Yutaka Oyama
Tohoku University, Japan
Title: Synthesis of 2D layered semiconductor GaSe for the application of Terahertz non-destructive inspection
Biography
Biography: Yutaka Oyama
Abstract
Terahertz (THz) wave has both superior characteristics of radio wave and light, in which high permeability for non-polar materials and efficient reflection from metal surface are principal features. Thus, THz wave reflected from the opaque coated metal surface can be used for nondestructive testing (NDT). In addition, specific inter molecular vibrations (finger print spectra) of soft and hard materials are appeared in THz frequency region. We have developed various THz wave generators by careful control of lattice vibrations in semi conducting GaSe crystals. THz wave has low quantum photon energy, thus it is safe for human tissues even for radiation. We have established a data base of terahertz permeability characteristics for industrial materials and successfully constructed non-destructive THz diagnosis of building blocks, polymers, insulated copper cable and hot-dip galvanized steel sheet, etc. For the efficient THz light sources, two-dimensional (2D) layered GaSe has been attracted much interest because of its superior crystallographic, optical features and even for spintronics. Layered crystals combine thin sheets by out-of-plane Vander Waals interactions. For the use of practical applications, mechanical strength needs to be improved. However, no direct experimental determination has been performed up to now for Vander Waals bonding energy. In our group, a precise tensile testing machine was constructed for the quantitative determination of the inter layer Vander Waals bonding force. In this study, low temperature liquid phase growth of GaSe and its characterization are shown with the improvement of Vander Waals bonding energy by the addition of Te and In. Then, some killer applications of THz wave for the health evaluation of infrastructures will be shown.