Mechanisms of Molecular Manipulation with the Scanning Tunneling Microscope at Room Temperature: Chlorobenzene/Si(111)−(7×7

Abstract

We report a systematic experimental investigation of the mechanism of desorption of chlorobenzene molecules from the Si(111)-(7 x 7) surface induced by the STM at room temperature. We measure the desorption probability as a function of both tunneling current and a wide range of sample bias voltages between -3 V and +4 V. The results exclude field desorption, thermally induced desorption, and mechanical tip-surface effects. They indicate that desorption is driven by the population of negative (or positive) ion resonances of the chemisorbed molecule by the tunneling electrons (or holes). Density functional calculations suggest that these resonant states are associated with the pi orbitals of the benzene ring.

Local resonances in STM manipulation of chlorobenzene on Si(111)-7×7: performance of different cluster models and density functionals

“…Both, STM-induced desorption [22] and dissociation [23] of the carbon-chlorine-bond, have been reported in experiments at room temperature. Desorption can be induced by electrons or holes (positive or negative bias voltage) and was found to be largely non-local [8,24].…”

“…[7] and references therein), the chemisorption energy seemed to be too high compared to 1.0 eV derived from thermal desorption spectra [26] assuming first-order kinetics and a pre-exponential factor of 10 13 s −1 . Also, periodic DFT calculations [22] using a 2×2 mimic surface reported 1.2 eV chemisorption energy. However, new time-lapse STM experiments [28] indicate that the used pre-factor is too small and result in a chemisorption energy of 1.4 eV, well in line with our cluster calculations.…”

An STM study of the localized atomic reaction of 1,2- and 1,4-dibromobenzene at Si(111)-7×7

“…First results from this laboratory have described the electron and photon-induced reactions of chlorobenzene [14] and dichlorobenzenes [15], in which the parent molecule dissociates to give preferred patterns of Si-Cl and also can yield organic radicals that react at Si(1 1 1)-7 · 7 [16] and at Si(1 0 0)-2 · 1 [17,18]. The reaction of elemental Br 2 , Cl 2 [19][20][21][22][23][24] and of chlorobenzene [25][26][27] at silicon surfaces has been the subject of a number of recent studies.…”

Surface Chemistry of Monochlorinated and Dichlorinated Benzenes on Si(100)2×1: Comparison Study of Chlorine Content and Isomeric Effects

“…At issue are some of the key questions, including the number of benzene adstructures on Si(100)2×1 and the relative stabilities of these adstructures. 12,25 Furthermore, substituted derivatives of benzene that replace H atoms on the ring with chemically active functional groups (including amine 9 and the halogen atom [27][28][29][30][31][32][33][34] have attracted a lot of recent attention. Some of these studies examine the reaction mechanisms and the possibilities of generating an organo-silicon interface by manipulating the frontier orbitals and the energy gaps of the adstructures.…”