Youiti Yamamoto

Study of a Si(110) surface by using reflection high-energy electron diffraction-total reflection angle X-ray spectroscopy and high temperature scanning tunneling microscopy

Abstract A “16 × 2” (16-structure) was only found on a clean Si(110) surface using reflection high-energy electron diffraction (RHEED). A detailed study using reflection high-energy electron diffraction-total reflection angle X-ray spectroscopy (RHEED-TRAXS) has shown that 5 × 4, 1 × 2, 1 × 5, 1 × 7 and 1 × 9 structures were formed when Ni adhered to a clean Si(110) surface with the 16-structure. It also showed that reversible phase transitions took place among the structures, namely 5× 4, 1 × 2, 1 × 5, 1 × 7 and 1× 9, depending on the amount of Ni deposition and the surface temperature. High temperature scanning tunneling microscopy (HTSTM) was applied to study the crystal growth of a (15, 17, 1) vicinal plane on a Si(110) surface. It was found that an impurity hillock, which must be a fine particle of SiC on the surface, pins step-flows and bunches them to form a vicinal plane, such as (17, 15, 1), (17, 15, 1 ), (15, 17, 1) and (15, 17, 1 ), at 710°C. A series of experimental results is reviewed in detail.

Scanning Tunneling Microscopy Study of the 16-Structure Appearing on a Si(110) Surface

High-resolution scanning tunneling microscopy (STM) was applied to observe the 16-structure appearing on a Si(110) surface. It was reaffirmed that the 16-structure coexisting with a facet structure was not found and could not be explained by the vicinal surface model. Bright and faint zigzag chains consisting of spheres, and the repetition of the upper and the lower layers with the height difference of 2.0 A were observed. Based on the above result, a structure model was proposed.

Study of the crystal growth of a (15,17,1) vicinal plane on a Si(110) surface using high‐temperature scanning tunneling microscopy

High‐temperature scanning tunneling microscopy was used to study the crystal growth of a (15,17,1) vicinal plane on a Si(110) surface, and the dynamic behavior of surface Si atoms at high temperature was directly observed. It was found that an impurity hillock, which may be SiC on the surface, pins step flows and bunches them together to form a vicinal plane such as (17,15,1), (17,15,1), (15,17,1), and (15,17,1) at 710 °C. The vicinal plane has a faceted structure and is formed by a periodic arrangement of monolayer steps and has a terrace of 2.5 nm in the 〈111〉 direction. The step‐edge direction is 〈112〉. At 695 °C, it was also found that the 16 structure was formed on a flat area. It was confirmed that the 16 structure and the vicinal plane (15,17,1) coexisted in a temperature range of about 700 °C to room temperature.

High-temperature scanning tunneling microscopy study of the phase transition of 16-structure appearing on a Si(110) surface

High-temperature scanning tunneling microscopy (HTSTM) has been developed which enables distortionless observation of the dynamic behavior of surface atoms at high temperatures up to 900°C on an atomic scale, and it was applied to analyze the mechanism of reversible phase transition between the 16-structure and the 1x1 structure appearing on a clean Si(110) surface. It has been found that, at first, the reconstruction and destruction of the 16-structure begin on the unit-cell level along the direction and then progress along the direction as a whole in order to complete the phase transition. The direct observation of the reconstruction at high temperatures is very important to investigate the mechanism of crystal growth.

High-Temperature Scanning Tunneling Microscopy Observation of a (15, 17, 1) Facet Structure on a Si(110) Surface

High-temperature scanning tunneling microscopy (HTSTM) was applied to observe a facet structure on a Si(110) surface. The facet structures of (15, 17, 1) and (17, 15, 1) and the 16-structure were observed at 655°C. The 16-structure was formed on flat parts. It was confirmed that the 16-structure and the facet structures of (15, 17, 1) and (17, 15, 1) coexisted on the surface on which hillocks are dispersed. The hillock may be a contamination.

High-temperature STM for atomic processes on semiconductor surfaces

Abstract This paper describes a new ultrahigh-vacuum scanning tunneling microscope (UHV-STM) which allows atomic-level observation as a function of temperature. It also reports on the use of this instrument for some high-temperature (HT) and low-temperature (LT) studies of semiconductor surfaces including various surface changes of the Si(111), Si(110) and Si(100) surfaces to new reconstructed structures at high temperatures, various surface behaviors, ultra-micro-processing; adsorption of different atom species and growth processes and low-temperature buckling structures of Si(100) dimer rows during ultra-low temperature observation.

RHEED-TRAXS study of superstructures induced by Au on a Si(110) surface

Abstract The Au/Si(110) system was investigated by RHEED-TRAXS (reflection high energy electron diffraction-total reflection angle X-ray spectroscopy). In this system, 1×2, 2×5 and (4, 0)×( 1 , 3) structures were formed depending on the amount of adsorbed Au. The respective structures transformed reversibly to the 1 × 1 structure at high temperatures. A two-dimensional phase diagram is obtained for the superstructures, aor these structures, arrangements of adsorbed atoms are deduced on the basis of RHEED-TRAXS.

Superstructures Induced by Ni Adsorption on a Clean Si(110) Surface Studied by Reflection High-Energy Electron Diffraction-Total Reflection Angle X-Ray Spectroscopy

Detailed study using RHEED-TRAXS (reflection high-energy electron diffraction-total reflection angle X-ray spectroscopy) has shown that 4×5, 5×4, 1×2, 1×5, 1×7 and 1×9 structures were formed when Ni adhered to a clean Si(110) surface with (11, 5)×(,2) structure. It also showed that reversible phase transitions took place among structures other than the 4×5 structure depending on the amount of Ni adsorption and the surface temperature. The atomic arrangements of Ni atoms of the 4×5 and 5×4 structures were deduced on the basis of the intensity analysis and RHEED-TRAXS results.

Time variation of the work function of field emitter tip surface and the development of adsorption of residual gas molecules studied by sawtoothlike emission current method

The sawtoothlike emission current (STEC) method and its theory are described, and this method is shown to make possible the simultaneous measurement of the time variation of the work function φ(t) and its derivative dφ/dt. Application of the STEC method to the field emission (FE) current from a tungsten emitter tip in an ultra-high vacuum of 2×10−8 Pa shows that the time variation of φ(t) and dφ/dt can be divided into four stages. In addition, it gives the effective tip radius αr0=1.1 μm, resulting in α=6.9 for the observed tip radius r0=0.16 μm. The observed time variation of φ(t) and dφ/dt is analyzed from the viewpoint of the development of the adsorption of residual gas molecules on the emitter tip surface, and each stage is successfully identified as follows: The first stage is the formation stage of adsorption nuclei and clusters, the second stage is the free growth stage of adsorption islands, the third stage is their coalescence growth stage, and the fourth stage is their Langmuir growth stage. Th...

Development of heating holders for the field-emission scanning electron microscope

We have developed a practical heating holder for the field-emission scanning electron microscope (FESEM, JSM-6000F) to study and apply the specimen heated and electron beam induced conductivity. The design is described in detail. A surface temperature up to 943 K is achieved. The temperature fluctuation is less than 0.5%/h at about 20 min after the heating up to 943 K, and the thermal drift is suppressed to less than 5 nm/min up to 873 K. The temperature of the observation area is proportional to the input power of the heater up to about 700 K. The charging on a nonconducting surface such as porous pipe glass can be prevented at a surface temperature above about 673 K. It is demonstrated that this is useful to the high resolution observations of the nonconducting surfaces.