Showing papers on "Photoemission spectroscopy published in 1997"
TL;DR: ZnS:Cu nanocrystals were synthesized in polymeric networks as discussed by the authors, and they were used to fabricate lightemitting diode (LED), as the emitting layer of LED, the blue light of electroluminescence was observed at room temperature, and its turn-on voltage was less than 4 V.
Abstract: ZnS:Cu nanocrystals were synthesized in polymeric networks. X-ray photoemission spectroscopy and atomic absorption data show that the Zn and Cu ion mass contents were about 8.2% and 0.12%, respectively. The particle size of ZnS:Cu nanocrystals was about 3.0 nm, measured by UV-vis spectrum. Due to the quantum size effects, the band gap energy of ZnS nanocrystals was about 4.2 eV. Compared with the photoluminescence of ZnS which peaks at 390 nm, the photoemission of ZnS:Cu/polymer thin films was peaking at 415 nm because of Cu acting as luminescent centers. The ZnS:Cu/polymer was also used to fabricate light-emitting diode (LED), as the emitting layer of LED, the blue light of electroluminescence was observed at room temperature, and its turn-on voltage was less than 4 V.
301 citations
TL;DR: In this paper, the electrical properties of model interfaces of organic electroluminescent (EL) devices and porphyrin/metal interfaces were investigated by UV photoemission spectroscopy (UPS).
Abstract: Electronic structures of model interfaces of organic electroluminescent (EL) devices and porphyrin/metal interfaces were investigated by UV photoemission spectroscopy (UPS). At all the measured interfaces, shift of the vacuum level was observed, showing the formation of an interfacial electric dipole layer. For Alq/sub 3/ (tris(8-hydroxyquinolino) aluminum), TPD (N,N'-diphenyl-N,N'-(3-methylphenyl)-1,1-biphenyl-4,4'-diamine), and DP-NTCI (N,N'-diphenyl-1,4,5,8-naphthyltetracarboxylimide)/metal interfaces, interfacial energy diagrams determined by UPS correspond well with the actually observed carrier-injecting character at the interfaces. For ZnTPP (15,10,15,20-zinc-tetraphenylporphyrin), H/sub 2/TPP (5,10,15,20-tetraphenylporphyrin), and H/sub 2/T(4-Py)P (5,10,15,20-tetra(4-pyridyl) porphyrin)/metal interfaces, the shifts of the vacuum level as well as the energies of the levels in porphyrins could be expressed as a linear function of work function of the metal substrate. The slope of the linear function depended on the compound. These findings are in contrast to the traditional assumption of common vacuum level at the interfaces, For ZnTPP/metal interfaces, sample exposure to oxygen induced energy level shift in close relation with the change of the substrate work function at oxygen exposure. The present results have clearly demonstrated that direct observation of the interfacial electronic structure by microscopic method such as UPS is necessary for understanding the organic electronic devices such as EL devices and organic solar cells.
206 citations
TL;DR: In this article, femtosecond photoelectron spectroscopy was used to follow the dynamics of the I2−(Ar)6 and I2 − (Ar)20 clusters subsequent to photodissociation of the chromophore.
Abstract: Anion femtosecond photoelectron spectroscopy was used to follow the dynamics of the I2−(Ar)6 and I2−(Ar)20 clusters subsequent to photodissociation of the I2− chromophore. The experiments showed that photodissociation of the I2− moiety in I2−(Ar)6 is complete by approximately 200 femtoseconds, just as in bare I2−, but also that attractive interactions between the departing anion fragment and the solvent atoms persisted for 1200 femtoseconds. Photodissociation of I2−(Ar)20 results in caging of the I2− followed by recombination and vibrational relaxation on the excited A2Πg,3/2 and the groundX2Σu+states; these processes are complete in 35 and 200 picoseconds, respectively.
132 citations
TL;DR: In this article, a qualitative agreement with the theory was obtained by calculating the e-e scattering times from the band structure of Cu, but the magnitude of the calculated lifetimes, assuming Thomas-Fermi screening length, is still about six times smaller than the measured.
Abstract: Lifetimes of hot electrons in the 1.3--3.2-eV energy range at low index surfaces of Cu((100),(110),(111)) are measured by two-photon time-resolved photoemission spectroscopy with 10 fs resolution. Energy dependence of the lifetimes deviates from the (E-${\mathrm{E}}_{\mathrm{F}}$${)}^{\mathrm{\ensuremath{-}}2}$ functional form predicted by the standard Fermi-liquid theory for free-electron metals, but a qualitative agreement with the theory is obtained by calculating the e-e scattering times from the band structure of Cu. However, the magnitude of the calculated lifetimes, assuming Thomas-Fermi screening length, is still about six times smaller than the measured. The failure of the free-electron model in predicting the energy dependence and magnitude of the scattering times is attributed in part to d-band electrons, which have a maximum density at -2 eV and can participate both in scattering and screening of hot electrons. The measured lifetimes also show a modest dependence on the crystal face, which is not reproduced by the band-structure calculations. The origins of this anisotropy may include coherence effects in the excitation, anisotropies in the e-e scattering cross sections, a contribution from e-p scattering to the hot-electron decay, or differences in surface electronic structure.
126 citations
TL;DR: In this paper, the authors investigated the resonance lifetime and energy of an excited Cs state on Cu(111) in the low-coverage case and found a pronounced lifetime increase of up to 11.3 fs on a copper surface covered with cesium.
Abstract: Using time-resolved two-photon photoemission spectroscopy, we investigated the resonance lifetime and energy of an excited Cs state on Cu(111) in the low-coverage case. We found a pronounced lifetime increase of up to 11\ifmmode\pm\else\textpm\fi{}3 fs on a copper surface covered with cesium as compared to a clean copper surface in the energy range of an excited electronic Cs state in the spectrum. This result is in agreement with recent theoretical predictions of hybridization among excited atomic levels of alkali atoms near metal surfaces.
112 citations
TL;DR: In this article, the photoelectron spectrum of the negative ion of 1,3-benzoquinodimethane (m-xylylene) is reported, and the active modes are assigned to R-carbon bending, ring deformation, and methylene bending, respectively.
Abstract: The 351-nm photoelectron spectrum of the negative ion of 1,3-benzoquinodimethane (m-xylylene) is reported. Features are observed in the photoelectron spectrum corresponding to formation of the 3 B2, 1 A1, and 1 B2 states of m-xylylene. The electron affinity of the triplet ground state is found to be 0.919 ( 0.008 eV, and vibrational frequencies of 290, 540, and 1500 cm -1 are obtained. The active modes are assigned to R-carbon bending, ring deformation, and methylene bending, respectively. The 1 A1 state is found to lie 9.6 ( 0.2 kcal/mol higher in energy than the ground state, in good agreement with theoretical predictions. Vibrational frequencies of 265, 1000, and 1265 cm-1 are found for this state. The 1B2 is estimated to be <21.5 kcal/mol higher in energy than the ground state. Density functional calculations have been carried out on the negative ion, indicating that the 2 B1 ion is a minimum on the potential energy surface, lying 2.9 kcal/mol lower in energy than the 2 A2 ion, which is a transition state.
107 citations
15 Nov 1997
TL;DR: In this paper, the photoelectron spectrum of the chlorobenzene molecule has been studied using both monochromated synchrotron radiation with photon energies between 15 and 120 eV and HeI radiation at 21.22 eV.
Abstract: The photoelectron spectrum of the chlorobenzene molecule has been studied using both monochromated synchrotron radiation with photon energies between 15 and 120 eV and HeI radiation at 21.22 eV. Photoelectron angular distributions and branching ratios have been determined over the entire energy range studied. Theoretical investigations have been performed using ab initio SCF and many-body Green’s function methods to evaluate wave functions, binding energies and relative intensities. The ADC(3) calculations of binding energies and pole strengths were particularly important for the interpretation of the inner valence spectrum where electron correlation effects are found to be important. The main part of the photoelectron spectrum is similar to that of benzene but some of the bands are characteristic of the chlorine atom. The Cooper minimum of the Cl 3p orbital is clearly reflected in some of the bands and is used to assess the mixing between ring orbitals and chlorine atomic orbitals. The HeI-excited spectra show extensive vibrational structure in the X 2 B 1 , A 2 A 2 , B 2 B 2 , C 2 B 1 and K 2 A 1 photoelectron bands. The vibrational structure is analysed in detail and compared to results obtained from multiphoton ionisation photoelectron spectroscopy.
89 citations
88 citations
TL;DR: In this article, the HCOOH saturation coverages were 0.58 ML, 0.77 ML and 0.92 ML (1 ML ≈ 5.2 × 1014 cm−2) for nearly defect-free surfaces, for electron-beam exposed surfaces, and for Ar+ ion bombarded surfaces, respectively.
88 citations
83 citations
TL;DR: In this paper, it was shown that the surface state acts as a surface conduction band and the electron mobility in this band is estimated to be on the order of 10 cm{}^{2}$/V s.
Abstract: Photoemission spectroscopy has shown that each Ag atom in its two-dimensional adatom gas (2DAG) phase deposited on the Si(111)-$\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$-Ag surface at room temperature donates one electron into an antibonding surface-state band of this substrate, resulting in a steep increase in electrical conductance through the band. The surface space-charge layer makes no contribution to the conductance increase by the 2DAG adsorption, estimated from the band-bending measurements. When the 2DAG nucleates into three-dimensional Ag microcrystals by further deposition beyond a critical supersaturation coverage, the carrier-doping effect vanishes, returning to a lower conductance. These results reveal that the surface state acts as a surface conduction band. The electron mobility in this band is estimated to be on the order of 10 cm${}^{2}$/V s.
TL;DR: In this article, the authors measured the energy level alignment at various organic compound/metal interfaces by UV photo-emission spectroscopy (UPS) and showed that a shift of the vacuum level at the interface was observed, showing the formation of an interfacial electric dipole layer.
TL;DR: In this paper, a comparison of the La 3d core level spectrum with those of various La trihalides showed that the La is trivalent, with the sC82d 32 providing an environment slightly less electronegative than that in LaBr 3.
Abstract: 82 in agreement with the observation of a signal in electron spin resonance experiments [4 ‐ 6]. This view is also consistent with theoretical predictions [9] and with the analysis of the electron density distribution of a Y@C82 microcrystal as measured by x-ray diffraction [10]. Very few direct studies of the valency of the various endohedral metal ions have been reported. Xray photoemission spectroscopy (XPS) has been shown to be a suitable probe of the valency of the La in La@C82 [5,11]. In this case, the comparison of the La 3d core level spectrum with those of various La trihalides showed that the La is trivalent, with the sC82d 32 providing an environment slightly less electronegative than that in LaBr 3 [11]. In the case of the lanthanide monometallofullerene Tm@C82, a series of physical and chemical studies in solution of the three different isomers has been found to be consistent with a Tm 21 @C 22
TL;DR: In this paper, a detailed photon energy-dependent and angle-dependent SRXPS study was performed in the 120 ÷ 175 eV photon energy range and the compatibility of the experimental findings with models of the current literature was examined.
Abstract: Synchrotron radiation X-ray photoemission spectroscopy (SRXPS), used with an optimized surface and interface sensitivity, is a unique tool to determine the chemical composition and spatial extension of the suboxide layer present at the Si/SiO2 interface. The bonding at ‘thermal interfaces’ appear to be essentially dependent on the Si crystal orientation. For Si(001)/SiO2 a detailed photon energy-dependent and angle-dependent. SRXPS study (in the 120 ÷ 175 eV photon energy range) has been performed. Previous results on higher-oxidation states cross-section resonances around hv = 130 eV are re-examined. The various oxide states do not present photoelectron diffraction peaks, when polar scans are performed in the (110) azimuthal plane. On the other hand, there is evidence that substrate silicon atoms close to the interface retain orientational order. Limits in the vertical distribution of the suboxides are given. The compatibility of our experimental findings with models of the current literature — in particular the so-called ‘dimerized interface’ model — is examined.
TL;DR: In this article, the carbonization process of a single domain 2-times-1-reconstructed Si(001) vicinal surface (5{degree} off axis from [001] in the [{bar 1}10] direction) in acetylene has been studied by combining in situ surface science techniques (x-ray photoemission spectroscopy, xray photoelectron diffraction, reflection-electron energy loss spectrography, low-energy electron diffraction) and ex situ analytical techniques ({sup 12}C and {sup 2}H d
Abstract: The carbonization process of a single domain 2{times}1-reconstructed Si(001) vicinal surface (5{degree} off axis from [001] in the [{bar 1}10] direction) in acetylene has been studied by combining in situ surface science techniques (x-ray photoemission spectroscopy, x-ray photoelectron diffraction, reflection-electron energy loss spectroscopy, low-energy electron diffraction) and ex situ analytical techniques ({sup 12}C and {sup 2}H dosing by nuclear reaction analysis, scanning electron microscopy, and reflection high-energy electron diffraction). It is found that at a growth temperature of about 820{degree}C a variety of growth mechanisms can be observed, particularly during the first step of carbonization. An analysis of C1s and Si2p core-level shifts and of the respective intensities of them, combined with the examination of photoelectron diffraction curves, gives evidence for a penetration of C atoms into the silicon substrate, to form a nonstoichiometric compound. Contemporaneously 3C-SiC nuclei form, aligned with respect to the substrate. Then a quasicontinuous 3C-SiC film grows heteroepitaxially (cube on cube unstrained growth) on the substrate up to a thickness of {approximately}40{Angstrom}. C1s and Si2p photoelectron diffraction patterns, compared with calculated ones, show that the single domain initial surface does not necessarily force a preferential alignment of one of the two inequivalent SiC{l_brace}110{r_brace} planes with respectmore » to the (110) Si plane. Consequently, such vicinal Si(001) surfaces are not necessarily templates for the growth of crystalline films free of antiphase boundary domains. Finally, we have observed that an imperfect coalescence of 3C-SiC nuclei leaves easy paths for Si out migration from the substrate and SiC polycrystalline growth, even at a temperature as low as 820{degree}C. The current models of Si(001) carbonization are examined and compared to our experimental findings. (Abstract Truncated)« less
TL;DR: In this article, the electronic structure of the heterofullerene (C59N)2 using electron energy-loss spectroscopy in transmission, photo-emission, and density functional theory calculations was studied.
Abstract: We present the first studies of the electronic structure of the heterofullerene (C59N)2 using electron energy-loss spectroscopy in transmission, photoemission spectroscopy, and density functional theory calculations. Both the C 1s excitation spectra and valence band photoemission show negligible occupation of the C-derived lowest unoccupied electronic states and indicate localization of the excess electrons at the N atoms. The experimental results, together with the detailed analysis of our theoretical data, provide compelling evidence for the chemical picture of a triply coordinated N atom with a lone pair in each heterofullerene unit, and confirm the theoretically predicted “6,6 closed” structure for the dimer.
TL;DR: In this article, the influence of n-type doping CdO with In or Y has been investigated by high-resolution ultraviolet and x-ray photoemission spectroscopy.
Abstract: The influence of n-type doping CdO with In or Y has been investigated by high-resolution ultraviolet and x-ray photoemission spectroscopy. It is found that core levels and valence band features suffer a shift to high binding energy due to doping. However this shift is less than the change in the width of the occupied conduction band. This provides a direct measurement of band gap shrinkage as a result of doping in an oxide semiconductor.
TL;DR: In this article, the dynamics of excited electrons in insulator quantum well states on a metal substrate were determined by femtosecond two-photon photoemission for the first time.
Abstract: The dynamics of excited electrons in insulator quantum well states on a metal substrate were determined by femtosecond two-photon photoemission for the first time. Lifetimes are reported for the first three excited states for 1{endash}6 atomic layers of Xe on Ag(111). As the image states evolve into quantum well states with increasing coverage, the lifetimes undergo an oscillation as the layer boundary crosses each node of the wave function. The lifetime data are modeled by extending the two-band nearly free-electron approximation to account for the presence of a dielectric layer. The lifetimes are shown to depend on the spatial distribution of the interfacial electron. {copyright} {ital 1997} {ital The American Physical Society}
TL;DR: In this paper, the electronic properties of the SiC SiO 2 interface were studied for a series of SiC polytypes using various electrical methods and internal photo-emission spectroscopy.
TL;DR: The vibrational fine structure on the O $1s$ line is completely dominated by the antisymmetric stretching mode with a frequency of 307 $(\ifmmode\pm\else\textpm\fi{}3)\mathrm{meV}$ as discussed by the authors.
Abstract: The C and O $1s$ photoelectron lines of the C${\mathrm{O}}_{2}$ molecule in the gas phase have been measured with vibrational resolution in the threshold region. The vibrational fine structure on the O $1s$ line is completely dominated by the antisymmetric stretching mode with a frequency of 307 $(\ifmmode\pm\else\textpm\fi{}3)\mathrm{meV}$. This mode can be excited only via vibronic coupling, as predicted by Domcke and Cederbaum [Chem. Phys. 25, 189 (1977)], and provides a mechanism for dynamic core-hole localization. Relaxation effects are found to affect strongly the vibrational intensity distribution of the photoelectron line.
TL;DR: In this paper, the mass spectral and photoelectron spectroscopic results of the (HF)2− anion were analyzed experimentally for the first time, confirming the 20 year old prediction of Jordan and Wendoloski.
Abstract: We present the mass spectral and photoelectron spectroscopic results of our study of (HF)2−. Our main findings are as follows. The (HF)2− anion was observed experimentally for the first time, confirming the 20 year old prediction of Jordan and Wendoloski. The photoelectron spectrum of (HF)2− exhibits a distinctive spectral signature, which we have come to recognize as being characteristic of dipole bound anions. The vertical detachment energy (VDE) of (HF)2− has been determined to be 63±3 meV, and the adiabatic electron affinity (EAa) of (HF)2 was judged to be close to this value as well. Relatively weak spectral features, characteristic of intramolecular vibrations in the final (neutral dimer) state, were also observed. We have interpreted these results in terms of slight distortions of the dimer anion’s geometric structure which lead to an enhanced dipole moment. This interpretation is supported to a considerable extent by theoretical calculations reported in the companion paper by Gutowski and Skurski.
TL;DR: In this article, the first rotationally resolved photoelectron spectra for a tetrahedral molecule were obtained and the analysis of the rotational structure was accompanied by a description of the observed symmetry selection rules and propensity rules for core rotational angular momentum changes that characterize the photoionization process.
Abstract: High-resolution zero-kinetic-energy photoelectron spectroscopy has been used to record the transition between the lowest bound state (3s 2A1) of the perdeuterated ammonium radical (ND4) and the X 1A1 ground vibronic state of the perdeuterated ammonium ion (ND4+). The spectra obtained are the first rotationally resolved photoelectron spectra ever measured for a tetrahedral molecule. The analysis of the rotational structure is accompanied by a description of the observed symmetry selection rules and propensity rules for core rotational angular momentum changes that characterize the photoionization process. Rotational constants (B0=2.8560±0.0037 cm−1 and B0+=2.9855±0.0037 cm−1) and centrifugal distortion constants (D0=(4.78±1.4)×10−5 cm−1 and D0+=(4.77±1.5)×10−5 cm−1) have been determined for the 3s 2A1 state of ND4 and the X 1A1 state of ND4+, respectively. The ionic rotational constant is in good agreement with the value B0+=2.9787±0.0029 cm−1 determined indirectly by Crofton and Oka (J. Chem. Phys. 86, ...
TL;DR: The 351 nm photoelectron spectrum of BO- is reported in this article, and the electron affinity of BO is determined to be 2.508 ± 0.008 eV. The results from multiconfigurational SCF, G2 and complete basis set calculations are in good agreement with experiment.
Abstract: The 351 nm photoelectron spectrum of BO- is reported. Detachment to form 2∑+ BO is observed, and the electron affinity of BO is determined to be 2.508 ± 0.008 eV. From the photoelectron spectra, vibrational frequencies of 1875 ± 30 cm-1 and 1665 ± 30 cm-1 are obtained for X BO and BO-, respectively, and the bond length in BO- is found to be 1.236 ± 0.010 A. The measured EA is used to derive a bond energy in BO- of 9.39 eV. High-level molecular orbital calculations of the electron affinity are reported. The results from multiconfigurational SCF, G2, and complete basis set calculations are in good agreement with experiment.
TL;DR: In this article, a study employing picosecond and subpicosecond excitation in a mass and photoelectron spectrometer was reported for the 7-azaindole (7-AI) dimers, reactive and unreactive.
02 Dec 1997-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, Hricovini et al. studied the reactivity of the Si (1 1 1) surface in the presence of Cl 2, Br 2, and 1-alkenes with photo-emission spectroscopy.
Abstract: The HSi (1 1 1) surface has been well characterized [Hricovini et al., Phys. Rev. Lett. 70 (1993) 1992], so the reactivity of this surface was studied. HSi (1 1 1) surfaces exposed to Cl 2 , Br 2 , and 1-alkenes were studied with photoemission spectroscopy. These particular compounds were chosen because of their importance in semiconductor processing and surface functionalization. The observation of the growth of a Si 2p component at high binding energy, characteristic of halogen reactivity, confirmed that bromine and chlorine gases both reacted with the HSi (1 1 1) surface. Reactions with 1-alkenes were confirmed by measuring both the Si 2p and the C 1s core level spectra. The C 2s-based molecular orbitals in the valence band revealed the identity of the alkyl monolayer on the Si (1 1 1) surface. Therefore, we found that the HSi (1 1 1) surface, under certain conditions, was reactive.
TL;DR: In this article, the energy dependence of photoexcited electrons in copper was measured using femtosecond time-resolved photoemission spectroscopy to within 0.3 eV above the Fermi level.
Abstract: The energy dependence of the relaxation of photoexcited electrons in copper was measured using femtosecond time-resolved photoemission spectroscopy to within 0.3 eV above the Fermi level. By performing lifetime measurements under different surface conditions, several surface dynamical processes were investigated. In particular, an anomalous long lifetime feature, which cannot be explained with Fermi-liquid theory, was observed in the lifetime-energy curve. This feature was found originating from the photoexcitation of the strongly localized Cu $3d$ electrons.
TL;DR: In this article, the adsorption of S2 on ZnO and Cu/ZnO has been investigated using synchrotron-based high-resolution photoemission spectroscopy.
Abstract: The adsorption of S2 on ZnO and Cu/ZnO has been investigated using synchrotron-based high-resolution photoemission spectroscopy. On dosing a clean ZnO surface with S2 at 300 K, the molecule dissociates. The S is associated first with Zn and at medium coverages with Zn−O sites. When the sulfur coverage is increased to θS = 0.5 ML, evidence is found for sulfur bound purely to the O sites of ZnO. The sulfur species associated with O and the Zn−O sites are unstable at temperatures above 500 K. Possible reaction pathways for the dissociation of S2 on ZnO(0001)−Zn and Zn(1010) surfaces were studied using ab initio SCF calculations. At low sulfur coverages, an adsorption complex in which S2 is bridge bonded to two adjacent Zn atoms (Zn−S−S−Zn) is probably the precursor state for the dissociation for the molecule. It is possible to get much higher coverages of sulfur on ZnO (0.7 ML) than on Al2O3 (0.1 ML) at similar S2 exposures. This, in conjunction with results previously reported for H2S adsorption on Cr2O3 a...
TL;DR: In this paper, the valence band discontinuity of the n-type cubic GaN/GaAs heterojunction is measured by means of angle-resolved photoemission spectroscopy using synchrotron radiation.
Abstract: The valence band discontinuity of the n-type cubic GaN/GaAs heterojunction is measured by means of angle-resolved photoemission spectroscopy using synchrotron radiation. High quality cubic GaN films are grown on GaAs(100) substrates by nitrogen plasma-assisted molecular beam epitaxy, and the valence band discontinuity is determined by a combination of core and valence level spectra. A value of ΔEV=(1.84±0.1) eV across the GaN/GaAs heterojunction is obtained, which means that the discontinuity in the conduction bands at this interface is very small, such that a vertical contact scheme may be realized for GaN/GaAs heterojunctions.
TL;DR: In this paper, the hydroxylation of a-Al2O3(000l) and MgO surfaces is studied in ultra-high vacuum by high-resolution electron energy loss spectroscopy (adsorbate and phonon losses being distinguished via resonance scattering) and X-ray photoemission Spectroscopy.
Abstract: The hydroxylation of a-Al2O3(000l) and MgO surfaces is studied in ultra-high vacuum by high-resolution electron energy loss spectroscopy (adsorbate and phonon losses being distinguished via resonance scattering) and X-ray photoemission spectroscopy. Hydroxyl groups which arise from the dissociative adsorption of H2O on a-Al2O3(0001) surfaces and low-coordinated MgO surface sites are characterized by chemical shifts and stretching frequencies.
TL;DR: In this article, angle-resolved ultraviolet photoelectron spectroscopy on ultrathin films of bis(1,2,5-thiadiazolo)-p-quinobis (1,3-dithiole) (BTQBT) deposited on a MoS2 surface with synchrotron radiation was described.
Abstract: In this paper we report on the angle-resolved ultraviolet photoelectron spectroscopy on ultrathin films of bis(1,2,5-thiadiazolo)-p-quinobis (1,3-dithiole) (BTQBT) deposited on a MoS2 surface with synchrotron radiation, and describe the quantitative analysis of the angular distribution of photoelectron from the highest occupied state. The observed angular distributions were better explained by those calculated with the single-scattering approximation combined with molecular orbital calculation considering intramolecularly scattered waves than the previously used independent-atomic-center approximation combined with molecular orbital calculation. Further, the low-energy-electron diffraction measurements were performed on the film. From the low-energy-electron diffraction, the two-dimensional lattice of the ultrathin films on the MoS2 was found to be MoS2(0001)−(13×13, R=±13.9°)-BTQBT, and from the analysis of the photoelectron angular distributions, it was found that at the lattice points the molecules lie flat with azimuthal orientations of 19° and 47° with respect to each surface crystal axis of MoS2. On the basis of these results, the full structure of the thin film, the two-dimensional lattice, and full molecular orientations at the lattice points, is proposed.