Single electron devices
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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


Si se inverter contd

Si SE Inverter (contd.)


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


Al al 2 o 3 se inverter contd

Al/Al2O3 SE Inverter (contd.)

  • Working of Inverter


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


Se inverter from carbon nanotubes contd

SE Inverter from carbon nanotubes (contd.)

  • Working of the Inverter


Memory

Memory


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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