2008.3.6 Atomic Switch for making new type of electronic devices and systems Tsuyoshi Hasegawa WPI Center for Materials Nanoarchitectonics National Institute for Materials Science, Japan
Further Progress by Nanotechnology Nanotechnology driven Nano-electronics Si-electronics Performance Molecular Electronics Technology 4G DRAM Spin-Electronics Vacuum ULSI Alchemy of 20 th c. Technology Carbon-Electronics VLSI LSI Atomic Electronics IC Transistor Quantum Computing 1900 2050 1950 2000 Year
Key point for the further progress Miniaturization Using new functions by new materials & new structures Molecules & Atoms smallest building blocks
Atomic Switch D. M. Eigler et al., Nature 352 (1991) 600. OFF ON Atomic movement was achieved W tip by electrical field. Xe ON/OFF : 10 Ni K. Terabe et al., Nature 433 (2005) 47. OFF Atomic movement was achieved by solid electrochemical reaction. ON ON/OFF : >10 3
OUTLINE １． Mechanism and Characteristics ２． Application for Commercial Devices ３． New Type of Atomic Switch
Small Size and Low On-resistance Atomic switch Semiconductor Switch OFF OFF ON ON Electronic distribution is controlled Atomic movement is controlled. 10k ON resistance （Ω） GaAs-FET 1k MOSFET 100 10 Atomic switch 1 1 μ m 1mm 1nm Switch size
Operating Mechanism Ag 2+ δ S switched off switched on + + - - e - Ag + Ag 2 S Ag Pt S 2- Ag wire + + Ag Ag Ag e - e - + + - - Ag Ag + e Ag + e Ag 200 μ m
Ag nanowire growth by e-beam Ag 2 S Crystal
Single Ag protrusion growth by STM The two electrodes are fixed in the case of atomic switch operation.
Controlled growth and shrinkage 200 1: Vs= -2.0V It=0.05nA 2: Vs= -2.0V It=1.35nA 3: Vs=+2.0V It=0.05nA 4: Vs=+2.0V It=0.35nA 1 3 4 150 Change of tip height (nm) 1 3 4 1 3 4 100 50 3 1 2 2 3 1 2 3 1 0 0 2000 4000 6000 8000 Time (sec.) Ag Ag2S Ag tip - + sample sample bias K. Terabe, T. Nakayama, T. Hasegawa and M. Aono, J. Appl. Phys., 91 (2002) 10110.
Growth and Shrinkage speed of Ag 1 Ag 2+ δ S Rate of change in length of Ag protrusion (nm/sec.) shrink E +1.5 V 10 -1 +2.0 V +2.5 V Ag + +3.0 V Ag Ag + growth 10 -2 -1.5 V -2.0 V growth -2.5 V -3.0 V 10 -3 Ag + Ag D ｇ I t ・ 10 -4 0.0 0.4 0.8 1.2 1.6 Tunneling current (nA) shrink dN E – D It = A exp( ) dt kT Ag D s I t Ag + ・
Switching time vs. switching voltage Switching characteristics depend on the materials. Atomic switch using Α g 2+δ S Atomic switch using Cu 2- δ S Switching time t (s) Switching time t (s) Switching voltage V s (V) Switching voltage V s (V) : 1M Ω to 12.9 k Ω : 100 k Ω to 12.9 k Ω T. Tamura, T. Hasegawa, K. Terabe, T. Nakayama, T. Sakamoto, H. Sunamura, H. Kawaura, S. Hosaka and M. Aono, Jpn. J. Appl. Phys. 45 (2006) L364.
Two types of atomic switch ‘ with gap ’ and ‘ without dap ’ Switch Off Switch On Ag Ag 2 S Ag Pt Initial type of Atomic switch Switch On Switch Off Ti Cross-section of NanoBridge Cu 2 S Cu Cu Gapless atomic switch (NanoBridge TM )
Switching Mechanism of gapless atomic switch Operating Model Switch ON Cu Cu Cu Cu Pt Cu Pt Pt Pt Pt Applying Voltage Cu 2 S Ta 2 O 5 Cu + Growth toward Metal deposition Super-saturation Metal Bridge Cation formation Cu electrode parallel to electrode @ Pt electrode Formation and migration
OUTLINE １． Mechanism and Characteristics ２． Application for Commercial Devices ３． New Type of Atomic Switch
１ k-bit nonvolatile memory Sense Amp., Controller, etc. Decoder Decoder Cell array 50 µm T. Sakamoto, H. Sunamura, M. Mizuno, H. Kawaura, T. Hasegawa, K. Terabe, T. Nakayama and M. Aono, IEEE J. Solid-State Circuits 40 (2005) 168.
Apply to Programmable Devices Switch size reduces to 1/30, On-resistance reduces to 1/40. Nowadays Switch Atomic Switch Area = 120F 2 Area = 4F 2 On-resistance = 2k Ω On-resistance = 50 Ω F: minimum feature size New device “Programmable CBIC” is proposed. T. Sakamoto, H. Sunamura, M. Mizuno, H. Kawaura, T. Hasegawa, K. Terabe, T. Nakayama and M. Aono, IEEE J. Solid-State Circuits 40 (2005) 168.
Programmable CBIC It enables many functions by a single chip It enables many functions by a single chip ・ Larger number of fine-grain logic cells ・ Size reduction due to the small switches Chip size: 1/10th, or 10 times larger application Number of programs increases vastly. Logic cell Conventional FPGA Programmable CBIC FPGA: Field Programmable Gate Array CBIC: Cell Based Integrated Circuit
4x4 crossbar circuit Atomic switch Atomic switch Insulating film Au/Pt/Ti Cu 2 S Cu μ m 20 μ m 20 CMOS 4 X 4crossbar switch 1.8V 0.18µm CMOS logic INPUT T. Sakamoto, et al., Program 2 Program 1 IEEE J. Solid-State Circuits 40 (2005) 168. 10 μ sec. OUTPUT2 OUTPUT1
OUTLINE １． Mechanism and Characteristics ２． Application for Commercial Devices ３． New Type of Atomic Switch 1) Atomic Switch Array using AAO Template 2) Three terminal Atomic Switch 3) Photon-assisted Atomic Switch
Atomic switch array using AAO Ag 2 S/Ag nanorod and its switching property Electrochemical Electrochemical Removing (a) sulfurization template plating Ag 2 S Ag Ag Ag Ag 2 S Ag nanowire array Ag/Ag 2 S nanowire array Self-made porous-alumina template (~10nm pore) (b) “On” 2.0 Ag 1.5 1.0 I out (mA) Ag 2 S 0.5 Start 0.0 -0.5 Ag -1.0 “Off” -1.5 − -1.0 -0.5 0.0 0.5 1.0 V in (V) d ： 20 nm Ch. Liang, K. Terabe, T. Hasegawa, R. Negishi, T. Tamura and M. Aono, Small 10 (2005) 971.
3-terminal Atomic Switch For more controllability, large current, etc. - Source Gate Pt ＋ ＋ ＋ ＋ Cu ＋ ＋ ＋ ＋ ＋ ＋ ＋ Drain F. Xie et al., Phys. Rev. Lett., 93, 128303 (2004).
For more controllability, large current, etc. 3-terminal Atomic Switch
All functions enabled by a single chip using Atomic Switch GPS Sensor Ubiquitous Network Video decoder Robot Communication Cell phones High Performance Programmable Device MP3 decoder Digital TV Health care Car
１． Mechanism and Characteristics 1) Atomic Switch with 1 nm gap 2) Gapless Atomic Switch (Nano Bridge TM ) ２． Application for Commercial Devices 1) Nonvolatile Memory 2) Programmable Logic Device ３． New Type of Atomic Switch 1) Atomic Switch Array using AAO Template 2) Three terminal Atomic Switch 3) Photon-assisted Atomic Switch
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