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Single Electron Devices. Vishwanath Joshi Advanced Semiconductor Devices EE 698 A. Outline. Introduction Single Electron (SE) Transistor SE Turnstiles SE Pump SE Inverters Metal, Semiconductor, Carbon nano-tube SE Memory. Introduction.

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single electron devices

Single Electron Devices

Vishwanath Joshi

Advanced Semiconductor Devices

EE 698 A

outline
Outline
  • Introduction
  • Single Electron (SE) Transistor
  • SE Turnstiles
  • SE Pump
  • SE Inverters
    • Metal, Semiconductor, Carbon nano-tube
  • SE Memory
introduction
Introduction
  • Devices that can control the motion of even a single electron
  • Consist of quantum dots with tunnel junctions
  • Simplest device
    • Single electron box
single electron box
Single electron box
  • Conditions for observing single electron tunneling phenomena
    • Ec > kbT
      • Ec = e2/2CΣ
    • Rt > Rk
      • Rk = h/e2 (25.8 KOhms)
single electron transistor
Single electron transistor
  • 3 terminal switching device

Current flows when Vg = ne/2Cg

turnstile
Turnstile
  • Single electron is transferred per cycle of an external RF signal
  • ΔEk = -e(|Q|k – Qck)/Ck
  • Qck = e(1+Cek/Ck)/2
  • Cek = capacitance of circuit in parallel with junction k
  • Ck = junction capacitance

Frequency Locked Turnstile Device for Single Electrons, Physical Review Letters, Vol 64(22), 28 May 1990, 2691

pumps
Pumps

Accuracy of electron counting using a 7-junction electron pump, Applied Physics Letters, Vol 69 (12), 16 Sept 1996, 1804

pumps contd
Pumps (contd.)
  • Al/Al2O3 structures have limited operational temperature and poor operational stability
  • Si-based SETs operate at higher temperature
  • Place MOSFETs near SET – control of channels

Electron pump by combined single-electron/field effect transistor structure, Applied Physics Letters, Vol 82 (8), 24 Feb 2003, 1221

fabrication
Fabrication
  • Fabricated on SOI substrate using standard MOS process
  • Formation of Si island by PADOX method
  • Dual gates made of Phosphorous doped poly-Si are defined
  • Again deposit Phosphorous doped poly-Si and define a broad gate covering entire pattern
measurements
Measurements
  • Measurements at 25 K
  • Vth of MOSFET1 = 0.3V
  • Vth of MOSFET2 =-0.2V
charge coupled device
Charge Coupled Device
  • 30 nm wide Si-wire channel and poly-Si gates defined by E-beam lithography

Current quantization due to single electron transfer in Si-wire charge coupled device, Applied Physics Letters, Vol 84 (8), 23 Feb 2004, 1323

si se inverter
Si SE Inverter
  • Twin Si single electron islands are formed by V-PADOX

Si complementary single-electron inverter with voltage gain, Applied Physics Letters, Vol 76 (21), 22 May 2000, 3121

se inverter contd
SE Inverter (contd.)
  • Working of Inverter
al al 2 o 3 se inverter
Al/Al2O3 SE Inverter
  • 25 nm thick Al patterned to form the lower electrodes
  • Al oxidized in an O2 plasma, 200 mTorr, 5 min, 200 oC
  • Second Al deposition

Single-electron inverter, Applied Physics Letters, Vol 78 (5), 19 Feb 2001, 1140

se inverter from carbon nanotubes
SE Inverter from carbon nanotubes
  • Tunnel barriers fabricated with the local irradiation of an Ar beam

Fabrication of single-electron inverter in multiwall carbon nanotubes, Applied Physics Letters, Vol 82 (19), 12 May 2003, 3307

references
References
  • Frequency Locked Turnstile Device for Single Electrons, Physical Review Letters, Vol 64(22), 28 May 1990, 2691
  • Accuracy of electron counting using a 7-junction electron pump, Applied Physics Letters, Vol 69 (12), 16 Sept 1996, 1804
  • Electron pump by combined single-electron/field effect transistor structure, Applied Physics Letters, Vol 82 (8), 24 Feb 2003, 1221
  • Current quantization due to single electron transfer in Si-wire charge coupled device, Applied Physics Letters, Vol 84 (8), 23 Feb 2004, 1323
  • Si complementary single-electron inverter with voltage gain, Applied Physics Letters, Vol 76 (21), 22 May 2000, 3121
  • Single-electron inverter, Applied Physics Letters, Vol 78 (5), 19 Feb 2001, 1140
  • Fabrication of single-electron inverter in multiwall carbon nanotubes, Applied Physics Letters, Vol 82 (19), 12 May 2003, 3307
  • A high-speed silicon single-electron random access memory, IEEE Electron Device Letters, Vol. 20, No. 11, November 1999, 583
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