FI-STM Investigation of Fullerenes Adsorbed on the Semiconductor and Metal Surfaces(STM-C_<60>)

Our systematic investigation using field-ion scanning tunneling microscopy (FI-STM) is reviewed for the adsorption and film growth of fullerenes (C_, C_, C_, and C_) and metallofullerenes (Sc@C_/Sc_2@C_, Sc_2@C_, Y@C_, and Gd@C_) on the Si(100)-2x1, Si(111)-7x7, GaAs(001)-2x4-As, Cu(111)1x1, and Ag(111)1x1 surfaces. The fullerene molecules are stable on the Si(100)-2x1 and Si(111)-7x7 surfaces at room temperature because of the strong bonding to the substrate dangling bonds. As a result, unique intramolecular structures of C_ molecule are observed. The STM images of the C_, Sc@C_/Sc_2@C_, and Sc_2@C_ molecules are used to draw information on the molecular structures. In contrast to the Si surfaces, the fullerene molecules are mobile on the terrace of the metal surfaces and initially segregate to the step. A well-ordered two dimensional overlayer forms with a close-packed arrangement upon annealing the fullerene covered surfaces. On the Cu(111) surface, the commensurate (4x4) phase forms for the cases of the C_, C_ and C_C_ adsorption, indicating a strong interaction between the Cu substrate and fullerenes. Beautiful intramolecular structures of the C_ and C_ molecules are observed and are interpreted as the local mappings of the electron density of states. One-dimensional cluster formation of C_, Y@C_, and Gd@C_ on the step of the Cu(111)-1x1 surface is analyzed and the preferential dimer formation is only observed for the case of Y@C_, which is attributed to the interaction between the unpaired electrons of the Y@C_ molecules. On the Ag(111) surface, the C_ and Sc_2@C_ monolayer films show several phases that have an almost identical nearest neighbour distance but are rotated from each other. Among the systems studied, C_ on the GaAs(001)-2x4-As surface shows a unique highly-strained fcc(110)-oriented multi-layer film growth, while all other systems show the well-known fcc(111)-oriented multi-layer growth

Field Ion Microscopy of C_<60> Molecules(APFIM/FIM)

Field ion microscopy of C_ on the tungsten substrate showed that (1) the field ion image of the C_ adsorbate reflects the LUMO (lowest unoccupied molecular orbital)-induced local density of states of the C_, similar to the recent STM image of the C60 on the Cu(111)1 x 1 surface and that (2) the field evaporation occurs as a C_ molecule, in glaring contrast to the recent report by Ohmae et al

Recent Atom Probe Studies at IMR : a Comprehensive Review(APFIM/FIM)

This paper reviews our recent atom probe research activities conducted at Institute for Materials Research (IMR), Tohoku University, during a period of 1990 to date. The atom probe research started at IMR when the authors constructed an energy compensated time-of-flight atom probe in 1990. Since then, this instrument has been employed for various metallurgical problems, providing better understandings to mechanisms of microstructural evolution in various metallic materials. Notable achievements are studies of precipitation processes in aluminum alloys, nanocrystallization processes of amorphous alloys, microstructural characterizations of magnetic thin films and various other metallic materials. A new instrument equipped with a reflectron type time-of-flight atom probe and a position sensitive atom probe (PoSAP) was constructed in 1994. This instrument allowed three dimensional visualizations of atom distributions in alloys with an atomic resolution. PoSAP has been employed to characterize microstructures in Cr-Fe and Co-Cr(-Ta) magnetic alloys

Studies on the Relationship between Bone Strength and Bone Quality in Rats Fed with a Low-magnesium Diet

AbstractThe relationship between bone strength and bone quality in rats fed with a low-magnesium (low-Mg) diet was examined. Twenty four-week-old male Wistar rats were divided into a control group (n = 10) and a low-Mg group (n = 10). Each group was fed with a conventional diet or a low-Mg diet (Mg, 6 mg/100 g diet) for 8 weeks, respectively. After the rats were sacrificed, bone strength, bone mineral content (BMC) and three-dimensional (3D) trabecular structure of the lumbar vertebra were measured, respectively. The results showed that the values of the BMC were almost the same between the control and the low-Mg diet groups. On the other hand, the bone strength of the low-Mg diet group was significantly lower than that of the control group (p < 0.01). 3D trabecular structure analysis showed a significant decrease (p < 0.05 or 0.01) in the trabecular structure of the low-Mg diet group as compared to the control group. These findings suggest that the bone strength in this model is not affected by the BMC but is strongly affected by the trabecular structure. The low-Mg diet model is considered to be an excellent model for examining bone quality

Scanning Tunneling Microscopy Measurements of the Local Work Function around Steps on the Au/Cu(111) Surface(STM-local states)

With a scanning tunneling microscope we have taken local work function images of the Au/Cu(111) surface. The local work function measured from large Au-covered terraces is in good agreement with the result obtained by non-local techniques, and the local work function around step edges is significantly lower than that on terraces. The experimental details of the local work function lowering around a step can be reproduced nicely with a simple simulation if a dipole moment row with a proper linear density is put at the center of the step and if the influence of the topographic change of the step due to formation of the dipole moment is taken into account. It is demonstrated that STM has the ability to reveal the details of how local work function varies around steps and other defects on metal surfaces

Clustering and Precipitation Processes in Microalloyed Aluminium Alloys(APFIM/FIM)

Recent progress in understanding the origins of hardening in Al-1.7Cu-0.01Sn (at. %) and Al-1.1Cu-1.7Mg-(0.1Ag, 0.3-0.5Si) (at. %) microalloyed alloys is presented. The results of systematic studies involving atom probe field ion microscopy in conjunction with transmission electron microscopy indicate that the precipitation processes depend to a considerable degree upon the nature of pre-precipitate clustering reactions which occur early in the decomposition of the solid solution. Furthermore, it is shown that the presence of these co-clusters can influence significantly the alloy properties