Yasuhiro Higashi

Differences between corrosion products formed on copper exposed in Tokyo in summer and winter

We analyzed the copper corrosion products that formed during a month in summer and a month in winter at three sites in Tokyo using several analytical techniques. The X-ray diffraction patterns revealed that cuprite Cu2O and posnjakite Cu4SO4(OH)6·H2O formed on copper exposed in summer. By contrast, only cuprite was found in winter exposed copper. The X-ray fluorescence results indicated that the amounts of sulfur and chlorine on the copper plates exposed in summer were much greater than those in winter. This could be explained by the change in particulate sulfate and sea salt concentrations. Depth profiling analysis by Auger electron spectroscopy revealed that the oxide layer formed in summer was thicker than that in winter. This difference in oxide layer thickness could have been due to the differences in temperature, relative humidity, and the amount of sulfur and chlorine on the copper plate.

Photoion detection with a wide dynamic range using a quadrupole mass spectrometer for nonresonant multiphoton ionization of sputtered neutrals

A sputtered neutral mass spectrometer using nonresonant multiphoton ionization by an excimer laser has been developed. The composition of this instrument is similar to the dynamic secondary ion mass spectrometer. Depth profiling with a wide dynamic range can easily be performed by the combination of a quadrupole mass spectrometer and pulse‐counting ion detection. The mass spectrum of photoionized neutrals of GaAs shows that the dynamic range of detection is more than six orders of magnitude and that the product of ionization efficiency and mass spectrometer transmission is about 2.1×10−3. The detection limit for Zn impurity in GaAs is under 1 ppm at a laser repetition rate of 50 Hz.

Depth Profiling of As in an AlAs/GaAs Multilayer by a New Laser-Induced Sputtered Neutral Mass Spectrometry System

Depth profiling of As in an AlAs/GaAs multilayer has been measured with a pulse-counting photoion mass spectrometer (PPMS) that can perform depth profiling in two different modes: a secondary ion mass spectrometry (SIMS) mode and a laser-induced sputtered neutral mass spectrometry (SNMS) mode. In SIMS mode, the As secondary ion intensity in GaAs layers is about three orders of magnitude less than that in AlAs layers under O2+ bombardment even though the As concentration is the same in both layers. In SNMS mode, the As photoion intensity in GaAs is only about twice that in AlAs. This difference can be attributed to sputtering yield differences between GaAs and AlAs. This result suggests that laser-induced SNMS by PPMS will give quantitative information and accurate depth profiling of layered samples by simply correcting sputtering yields.

Hydrogen measurements using new temperature-programmed desorption mass spectrometry system with double cryopanel-attached quadrupole mass spectrometers

The authors developed a temperature-programmed desorption mass spectrometry system equipped with two quadrupole mass spectrometers (QMSs) positioned in the line and out of the line of sight for a sample, respectively. This enables us to directly compare and discuss detection efficiencies and limits of detection of a gas species due to the QMS positions in the same desorption at the same time. Cryopanels are attached to cover the QMS heads, which function as cold traps to decrease interference from unexpected gas species, especially for eliminating the effect of water on hydrogen measurement. The authors evaluated and compared detection efficiencies during hydrogen measurements at room temperature and 50u2009K using standard hydrogen ion-implanted samples. The cold measurements enhanced detection efficiencies of hydrogen at both QMS positions since ionization efficiencies increased as a result of lowered velocity of the hydrogen molecules after collision with the cryopanels. The authors measured hydrogen conte...

A low‐energy reactive‐ion gun using an ECR ion source and acceleration‐deceleration system

A low‐energy reactive‐ion gun has been developed as a sputtering gun for high‐depth‐resolution analysis. It consists of an electron cyclotron resonance ion source and an acceleration‐deceleration system. The current density, the energy distribution, and the amount of impurity particles were measured to characterize the ion gun. The current density was estimated by measuring the ion current and the beam diameter for various ion beams. The maximum ion current density at 100 eV is 8.42 μA/cm2, and this means that it takes 19 s to sputter atoms on the monolayer of 1015 atoms/cm2 assuming that each ion sputters an atom. The energy width calculated from the full width at half maximum of the energy distribution was very narrow, 2 eV for the 15‐eV beam. The neutralization efficiencies evaluated by measuring secondary‐ion emission under bombardment by only neutral particles were 2.9, 0.5, and 0.33 for 1000‐eV Ar+, O2+, and BF2+, respectively. This order corresponds to the decreasing ionization potentials of the io...