Electronic Structure of Adsorbed Trimethylaluminum on Clean Si(100) Surfaces

1988 ◽  
Vol 131 ◽  
Author(s):  
T. Motooka ◽  
P. Fons ◽  
J. E. Greene
Keyword(s):  
Electronic Structure ◽  
Charge Transfer ◽  
Molecular Orbital ◽  
Electron Acceptor ◽  
Core Level ◽  
Photoelectron Spectra ◽  
Dangling Bond ◽  
Mo Calculations

ABSTRACTThe electronic structure of dimerized trimethylaluminum (TMA), Al2(CH3)6. adsorbed on Si(100) surfaces has been investigated using molecular orbital (MO) calculations based on a cluster description of TMA/Si(100). The calculated results suggest that the interactions between TMA and the Si(100) surface are described by overlap of the TMA electron-deficient bond and Si surface dangling-bond orbitals. The electron-deficient bond orbital is the highest occupied MO of TMA and acts as an electron acceptor for charge transfer from a surface Si atom to TMA consistent with observed core-level and valence photoelectron spectra.

Introduction

2003 ◽  
Author(s):  
Toshiaki Enoki ◽  
Morinobu Endo ◽  
Masatsugu Suzuki
Keyword(s):  
Electronic Structure ◽  
Charge Transfer ◽  
Ionization Potential ◽  
Molecular Orbital ◽  
Electron Affinity ◽  
Basic Unit ◽  
Charge Transfer Complexes ◽  
Vacuum Level ◽  
2D System ◽  
Lowest Unoccupied Molecular Orbital

There are two important features in the structure and electronic properties of graphite: a two-dimensional (2D) layered structure and an amphoteric feature (Kelly, 1981). The basic unit of graphite, called graphene is an extreme state of condensed aromatic hydrocarbons with an infinite in-plane dimension, in which an infinite number of benzene hexagon rings are condensed to form a rigid planar sheet, as shown in Figure 1.1. In a graphene sheet, π-electrons form a 2D extended electronic structure. The top of the HOMO (highest occupied molecular orbital) level featured by the bonding π-band touches the bottom of the LUMO (lowest unoccupied molecular orbital) level featured by the π*-antibonding band at the Fermi energy EF, the zero-gap semiconductor state being stabilized as shown in Figure 1.2a. The AB stacking of graphene sheets gives graphite, as shown in Figure 1.3, in which the weak inter-sheet interaction modifies the electronic structure into a semimetallic one having a quasi-2D nature, as shown in Figure 1.2b. Graphite thus features a 2D system from both structural and electronic aspects. The amphoteric feature is characterized by the fact that graphite works not only as an oxidizer but also as a reducer in chemical reactions. This characteristic stems from the zero-gap-semiconductor-type or semimetallic electronic structure, in which the ionization potential and the electron affinity have the same value of 4.6 eV (Kelly, 1981). Here, the ionization potential is defined as the energy required when we take one electron from the top of the bonding π-band to the vacuum level, while the electron affinity is defined as the energy produced by taking an electron from the vacuum level to the bottom of the anti-bonding π*-band. The amphoteric character gives graphite (or graphene) a unique property in the charge transfer reaction with a variety of materials: namely, not only an electron donor but also an electron acceptor gives charge transfer complexes with graphite, as shown in the following reactions: . . .xC + D → D+ C+x. . . . . .(1.1). . . . . .xC + A → C+x A−. . . . . .(1.2). . . where C, D, and A are graphite, donor, and acceptor, respectively.

Photoelectron Spectrum and Electronic Structure of Tetrathiofulvalene (TTF)

1974 ◽  
Vol 52 (19) ◽  
pp. 3373-3377 ◽  
Author(s):  
A. John Berlinsky ◽  
James F. Carolan ◽  
Larry Weiler
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Molecular Orbital ◽  
Photoelectron Spectrum ◽  
Crystal Packing ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Molecular Orbital Calculations ◽  
Conducting Salt

The electronic structure of tetrathiofulvalene (TTF) has been determined from its photoelectron spectrum and the photoelectron data for the tetrahydro derivative of TTF and 1,3-dithiolane. Correlations of the ionization potentials (i.p.) and several molecular orbital calculations are used in the assignment of the photoelectron spectra of these three compounds. The first five i.p. of TTF and their assignment are as follows: 6.92 (3b1u), 8.67 (2b2g), 9.73 (2b1u), 10.16 (au) and 10.49 eV (b3g). The sixth i.p. at 11.00 eV is tentatively assigned to the 1b2g level. The electronic structure of TTF is important in understanding the crystal packing and band structure of the highly conducting salt, TTF•TCNQ.

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