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Department of Electronics Nanoelectronics 12 Atsufumi Hirohata 12:00 21/February/2014 Friday (D/L 002)

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Presentation on theme: "Department of Electronics Nanoelectronics 12 Atsufumi Hirohata 12:00 21/February/2014 Friday (D/L 002)"— Presentation transcript:

1 Department of Electronics Nanoelectronics 12 Atsufumi Hirohata 12:00 21/February/2014 Friday (D/L 002)

2 Quick Review over the Last Lecture ( Circular current ) is equivalent to a ( magnetic moment ). Origin of magnetism : Dipole moment arrangement : Paramagnetism Antiferromagnetism Ferromagnetism Ferrimagnetism (T C ) : Curie temperature (T N ) : Néel temperature PM AFM PM FM

3 Contents of Nanoelectonics I. Introduction to Nanoelectronics (01) 01 Micro- or nano-electronics ? II. Electromagnetism (02 & 03) 02 Maxwell equations 03 Scholar and vector potentials III. Basics of quantum mechanics (04 ~ 06) 04 History of quantum mechanics 1 05 History of quantum mechanics 2 06 Schrödinger equation IV. Applications of quantum mechanics (07, 10, 11, 13 & 14) 07 Quantum well 10 Harmonic oscillator 11 Magnetic spin V. Nanodevices (08, 09, 12, 15 ~ 18) 08 Tunnelling nanodevices 09 Nanomeasurements 12 Spintronic nanodevices

4 12 Spintronic Nanodevices Magnetoresistance Hard disk drive Magnetic random access memory Spin-polarised three-terminal devices

5 Recent Progress in Magnetoelectronics I - Giant Magnetoresistance * After K. Inomata, J. Magn. Soc. Jpn. 23, 1826 (1999).

6 Discovery of Giant Magnetoresistance * M. N. Baibich et al., Phys. Rev. Lett. 61, 2472 (1988); P. Grünberg et al., Phys. Rev. Lett. 57, 2442 (1986). Giant magnetoresistance ( GMR ) : [ 3 nm Fe / 0.9 nm Cr ] 60 * MR Ratio 50 % resistance change at 4.2 K MR H = 0H = Saturation Spin-valve OFF Spin-valve ON

7 How Can We Find a Hard Disc Drive ? Open your computer … This is a HDD !

8 Do NOT Try This at Home ! Open a metal frame of a HDD … Arm is operated by a linear motor with a very strong permanent magnet. - Arm moves ~ 100 times/sec. - Platter records data. - Platter rotates 5400 ~ rpm. Platter Magnet Arm

9 Video game Where Can We Find a Hard Disc Drive ? Most popular recording media now : Cheap Random access Large capacity High speed Non-volatility Infinite usage PC Hard disc recorder Data storage PDA Mobile phone mp3 player GPS navigation Digital camera Video camera

10 HDD Operation

11 HDD Writing / Reading Operation HDD writing operation : HDD reading operation :

12 Aerial Density Increase by GMR Introduction Aerial density growth of hard disk drives : * D. A. Thompson et al., IBM J. Res. Develop 44, 311 (2000). 30 % / yr. with AMR heads 60 % / yr. with GMR heads Superparamagnetic limit

13 Computer Operation In a computer, data is transferred from a HDD to a Dynamic Random Access Memory : * Data stored in a capacitor. Electric charge needs to be refreshed. DRAM requires large power consumption.

14 Gap between HDD and DRAM A gap between data storage and operation : *

15 Flash Memory In 1980, Fujio Masuoka invented a NOR-type flash memory : * * 1 byte high-speed read-out Low writing speed Difficult to integrate In 1986, Fujio Masuoka invented a NAND-type flash memory : No 1 byte high-speed read-out High writing speed Ideal for integration Flash erase for a unit block ( 1 ~ 10 kbyte ) only !

16 Solid State Drive with Flash Memory Solid state drive (SSD) started to replace HDD : pureSi introduced TB SDD in 2009 : Data transfer speed at 300 MB/s Slow write speed For example, a system with a units of 2kB for read / out and 256 kB for erase : in order to write 1 bit, the worst case scenario is 128 times read-out 1 time flash erase 128 times re-write

17 HDD vs Flash Memory Demand for flash memories : Price of flash memories : *

18 Advantages of MRAM * After K. Inomata, J. Magn. Soc. Jpn. 23, 1826 (1999). MRAMFeRAMFLASHDRAMSRAM1'' HDD Non- volatality Read time 300 ns (GMR) <60 ns (TMR) 100 ~ 200 ns 50 ns ~ 10 ms Write time< 10 ns~100 ns ~ 10 s ~ 10 ms Repetition> ~ Cell density6 ~ 12 F 2 8 F 2 4 F 2 Chip capacity > 1 Gb< 10 Mb> 1 Gb Power< 10 mW> 10 mW > 1 W Soft error hardness Process costRT processHT process Lower bit cost Lowest bit cost

19 Magnetic Random Access Memory * S. S. P. Parkin, 1 st Int'l Sch. on Spintronics and Quantum Info. Tech., May 13-15, 201 (Maui, HI, USA). Basic operation of magnetic random access memory (MRAM) :

20 MRAM Demonstration Freescale (now EverSpin Technologies) 4 Mbit MRAM : ** *

21 Improved MRAM Operation Required writing currents for several techniques dependent upon cell size : * S. Nakamura, Y. Saito and H. Morise, Toshiba Rev. 61, 40 (2006). Write current (mA) MRAM cell size (µm) Current-induced magnetisation reversal J C ~ 10 7 A / cm 2 (Current technology) Ampère-field-induced magnetisation reversal with a ferromagnetic overlayer (Current technology) Ampère-field-induced magnetisation reversal without a ferromagnetic overlayer (Current technology) Current-induced magnetisation reversal J C ~ 10 6 A / cm 2 Current-induced magnetisation reversal J C ~ A / cm 2

22 Current-Induced Magnetisation Reversal Anti-parallel (AP) parallel (P) reversal in a GMR / TMR junction : * M. Oogane and T. Miyazaki, Magnetic Random Access Memory, in Epitaxial Ferromagnetic Films and Spintronic Applications, A. Hirohata and Y. Otani (Eds.) (Research Signpost, Kerala, 2009) p Spin-transfer torque ** ** J. Slonczewski, J. Magn. Magn. Mater. 159, L1 (1996); L. Berger, Phys. Rev. B 54, 9353 (1996).

23 Recent Progress in Magnetoelectronics II - Tunnel Magnetoresistance * After K. Inomata, J. Magn. Soc. Jpn. 23, 1826 (1999).

24 Spin-Dependent Electron Tunneling Jullière's model : FM / insulator / FM junctions * * M. Jullière., Phys. Rep. 54A, 225 (1975). (r ) r Atom 1Barrier 4p4p 4s4s 3d3d Atom 2

25 TMR for Device Applications Recent progress in TMR ratios : ** S. S. P. Parkin, 1 st Int'l Sch. on Spintronics and Quantum Info. Tech., May 13-15, 2001 (Maui, HI, USA). > 400 % TMR ratio has been achieved ! > Gbit MRAM can be realised. NOT following Jullière's model : ** TMR = 2P 1 P 2 / ( 1 - P 1 P 2 ) * M. Jullière., Phys. Rep. 54A, 225 (1975).

26 Improved Tunnel Barriers Conventional amorphous barriers : * * After S. Yuasa et al., 28th Annual Conference on Magnetics, Sep , 2004 (Okinawa, Japan). 1 2, 5 Disorder at the interface : FM over-oxidation lattice defects Disorder at the interface : FM over-oxidation lattice defects island growth of the barrier Defects in the barrier Epitaxial (oriented) barriers : * 1 2, 5

27 Recent Progress in Spintronics * After K. Inomata, J. Magn. Soc. Jpn. 23, 1826 (1999).

28 Spin-Polarised Three-Terminal Devices Input Output Gate Voltage FM / SC hybrid Structures Magnetic tunnel junctions (MTJ) All metal and spin valve structures Interface Ohmic / Schottky barriers Tunnel barriersOhmic (no barrier) Spin carriersSCTunnel barriersNon-magnetic metals Device applications FM / 2DEG Schottky diodes Spin FET Spin LED Spin RTD MOS junctions Coulomb blockade structures SP-STM Supercond. point contacts Spin RTD Johnson transistors Spin valve transistors * After M. Johnson, IEEE Spectrum 37, 33 (2000).

29 Major Spin-Polarised Three-Terminal Devices Spin FETSpin LEDSpin RTDCoulomb blockade Input Spin-polarised electrons / holes Spin-polarised electrons / holes Spin-polarised electrons / holes Spin-polarised electrons SourceFerromagnets (FM) Dilute magnetic semiconductors (DMS) Double tunnel barriersFerromagnets (FM) GateBias voltage DrainFerromagnets (FM)Quantum wells (QW) Ferromagnets (FM) Output Electrical signals - Spin-polarised electrons / holes Circularly polarised electroluminescence (EL) Electrical signals Notes Low temperature High magnetic field Low temperature Refs. S. Datta and B. Das, Appl. Phys. Lett. 56, 665 (1990). Y. Ohno et al., Nature 402, 790 (1999). T. Gruber et al., Appl. Phys. Lett. 78, 1101 (2001). K. Yakushiji et al., Appl. Phys. Lett. 78, 515 (2001).

30 Spin Valve / Magnetic Tunnel Transistors * R. Sato and K. Mizushima, Appl. Phys. Lett. 79, 1157 (2001); D. J. Monsma et al., Science 281, 407 (1998); S. S. P. Parkin, 1 st Int'l Sch. on Spintronics and Quantum Info. Tech., May 13-15, 2001 (Maui, HI, USA). Spin valve transistor : * Magnetic tunnel transistor : Combining semiconductor with GMR / TMR devices : First step towards all metal devices


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