysteine and Pd. The results of SECO further confirm the weakening of the Pd–sulfur bond with increasing L-cysteine coverage on Pd. 相似文献
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影响TiAl合金塑性的电子结构因素 总被引：2，自引：0，他引：2
应用ＥＨＴ紧束缚能带计算方法, 系统研究了Ｔｉ－４８Ａｌ－２Ｍ 为模型的γ－ＴｉＡｌ掺杂合金的电子结构。发现能有效地改善合金塑性的元素Ｖ、Ｃｒ、Ｍｎ 主要在两方面改变了γ－ＴｉＡｌ合金的电子结构,即改善Ｔｉ周围成键强度的各向均衡性和改变Ｔｉ、Ａｌ参与成键的电子分布,使成键电子云的球形化成分增大。研究结果表明Ｖ、Ｃｒ、Ｍｎ 等取代Ａｌ时成键的均衡性及电子云球形化均增大,从而有利于材料变形改善塑性,而加入Ｆｅ、Ｃｏ、Ｎｉ虽然改善电子云的球形化但却不利于成键强度的均衡性,因而对合金的塑性无明显改善。 相似文献
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A theoretical study of structural and electronic properties of cis‐1,3,4,6‐tetranitrooctahydroimidazo‐[4,5‐d]imidazole (BCHMX) crystal is performed using density functional theory. The band structure, the total density of states, the atomic orbit projected density of states (PDOS) of C, N, O, and H, and Mulliken population analysis are discussed. The study by analyzing the PDOS shows that the structure of BCHMX crystal possesses C? H···O intra‐ and intermolecular hydrogen bonding. There are hydrogen bonds between H3‐1s and O5‐2p orbits, H2‐1s and O6‐2p orbits of intramolecules and between H2‐1s and O1‐2p orbits of intermolecules. The reasons for the smaller impact sensitivity compared with β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane and 1,3,5‐trinitro‐1,3,5‐triazinane are also explored from the band gap in the crystal and the weakest bond dissociation energy in single molecule. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
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Bindu Rani Aadil Fayaz Wani Utkir Bahodirovich Sharopov Lokanath Patra Jaspal Singh Atif Mossad Ali A. F. Abd El-Rehim Shakeel Ahmad Khandy Shobhna Dhiman Kulwinder Kaur 《Molecules (Basel, Switzerland)》2022,27(19)
We hereby discuss the thermoelectric properties of PdXSn(X = Zr, Hf) half Heuslers in relation to lattice thermal conductivity probed under effective mass (hole/electrons) calculations and deformation potential theory. In addition, we report the structural, electronic, mechanical, and lattice dynamics of these materials as well. Both alloys are indirect band gap semiconductors with a gap of 0.91 eV and 0.82 eV for PdZrSn and PdHfSn, respectively. Both half Heusler materials are mechanically and dynamically stable. The effective mass of electrons/holes is (0.13/1.23) for Zr-type and (0.12/1.12) for Hf-kind alloys, which is inversely proportional to the relaxation time and directly decides the electrical/thermal conductivity of these materials. At 300K, the magnitude of lattice thermal conductivity observed for PdZrSn is 15.16 W/mK and 9.53 W/mK for PdHfSn. The highest observed ZT value for PdZrSn and PdHfSn is 0.32 and 0.4, respectively. 相似文献
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Chang Yoon Yang Kyung Hyung Lee Prof. Jun Yeob Lee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(11):2429-2435
N-type hosts for long lifetime in sky-blue thermally-activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) were investigated by synthesizing four hosts with zig-zag-type backbone structure for high triplet energy. The four hosts had two CN units at different positions of the zig-zag-type backbone structure and two dibenzofuran units through either the 2 or 4-position of dibenzofuran. The position of the CN unit was controlled at the meta and para-positions in the zig-zag-type backbone to study the relationship between material parameters and lifetime of the TADF OLEDs. It was revealed that the meta-orientation of the CN units in the backbone was advantageous to extend device lifetime of the sky-blue TADF OLEDs. 相似文献
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Tao Yu Florence Fabunmi Jingsong Huang Bobby G. Sumpter Jacek Jakowski 《Journal of computational chemistry》2019,40(2):532-542
We propose a fast and accurate calculation method to compute the electronic couplings between molecular units in a thiophene-ring-based polymer chain mimicking a real organic semiconducting polymer, poly(3-hexylthiophene). Through a unit block diabatization scheme, the method employed minimal number of diabatic orbitals to compute the site energies and electronic couplings, which were validated by comparing with benchmark density functional theory calculations. In addition, by using the obtained electronic couplings, a quantum dynamics simulation was carried out to propagate a hole initially localized in a thiophene-ring unit of the polymer chain. This work establishes a simple, efficient, and robust means for the simulation of electron or hole transfer processes in organic semiconducting materials, an important capability for study and understanding of the class of organic optoelectronic and photovoltaic materials. © 2018 Wiley Periodicals, Inc. 相似文献
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The electronic band structure and stability of extended nanocrystallites (NCs) of titanium monocarbide TiC were investigated by the electron density functional-tight binding (DFTB) technique. The stability of prismatic NCs increases with the number of atomic layers; the electronic spectrum of these compounds changes from semiconductor (for NC of minimal atomic size) to metallike type inherent in crystalline titanium carbide. 相似文献
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Nobuhiko Kato Hidemi Nagao Kiyoshi Nishikawa Kazume Nishidate Kazunaka Endo 《International journal of quantum chemistry》2004,96(5):457-462
We investigated the electronic structure of MgB2 and intercalation compounds, MgBX (X = Li, Be, C), with fully relaxed crystal structure by using density functional theory. The compounds MgBLi and MgBBe could be similar two‐band superconductors to MgB2 because the Fermi surface crosses σ and π bands. Our results indicate that changing the lattice constants, hole or electron doping, and stacking of B? X effect the energy levels of the σ and π bands in MgBX compounds. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 相似文献
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Crystals of Ba3ZnSb2O9 have been grown by a high-temperature solid-state reaction and characterized by single-crystal X-ray diffraction.Ba3ZnSb2O9 crystallizes in the hexagonal P63/mmc space group with a = 5.8663(4),c = 14.478(2) ,V = 431.49(8) 3,Z = 2 and R(all data) = 0.0167.The structure of Ba3ZnSb2O9 consists of pairs of face-sharing Sb2O9 bi-octahedra connected via corners with two single layers of mutually isolated ZnO6 octahedra.Each Ba2+ ion is bonded to 12 oxygen atoms.The UV-vis absorption spectrum of the compound has been investigated.Additionally,the calculations of band structure and density of states have also been performed with density functional theory method.The obtained results tend to support the experimental data of the absorption spectrum. 相似文献
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Myong-Song Ryang Chol-Jun Kang Hyon-Chol Choe Nam-Hyok Kim 《International journal of quantum chemistry》2019,119(24):e26022
The best quantity correlated to the electronic energy band gap is found for alkali and alkaline-earth metal oxides and halides with face centered cubic (fcc) structure based on density functional theory and Bader's atom-in-molecule theory. Previous studies show the correlation of the band gap to the ground state electron density at the bond critical point (BCP). Whereas, in quantum mechanics, the gap between the energy levels of one dimensional square well potential is inversely proportional to the square of the width of the well which is the metal–nonmetal chemical bond length in our case. These motivate the proposition of a new quantity Q, the ratio of the density at the BCP to the square of the bond length. Our study reveals that, for the aforementioned materials, the band gap has a strong correlation to Q when they are multiplied by the density at the BCP. 相似文献
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In the present paper, the electronic band structure, density of states （DOS）, and projected density of states （PDOS） analysis of thiocarbamide hydrochloride are reported. Calculations of the electronic properties have been carried out on the basis of fully self-consistent pseudopotential method using DFT. The results show that near the Fermi level, more prominent densities of states are seen between -8 eV and -6 eV in the valence band mainly due to the Cl-3p, N-2p and S-3p orbitals. 相似文献
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The banding and electronic structures of crystalline 1,1,3,3,5,5‐hexaazidocyclotriphosphazene (P3N21) have been investigated at DFT‐B3LYP/6‐31G(d) level. Relaxed crystal structure compares well with experimental data. The energy gap is 5.57 eV, indicating that P3N21 is an insulator. The frontier orbital is mainly formed by atomic orbitals of azido group, so it is the most reactive part of the molecule. The intermolecular interaction is strong along the direction that is nearly perpendicular to the phosphazene ring. The distribution of electrostatic potential is quite uneven, so P3N21 has a very high impact sensitivity. The point charge electrostatic potential is very high between the azido groups of the neighboring molecules, which indicates that the crystal lattice in this position may easily be broken and becomes the explosion center when P3N21 is impacted. The overlap populations of P–Nα bonds are much less than those of other bonds, therefore the P–Nα bonds first rupture by external stimuli, which agrees well with the experimental study of mass spectrum. 相似文献
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《Surface and interface analysis : SIA》2018,50(6):623-627
The electronic structures of Alq3/Si(100), Alq3/LiBr/Si(100), and Alq3/KCl/Si(100) systems are presented in this report. Their energy level diagrams were prepared and discussed. The formation of the LiBr and KCl interfacial layers between an Alq3 film and a Si(100) substrate results in a decrease of the energy barrier at the interface. The studies were carried out in situ in ultrahigh vacuum by ultraviolet photoelectron spectroscopy. Alq3 as well as LiBr and KCl layers were vapour evaporated onto n‐type Si(100) crystal. The electron affinity of clean Si(100) surface was 4.0 eV, and the position of the valence band maximum was 0.7 eV below EF. The energetic distance between the valence band maximum of Si(100) and the highest occupied molecular orbital level were 1.5, 2.6, and 2.2 eV, for the Alq3/Si(100), Alq3/LiBr/Si(100), and Alq3/KCl/Si(100) systems, respectively. 相似文献
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Werner H. Gries 《Mikrochimica acta》1992,107(3-6):117-135
The angle-resolved self-ratio (AR/SR) technique is a non-destructive, low-damage measuring technique in which the intensity I of an excited, analyte-characteristic radiation is measured as a function of the take-off angle from the surface plane for the purpose of obtaining quantitative depth information about the chosen analyte from the gradient dI/d. The depth information may be any of the following: the type of depth profile, the centroid depth of this profile, the thickness of a uniform overlayer, the stoichiometry of a uniform overlayer, the thickness of a uniform buried layer, and others. The AR/SR technique is one of a number of variants of the angle-resolved technique which is particularly suited for practical application because this mode combines an acceptable measuring effort with a simplicity and transparency of evaluation (by use of analytical formulae) not available with other procedures. The capabilities and limitations of the AR/SR technique in particular are reviewed, with special reference to four methods with which the technique has found application, viz. X-ray fluorescence spectrometry (XFS), electron microbeam analysis (EMA), X-ray photoelectron spectrometry (XPS) and Auger electron spectrometry (AES). Emphasis is placed on the role assigned to AR/SR/XFS and AR/SR/EMA in certification of ion-implanted reference materials.Invited lecture at 15th Colloquium on Materials Analysis, Wien, May 27–29, 1991 相似文献
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A novel compound was designed and synthesized by connecting a dicyanobenzene acceptor and two 9,9-dimethyl-9,10-dihydroacridine donors to the 1,3,5-position of a phenyl ring by meta-position connection. This compound, which is a novel emitter for OLED devices, exhibits preferable heat stability. Moreover, the energy gap between its singlet and triplet states is as small as 0.04 eV, resulting in this molecule possesses thermally activated delayed fluorescence. Therefore, the corresponding device showed efficient electroluminescent performances. The maximum external quantum efficiency, maximum current efficiency, maximum power efficiency and maximum luminance were 16.5%, 40.8 cd A?1, 45.8 lm W?1 and 5120 cd m?2, respectively. In addition, the CIEx,y only changed from (0.22, 0.38) to (0.22, 0.39) over the entire operating voltage range, which confirms that the device possesses highly stable chromaticity with respect to the current density. Based on these experimental results, meta-connected type structures may provide a new approach for developing high-performance TADF emitters for OLED applications. 相似文献