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"Importance of questioning: From every day’s life to the discovery of a new type ReRAM" by Chang Uk Jung (Mon, 17 July 2023)

The Seminars and Training Committee kindly invites you to the following Periodical Lecture on topotactic Resistive Random Access Memories (ReRAM):

05 July 2023

Importance of questioning: From every day’s life to the discovery of a new type ReRAM

by Chang Uk Jung, Department of Physics, Hankuk University of Foreign Studies, Yong-in, South Korea


Monday, 17 July 2023
12 PM
ICMAB - Sala d'Actes Carles Miravitlles and ONLINE. Register here to attend by Zoom


“The important thing is not to stop questioning” is a famous sentence by A. Einstein. I applied this to basic textbook contents and everyday life and recently published a book whose potential readers span from 10s to 70s. At this talk, I introduce only a few original small examples. I found significant errors in handing ‘significant figures.[1-2] I = -dQ/dt is true in discharging capacitor? We can use the kinetic energy equation (E=(1/2)mv2) when deciding where to sit on a bus. What is the role of cord (Zipper Pull) Extension attached to the metal zipper pull?

 For the second part of the talk, I will stress on the discovery of topotactic Resistive Random Access Memories (ReRAM) rather than in their involved physics. ReRAMs had been regarded as a promising candidate to replace conventional Si-based memory. However, wide distribution in switching parameters observed for devices based on polycrystalline metal oxide thin films has been delaying practical applications.[3] After raising questions on the previous strategy to solve this problem, we discovered a new type of ReRAM by using oxides having a brownmillerite structure such as SrFeO2.5 and SrCoO2.5.[4-9] The multivalencey nature of Fe(Dr Jekyll and Mr Hyde) ion was found be very efficient way to get speed, stability, gradual switching.


  1. C. U. Jung. “Error in Handling Significant Figures in Polar Coordinates in University Physics Textbooks” New Physics: Sae Mulli, Vol. 71, No. 9, (2021), 771
  2. C. U. Jung et al. “Significant error in significant figures?” Journal of the Korean Physical Society (2021) 78:89
  3. S. C. Chae, C. U. Jung, et al, “Random circuit breaker network model for unipolar resistance switching”. Adv. Mater (2008), 20, 1154
  4. H. Jeen,, C. U. Jung, et al., “Topotactic phase transformation of the brownmillerite SrCoO2.5 to the perovskite SrCoO3-d”. Adv. Mater (2013), 25, 3651.
  5. O. T. Tambunan,, C. U. Jung et al., “ Resistance switching in epitaxial SrCoOx thin film”s. Appl. Phys. Lett. (2014), 105, 063507.
  6. S. K. Acharya, C. U. Jung et al., “Epitaxial Brownmillerite Oxide Thin Films for Reliable Switching Memory”. ACS Appl. Mater. Interfaces (2016), 8, 7902.
  7. S. Kumar Acharya,, C. U. Jung et al., ”Brownmillerite thin films as fast ion conductors for ultimate-performance resistance switching memory”. Nanoscale, (2017), 9, 10502.
  8. V. R. Nallagatla, C. U. Jung et al., ” Topotactic Phase Transition Driving Memristive Behavior ”. Adv. Mater. (2019), 1903391.
  9. USA patent (Reg. # US 10,886,466 B2), Reg. date Jan.5, 2021. Variable Resistor, Non-volatile memory element using the same, and method of fabricating


Bs.D and Ph. D at Seoul National University (1988-1999). Assistant, Associate, Professor (2004~present) at Hankuk University of Foreign Studies. Discovered ‘topotactic ReRAM’ in 2014. 135 SCI papers, citation 5500, H-index 35. Science advisor/general talk at TV and Press (KBS, SBS, tvN, YTN etc).

Hosted by Josep Fontcuberta, ICMAB-CSIC

If any of you would like a meeting with the speaker, please contact Josep Fontcuberta by mail at This email address is being protected from spambots. You need JavaScript enabled to view it. 

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