SIMS is widely used for the process control in the field of LSI manufacture. The reason is that SIMS is the only surface sensitive technique to quantify the low concentration of impurities like Arsenic (As), Boron (B), and Phosphorus (P). The concentration of the impurities would typically be lower than ppb (parts par billion). In this paper, Arsenic distribution was measured by O2+ beam bombardment for different primary beam energies, incident angles and raster sizes. The sample where the Arsenic ion was implanted into SiO2 layer was prepared to study the pile-up of Arsenic into the interface of SiOx/Si. The following two items are the results of this study. (1) The arsenic distortion heavily increased with both higher beam energy and lower incident angle. (2) To avoid the As distortion effect, experiments must be done with O2+ primary beam which has the energy lower than 8 keV and incident angle higher than 45°.
The VAMAS Project (Versailles Project on Advanced Materials and Standards) was set up at the Economic Summit of Versailles in June 1982. A number of technical working parties have been organized. The VAMAS-SCA (Surface Chemical Analysis) working group-Japan is one of them, and has been active since 1985. We have established the reliability of the quantitative analysis with AES using Au-Cu alloys as round robin specimens, and we have published the results elsewhere. As the next objective of VAMAS-SCA-JAPAN, we adopted the project on the improvement of the reliability of the quantitative analysis with XPS, To carry out this project, we decided to use Au-Cu alloys as round robin specimens To determine the measurement conditions, the effects of the followings on the quantitative analysis were investigated : (1) sputtering conditions, (2) X-ray source, (3) focus of analyzer, (4) angular dependence, (5) pass energy and (6) energy step of measurement. We found the measurement conditions that all participants in the round robin test could adopt.
Adsorption of ethers were carried out on fresh surfaces of transition metals (Cr, Fe and Ni) formed by scratching under high vacuum conditions. Adsorption rates increased proportionally with the scratching speed, that is, the formation rate of fresh surfaces, at the sample gas pressure of 8×10-4 Pa. The adsorption activity of ethers, which is estimated from the time-dependence curve of pressure decrease owing to adsorption, was affected by alkyl groups. The larger the electron releasing ability of alkyl groups, the higher the adsorption activity of the ether. The adsorption activity of 2-methyl tetra-hydrofuran was lower than that of tertahydrofuran. The result was explained by a steric hindrance of the methyl group. It is concluded that the adsorption activity of ethers was dependent on the electronic structure of lone pair electrons of the ether, even if the fresh surface was formed by mechanical treatment.
Metalorganic chemical vapor deposition (MOCVD) growth assisted by UV light illumination for nominally pure ZnS epitaxial films has been carried out in a low-pressure system. The effects of UV light (>3 eV) have been investigated using low-temperature photoluminescence (PL) measurement. As a result, an increase in Na-related emission lines and a reduction of deep level emission have been observed in the PL spectra. This suggests that the improvement of the crystallinity and introduction of the Na acceptor-impurity substituted on Zn lattice site occured during the epitaxial growth under UV light illumination. We consider that these effects arise from the migration enhancement of adsorbed Zn atoms and/or Zn vacancies by irradiation during the growth, which will lead to a significant change of Zn and S compositional ratio. Finally, we found it profitable to apply these UV light illumination effect to the Na acceptor doping, and thus carried out the photo-assisted Na doping in the same system. A typical PL spectral feature of p-type ZnS films can be successfully obtained.
The surface structure of κ- (BEDT-TTF) 2Cu (NCS) 2 [BEDT-TTF, his (ethylenedithio) tetrathia-fulvalene] crystal was studied by scanning tunneling microscopy (STM). The STM image over the crystal be plane has revealed the individual BEDT-TTF molecules, whose arrangement is in good agreement with the projected image of the bulk structure determined by X-ray diffraction. The alternative stacked structure of BEDT-TTF layer and Cu (NCS) 2 layer was also revealed by the measurement over the ab-plane.
There are many problems to be solved for SIMS analysis. In particular, true identification of the mass spectrum and accurate mass number tuning for the depth profile measurements of element concentrations are very important. The authors have developed and evaluated two standard mixture samples of the full mass range spectra. As a result, it was found that the standard mixture samples are practical and useful for accrate mass identification and can be used as reference samples for fast mass number tuning.
Cleavage plane surfaces of oxide superconductors, Bi2Sr2CuOν (2201 phase, Tc=20 K) and Bi2Sr2-Ca2Cu3Oν (2223 phase, Tc= 110 K), are examined by the high-resolution electron microscope profile imaging method. It is confirmed that the surfaces consist of single Bi0 plane indicating that the crystal is cleaved in the middle of two (BiO) 2 layers. It is also confirmed that incommensurate modulation in the bulk structure is preserved even at the cleavage plane to form wavy surface structure. The results are almost consistent with those previously reported for Bi2Sr2CaCu2Oν (2212 phase, Tc = 80 K).