Takashi Morii

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.

Radiative Auger study of transition-metal/silicon contacts

Abstract Silicon K-LL radiative Auger effect (RAE) spectra of annealed nickel/silicon and iron/silicon contacts together with that of a crystalline silicon were measured nondestructively using soft X-ray emission spectroscopy (SXES) apparatus. The K-LL RAE spectra give us similar information to K-edge X-ray absorption spectra, i.e. unoccupied p-electron density of states (DOS), while the SXES give us the information on occupied valence band DOS. We demonstrate that the single apparatus without synchrotron radiation facility can give the information on both occupied and unoccupied electron states. Also we carried out the similar analysis of the oscillation in the RAE spectra to that of the extended X-ray absorption fine structure (EXAFS) to obtain inter-atomic lengths around a central atom. The result for annealed nickel/silicon was in good agreement with the crystal data of NiSi2. The RAE and SXES complement each other in the investigation of buried interface.

Mn(Thin-Film)/Si(Substrate) Contacts: Analysis of the Buried Interface by Soft X-Ray Emission Spectroscopy

Electron-probe soft X-ray emission spectroscopy (SXES) has been applied to the nondestructive analysis of the buried interface of a Mn(thin-film)/Si(substrate) contact system, where the energy of the primary electrons, Ep, is varied below 20 keV. An important point of this analysis is that SXES gives a specific signal for each chemical element in different chemical bonding states. The Mn(thin-film)/Si(100) specimen not subjected to heat treatment did not show any additional phase except for Mn and Si at the interface region within the detection limit of the present experiment. The specimen subjected to heat treatment at 350°C for 3 min showed a layered structure of Mn/MnSi/MnSi1.7/Si(100) from the top to the substrate.