Masahiko Kusaka

Structural analysis of the heat-treated 4H(6H)-SiC(0001)Si surface

Abstract We have investigated heat-treated 4H- and 6H-SiC(001)Si surfaces using AES, LEED, EELS and STM in ultra high vacuum (UHV). √3 × √3 and 6 × 6 reconstructions were observed in the STM study at ∼1000 and ∼1200°C, respectively. On the other hand, 6√3 × 6√3 superstructure was observed by LEED at ∼1200°C. The AES p-p height ratio of Si ( LVV ) C ( KLL ) decreased at higher temperatures. EELS proved the existence of a graphite layer on top of the specimen surface. Considering these experimental results, the 6 × 6 reconstruction observed by STM can be explained as a moire pattern produced by a graphite layer sitting on top of the SiC surface.

Preparation of manganese silicide thin films by solid phase reaction

Abstract A thin film formation of MnSi and MnSi 1.7 on a silicon substrate through solid phase reaction has been studied, where MnSi 1.7 is one of the few semiconducting silicides, while MnSi is a metallic one. The growth process and electronic states of manganese silicides with composition of MnSi and MnSi 1.7 are investigated by several methods, including soft X-ray emission spectroscopy.

Construction of a Soft X-Ray Emission Spectroscopy (SXES) Apparatus and Its Application for Study of Electronic and Atomic Structures of a Multilayer System

A soft X-ray emission spectroscopy (SXES) apparatus was constructed using a grating monochromator. The resolution was sufficient to show differences in valence electronic structures of Si compounds including pure Si crystal. A nondestructive analysis of a Ni/Si(111) specimen with heat treatment was carried out using either a clear difference in Si L2,3 SXES spectra of Ni silicide and Si single crystals or the fact that the soft X-ray production depth increases in a solid with increasing energy of a primary electron, Ep. The electronic and atomic structures of the surface and interface of specimens adopted were clarified with Ep varying between 1.5 and 10 keV.

A new application of soft X-ray spectroscopy to a non-destructive analysis of a film/substrate contact system: Carbonized-layer (ultra-thin-film)/Si(100)

Abstract Valence band, Si L2.3 and C K, soft X-ray spectroscopy (SXS) by the electron excitation method has been applied for the first time to a non-destructive analysis of hetero-interfaces, i.e. Si(100) surfaces with an ultra-thin-film on top, and the valence band spectra show a clear change from that of pure SiC to that of pure Si with the primary electron energy, Ep, from 0.85 to 4 keV. The present work explores the usefulness of this new application of the SXS method by studying experimentally the carbonized-layer (ultra-thin-film)/Si(100) system and the following results were obtained: the carbonized-layer is found to be a thin SiC layer which grows uniformly on the Si(100) surface, the SiC/Si(100) interface shows a rather sharp transition to the Si substrate and the thickness of the SiC layer is estimated to be ≲ 20 nm with possible undulation.

Annealing effect on surfaces of 4H(6H)SiC(0001)Si face

Abstract We have investigated 4H- and 6HSiC(0001)Si faces prepared by heat treatment using Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) in ultra high vacuum (UHV). The following were elucidated: 3 × 3 reconstruction was observed on the surface prepared at ∼ 1000°C, while 6 × 6 superstructure was observed for a specimen prepared at ∼ 1200°C. The 6 × 6 reconstruction can be explained as a moire pattern produced by a graphite layer sitting on top of SiC surface. Also AES p-p height ration of Si(LVV) C(KLL) decreased at a higher temperature for 4HSiC than for 6HSiC, which could be due to the fact that the bond strength of 4HSiC is more than that of 6HSiC.

Analysis of Heat-Treated 6H-SiC(0001) Surface Using Scanning Tunneling Microscopy

A scanning tunneling microscopy in ultrahigh vacuum (UHV) has been used to study hexagonal (6H) silicon carbide (0001)Si face prepared by heat treatment. √3 x √3, 6 x 6 and 3 x 3 reconstructions were observed above 1100°C. With increasing heat-treatment temperature, surface structure changed drastically and step heights decreased to that of a double layer. The 6 x 6 and 3 x 3 reconstructions can be explained as the structure of a graphite layer on the SiC surface and as the structure proposed by Kaplan, respectively.

Thin film silicon compound growth mechanisms : CrSi2/Si(001)

Abstract CrSi2 is grown on Si(001) substrate with solid-phase reaction. Samples are prepared by one-step annealing and their structure is analyzed with transmission electron microscopy. A new epitaxial growth relation is found, that is, CrSi2(001)//Si(001) with CrSi2(110)//Si(110).

Nondestructive depth profiling using soft X-ray emission spectroscopy by incident angle variation method

We constructed a sample reclining stage for soft X-ray emission spectroscopy (SXES), where we intended to carry out nondestructive depth profiling using an incident angle variation (IAV) method. The penetration depth of an incident electron decreases with a reclining sample stage. One of the characteristics of the IAV method is that the incident electron beam energy is constant; thus, it is easy to obtain information related to a quantitative analysis of the integrated intensity of soft X-ray emission spectra. This method has been applied for a specimen with NiSi2/Si(111) structure. We have analyzed the change in shape of the Si L2,3 emission band spectrum in a region of the Si substrate to the NiSi2 layer, and have shown that we can determine the distribution of the Si element from the integrated intensity of Si L2,3 emission spectra.

Non-destructive Analysis of Buried Interfaces and Surface Layers: X-Ray Emission Spectroscopic Study

Soft X-ray emission spectroscopy (SXES) and extended X-ray emission fine structure (EXEFS) studies have been carried out on a heat-treated thin-film(Ni)/substrate(Si, SiC) contact system using a conventional X-ray micro-analysis (XMA) apparatus. We have successfully deduced information either the chemical bonding or atomic configuration by the former and the latter, respectively. Also, we have succeeded in analyzing an interface buried rather deep below an overlayer, e.g., more than a hundred nm. This is due to the fact that both an X-ray production depth of an energetic electron is much larger than the mean free path of an energetic electron and the mean free path of an X-ray photon in a solid is large. Namely, in the surface, or interface layer, Ni2Si and NiSi2 formation have been clarified for heat-treated Ni/SiC and Ni/Si systems, respectively.

Soft X-ray emission spectroscopy study of CaF2(film)/Si(111) : non-destructive buried interface analysis

Abstract A soft X-ray emission spectroscopy (SXES) study under an energetic electron irradiation is first applied to a non-destructive buried interface analysis of a CaF 2 (film ∼ 40 nm)/Si(111) contact system, where the energy of primary electrons, E p , is ≤ 5 keV. The present work has explored the usefulness of the application of the SXES method to the interface study to give rise to the following findings: the CaF 2 /Si(111) interface shows rather sharp transition from the top CaF 2 to the substrate Si, there certainly is a Ca-silicide layer at the CaF 2 /Si(111) interface, the thickness of the silicide layer is estimated to be less than several nm, and the e-beam excited SXES non-destructive study is very powerful to analyze a specimen with rather thick top film (> 40 nm) and thin interface layer (