A. Glachant

Monolayer adsorption of Kr and Xe on metal surfaces: Structures and uniaxial phase transitions on Cu(110)

Abstract Two-dimensional phase transitions in monolayers of Kr and Xe adsorbed on the (110) face of Cu were studied. As the external gas pressure is raised, a compression of adatoms along the close packed rows is observed. For Xe, first a c(2 × 2) commensurate structure is formed by a continuous transition, then a gradual compression gives rise to a commensurate-incommensurate phase transition, for which the misfit variation is consistent with recent theoretical models. On the other hand, for Kr a first order gas-solid transition is found, followed by a slight compression giving rise to a c(2 × 8) superstructure. A discussion of the results and a comparison between Xe and Kr is presented.

A LEED, AES and TDS study of very thin nitride film growth on Si(100) by direct thermal nitridation in NH3

Abstract Kinetics of Si(100) nitridation first stages by pure NH 3 have been investigated in the temperature range (26–1050°C) for pressures ranging from 10 −7 up to 10 −3 Torr. At T > 800°C, the kinetics nearly follows a layer-by-layer model of growth. The first reacted layer growth rate is proportional to the NH 3 pressure and only ≈1% of the impinging molecules contribute to film growth. The nitride film/silicon interface is quite abrupt. Formation of successive layers is slowed down by the transport mechanism of the reacting species through the film already formed.

Low energy electron-beam-enhanced formation of ultrathin insulating silicon oxynitride layers on Si(100) at moderate temperatures: in situ determination of the band gap energy using electron energy loss spectroscopy

Abstract Exposure of a Si(100)-2 × 1 surface to low pure NO gas pressures (≤ 8 × 10 −6 mbar) at moderate temperatures (room temperature (RT) — 600°C) leads to the formation of an amorphous passivating oxynitride layer (thickness ∼ 0.5 nm). However, we show that low energy (100 eV) electron bombardment of the surface, during exposure to NO, induces the formation of amorphous ultrathin (≤ 2 nm) silicon oxynitride films having different elemental compositions. At RT, oxygen-rich films were grown, while nitrogen-rich layers were formed at 600°C. This result confirms recent published data where synchrotron radiation (thermal activation) at RT (above 1000°C) was found to be an efficient promoter of the oxidation (nitridation) of silicon using low pure NO gas pressures. The thickness and the composition parameter O/(O + N) of the resulting insulating layers have been deduced from Auger electron spectroscopy (AES) measurements. The band gaps of various ultrathin films already formed have been determined in situ using reflection electron energy loss spectroscopy (EELS). For this purpose, the true N ( E ) distributions of inelastically-backscattered electrons have been deduced, using a numerical procedure, from EELS spectra recorded by means of a standard single-pass cylindrical mirror analyzer operated in the pulse counting mode.

LEED, AES and work function measurements on clean and cesium covered polar faces of GaP

Abstract After argon bombardment and annealing both the (111) and (111) faces of GaP show a (1 × 1) LEED pattern. The stabilization of the polar termination is probably obtained by charging of surface states. Measurements of the work function, the Auger spectrum and the LEED pattern during cesium deposition at room temperature suggest disordered cesium adsorption limited to a monolayer.

Surface science lettersUniaxial compressibility of a complete monolayer of Xe adsorbed on Cu(110)

The variation of the lattice parameter of a complete monolayer of xenon adsorbed on Cu(110) is measured, at constant pressure, as a function of temperature. The compression only occurs along the direction of the troughs [110]. The data are used to estimate the uniaxial compressibility of the layer at completion, KT = 1.5 ± 0.2 × 10−3A2K−1.

Symétries de translation et de rotation des diagrammes de diffraction d'électrons lents des faces polaires {111} de GaP

Abstract The (111) faces ending with gallium and (111) ending with phosphor in GaP crystal yield a 1 × 1 low energy diffraction pattern. This result is different from the ones previously given for the same faces of the III-V compounds exhibiting a 2 × 2 or 3 × 3 pattern. Furthermore it is not in agreement with the theories expecting a reconstruction or a faceting of the (111) faces of the blende type compounds. We think the surface equilibrium is brought about by surface electronic states. The rotation symmetry of the diffraction pattern of the (111) and (111) faces changes with the electron energy; it is alternatively trigonal and hexagonal. This phenomena is explained thanks to a diffraction kinematical model using a limited number of atomic layers.

Uniaxial compressibility of a complete monolayer of Xe adsorbed on Cu(110)

Abstract The variation of the lattice parameter of a complete monolayer of xenon adsorbed on Cu(110) is measured, at constant pressure, as a function of temperature. The compression only occurs along the direction of the troughs [110]. The data are used to estimate the uniaxial compressibility of the layer at completion, K T = 1.5 ± 0.2 × 10 −3 A 2 K −1 .