We investigate the adsorption of organic molecular semiconductor perylene on (7 × 7) reconstructed Si(111) surface by ultraviolet photoemission spectroscopy. It is observed that seven features that derive from the organic material are located at 0.71, 2.24, 4.0, 5.9, 7.46, 8.65 and 9.95 eV in binding energy. The theoretical calculation results reveal the most stable adsorption geometry of organic molecule perylene on Si(111) (7 × 7) substrates is at the beginning of deposition .

Self-assembled strategy has been proven to be a promising vista in constructing organized low-dimensional nanostructures with molecular precision and versatile functionalities on solid surfaces. Herein, we investigate by a combination of scanning tunneling microscopy (STM) and dispersion-corrected density functional theory (DFT), the adsorption of tetracene molecules on the silver substrate and the mechanism mediating the self-assembly on Ag(110). As expected, ordered domain is formed on Ag(110) after adsorption with adjacent molecules being imaged with alternating bright or dim pattern regularly. While such behavior has been assigned previously to the difference of molecular adsorption height, herein, it is possible to investigate essentially the mechanism leading to the periodic alternation of brightness and dimness for tetracene adsorbed on Ag(110) thanks to the consideration of Van der Waals (vdW) dispersion force. It is demonstrated that the adsorption height in fact is same for both bright and dim molecules, while the adsorption site and the corresponding interfacial charge transfer play an important role in the formation of such pattern. Our report reveals that vdW dispersion interaction is crucial to appropriately describe the adsorption of tetracene on the silver substrate, and the formation of delicate molecular architectures on metal surfaces might also offers a promising approach towards molecular electronics.

Iron phthalocyanine molecule (FePc) thin films were deposited on Cu(100) and Si(100) substrates in sequential steps and the interface was characterized by means of scanning tunneling microscope, X-ray photoemission spectroscopy, and its sister technique ultra violet photoemission spectroscopy. At room temperature disordered structures are observed. However at elevated temperature approximate to 480 degrees C, a long range ordered pattern is noticed indicating the increase of diffusion of adsorbed molecules on the substrate surface. All the photoemission spectra exhibited a clear change and shift in the adsorbed peaks. The change in binding energy of C 1 s core level as revealed by X-ray photoemission spectroscopy is V-b = 0:18 eV. Our calculated work function of the clean Si (100) surface is 4.09 eV. The hole and electron injection barriers are estimated as 1.22 eV and -1.38 eV, respectively. Based on the measured quantities, the interface dipole potential is found to be -0.04 eV. A minute charge transferred from each adsorbed molecule to the substrate is estimated as ca: 8.565 x 10(-22) C. Besides, our computational density functional theory findings revealed a strong adsorbate-substrate interaction.

Investigations on the bottom-up fabrication of graphene with 1,3,5-triphenylbenzene as precursor on Ru(0 0 0 1) was carried out using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. Upon annealing 1,3,5-triphenylbenzene overlayer on Ru(0 0 01) at 550 degrees C, the precursors dehydrogenated and coalesced into graphitized flakes, and subsequent annealing up to 600 degrees C results in complete graphene conversion. The migration behavior and close-packing morphology of precursors were captured during STM measurements, and DFT calculations indicated that the inter-molecular interaction is responsible for the accumulation and close-packing of the precursors. The noticeable increment in the dehydrogenation barrier from 1.27 eV for monomer adsorption to 1.62 eV for dimer adsorption is well consistent with the observed drastic reduction of the graphitization temperature at lower precursor coverage, suggesting the crucial influence of inter-molecular vdW interaction on the dehydrogenation process. (C) 2016 Elsevier B.V. All rights reserved.

Investigations on the bottom-up fabrication of graphene nanostructures with 10, 10'-dibromo-9, 9'-bianthryl (DBBA) as a precursor on Ru(1010) were carried out using scanning tunnelling microscopy (STM) and density functional theory (DFT) calculations. Upon annealing the sample at submonolayer DBBA coverage, N = 7 graphene nanoribbons (GNRs) aligned along the [1210] direction form. Higher DBBA coverage and higher annealing temperature lead to the merging of GNRs into ribbon-like graphene nanoflakes with multiple orientations. These nanoflakes show different Moiré patterns, and their structures were determined by DFT simulations. The results showed that GNRs possess growth preference on the Ru(1010) substrate with a rectangular unit cell, and GNRs with armchair and zigzag boundaries are obtainable. Further DFT calculations suggest that the interaction between graphene and the substrate controls the orientations of the graphene overlayer and the growth of graphene on Ru(1010).

The electronic property of CoPc/Au(111) interface was investigated by angle-resolved ultra-violet photoelectron spectroscopy (ARUPS). Combining the ARUPS data with density functional theory (DFT) simulation, the correspondences between the emission peaks and the molecular levels were established. The interfacial charge transfer and the variation of the spin polarization of the adsorbed CoPc and the underneath gold atom indicated a strong interaction between the adsorbate and the substrate. Several conductance resonance peaks at specific molecular energy levels for CoPc molecule, and an adsorbate–substrate interaction brought modification to the quantum conductance spectrum for CoPc/Au(111) system were found by the first principle transport calculations.

Combining the scanning tunneling microscopy (STM) and density functional theory (DFT), the adsorption properties of cobalt phthalocyanine (CoPc) on monolayer graphene/Ru(0 0 0 1) [MG/Ru(0 0 0 1)] have been investigated. At monolayer coverage, CoPc forms an ordered Kagome lattice, and a slight deformation for one lobe of CoPc and charge transfer from CoPc to Ru(0 0 0 1) substrate take place. The existence of the defect (vacancy) in graphene on Ru(0 0 0 1) increases the coupling between the Ru substrate and the epitaxial graphene. Such an increase of the coupling brings about an overall CoPc molecular energy level shift toward the low binding energy, which subsequently results in a central topographical contrast between the CoPc molecules on the intact and defective MG/Ru(0 0 0 1). (C) 2014 Elsevier B.V. All rights reserved.

The formation of the Mn/PbTe (111) interface is investigated by photoemission spectrum. The core level behavior of Mn 2p is consistent with Mn substitutional adsorption during the initial Mn deposition, forming a (√3 × √3)R30°-Pb0.67Mn0.33Te phase of the second layer. Further deposition of Mn can cause metallic Mn islands to cover the substitutional substrate. Ultraviolet photoemission measurements show that the Fermi level is shifted into the conduction band, indicating Ohmic contact formation at the Mn/PbTe (111) interface. The valence band maximum associated with the Pb0.67Mn0.33Te layer is located at 1.27 eV below the Fermi level, and a schematic electronic structure of the Mn/PbTe (111) interface is given. The work function of the substituted substrate with Pb-covered Mn islands is determined to be 4.16 eV, in comparison with 4.35 eV for the Pb-covered substituted substrate and 3.95 eV for the pristine PbTe (111) surface.

Thin and thick films of iron phthalocyanine (FePc) molecules are deposited on a Ag (110) surface. The nature of the FePc growth and the interaction with the substrate have been studied by X-ray photoelectron spectroscopy (XPS). All of the core level spectra exhibit rigid shifts towards lower binding energies following the deposition of the organic films, each by a different magnitude. A greater change and a larger shift in the Fe2p level as compared to C1s core level reveals that the adsorbate interacts with the substrate mainly via the Fe atom, located at the center of the molecule. An increase/decrease in the intensity of C1s/Ag3d level is found to be exponentially linked to the overlayer molecular coverage. Finally, the so-called growth/decay curve indicates that FePc thin films initially develop following the FM growth mode and then transform to SK mode, resulting in 3D island aggregation.

The process of templating a manganese nanocluster with the 12 × 12 moiré and other two slightly distorted graphene/Ru(0001) moirés was investigated by scanning tunneling microscopy (STM). At the initial stage of nucleation, different adsorption modes for Mn monomer, dimer and trimer guided by various moiré periodicities were observed. Upon Mn coverage increasing, STM measurements revealed that Mn clusters exhibit a detectable preference for adsorption sites on all the three different moirés. The most favorable adsorption sites for Mn clusters are the fcc regions, where ordering of Mn clusters was observable, and the lateral size of the clusters are tunable with coverage. A density functional theory calculation also showed that magnetism appears with a magnetic moment of 3.79μ(B) for Mn monomer on MLG/Ru(0001).

We prepare a well-defined C84 monolayer on the surface of Ag（111） and study the geometric structure by scanning tunneling microscopy（STM）. The C84 molecules form a nearly close-packed incommensurate R30 lattice. The lattice is long-distance ordered with numerous local disorders. The monolayer exhibits complex bright/dim contrast; the largest height difference between the molecules can be greater than 0.4 nm. Annealing the monolayer at 380 C can desorb part of the molecules, but more than sixty percent molecules stay on the Ag（111） surface even after the sample has been annealed at 650 C. Our analyses reveal that the 7-atom pits form beneath many molecules. Some other molecules sit at the 1-atom pits. Ag adatoms（those removed substrate atoms, accompanying the pit formation） play a very important role in this system. The adatoms can either stabilize or destabilize the monolayer, depending on the distribution manner of the adatoms at the interface. The distribution manner is determined by the co-play of the following factors: the dimension of the interstitial regions of the C84 overlayer, the number of the adatoms, and the long-distance migration of part adatoms.

The transition behavior of FePc on Ag(110) has been investigated by room temperature scanning tunneling microscopy (STM) and density functional theory (DFT) simulation. After FePc molecules deposited on Ag(110) surface, two adsorption structures were observed. The pathway between these different configurations was investigated by DFT simulation. The transition of electronic structures of FePc/Ag(110) interface and change in work function during the transformation were investigated by the calculated density of states (DOS) together with the application of induced density of interface states (IDIS).

A study of the electronic and structural properties of iron phthalocyanine (FePc) molecules adsorbed on coinage metal surfaces Cu (100) and Cu (110) has been conducted by means of density functional theory calculations. The strength of the molecule-substrate interactions is interpreted in terms of the lateral adsorption geometry and the site specific electronic structure of the molecule. In the case of FePc on a (100)-oriented copper surface, the benzopyrrole leg is found to be oriented at an angle of 9 degrees or 3 degrees from the [01-1] substrate direction. Further, an upward bend in the molecular plane ranging from 7 degrees to 10 degrees is also observed; giving an almost buckled shape to the molecule. However, in the case of FePc on Cu (110), neither a bend nor a sizable rotation is observed. From the knowledge of the principle structural and electronic properties, it is concluded that FePc-Cu (100) interaction is relatively stronger than FePc-Cu (110) interaction, which is further evidenced by the charge transfer, work function changes, changes in the shape of the adsorbed molecular orbitals, and the orbital shifts. Furthermore, density of states analysis shows that the valence band level shift is surface-and site-dependent.

The electronic structure of Sb(110) is studied by angle-resolved photoemission spectroscopy and first-principles calculations, revealing several electronic surface states in the projected bulk band gaps around the Fermi energy. The dispersion of the states can be interpreted in terms of a strong spin-orbit splitting. The bulk band structure of Sb has the characteristics of a strong topological insulator with a Z(2) invariant v(0) = 1. This puts constraints on the existence of metallic surface states and the expected topology of the surface Fermi contour. However, bulk Sb is a semimetal, not an insulator, and these constraints are therefore partly relaxed. This relation of bulk topology and expected surface-state dispersion for semimetals is discussed.

The adsorption behavior of iron phthalocyanine (FePc) on the Cu(100) surface at the initial stage has been investigated by combining scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. At low coverage, FePc molecules deposited on the sample surface at room temperature tend to adsorb dispersedly with their molecular planes parallel to the crystallographic directions of the substrate. Another interesting STM observation for the sub-monolayer coverage is that the molecular axes of FePc are aligned along [037] (as well as 03¯7) azimuth. At the monolayer coverage and elevated temperature, two types of ordered structures are observed. The FePc adsorption sites for the experimentally observed two distinct ordered domains have been revealed through DFT calculations. With further increasing the coverage, molecular clusters are formed particularly near the step edges.

Using scanning tunneling microscopy, we have investigated the adsorption geometry of a C-70 monolayer on the surface of Ag(111). C-70 molecules form the commensurate (root 13 x root 13)R +/- 13.9 degrees structure and present temperature-dependent bright/dim contrast. Our analyses reveal that the Coulomb repulsion between the charged molecules is the reason for the pits formed at various fullerene/metal interfaces. For the C-70 monolayer, the Coulomb repulsion still makes the upright molecular orientation preferable and leads to the invalidation of the rule of lattice match.

The adsorption of FePc on the Ag(110) substrate has been investigated by ultraviolet photoelectron spectroscopy (UPS). The emission features corresponding to the adsorbed organic molecules are located at 1.03, 4.04, 6.53 and 9.22eV below the Fermi level. The features shift in binding energy with increasing the thickness of the organic films indicates an interaction between FePc and the Ag(110) substrate. ARUPS measurements suggest that the molecular plane is nearly parallel to the substrate in the case of a monolayer. The theoretical calculation confirms the experimental results and indicates that the top site is the most stable adsorption configuration.

A systematic spectroscopic study on the interfaces between the organic molecular semiconductor and the (110) phase of the doped polysilicon has been carried out using valence and core-level photoemission spectroscopy. All photoemission spectra (UPS/XPS) exhibited shifts in the positions of the peaks following the deposition of the organic films. A set of clearly resolved valence band features is found associated to the dispersion of the molecular orbitals. The nonexistence of Fermi edge in the FePc films is thought to account for its semiconducting nature. The thickness dependent change in the work function of the substrate is noticed and a minute amount of charge transfer is found. The asymmetric C1s peak is resolved into three components, reflecting photoemission from multiple sites within the organic molecule. A larger shift in the benzene carbon (Cb) as compared to the pyrrole carbon (Cp) peak suggests that more charge transfers from the former carbon to the substrate. The observed negative sign of the sizable interface dipole potential indicates that the guest molecule and the hosting substrate have donor and acceptor character, respectively. Furthermore, the dipole width, i.e. d=1.35Å, is determined on the basis of the measured quantities and basic physics.