Postdoctoral researcher:  Strongly correlated oxides, Photovoltaic and Organic Field Effect Transistor under Prof. Vitaly Podzorov's supervision

  

Ph.D:  Functional (magnetic, electric) transport properties, Multiferroicity, Photovolataic and Non volatile RAM effect in transition metal oxides under  Prof. Sang-Wook Cheong's supervision in the R-CEM.

 

M.S: Development of Optical MEMS device and Design optical router using MOEMS and enhanced anisotropy wet eching technique with UV LED

 

Quantum well disordering for integrated optical devices in InGaAs/InGaAsP multi-quantum well system using by SiNx & SiO2 dielectric materials  

 

 Research Skills:


 Low & room temperature measurement 

        MPMS (Magnetic Property Mesurement System): temp. & magnetic field dependence of susceptibility

        PPMS(Physical Property Mesurement System): resistance,ac susceptibility and thermal conductivity

        I-V and C-V measurements, Photovoltaic and Field effect transistor measurement

 Growth of single & poly crystals (~400 samples)

     Flux method: e.g.Ca3Co2-xMnxO6, BiFeO3, Floating zone method: e.g. Ba2CoGe2O7, PLD (Pulsed Laser Deposition) method: e.g. MnV2O4

 Clean room fabrication

     Scanning Electron Microscope (SEM), E-beam and thermal evaporator, Sputtering, Photo lithography, Plasma-enhanced chemicalvapor deposition (PECVD), Photoluminescence, Ellipsometry, Rapid Thermal Annealing (RTA) etc 


 

Selected papers:


Hee Taek Yi, Bin Gao, Wei Xie, Sang-Wook Cheong, & Vitaly Podzorov “Tuning the metal-insulator crossover and magnetism in SrRuO3 by ionic gating.”,  Scientific Reports 4, 6604 (2014).

Hee Taek Yi, Marcia M. Payne, John E. Anthony & Vitaly Podzorov “Ultra flexible solution processed organic field-effect transistors.”, Nature communications 3, 1259 (2012).

H. T. Yi, Y. Chen, K. Czelen and V. Podzorov “Vacuum lamination approach to fabrication of high-performance single-crystal organic field-effect transistors”, Adv. Mater.  23, 5807-5811 (2011)

H. T. Yi, T. Choi, S. G. Choi, Y. S. Oh & S.-W. Cheong “Mechanism of the switchable photovoltaic effect in ferroelectric BiFeO3”, Adv. Mater. 23, 3403-3407 (2011).

H. T. Yi, T. Choi & Sang-Wook Cheong, "Reversible colossal resistance switching in (La,Pr,Ca)MnO3: Cryogenic nonvolatile memories" Appl. Phys. Lett. 95, 063509 (2009)

H. T. Yi, Y. J. Choi, S. Lee & Sang-Wook Cheong "Multiferroicity in the square-lattice antiferromagnet of Ba2CoGe2O7"Appl. Phys. Lett. 92, 212904 (2008)

2014


[1] Hee Taek Yi, Bin Gao, Wei Xie, Sang-Wook Cheong, & Vitaly Podzorov “Tuning the metal-insulator crossover and magnetism in SrRuO3 by ionic gating.”, Scientific Reports 4, 6604 (2014).

[2] Jae Wook Kim, Seunghyun Khim, Sae Hwan Chun, Y. Jo, L. Balicas, H. T. Yi, S.-W. Cheong, N. Harrison, C. D. Batista, Jung Hoon Han & Kee Hoon Kim “Manifestation of magnetic quantum fuctuations in the dielectric properties”, Nature Communications 5, 4419 (2014).  

[3] P. Lampen, N. S. Bingham, M. H. Phan, H. Srikanth, H. T. Yi & S. W. Cheong “Macroscopic phase diagram and magnetocaloric study of metamagnetic transitions in the spin chain system Ca3Co2O6” Phy. Rev. B. 89, 144414 (2014).

[4] Jae Wook Kim, Y. Kamiya, Eun Deok Mun, M. Jaime, N. Harrison, J. D. Thompson, V. Kiryukhin, H. T. Yi, Y. S. Oh, S.-W. Cheong, C. D. Batista & V. S. Zapf “Multiferroicity with coexisting isotropic and anisotropic spins in Ca3Co2−xMnxO6 Phy. Rev. B. 89, 060404(R) (2014).

2013


[5] B. Lee, Y. Chen, D. Fu, H. T. Yi, K. Czelen, H. Najafov & V. Podzorov “Trap healing and ultralow-noise Hall effect at the surface of organic semiconductors”, Nature Materials 12, 1125 (2013).

[6] U. Nagel, Randy S.Fishman, T. Katuwal, H. Engelkamp, D. Talbayev, Hee Taek Yi, S. -W. Cheong & T. Room Terahertz Spectroscopy of Spin Waves in Multiferroic BiFeO3 in High Magnetic Fields.”, Phys. Rev. Lett. 110, 257201 (2013).

2012


[7] Hee Taek Yi, Marcia M. Payne, John E. Anthony & Vitaly Podzorov “Ultra flexible solution processed organic field-effect transistors.”, Nature communications 3, 1259 (2012).

[8] Y. Chen, B. Lee, H. T. Yi, S. S. Lee, M. M. Payne, S. Pola, C.-H. Kuo, Y.-L. Loo, J. E. Anthony, Y. T. Tao and V. Podzorov “Dynamic character of charge transport parameters in disordered organic semiconductor field-effect transistors.”, Phys. Chem. Chem. Phys. 14, 14142 (2012).

[9] Y. M. Sheu, S. A. Trugman, Y.-S. Park, S. Lee, H. T. Yi, S.-W. Cheong, Q. X. Jia, A. J. Taylor & R. P. Prasankumar “Ultrafast carrier dynamics and radiative recombination in multiferroic BiFeO3”, Appl. Phys. Lett. 100, 242904 (2012).

2011


[10] H. T. Yi, Y. Chen, K. Czelen and V. Podzorov “Vacuum lamination approach to fabrication of high-performance single-crystal organic field-effect transistors”, Adv. Mater.  23, 5807-5811 (2011)

[11] M. Ramazanoglu, W. Ratcliff II, H. T. Yi, A. A. Sirenko, S.-W. Cheong & V.Kiryukhin “Giant effect of uniaxial pressure on magnetic domain populations in multiferroic bismuth ferrite”, Phys. Rev. Lett. 107, 067203 (2011).

[12] H. T. Yi, T. Choi, S. G. Choi, Y. S. Oh & S.-W. Cheong “Mechanism of the switchable photovoltaic effect in ferroelectric BiFeO3”, Adv. Mater. 23, 3403-3407 (2011).

[13] S. G. Choi, H. T. Yi, S. -W. Cheong, J. N. Hilfiker, R. France & A. G. Norman “Optical anisotropy and charge-transfer transition energies in BiFeO3 from 1.0 to 5.5 eV”, Phy. Rev. B. 83, 100101 (2011).

[14] D. Talbayev, S. A. Trugman, Seongsu Lee, Hee Taek Yi, S-W Cheong & A. J. Taylor “Long-wavelength magnetic and magnetoelectric excitations in the ferroelectric antiferromagnet BiFeO3”, Phy. Rev. B. 83, 094403 (2011).

<2010


[15] T. Choi, Y. Horibe, H. T. Yi, Y. J. Choi, W. Wu & S-W. Cheong “Insulating Interlocked Ferroelectric and Structural Antiphase Domain Walls in Multiferroic YMnO3”, Nature Materials 9, 253 (2010). 

[16] R. Flint, H. T. Yi, P. Chandra, S.-W.Cheong & V. Kiryukhin "Spin-state crossover in multiferroic Ca3Co2-xMnxO6 ”, Phys. Rev. B  81, 092402 (2010).

[17] H. T. Yi, T. Choi & Sang-Wook Cheong, "Reversible colossal resistance switching in (La,Pr,Ca)MnO3: Cryogenic nonvolatile memories" Appl. Phys. Lett. 95, 063509 (2009) [link]

[18] T. Lancaster, S. J. Blundell, P. J. Baker, H. J. Lewtas, W. Hayes, F. L. Pratt, H. T. Yi, & S.-W.Cheong, "Spin freezing and dynamics in Ca3Co2-xMnxO6 (x~0.95) investigated with implanted muons: Disorder in the anisotropic next-nearest-neighbor Ising model", Phys. Rev. B  80, 020409(R) (2009) [link]

[19] V. Kiryukhin, Seongsu Lee, W. Ratcliff II, Q. Huang, H. T. Yi, Y. J. Choi, & S-W. Cheong "Order by Static Disorder in the Ising Chain Magnet Ca3Co2-xMnxO6Phys. Rev. Lett. 102, 187202 (2009) [link]

[20] Y. J. Jo, S. Lee, E. S. Choi, H. T. Yi, W. Ratcliff II, Y. J. Choi, V. Kiryukhin, S. W. Cheong, & L. Balicas, "3:1 magnetization plateau and suppression of ferroelectric polarization in an Ising chain multiferroic" Phys. Rev. B 79, 012407(2009) [link]

[21] WeidaWu, V. Kiryukhin, H.-J. Noh, K.-T. Ko, J.-H. Park, W. Ratcliff II, P. A. Sharma, N. Harrison, Y. J. Choi, Y. Horibe, S. Lee, S. Park, H. T. Yi, C. L. Zhang, & S.-W. Cheong, "Formation of pancakelike ising domains and giant magnetic coercivity in ferrimagnetic LuFe2O4Phys. Rev. Lett. 101, 137203 (2008) [link]

[22] H. T. Yi, Y. J. Choi, S. Lee & Sang-Wook Cheong "Multiferroicity in the square-lattice antiferromagnet of Ba2CoGe2O7"Appl. Phys. Lett. 92, 212904 (2008) [link]

[23] Y. J. Choi, H. T. Yi, S. Lee, Q. Huang, V. Kiryukhin, & S.-W. Cheong, "Ferroelectricity in an Ising chain magnet" Phys. Rev. Lett.  100, 047601 (2008) [link]

[24] H. T. Yi, M. Thakurdesai, & M. A. Parker “Control of Sidewall Angles Using UV LEDs During Wet Etching of GaAs”, Electrochemical and Solid-State Letters, 7,C137 (2004)

[25] W. J. Choi, H. T. Yi, J. I. Lee, & D. W. Woo "“Dependence of the intermixing in InGaAs/InGaAsP Quantum Well on Capping Layer" J. Korean Phys. Soc. 45, 773 (2004)

[26] H. T. Yi, J. Cho, W. J. Choi, D. H. Woo, S. H. Kim, & K. N. Kang, "Dielectric cap quantum well disordering for band gap tuning of InGaAs/InGaAsP quantum well structure using various combinations of semiconductor-dielectric capping layers" J. Mat. Sci. Lett., 21, 1739 (2002)

[27] H. T. Yi, J. Cho, W. J. Cho, D. H. Woo, S. H. Kim, & K. N. Kang, "Dependence of quantum well disordering of InGaAs/InGaAsP quantum well structure on the various combination of semiconductor-dielectric capping layers" J. Mat. Sci. Lett., 19, 835 (2000)

[28] W. J. Choi, H. T. Yi, D. H. Woo, S. H. Kim, & J. Y. Cho, "Dependence of the Intermixing of an InGaAs/InGaAsP Quantum Well in Impurity Free Vacancy Disordering on the NH3 Flow Rate During the Growth of a SiNx Capping Layer" Sae-Mulli, 40, 349 (2000)

[29] H. T. Yi, W. J. Choi, D. H. Woo, S. H. Kim, & J. Cho, "Effect of Dielectric and Semiconductor Cap Layer Combinations in Impurity Free Vacancy Disordering of an InGaAs/InGaAsP Single Quantum Well Structure" Sae-Mulli, 41, 193 (2000)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bible

Nature

Science

Web elements  

NY times

Hibrain

 Holy bible  

Nature Materials

Advanced Materials

Crystallographic 

Washington Post

Facebook

Chanyang church

Nature Communications

Physical Review Lett.

Research ID

NPR news

Missycoupon

Our daily bread

Applied Physics Lett.

Web of knowledge 

Scifinder

Naver Dictionary

Exchange rate

Weather.com

Physorg

Pandora

Youtube

The Huffington Post

TED