Direct Photodesorption of Atomic Hydrogen from Si(100) at 157 nm:  Experiment and Simulation

Abstract

Atomic hydrogen photodesorbs from the Si(100)−(2 × 1):H monohydride surface at 157 nm, with a cross section of ∼3 × 10-21 cm2. We determine using polarized light that the transition dipole moment for the optical excitation is oriented at ∼18° from the surface normal, as expected for the σ → σ* transition within the H−Si bond. This result unambiguously establishes the dissociation of the H−Si surface bond by direct optical excitation. The dynamics of this process is characterized by a translational energy of 〈E trans〉 = 0.24 ± 0.02 eV for atomic H and an isotope effect in photodesorption yield of y H/y D = 10 ± 3. We carry out time-dependent quantum mechanical simulation on ab initio potential energy surfaces. The simulation suggests a subfemtosecond lifetime in the excited state and a quantum yield for atomic hydrogen desorption of the order 10-5. This study provides an extreme example for bond-selective photochemistry in large chemical systems. In addition to its significance in understanding ultrafast surface dynamic processes, the direct photodesorption process demonstrated here may also find applications as resistless photolithography in semiconductor technology.

Two-photon polarization-selective etching of emergent nano-structures on diamond surfaces

“…To date, only bonds in gas phase species or between H adsorbates on Si surfaces have exhibited photo-selective bond scission [8][9][10] . We have investigated single-crystal diamond as a promising candidate for revealing photo-selective scission of structural bonds in a strong covalently bound system.…”

Inherent density of point defects in thermal tensile strained (100)Si∕SiO2 entities probed by electron spin resonance

“…This was attained in the used high-vacuum laboratory facility, as verified previously. 9 Some samples were additionally subjected to vacuum ultraviolet ͑vuv͒ irradiation ͑10 eV photons, flux ϳ10 15 cm −2 s −1 ͒ in room ambient to photodissociate H from potentially H-inactivated point defects, 17 in order to maximally ESR-activate ͑reveal͒ defects. Possibly, this treatment may additionally expose strained and/or weak bondings ͑bond rupture͒.…”

Aqueous Synthesis of Triphenylphosphine‐Modified Gold Nanoparticles for Synergistic In Vitro and In Vivo Photothermal Chemotherapy

“…Bulk Au 0 atoms are known to have Au 4f 7/2 and Au 4f 5/2 binding energy of 84.1 eV and 87.8 eV,r espectively. [15] The observed negative binding shift in F-108@TPP-AuNPs (Au 4f 7/2 at 82.7 eV and Au 4f 5/2 at 86.3 eV) could arise from (1) the presence of organic layerso n the surfaceo fg olda toms, [16] (2) the coordinationo fp hosphine to the gold surface inducing ac harget ransfer from the phosphorous atoms to the Au atoms, [17] and/or (3) the coulomb blockeds hift indicating that the coated nanoparticles are more separated from each other,b ecause the coulombb lockeds hift is greater for isolated nanoparticles. [18] In addition, the broadening of Au 4f peaks could be attributed to the surface vibration modes causing ac hemical shift.…”