Adsorption and decomposition of nickelocene on Ag(100): a high-resolution electron energy loss spectroscopy and temperature programmed desorption study

Adhesion and Cu Diffusion Barrier Properties of a MnOx Barrier Layer Formed with Thermal MOCVD

“…Below the decomposition temperature of the cyclopentadienyl precursors of Cp 2 Ni and Cp 2 Fe, it is reported that the precursor is adsorbed on the metal substrate and undergo decomposition to cyclopentadiene under electron or photon irradiation [9][10][11]. The decomposed species react with the substrate and form the moderate amount of the carbidic carbon of (EtCp)-Mn compared to the case below 300 o C. Moreover, it is reported that the decomposition of the absorbed Cp ligands on Ag substrate resulted in the formation of carbon atoms [12]. Meanwhile, above the decomposition temperature of 400 o C, the part of the Mn precursor thermally decomposes to Mn atoms and reactive (EtCp) ligands.…”

Cobaltocene adsorption and dissociation on Cu(111)

“…This preferential orientation is with the molecular axis canted away from the surface normal, so that the light polarization dependent photoemission effects are small or, only a small fraction of cobaltocene molecules are oriented with the molecular axis along the surface normal. A canting of the molecular axis away from the surface normal would make the bonding orientation adopted by molecular cobaltocene, resemble that of nickelocene on Ag(1 0 0) at some coverages [26][27]. So that cobaltocene adopting a somewhat canted molecular adsorption confi guration need not be considered surprising even though most studies place the metallocene molecular axis along the surface normal of Ag(1 0 0) [15], [21][22] and graphite [16] and [18].…”

“…When comparing initial cobaltocene adsorption on graphite [32] and Cu(1 1 1) (the work presented here) with other metallocenes, it seems fairly clear that cobaltocene is far less stable as a molecule on surfaces than ferrocene (Z − 1) [13][14][15][16][17][18][19][20][21][22] or nickelocene (Z + 1) [20], [23][24][25][26][27]. The big difference among these three metallocenes appears to be that the "nineteen electron" cobaltocene has a single unpaired electron resulting in a low ionization potential [32] of 5.56 eV [37] when compared to ferrocene (6.88 eV [37]) and nickelocene (6.51 eV [37]).…”

“…This results in formation of a surface species that somewhat resembles [Co(Cp) 2 ] + on graphite [32] but apparently leads to fragmentation on Cu (1 1 1). Ferrocene, with greater stability as an adsorbate, is a paired electron system in a singlet state, while nickelocene, which exists as a triplet state as an isolated molecule, almost certainly adopts a singlet state on adsorption due to lowered molecular symmetry [26] and [27] and possibly localization of an electron pair on a double bond arising from ring slippage of the carbocyclic ligand [36]. With absorption other than end-on, nickelocene MUST adopt a singlet state as the off normal adsorption orientation has reduced the molecular symmetry to such an extent that a triplet state is simply not possibly.…”

“…Of the many studies of molecular ferrocene [13][14][15][16][17][18][19][20][21][22], nickelocene [20][21][22][23][24][25][26][27][28][29][30][31] and cobaltocene [32] adsorption, the initial adsorption is associated (molecular) on most surfaces, when the adsorption is undertaken at substrate temperatures in the region of 100-200 K. Molecular metallocene adsorption has been observed on Ag(1 0 0) [13][14][15], [21], [22], [26], and [27], Cu(1 0 0) [15], [19], [21][22][23][24][25], Mo(1 1 2) [17] and [22], graphite [16], [18], and [32] and Si(1 1 1)-2 × 1 [20]. Nonetheless, initial nickelocene adsorption on Ni(1 0 0) [25] and NiO(1 0 0) [25] is dissociative even for substrate temperatures of 135 K. We might expect that cobaltocene adsorption, like that observed for other metallocenes, would also be molecular on substrates well below r...…”