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Abstract: We studied adsorption of pyridine on Si(100) at room temperature using high resolution photoemission spectroscopy (PES) and near edge X-ray adsorption fine structure (NEXAFS) in the partial electron yield (PEY) mode. The Si 2p, C 1s, N 1s spectra of pyridine on Si(100) showed that pyridine is chemisorbed on Si(100)-2×1 through the formation of the tetra-σ-bonded structure with the N atom and three C atoms. NEXAFS was conducted to characterize the adsorption geometry of pyridine on Si(100). The π* orbital of Cowed a good angle dependence in C K-edge NEXAFS spectra, and we were able to estimate the adsorption angle between chemisorbed pyridine of Cd the Si(100) surface using an analytical solution of NEXAFS intensity. We find the coexistence of two different tight bridges with the adsorption angles 42±2° and 45±2° with almost equal abundance. [Copyright &y& Elsevier]

Abstract: We have investigated adsorption of furan on Si(100) at room temperature using high resolution photoemission spectroscopy (PES) and near edge X-ray absorption fine structure (NEXAFS) in the partial electron yield (PEY) mode. The Si 2p, C 1s, O 1s spectra of furan on Si(100) show that furan is chemisorbed on Si(100)-2×1 through [4+2] cycloaddition. NEXAFS has been conducted to characterize the adsorption geometry of furan on Si(100). Since the π∗ orbital of Cowed a good angle dependence in carbon K-edge NEXAFS spectra, the angle 28±2° determined from NEXAFS spectra appears to deviate from a theoretical value of 19° for the [4+2] cycloaddition by 9°, mostly due to the intrinsic defects on the Si(100)-2×1 substrate surface. [Copyright &y& Elsevier]

Abstract: Pentacene films on Si(100)-(2×1) surface at 300K were investigated using near edge X-ray absorption fine structure (NEXAFS) at the carbon K-edge. NEXAFS spectra show that pentacene molecules are chemisorbed on the Si(100)-(2×1) surface for monolayer with flat-laying and predominantly physisorbed on the Si(100)-(2×1) surface for multilayer films with an upright molecular orientation. Absorption angle of pentacene molecules were measured through π∗ transition. The angles between the double bond and the silicon surface were 35–55°, 65° and 76° at monolayer, 24 and 48nm pentacene deposited on the Si(100) surface, respectively. We observed that the intermediate flat-laying phase is favored for monolayer coverage, while the films of molecules standing perpendicular to the Si(100) surface are favored for multilayer coverage. [Copyright &y& Elsevier]

• Investigate chemical/physical properties of a hetero-small molecule DNTT/PTCDI-C13. • Report an edge-on molecular packing of a hetero-small molecule DNTT/PTCDI-C13. • Charge transport characteristics of ambipolar and anti-ambipolar heterostructure devices. • Demonstrate CMOS-like and ternary circuits using a hetero-small molecule DNTT/PTCDI-C13. Heterostructure electronic devices potentially provide opportunities for novel transistor operations, including ambipolar and anti-ambipolar switching characteristics. However, there are still no previous studies investigating the physical, chemical, and morphological properties of small-molecule semiconductor films deposited as heterojunctions. Here, we systemically investigate chemical and morphological structure in a heterostructure of small-molecule organic semiconductors using X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption of fine structure (NEXAFS), and ultraviolet photoelectron spectroscopy (UPS). The analysis reveals that dinaphtho[2,3- b :2′,3′- f ]thieno[3,2- b ]thiophene (DNTT) and N,N ′-ditridecylperylenediimide (PTCDI-C13) maintain their chemical compositions, energy structure, and edge-on molecular orientations (tilt angle = 66°). Furthermore, ambipolar and anti-ambipolar transistors are demonstrated using the edge-on DNTT/PTCDI-C13 heterostructure. These transistors enable CMOS-like inverter and ternary inverter operations as respective example applications of ambipolar and anti-ambipolar transistors. [ABSTRACT FROM AUTHOR]

A new anthracene derivative of 9,10-bis(2,5-dimethyl-4-(naphthalen-2-yl)phenyl)-2,3-diphenylanthracene (BDNPA) was designed and synthesized as a non-doped blue emitter in organic light emitting diodes (OLEDs). BDNPA has highly rigid structure and thermal stability with decomposition temperature (corresponding to 5% weight loss) of 490 °C, because p -naphthyl xylene groups in 9,10-positions were highly twisted to anthracene core due to steric hindrance of xylene groups, and because the 2,3-diphenyl groups were also twisted about 45–49° to anthracene. OLEDs with BDNPA non-doped emitter showed high efficiency of 5.21 cd/A due to the carrier mobility with well-aligned π -stacking structure toward out-of-plane by the face-on orientation by grazing incidence X-ray diffraction. [ABSTRACT FROM AUTHOR]