Hiroshi Daimon

New display‐type analyzer for the energy and the angular distribution of charged particles

A new principle for analyzing the kinetic energy as well as the angular distribution of charged particles has been discovered. A new display type analyzer was constructed according to theory. It consists of an inner hemispherical grid and an outer hemispherical electrode which has a radius two times larger than that of the inner grid. Charged particles with the same kinetic energy radiate from one point to all directions inside the inner grid, are repelled by the electric field between the two spheres, and converge at the point which is symmetric to the center of the hemispheres. When an aperture is put at the point, the angular distribution of the charged particles can be observed using a two‐dimensional detector which is positioned out of the aperture. The characteristics of the analyzer are (1) the acceptance cone is ultimately wide, for instance, 2π sr for the charged particles emitted from a flat surface, (2) the pattern obtained is not distorted, and (3) the two electrodes are very simple and easy t...

Temperature dependence of electrical properties of n‐ and p‐type 3C‐SiC

Electrical properties of unintentionally doped n‐type and Al‐doped p‐type 3C‐SiC layers, epitaxially grown on Si by chemical vapor deposition, have been investigated at temperatures between 10 and 1000 K. Activation energies of Al acceptors and residual donors obtained from the temperature dependence of carrier density are 160 and 18 meV, respectively. 40%–60% of Al acceptors in the p‐type epilayers are compensated, and hole mobility is limited by acoustic phonon scattering above 300 K and by ionized impurity scattering below 250 K.

Study of the Si(111) 7 × 7 surface structure by alkali- metal adsorption

Abstract When alkali-metals such as Li, Na, K, Rb and Cs were adsorbed on clean Si(111) 7 × 7 surface at room temperature, the intensity distribution of the original 7 × 7 RHEED pattern changes gradually with the increase of alkali-metal adsorption, and at last a new superstructure with 7 × 7 periodicity, here named δ-7 × 7 structure, has been observed. This change at room temperature can be explained if the 7 × 7 structure is mostly made of displacement. The structure model estimated from the intensity distribution of the δ-7 × 7 pattern is the one that has one vacancy at the corners of the 7 × 7 unit mesh and relaxed surrounding atoms. The change of the 7 × 7 structure by alkali-metal adsorption to this model is naturally understood with our new model (1984). For all alkali metals, by adsorption at high temperature 3 × 1 superstructure has also been observed for the first time.

Chemical Analysis of Surfaces by Total-Reflection-Angle X-Ray Spectroscopy in RHEED Experiments (RHEED-TRAXS)

A new method for chemical analysis of surfaces by total-reflection-angle X-ray spectroscopy in RHEED experiments (RHEED-TRAXS) has been developed. When the X-ray take-off angle is set to be the critical angle for total reflection of the characteristic X-ray emitted from the deposited atoms on surfaces, the detection efficiency for the deposit becomes drastically higher owing to the refraction effect of the X-ray. This enhancement of surface sensitivity is demonstrated with Ag on Si(111). The smallest detectable amount of Ag is about 0.01 monolayer or less. This sensitivity is comparable to or higher than that of AES.

A study of adsorption and desorption processes of Ag on Si(111) surface by means of RHEED-TRAXS

The Si(111)-Ag system was investigated by a new experimental technique for chemical analysis of solid surfaces, called total reflection angle X-ray spectroscopy in RHEED experiments (RHEED-TRAXS). By applying this method to the isothermal condensation and desorption experiments of Ag atoms, saturation coverages of surface structures and desorption energies of Ag atoms could be measured. The sticking probability and the desorption rate of Ag atoms can be directly measured in principle by the RHEED-TRAXS experiment, which is generally difficult by AES. By comparing the experimental results with those of AES, the features of the X-ray spectroscopy are discussed

Experimental 3C-SiC MOSFET

Cubic-SiC (3C-SiC) MOSFETs were successfully fabricated for the first time on a 3C-SiC film heteroepitaxially grown on an Si substrate. The device showed acceptable static characteristics. A novel device structure was devised, which enabled the use of conventional equipment for silicon devices, and eliminated dedicated processes for a stable and rigid SiC film.

Raman scattering of SiC: Estimation of the internal stress in 3C‐SiC on Si

Internal stress in 3C‐silicon carbide (SiC) epilayers grown on Si substrates by chemical vapor deposition was studied using Raman scattering. The stress in the epilayers grown on Si(001) at 1350 °C was found to be 5.4×109 dyn/cm2 tensile, which is comparable to that of silicon on sapphire. The magnitude of the stress is discussed in terms of the elastic deformation theory. It was found that there is not so much difference between the stress in 3C‐SiC epilayers grown on Si(001) and that in 3C‐SiC on Si(111) as the elastic deformation theory suggests.

Improvement of the spherical mirror analyzer

With the use of some obstacle rings and a set of retarding grids, the resolution of the prototype spherical mirror analyzer, which has been developed in a previous paper [H. Daimon, Rev. Sci. Instrum. 59, 545 (1988)], was improved. The uniformity of the resolution with respect to the emission angle was also achieved. Some examples of electron energy‐loss spectra and XPS spectrum were presented.

Strong Circular Dichroism in Photoelectron Diffraction from Nonchiral, Nonmagnetic Material–Direct Observation of Rotational Motion of Electrons

Strong circular dichroism is found in 2-dimensional angular distribution patterns of the Si 2p photoelectrons from the Si(001) surface, which has no chirality and magnetism. The forward focusing peaks in the pattern rotate clockwise or counterclockwise when the helicity of the incident circularly polarized light is reversed. These rotations of the pattern are explained by rotational motion of photoelectrons around the nuclei. This is the first direct observation of the rotational motion of the electrons and clarifies the correspondence between the classical and the quantum mechanical ideas of angular momentum.

A study of Si(111) 5 × 2-Au structures by Li adsorption and their coadsorbed superstructures

Abstract Changes of the Si(111)5 × 2-Au surface structure upon Li adsorption were investigated by RHEED. The reciprocal lattice of the 5 × 2-Au structure consists of 1 5 order spots and 1 2 order streaks. Continuing the adsorption of Li on the 5 × 2-Au structure at room temperature, the 1 2 order streaks split at first into superlattice spots, changed their positions, and finally disappeared, whereas the 1 5 order spots survived. These facts suggest that the origins of the 1 5 order spots and the 1 2 order streaks are differe the atoms of the structure producing the 1 2 order streaks are movable at room temperature upon Li adsorption. The origin of the 1 2 order streaks was inferred to be displacement of loosely bound Au atoms. Including the results of the analysis of the RHEED intensity, a new model for the Si(111)5 × 2-Au was proposed. Besides, some new superstructures of coadsorption systems such as Si(lll)2√3 × 2√3-(Au, Li), Si(111)√3 × √3-(Au, Li) and Si(111)8 × 1-(Au, Li) have been found for the first time.