Electric field dependent structural and vibrational properties of the Si(100)-H(2×1) surface and its implications for STM induced hydrogen desorption

Abstract

We report a first principles study of the structure and the vibrational properties of the Si(100)-H(2×1) surface in an electric field. The calculated vibrational parameters are used to model the vibrational modes in the presence of the electric field corresponding to a realistic STM tip-surface geometry. We find that local one-phonon excitations have short lifetimes (10 ps at room temperature) due to incoherent lateral diffusion, while diffusion of local multi-phonon excitations are suppressed due to anharmonic frequency shifts and have much longer lifetimes (10 ns at room temperature). We calculate the implications for current induced desorption of H using a recently developed first principles model of electron inelastic scattering. The calculations show that inelastic scattering events with energy transfer nhω, where n > 1, play an important role in the desorption process.

Tip-Induced Molecule Anchoring in Ni–Phthalocyanine on Au(111) Substrate

“…The excitation energy of the injected electrons in the NiPC can be efficiently dissipated to the kinetic energy of the H atoms in the NiPC through electron-phonon coupling. 26 Consequently, the H atoms can be desorbed from the NiPC, forming an H2 molecule. Then, the dehydrogenated benzene-like ligand bends toward the substrate to form two C-Au bonds [ Fig.…”

Electrostatic field effect on molecular structures at metal surfaces

“…Even in the high resolution STM images with sharper tips, the apex of the tip is mostly not smaller than the size of a molecule [27]. For a single molecule, the variation of electric field between STM tip and substrate with lateral distance is not dramatic, as established in model calculations on semiconductors [28]. To show that this is also the case for the metal-molecule-metal tip system, we consider a negatively charged W(1 0 0) tip (Fig.…”

Theoretical study of vibration-phonon coupling of H adsorbed on a Si(100) surface

“…Such a potential may be either evaluated ab initio 9 or else be empirically postulated in an analytical form, and then fitted to the available experimental and quantum chemical data. We chose to use a semiempirical potential here, since it allows treatment of larger H-Si clusters, and, more important, to evaluate the potentials, forces, and coupling matrix elements analytically.…”