Research Institute of Electrical Communication Tohoku University

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Yasuo Cho,Professor

Kohei Yamasue,Associate Professor

Yoshiomi Hiranaga,Assistant Professor

Yuji Yamagishi,Specially Appointed Assistant Professor

Y.Hiranaga K.Yamasue Y.Cho Y.Yamagishi

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Research Activities

The aim and target of the dielectric nano-devices laboratory are developing the research on the dielectric measurement of electronic materials using nano-technologies and applying its fruits to high-performance next generation electronic devices. It is also very important aim of our laboratory to bring up leaders of the next generation by cultivating young researchers and students through the research activities.

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Dielectric Nano-Devices (Prof.Cho)

Our main area of interest is evaluation and development of dielectric materials, including ferroelectric and piezoelectric materials and their application to communication devices and ferroelectric data storage systems.
Our measure contributions to advancement in these fields are the invention and the development of “Scanning Nonlinear Dielectric Microscope” (SNDM) which is the first successful purely electrical method for observing the ferroelectric polarization distribution without the influence of the shielding effect by free charges and it has already been put into practical use. The resolution of the microscope has been improved up to atomic scale-order. Therefore, it has a great potential for realizing the ultra-high density ferroelectric recording system. Our recent research achieved to fabricate an ultra-small domain inversion dot, which has the diameter of 2.8 nm in case of single dot fabrication, and achieved the recording density of 4 Tbit/inch in actual information storage, requiring an abundance of bits to be packed together. (Fig.2)
Moreover, we have started to make a measurement and an evaluation of flash-memory device and dopant profile in semiconductor devices using SNDM. (Fig.3) Because SNDM can detect very small capacitance variation, it can be a very powerful evaluation tool for various materials. Now SNDM evolves into a new evaluation technique for insulator material and semiconductor materials besides ferroelectric materials.

Research topics

  • Development of scanning nonlinear dielectric microscope (SNDM) with super high (atomic-scale) resolution.
  • Ultra-high density ferroelectric recording system using SNDM.
  • Atomically resolved imaging of dipole-induced local surface potential by newly developed scanning nonlinear dielectric Potentiometry (SNDP).
  • Evaluation of ferroelectric material and piezoelectric material using SNDM.
  • Evaluation of dopant profile in semiconductor devices (Si or SiC system etc.) using newly developed super-higher order scanning nonlinear dielectric microscopy.

Nanoscale Dielectric Measurement Systems (Assoc. Prof. Yamasue)

We intend to contribute future information and communication technology through the development of novel nano-scale dielectric measurement systems for the evaluation of the emerging electronic materials and devices. In particular, we are developing a new scanning probe potentiometry method called scanning nonlinear dielectric potentiometry for the atomic-scale quantitative investigation of material properties regarding electric polarization on surfaces and interfaces. By integrating the new method with the existing microscopy methods, we are also working on the establishment of a multifunctional scanning probe microscopy system towards the advanced analysis and characterization of the next-generation materials and devices including two-dimensional crystals (Fig.3).

Research topics

  • Development of noncontact scanning nonlinear dielectric potentiometry with atomic-resolution.
  • Development of atomic resolution multifunctional scanning probe microscopy and its application to the evaluation of the next-generation electronic materials and devices.

Fig1. Ultra-high density actual information storage using ferroelectric nano-domain manipulation (4Tbit/inch2)
Fig2. Dopant profile measurement of SiC power MOSFET
Fig3. Atomic resolution imaging of graphene on SiC by ultrahigh vacuum noncontact scanning nonlinear dielectric potentiometry