An InP(001)-͑2 3 1͒ reconstruction was prepared by metal-organic vapor-phase epitaxy. Scanning tunneling micrographs and infrared spectra of adsorbed hydrogen revealed that the ͑2 3 1͒ is terminated with a complete layer of buckled phosphorous dimers, giving rise to p͑2 3 2͒ and c͑4 3 2͒ domains. A surface band gap of 1.2 6 0.2 eV was measured by scanning tunneling spectroscopy. The buckling can be explained by electron correlation among the dangling bonds of pairs of phosphorous dimers. This allows the surface to achieve a lower energy, semiconducting state. This reconstruction mimics the Si(100)-͑2 3 1͒, which is terminated with buckled silicon dimers. [S0031-9007(99)08534-8]

The atomic structure of the InP͑001͒ reconstructions has been identified by scanning tunneling microscopy and infrared spectroscopy of adsorbed hydrogen. The four phases, in order of decreasing phosphorous coverage, are c(2ϫ2)/p(2ϫ2), P ϭ2.0 ML; (2ϫ1), P ϭ1.0 ML; (2ϫ4), P ϭ0.25 ML, and ␦(2ϫ4), P ϭ0.125 ML. The (2ϫ2) consists of phosphorous dimers adsorbed onto a layer of P atoms. Removal of the P adatoms at 300°C, produces the (2ϫ1), which is terminated with a complete layer of buckled phosphorous dimers. Further annealing at 400 to 500°C, yields the indium-rich (2ϫ4) and ␦(2ϫ4) reconstructions. The (2ϫ4) reconstruction comprises a single phosphorous dimer in the top layer and four indium dimers in the second layer. The ␦(2ϫ4) differs from the (2ϫ4) reconstruction in that one of the P atoms is replaced with an In atom to make an In-P heterodimer. This difference is evident by comparison of the intensities of P-H, In-H, and In-H-In stretching vibrations for the two surfaces.

No abstract

Surfaces of GaAs (001) were prepared by metalorganic vapor-phase epitaxy and characterized by scanning tunneling microscopy, x-ray photoelectron spectroscopy, infrared spectroscopy, and low-energy electron diffraction. Upon removal from the reactor, the gallium arsenide surface exhibits a (1×2) reconstruction, which is a disordered variant of the c(4×4). The disorder arises from the presence of adsorbed alkyl groups. Heating the sample to 350 °C desorbs the hydrocarbons and produces a well-ordered c(4×4) structure. A model is proposed for the alkyl-terminated (1×2) reconstruction.

Hydrogen adsorption on the c(4ϫ4), ͑2ϫ4͒, ͑2ϫ6͒, and ͑4ϫ2͒ reconstructions of GaAs ͑001͒ have been characterized by internal-reflection infrared spectroscopy. The infrared spectra contain up to 15 bands due to the stretching vibrations of arsenic hydrides ͑2150-1950 cm Ϫ1 ͒, terminal gallium hydrides ͑1950-1800 cm Ϫ1 ͒, and bridging gallium hydrides ͑1800-950 cm Ϫ1 ͒. These features arise from hydrogen adsorption on arsenic and gallium dimers, and second-layer arsenic and gallium atoms. The large number of peaks observed indicates that the surface atoms exist in a variety of different chemical environments.