We observed the LEED patterns of Fe silicide produced by solid phase epitaxy (SPE) on Si(111) surface. Besides 1×1 and 2×2 LEED pattern observed before, c(8×4) pattern with 575°C annealing after Fe1.5ML deposition at room temperature, 2×2+√3×√3 pattern with 550°C annealing after 5ML deposition and c(4×2) pattern with 550°C annealing after 10 ML deposition were newly observed. Then we acquired I-V curves (Intensity-Energy curve) of typical LEED pattern. To evaluate the reliability of the I-V curve, we compared them each other to be sure the symmetry on the three-fold symmetrical surface and to evaluate the structure change with elevating the annealing temperature. The similarity was evaluated by Pendry's R-factor value. From the experimental result, the I-V curves that can be endured to the structure analysis were obtained.

Cesium adsorption was investigated by means of thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and metastable de-excitation spectroscopy (MDS) in order to clarify why only a small amount of Cs is adsorbed on H-terminated diamond at room temperature. H-termination is not perfect and H-patches are formed on diamond surface. At room temperature this H-terminated surface can adsorb no Cs atoms and only bare diamond surface catches them. Therefore only a small amount of Cs is adsorbed on the H-terminated diamond surface at room temperature.

In order to understand the fundamental character for forming Ba3N on Si (111) surface, the following two studies have been carried out by means of Low Energy Electron Diffraction (LEED), and Auger Electron Spectroscopy (AES) and Ultraviolet Photoemission Spectroscopy (UPS). 1) Whether silicon nitride layer would be accepted as a diffusion barrier between Ba and Si layer was examined. Ba and Si atoms formed a compound layer above 400 degree Centigrade, so that the silicon nitride layer was disqualified as a diffusion barrier between Ba and Si layer. 2) The electronic states in the coadsorption of Ba and NH3 on Si (111) surface were investigated. When less than 2 MLs Ba adsorbed Si (111) surface was exposed to NH3, the electronic states of Ba-N, N-H, and the lonepair electron pair of NH3 appeared, and when more than 2 MLs Ba adsorbed Si (111) surface was exposed to NH3, the electronic states of Ba-H appeared in addition to three electronic states mentioned above.

Sb adsorbed Si(001) surfaces have been investigated by LEED and AES. After a few monolayer (ML) deposition at room temperature, the LEED patterns of 1×1, 2×1 and c(4×4) have been observed successively as elevating the annealing temperature. Two structures (1×1 and 2×1) were examined by LEED I–V curve analysis. The genetic algorithm (GA) was operated to search a global optimum structure. For the 1×1 structure, a good R-factor value of 0.22 was obtained for the model in which topmost 1 ML Sb atoms sit on the Si atoms of fourth substrate layer. For the 2×1 structure, two cases of 1 ML and a half ML Sb coverage was examined, and an Sb dimer model with 1 ML coverage gave a better R-factor value.

Adsorbed structures of Ba on Si(111) surfaces have been observed by LEED. In elevating the annealing temperature after a few monolayers (MLs) deposition at room temperature (√3×2√3)R30°, 2×8 and 3×1 patterns were observed as reported by Weitering [H.H. Weitering, Surf. Sci. 355 (1996) L271]. Additionally a one-dimensional 10×1 pattern was observed in the temperature range between the appearance of two-dimensional 2×8 and 3×1 patterns. This pattern is considered to be produced by a combination of the periodical terrace with a width of 10 unit lengths separating each step and a 5×1 reconstruction on the terrace.

Sb adsorbed Si(001) surfaces have been investigated by LEED and AES. After a few monolayer (ML) deposition at room temperature, the LEED patterns of 1 x 1, 2 x 1 and c(4 x 4) have been observed successively as elevating the annealing temperature. Two structures (1 x 1 and 2 x 1) were examined by LEED I-V curve analysis. The genetic algorithm (GA) was operated to search a global optimum structure. For the I x 1 structure, a good R-factor value of 0.22 was obtained for the model in which topmost 1 ML Sb atoms sit on the Si atoms of fourth substrate layer. For the 2 x 1 structure, two cases of 1 ML and a half ML Sb coverage was examined, and an Sb dimer model with 1 ML coverage gave a better R-factor value. (C) 2001 Elsevier Science B.V. All rights reserved.

The multilayer adsorption of Li on Ta foil and Li on Si(100)2×1 surfaces is discussed, based on the experimental data of thermal desorption spectroscopy and metastable de-excitation spectroscopy. Taking the former results of Ba adsorption on Si(100)2×1 into account, it can be understood that above about 1ML of Li coverage, intermixing or silicide formation starts at room temperature. However, the outermost surface adsorbed by more than 3.3ML is like pure Li. When this sample (with an adsorption of more than 3.3ML of Li and with a surface like that of pure Li) is heated to 250°C, its outermost surface is changed into silicide.

We have studied the molecular orbitals and arrangements of N,N′-dimethylperylene-3,4,9,10-bis(dicarboximide) (Me-PTC) molecules deposited on clean Si(100)2 × 1 and the H-terminated Si(100) surfaces on the basis of metastable de-excitation spectroscopy (MDS) experiments. The charge density of the second layer Me-PTC molecular orbitals differs somewhat from that of the first layer. The desorption temperature of Me-PTC from H-terminated Si surface is lower than that from clean Si. This is because Me-PTC molecules combine weakly with the H-terminated Si substrate.

On Si(001) surfaces annealed at 700°C after the deposition of 1.5 monolayer (ML) of Ba at room temperature, facet spots were observed in addition to the 2×1 pattern of the Si(001) clean surface. These patterns were recorded using a TV camera and stored in a personal computer as an image. Line profiles were obtained on the line along which the facet spot moved. From these profiles the peak position of facet spots was extracted and superposed on a reciprocal lattice space to construct reciprocal lattice rods. From the angle of these rods to those of the Si(001) substrate, the facet is indicated to be a metal-induced Si(113) face.

The coadsorption of lithium and hydrogen on Si(100)2×1 surfaces has been investigated using metastable de-excitation spectroscopy and thermal desorption spectroscopy. When one-monolayer lithium is adsorbed on to one-monolayer hydrogen precovered Si(100)2×1 surfaces, most of the hydrogen atoms are expelled from the dangling bond site to form a new bond with adsorbed Li atoms. This is quite different from the case of adsorption of other alkali atoms on hydrogen precovered Si(100)2×1. The difference is discussed in terms of the adsorption site of alkali atoms and their bonds with neighboring dangling bonds.

The influence of annealing for multilayer-Ba deposited Si(100) prior to hydrogen exposure was investigated in order to explain the mechanism of H-2 desorption from Ba and H coadsorbed Si(100) by means of MDS (metastable de-excitation spectroscopy), AES (Auger electron spectroscopy) and TDS (thermal desorption spectroscopy). AES measurements suggest that annealing > 200 degrees C prior to hydrogen exposure results in the silicide formation inside Ba overlayers. The Ba-H peak for MDS and the H, thermal desorption peak at 280 degrees C start to decrease in intensity at the similar temperature. On the basis of these results, it can be concluded that low temperature decomposition of BaH2 on Si(100) is caused by silicide formation inside BaH2 overlayers. (C) 1998 Elsevier Science B.V. All rights reserved.

The electronic states depending on the substrate temperature and the Ba coverage have been investigated by ultraviolet photoelectron spectroscopy (UPS). With the Ba deposition at the room temperature, the surface states of the clean Si(001) decrease and the valence band states of Ba adsorbate appear at 0.4 and 1.4 eV below the Fermilevel(EF). With the substrate being annealed at 350°C after a few ML deposition, the peaks decrease and a signal due to the formation of barium-silicide appears at 2.9 eV. With the temperature elevated, this signal shifts to 2.7 eV in accordance with the phase transition from BaSi to BaSi2. This signal is removed completely at 800°C by the evaporation of Ba atoms in excess of 1 ML and a featureless broad spectrum is observed. This spectrum keeps up to 1000°C, above which the intensity of the spectrum is weakened. Above 1100°C, the surface states of the clean Si reappear. These features are related to various surface structures.

Adsorbed structures of Te on Si(001) surface have been studied by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). As elevating the temperature after the deposition of Te onto the Si(001) single-domain 1×2 surface by a few monolayers at room temperature, 1×1, 2×1, 1×3 and double-domain 1×2 LEED patterns were observed at about 350°C, 600°C, 680°C and 800°C, respectively. During the phase transitions from 1×1 to 2×1 and from 1×3 to 1×2 clean surface, continuous shifts of diffraction spots were observed. This phenomenon is explained by the formation of the domain walls. We considered a one-dimensional chain of scatterers on the surface which had a statistical distribution of domain length, and calculated the structure factor with a simple kinematic scattering based on the theory proposed by J.E. Houston and R.L. Park. The results of calculated intensity distributions were in good agreement with experiment.

Adsorption structures of Te on a Si(001) surface have been investigated by low energy electron diffraction (LEED), thermal desorption spectroscopy and Auger electron spectroscopy. After the deposition of Te atoms > 3 monolayer (ML) on a single-domain Si(001)-(1 x 2) surface at room temperature, a LEED pattern corresponding to a (10 (1) over bar 0) surface of Te bulk crystal appeared. Raising the substrate temperature, Te atoms in excess of 1 ML desorbed at about 350 degrees C and a (1 x 1)structure appeared. Furthermore, (2 x 1) and (1 x 3) structures appeared at about 600 and 680 degrees C, and amounts of Te atoms in these structures were about 1 and 2/3 ML, respectively. Finally, Te atoms desorbed at about 800 degrees C completely. (C) 1998 Elsevier Science B.V. All rights reserved.

The behaviour of Ba atoms on the Si(001) surface was investigated by low-energy electron diffraction (LEED). An epitaxial silicide formation was observed for surfaces obtained both by deposition onto a substrate kept at 700°C and by annealing at 600°C after deposition at room temperature. These surfaces show 40816 and 4048 oblique patterns which have a unit cell close to six times and three times, respectively, as large as that of the BaSi2(111) surface. In addition to the (2×3), (2×1) and (2×4) structures at submonolayer coverage, a c(2×6) pattern was found. The two-fold periodicities of the (2×4) and (2×3) superstructures were determined to be parallel to the dimer direction using a single-domain Si(001)-(2×1) substrate.

Computer simulation of electron trajectories in a Cascade Static Lens Gauge (CSLG) has been carried out in consideration of space charge effect. The space charge distribution was estimated by the accumulation of residence time of electrons in each mesh. It was confirmed that electron trajectories were spread by a proper amount of space charge, but trajectories have not been spread so to bump into anode electrodes. This is caused by the impossibility of electron emission from the filament due to the intense space charge around it. It is considered that this will be solved by the increase of initial velocity of emitted electrons.

The coadsorption structure and electronic states of Cs and H on Si(100)2×1 were investigated by means of MDS (metastable de-excitation spectroscopy) and TDS (thermal desorption spectroscopy). The both systems of Cs/H/Si and H/Cs/Si have the same TDS profile, which indicates that Si dangling bonds are partly terminated with H atoms in both systems and CsH formed at the Cs coverages above about 0.4 ML is dissociated into H and Cs, resulting in H2 desorption at about 20°C. On the other hand, MDS spectra for the H/Cs/Si system differ from those for Cs/H/Si one, i.e., Cs–H bonds can be clearly seen in case of the H/Cs/Si systems, while not in case of the Cs/H/Si systems. The difference in MDS spectra between both systems can be explained as follows: in case of the Cs/H/Si systems, all hydrogen atoms including Cs–H bonds are located between Cs layer and Si substrate, while in case of the H/Cs/Si systems, some of the hydrogen atoms forming Cs–H bonds are on the outermost surface.

MDS was used to investigate how sodium adsorbs on deuterium precovered Si(100) surface. Upon depositing sodium atoms on the deuterated silicon, some of the pre-adsorbed deuterium atoms bound to the Si surface break the bonds to produce Na+-D− bonds with its D− end toward the vacuum. The produced system on the Si(100) is not independent layers of Na and D but a mixture of Na–D and metallic Na, whose ratio is dependent on the quantity of adsorbed Na and D. The surface of 5 ML Na adsorption on deuterated Si(100) might consist of islands of metallic Na and Na–D layers.

The system of Ba overlayers deposited on a deuterium-terminated Si(100) surface was investigated by means of MDS (metastable de-excitation spectroscopy) and TDS (thermal desorption spectroscopy). Deposition of Ba overlayers caused the reduction of SiD bond strength because of charge donation to Si substrate from Ba atoms. As a result, about half of preadsorbed D atoms was released from the sample surface at 1 ML Ba deposition. The other half reacted with adsorbed Ba atoms entirely to form BaD bonds. Therefore, all the SiD bonds were lost, which is quite different from the alkali/D/Si(100) system. More Ba deposition did not induce the desorption of D atoms. The formed BaD bonds are considered to stay between the first and the second layer.