A Si nano-pillar grown on a Si tip by AFM in UHV for a high-quality scanning probe

金沢大学理工研究域　数物科学系We grow a Si nanopillar on a commercial Si tip on an atomic force microscopy (AFM) cantilever using AFM in ultrahigh vacuum for a high-quality scanning force probe, and observe noncontact-AFM (nc-AFM) images of Si (111) 7×7 and Ge deposited Si(111) with the nanopillar. We observe it ex situ by transmission electron microscopy to confirm its growth and crystallinity. The nc-AFM image clearly showed the high performance of the nanopillar as a probe with respect to the spatial resolution, image stability, and reproducibility. This nanopillar growth technique can elongate the lifetime of the cantilever and be applied to other materials. © 2005 American Institute of Physics

Electric conductance through chemical bonding states being formed between a Si tip and a Si(111)7x7 surface by bias-voltage noncontact atomic force spectroscopy

金沢大学理工研究域　数物科学系The change in electric conductance through bonding states being formed between a Si tip and a Si surface is examined by bias-voltage noncontact atomic force spectroscopy: current I and force interaction Δf (AFM cantilever resonance frequency shift) are simultaneously measured versus bias voltage V. A peak in I-V curves appears at close tip-sample separation over adatoms at the same V as a sharp peak in the Δf-V does. The peak possibly corresponds to channel formation through bonding states induced by changing V, leading to current saturation on tunnel barrier collapse with decreasing separation

Observation of Electronic States on Si(111)-7x7 through Short-Range Attractive Force with Noncontact Atomic Force Spectroscopy

金沢大学理工研究域　数物科学系The electronic states between Si(111) and a Si(111)-(7×7) surface was observed using the noncontact atomic force spectroscopy (nc-AFS). The nc-AFS provides new analytical prospects for force interaction between solid bodies, including metals. The spectra show prominent peaks and a broad peak, which are attributed to quantum mechanical resonance as the energy levels of sample surface states are tuned to those of the tip states by shifting the Fermi level through changing bias voltage. The energy level tuning by shifting the Fermi level has great potential for atom recognition and manipulation

Evidence of temperature dependence of initial adsorption sites of Ge atoms on Si(111)-7x7

金沢大学理工研究域　数物科学系Small amounts of Ge atoms are deposited on Si (111) -7×7 surfaces at room temperature (RT) and at 100 °C to clarify the initial adsorption sites using scanning tunneling microscopy. At RT Ge atoms are adsorbed at high coordination B2 sites around the rest atoms, as predicted by Cho and Kaxiras [Surf. Sci. 396, L261 (1998)]. On one hand, at 100 °C Ge atoms are adsorbed on corner adatom sites. With increasing Ge coverage the corner sites are gradually occupied, followed by Ge adsorption at center adatom sites, resulting in Ge cluster growth with a size of the half unit cell. © 2006 American Institute of Physics

Low-flux elucidation of initial growth of Ge clusters deposited on Si(111)-7x7 observed by scanning tunneling microscopy

金沢大学理工研究域　数物科学系Deposition of Ge on Si (111) -7×7 under very low Ge flux is examined using ultrahigh vacuum scanning tunneling microscopy; Ge atoms are deposited at 150°C under a flux of ∼0.005 or 0.05 ML/min. Initially Ge atoms are substituted for Si atoms on corner adatom sites of faulted half unit cells. At a Ge coverage of 0.08 ML under the lower flux, hollow-centered hexagonal Ge clusters with six protrusions are formed preferentially on faulted half unit cells, which are uniform and separated from other clusters. At the higher flux various types of clusters grow, frequently neighboring with others. This indicates that the low flux is needed to elucidate the stable type of Ge clusters grown on Si (111) -7×7. © 2009 The American Physical Society

Interplay between nonlinearity, scan speed, damping, and electronics in frequency modulation atomic-force microscopy

金沢大学理工研究域　数物科学系The importance of identifying effects that pertain to the operation of frequency modulation - atomic force microscopy (FM-AFM), and consequently those which do not was addressed. Numerical simulations of FM-AFM were carried out. It was found that the cantilever dynamics is conditionally stable and that there is a direct link between the electronics and the nonlinearity of the interaction may significantly affect the damping

Ge quantum dot arrays grown by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface: nucleation, morphology and CMOS compatibility

Issues of morphology, nucleation and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (<600 deg C) and high (>600 deg. C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts---pyramids and wedges---are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001) surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature.Comment: 30 pages, 11 figure

The HOG Pathway Dictates the Short-Term Translational Response after Hyperosmotic Shock

In the global osmoshock translational response in yeast, some gene products were translationally mobilized without transcriptional up-regulation. Conversely, other transcriptionally up-regulated mRNAs were translationally inhibited. Analogous changes occurred on the protein level. These translational responses were strongly dependent on Hog1 and Rck2