Sonoko Tsukahara

Determination of Evaporation Rate and Vapor Pressure of Organic Monomers Used for Vapor Deposition Polymerization

Thermogravimetry (TG) and the Langmuir equation have been employed for the determination of the temperature dependence of the evaporation rate and saturated pressure of monomers used in vapor deposition polymerization (VDP). The measuring process utilizes the evaporation of monomers in vacuum. The ranges of the evaporation rate and saturated pressure of monomers as determined by the TG technique are from 10-2 to 10-5 mol/m2s and from 1 to 10-3 Pa, respectively. Comparison of the evaporation rate vs temperature relation and the melting point of monomers determines whether the evaporation involves sublimation from a solid surface or evaporation from a liquid surface.

Measurement system for low outgassing materials by switching between two pumping paths

Abstract A method of switching between two pumping paths (SPP) has been developed to measure a low outgassing rate accurately by subtracting the outgassing of all the elemental parts of a measurement system. The mass spectra of only the sample can also be measured by the SPP method. To prove the capability of the SPP method, outgassing properties of two stainless steel chambers with different treatments were examined. One chamber was electrolytically polished and subsequently 450 °C vacuum baked, and the other was glass beads blasted. The specific outgassing rate of the electrolytically polished and vacuum baked sample was less than 1 × 10 −11 Pa · m · s −1 at 28 °C after in situ 150 °C bakeout. The outgassing species was only hydrogen which was mainly caused by diffusion from the bulk stainless steel chamber wall.

Observation of Initial Growth of In on Silicon(100) Surface

The initial growth of In on a Si(100) surface as a function of the coverage has been investigated using scanning tunneling microscopy (STM). In(2×2) is a frequently observed phase at coverages below 0.5 monolayer (ML), the In(2×1) phase appears at the coverage above 0.5 ML, and the coexistence of the In(2×2) and In(2×1) reconstructions becomes a dominant phase at the coverage between 0.5 ML and 1.0 ML. Further deposition of In above 1.0 ML gives rise to the onset of three-dimensional island nucleation and growth associated with layer-by-layer growth. The island is highly oriented with major axes along the directions. The island is located on the terrace adjacent to the step edge, suggesting that the step edge should be a preferred site for island nucleation.

An improved throughput method for the measurement of outgassing rates of materials

Abstract A modified throughput method using a system with an extremely high vacuum (XHV) pump was developed to determine the outgassing rate of a vacuum chamber type sample accurately eliminating the contribution of outgassing from the vacuum gauge. The up-stream and down-stream sides of an orifice were connected with two sets of bridges, each of which consisted of one gauge head on a T-tube and two valves to terminate the tube. Hence the combination of the space being measured and the gauge was selected by the valve operation. A mass spectrometer was also set to the similar bridge to analyse the outgassing species. The outgassing rates of the total and the gauge were measured using the different valve combinations and the true outgassing rate of the sample was that of their difference. The outgassing rate of an electrolytically polished stainless steel chamber with TiN inner coating was determined at various temperatures after baking at 150 °C. Only hydrogen was then released at a specific rate at room temperature, of 7 × 10 −11 Pa·m·s −1 , which was sufficiently low for use of the wall material in XHV equipment.

Initial stage of aluminum thin film growth on Si(100) surfaces as observed by scanning tunneling microscopy

Abstract The phases of aluminum (Al) adsorbed on Si(100)-2 × 1 surfaces were investigated by using scanning tunneling microscopy (STM). The changes were observed as a function of the Al coverage over the range from 0.5 to 9 monolayers (ML). The STM images revealed that once a well-ordered Al-2 × 2 adlayer is completed at 0.5 ML, further deposition of aluminum results in surface roughness and disappearance of the Al-2 × 2 phase. This is due to the formation of Al clusters that absorb the Al ad-dimers without disruption of the Si-2 × 1 structure. The structure of the Al-2 × 1 phase was not observed at coverages above 0.5 ML. As the growth proceeds, the pseudomorphic layer relaxes to form islands at 2 ML. These islands are highly oriented and have a prominent epitaxial relationship between Al(110) and Si(100). This indicates that the Si-2 × 1 structure has a strong effect on the epitaxial growth of the Al islands.

Outgassing properties and structure of TiN films on stainless steel substrates

Abstract An ultra high vacuum system of thermal desorption spectroscopy (TDS) was constructed in order to compare the outgassing property of many different short samples rapidly. TiN films deposited on stailness steel plates were measured by TDS. The property of the TiN film depended highly on the preparation technique and condition, i.e. the structure of the film. High bias voltage and low nitrogen pressure during the deposition process by hollow cathode discharge and reactive sputtering resulted in a low outgassing rate in the TiN films. The TiN film prepared at the controlled conditions worked as a gas barrier for hydrogen desorption from the stainless steel substrate and showed a lower outgassing rate than stainless steel under the same conditions (

Growth kinetics of aluminum on the Si(100) surface studied by scanning tunneling microscopy

Abstract The kinetic processes at the initial stage of Al on Si(100) were investigated as a function of the substrate temperatures by using scanning tunneling microscopy (STM). The experimental relationship between the island number density and the substrate temperature was obtained. It was found that there was a transition temperature T0 at which the island number density had a minimum value. The existence of the transition temperature was interpreted in terms of the competition between the reevaporation and capture of adatoms. Experimental results were quantitatively discussed through establishing the theoretical dependences of the island number density on the substrate temperatures below and above T0 by using probability analysis method. Then the adsorption energy Ea and the activation energy for surface diffusion, Ed, were determined.

STRUCTURES OF AL/SI(100) SURFACES AS DETERMINED BY SCANNING TUNNELING MICROSCOPY

The structures of Al/Si(100) surfaces with coverages below 0.5 monolayer have been determined using scanning tunneling microscopy (STM). Through careful STM measurements, Al dimers are atomically resolved, where the Al dimer bond is intuitively demonstrated to be parallel to the Si dimer bond. The atomic arrangements at the ends of Al dimer rows have been discussed on the basis of the interpretation of dual‐bias STM images. Two possible structures at the end of an Al dimer row are a single atom termination and a dimer termination, depending on whether the Al dimer row ends at a surface defect, respectively.