My Research and Inventions

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Contact:


Dr. Vadym Zayets


Spintronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Room C314b,
Umezono 1-1-1, Tsukuba,
Ibaraki-ken 305-8568, Japan.

 

tel: +81-298-61-5426
fax: +81-298-61-3432

email:
v.zayets (at symbol)gmail.com
v.zayets (at symbol)aist.go.jp
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Research fields:

Spintronics, nano photonics, optoelectronics, nano electronics, silicon photonics, magneto-optics, nano-electronics, nano-fabrication

Research objectives:

  • Developing of optical non-volatile memory with operation speed above 1 TBit/sec, where the data recorded by photo-excited spin-polarized electrons.
  • Developing of a transistor, in which a semiconductor is replaced by a metal, for a dense 3D integration of electronic circuits.

Research achievement in short:

In 1995 I proposed to use diluted magnetic semiconductor (DMS) as a material for the integrated optical isolator. Advantage of DMS is that the DMS isolator can be integrated with semiconductor laser diode and amplifier. In 2001 I won NEDO project for the realization of DMS waveguide isolator, which in 2006 was completed with successful demonstration of the isolator. For the success of DMS waveguide isolator I received award from Japanese Magnetic Society.

In 1999 I invented new type of the optical isolator, which is made of ferromagnetic-metal/semiconductor hybrid. It has many benefits for the integration. In 2001 I won JST project to fabricate such isolator, which in 2006 was completed with successful demonstration of the isolator. Furthermore, several other groups were followed my idea with demonstration of the isolator.

In 2004 I invented a new type of non-volatile optical memory, which operational speed exceeds several TBit/sec. In 2006, I won NEDO project to fabricate it. The prototype device was fabricated. Demultiplexing at 2.2 TBit/sec was demonstrated. Functions of reading, writing and multiplexing function were demonstrated, studied and optimized.

In 2009 I proposed a new design of a plasmonic isolator. In 2012 I demonstrated a plasmonic isolator integrated on a GaAs substrate. In 2015 I demonstrated integration a plasmonic isolator with Si nanowire waveguides. In 2016-2017 I developed a new fabrication technology of plasmonic waveguides with very low optical loss.

In 2016 I obtained a very high ~25 % magneto-resistance in a FeBTb nanowire with a periodical Pt electrode. In 2017 I was granted a patent on a design and fabrication of an all-metal transistor

2017-2018 I developed a new measurement method, which allows a high- precision measurements of coercive field, retention time and Δ of a magnetic nano structure. Using this method, a high-precision measurements on the VCMA effect in FeB:MgO and (FeB/W)n : MgO nanowires were demonstrated with sensitivity better than 0.2 Oe/V.

Academic & Professional Experience:

1994 - 2000: postdoc researcher, AIST, Tsukuba, Japan

2000 - till now: Senior Research Scientist, Spintronics Research Center, AIST, Tsukuba, Japan

Education:

1984-1994 graduate and postgraduate study, Quantum Radiophysics Department, Kiev University, Final degree (03.1995): Ph.D. in Physics.
Thesis "Anisotropic planar waveguides for non-reciprocal elements of
integrated optics". Adviser: Prof A.Solomko

Awards :

  • "Excellent Research Price" of Magnetic Society of Japan, 2004.09
  • Award of Ukraine cabinet council for young researchers, 1995

Research Projects (Principal Investigator) :

  • "Next generation magneto-optical element for broadband networks", Industrial, technological research promotion with cooperation with Photo-Crystal Co. Ltd, NEDO, 2001-2006, 100,000,000 yen, 5 years (Initially 3 years, extended to 5 years due to successful results).(Final report)
  • "Spin-light function element for high-speed networks", The Ministry of Education, Culture, Sports, Science and Technology (MEXT) young researchers promotion project,2001-2006, 70,000,000 yen 5 years. (Final report 1) , (Final report 2)
  • "Spin-photon nonvolatile memory". Industrial, technological research promotion,NEDO,2006-2009, 60,000,000 yen, 3 years.
  • "Plasmonic isolator for Photonic Integrated Circuits (PIC)" Kahenhi, 2016-2019 20,000,000 yen, 3 years

Main Research results :

  • 1) Realization of a semiconductor-based magneto-optical waveguide isolator for high-speed optical network .
    Magnetic garnets are used as a magneto-optical material for isolator, but the integration of the isolator with semiconductor laser diode and amplifier was impossible, because incompatibility of the magnetic garnets with semiconductors. I proposed to use diluted magnetic semiconductor (DMS) as a material for the waveguide optical isolator. Due to the high quality of the film and optimized device structure, I obtained the low optical loss, high Faraday effect, low dispersion of magneto-optical constants, high magneto-optical figure-of-merit and high isolation in wide wavelength range. Performance of DMS isolator, which was fabricated on semiconductor substrate, was better that that of conventional garnet isolator.
  • 2) Proposal of ferromagnetic-metal-semiconductor amplifier hybrids as new spintronics optical function devices
    Ferromagnetic metals have large magneto-optical effect. However they have never been used for magneto-optical device for optical communication because of their huge optical loss. I have proposed a new idea, i.e. ferromagnetic-metal-semiconductor amplifier hybrids . It can work as an optical isolator that can be very small and integratable into optoelectronics circuits with a simple process. My proposal attracted much attention, and some groups of Tokyo University and IMEC, Belgium (European Isolaser project) have started up research projects to realize it. In 2004, I demonstrated isolation effect in the hybrid isolator.
  • 3) Realization of Room-Temperature magnetic semiconductors.
    While ferromagnetic semiconductor is indispensable for spintronics applications, its ferromagnetic Curie temperature has been far below room temperature. Several years ago, my group succeeded to create a first room-temperature ferromagnetic semiconductor (Zn,Cr)Te. I did an essential contribution to this work by using my ability to grow high quality magnetic semiconductors films.
  • 4) Proposal on non-volatile optical memory with operational speed above 1 TBit/sec. Magnetic random access memory (MRAM) is quickly emerging technology. However, any magnetic memory has limitation of recording speed due to the magnetization reversal time (500 -2000 ps). To overcome this problem, in 2004 I invented new type of non-volatile optical memory, which is expected to operate at speed of several TBit/sec. It uses unique properties of light-spin interaction. Demultiplexing at 2.2 TBit/sec was already demonstrated. Functions of reading, writing and multiplexing function were demonstrated, studied and optimized.
  • 5) Fabrication of a plasmonic isolator for Photonic Integrated Circuits (PIC)
  • 6) Proposal on transistor, in which a semiconductor is replaced by a metal, for a dense 3D integration of electronic circuits.
  • 7) High-precision measurements of the voltage controlled magnetism in ferromagnetic nanowires.

 


    Major Skills :

1) Nano- and micro fabrication (see here)

  • design and optimization a multi-layer fabrication process, which involves several steps of a photo-lithography (a stepper) and a EB lithography and a high precision alignment;
  • I am an expert in EB lithography. (a) fabrication of a ultra-small device (size~ 30-50 nm); (b) fabrication of a complex device of a complex shape; (c) fabrication of long devices (nanowire waveguides); (d) a precise alignment (~10-20 nm) between different steps of EB lithography
  • growth a high- quality thin films of III-V semiconductors ((AlGaIn)(AsP)), II-VI semiconductor (CdZnMnCrTe), ferromagnetic metals (FeCoB,FeBTb) and oxide (MgO) using MBE and sputtering methods.

2) Optical measurements

  • fiber/waveguide measurements. (a) high-precision alignment (b) high-speed evaluation ( up to 100 GHz); (c) fabrication of a semiconductor waveguide, a semiconductor optical amplifier, a semiconductor laser diode, a Si nanowire waveguide and a plasmonic waveguide
  • pump-probe measurements (a) conventional pump-probe (b) phase-locked pump-probe (c) fiber-based pump-probe.

3) Automatization of experiment and fabrication technology

  • Software. I am expert in LabView, VisualBasic and Visual C++.
  • Multi- instrument automatic measurements. High-speed automatic measurements
  • Automatization of the fabrication technology

4) Magneto-transport measurements

  • Evaluation of nano-size spintronics devices
  • High-precision measurements of coercive field (~0.1 Oe), anisotropic field, retention time, effective magnetization and delta using the Hall effect
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I will try to answer your questions as soon as possible

 

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