11/30 Seminar Speech

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Speaker：Professor PI-HO HU

Organization：Department of Electrical Engineering, National Taiwan University  

Topic：Ferroelectric FET Non-volatile Memory

 Date：10:20 am , 2020.11.30

Location：Room 203, College of Engineering

Abstract；Artificial intelligence (AI) and Internet-of-Things (IoT) play a vital role in the future. For the von Neumann architecture, communication bottleneck between memory and processors becomes one of the most series problems due to low data throughput and high-power consumption. Non-volatile memory (NVM) based synapse and logic-in-memory circuit have been proposed to alleviate these problems. Ferroelectric Field-Effect-Transistor (FeFET) has been explored actively for emerging non-volatile memory and neuromorphic computing due to its high compatibility with CMOS platform. In this talk, I will introduce the operation principles and the challenges of FeFET memory. We have proposed a novel split-gate FeFET (SG-FeFET) for non-volatile memory and neuromorphic applications, which significantly improves the energy efficiency and reduces the power consumption. The reliability and endurance of SG-FeFET memory have also been improved owing to the lowered write voltage. SG-FeFET as a synaptic device has also been investigated including the non-linearity, asymmetry, and dynamic range of conductance updates.

11/23 Seminar Speech

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Speaker：Professor Chia-Shain Chuang

Organization：Department of Electronic Engineering, Chung Yuan Christian University  

Topic：Investigations for magnetoresistance of ultralow-hole-density monolayer epitaxial graphene grown on SiC systems

 Date：10:20 am , 2020.11.23

Location：Room 203, College of Engineering

Abstract；In this talk, I focus on detailed measurements on ultralow-density p-type monolayer epitaxial graphene, which has yet to be extensively studied. The measured resistivity ρxx shows insulating behavior in the sense that ρxx decreases with increasing temperature T over a wide range of T (1.5 K ≤ T ≤ 300 K). The crossover from negative magnetoresistivity (MR) to positive magnetoresistivity at T = 40 K in the low-field regime is ascribed to a transition from low-T quantum transport to high-T classical transport. For T ≥ 120 K, the measured positive MR ratio [ρxx(B) − ρxx(B = 0)]/ρxx(B = 0) at B = 2 T decreases with increasing T, but the positive MR persists up to room temperature. Our experimental results suggest that the large MR ratio (~100% at B = 9 T) is an intrinsic property of ultralow-charge-density graphene, regardless of the carrier type. This effect may find applications in magnetic sensors and magnetoresistance devices.
Keywords: epitaxial graphene, resistance standard, magnetoresistance, quantum hall

11/16 Seminar Speech

Hits:24

Speaker：Professor Pin-Jui Hsu

Organization：Department of Physics, National Tsing Hua University  

Topic：Proximity-Effect-Induced Superconductivity in Monatomic Ni-Pb Alloy and Ni Nanoislands

 Date：10:20 am , 2020.11.16

Location：Room 203, College of Engineering

Abstract；Proximity effect facilitates the penetration of Cooper pairs that permits superconductivity in normal metal with reduced dimensionality, offering a promising approach to develop novel quantum phenomena and emergent phases of matters in hybrid magnetic/superconducting nanostructures. Here, we have investigated proximity-induced superconductivity in monatomic Ni-Pb alloy and Ni nanoislands grown on Pb(111) by scanning tunneling microscopy/ spectroscopy (STM/STS) combined with theoretical calculations. Through elemental Pb superconducting substrate, tunneling conductance spectra have resolved an induced superconductivity with a gap size Δ about 0.85 meV in Ni-Pb alloy, which is about 0.11 meV smaller than Pb(111). On the contrary, Ni nanoislands with honeycomb lattice display a superconductivity gap with the same size of the Pb(111) substrate. From spatially monotonic decrease of Δ across the interface between Ni-Pb alloy and Pb(111), the decay length ξ_L about 5 nm has been extracted. According to the Usadel fittings and the BdG model, a weak ferromagnetism with an effective temperature about 6 ~ 15 K explains such rather short decay length as well as reduced superconductivity gap in the Ni-Pb surface alloy. As for honeycomb-structured Ni nanoislands, asymmetric edge scattering of surface electrons on Pb(111) has been revealed and further theoretical insights on the details of strong suppression of backscattering at the bearded type of edges are currently in progress.

11/02 Seminar Speech

Hits:58

Speaker:Dr. Tien-Ming Chuang

Topic: Visualizing Emergent Superconductivity by Spectroscopic Imaging - Scanning Tunneling Microscopy

10/26 Seminar Speech

Hits:123

Speaker: Professor Hsin-Jay Wu

Topic: Phase diagram engineering - A New Avenue Towards High Performance Thermoelectric Materials

10/19 Seminar Speech

Hits:65

Speaker: Professor Jan Chi Yang

Topic: Advanced Growth and Manipulation of Complex Oxides

10/12 Seminar Speech

Hits:72

Speaker: Mr. Ivan Li

Topic: Out of the giant tower, brave to create a life that takes a long journey

10/05 Seminar Speech

Hits:74

Speaker: Professor Yu-Lin, Joseph, Kuo

Topic: Surface Treatment on Metals via Atmospheric Pressure Plasma

9/28 Seminar Speech

Hits:86

Speaker: Dr. Tzu-Hung Chuang

Topic: Photoemission electron microscopy at Taiwan Light Source and Taiwan Photon Source