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

Abstract

The formation of hydrogen bonds was investigated on the P-rich InP͑001͒ surface employing attenuated total-reflection Fourier-transform infrared spectroscopy, low-energy electron diffraction, and total-energy density-functional theory calculations. Strong evidence was found for a c͑2 ϫ 2͒-2P-3H reconstruction with a higher hydrogen coverage than is characteristic for the metal-organic chemical-vapor deposition prepared hydrogen-stabilized ͑2 ϫ 2͒-2D-2H surface. The new surface reconstruction was formed upon exposure to atomic hydrogen. Complete transformation of all the metastable atomic configurations to form the new surface reconstruction was not achieved, since prior to this the surface began to deteriorate. The latter effect was monitored as the formation of In-H bonds. Two observations, i.e., nearly complete screening of the infrared peaks for excitation with p-polarized light and a pronounced redshift of P-H peaks with increasing hydrogen coverage were attributed to dipole-dipole interaction between the vibrating adsorbates.

P-H bonds in the reconstruction of P-rich InP(100) measured with FTIR

“…1 obeys the electron counting rule and contains more P-H bonds than the unit cell (2x2)-2D-2H [2]. Recently, first principles calculations have confirmed that the former unit cell also forms a stable phase, however, at a much higher concentration of hydrogen [4]. The corresponding phase transition was, however, not observed when the hydrogen pressure was increased to the maximum 900 mbar that is available in our MOCVD reactor.…”

“…The FTIR spectra were measured with a Bruker Optics IFS66v spectrometer, other experimental details can be found below and in references [3,4]. Polarized and orientation dependent FTIR signals have confirmed the formation of the (2x2)-2D-2H unit cell [3] for the P-rich ordered InP(100) surface grown in an MOCVD reactor.…”

“…The new c(2x2)-2P-3H phase has turned out very robust in first principle calculations [4], similar to the (2x2) phase that is formed under normal MOCVD growth conditions.…”

“…Experiments with a higher concentration of molecular hydrogen have not yet been attempted. On the basis of the new experimental and theoretical results [4] the modified phase diagram shown in Fig. 3 is proposed for the InP(100) surface.…”

“…Phase diagram of InP(100) where the chemical potential of In at the ordinate spans the range from In-rich to P-rich reconstructions and the chemical potential of hydrogen at the abcissa reaches from the absence to a high concentration of hydrogen over the crystal surface. The new hydrogen-rich reconstruction appears at the right hand side of the phase diagram [4].…”