Hydrogen Adsorption on the Indium-Rich Indium Phosphide (001) Surface:  A Novel Way to Produce Bridging In−H−In Bonds

Abstract

The indium phosphide (001) surface provides a unique chemical environment for studying the reactivity of hydrogen toward the electron-deficient group IIIA element, indium. Hydrogen adsorption on the In-rich delta(2 x 4) reconstruction produced a neutral, covalently bound bridging indium hydride. Using vibrational spectroscopy and ab initio cluster calculations, two types of bridging hydrides were identified, a (mu-H)In(2) and a (mu-H)(2)In(3) "butterfly-like" structure. These structures were formed owing to the large thermodynamic driving force for adsorption of H atoms on solid-state indium dimers.

Spectroscopic studies of the mechanism for hydrogen-induced exfoliation of InP

“…1͑a͒ are associated with the vibration of In-H modes, specifically to terminal In hydrides. [13][14][15] These modes are slightly shifted from the modes found on In-terminated surfaces. We attribute this shift to the different environment where the H is located.…”

“…It has been found that the insertion of hydrogen into metal dimer bonds releases a substantial amount of strain in the In-P back-bonds. 14 The enthalpy of formation of this process is +52.2 kcal mol −1 , corresponding to a bondformation energy of 2.6 eV, 18 meaning that the final state is more stable. The stress release and large bond-formation energy are two possible origins of the observed thermal stability of the In-H bonding configurations.…”

“…The mode at 2268 cm −1 is close to the frequency of 2265 cm −1 attributed in previous work to symmetric stretch modes of H-terminated ͑100͒ surfaces with a 2 ϫ 1 reconstruction. 14 The mode corresponds to a dimer formed by two adjacent atoms, as depicted in Fig. 7͑d͒.…”

Experimental and theoretical evidence for a hydrogen stabilizedc(2×2)reconstruction of the P-rich InP(001) surface

“…Vibrations have appeared that should not occur at an ordered P-rich surface, most notably peaks of In-H vibrations ͑between 1800 and 1200 cm −1 ͒. 16 Peaks B 1 -B 6 have vanished now and the rather broad P-H band appearing around 2300 cm −1 is tentatively attributed here to −PH 3 species. Silicon surfaces terminated with −PH 3 exhibit vibrational bands around this frequency.…”

Infrared Spectra of Indium Hydrides in Solid Hydrogen and of Solid Indane

“…[8] However, bridging InÀHÀIn bonds formed on indium-rich InP semiconductor surfaces are stable at room temperature. [9] There is spectroscopic evidence for the intermediate InH, InH 2 , and InH 3 molecules. [10][11][12][13][14] Recently Mitzel concluded that the next question remaining to be answered concerns the possible isolation of InH 3 .…”