ENEE-698E

1st presentation by:

Saeed Esmaili Sardari

September 11, 2007

Piezoelectric Field Effect Transistor andNanoforce Sensor Based on a Single ZnO Nanowire

Xudong Wang, Jun Zhou, Jinhui Song, Jin Liu, Ningsheng Xu, andZhong L. Wang

School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, andSchool of Physics and Engineering, State Key Labof Optoelectronic Materials and Technologies, SunYat-Sen (Zhongshan) University, Guangzhou, 510275, China

NANO LETTERS 2006 Vol. 6, No. 12. 2768-2772

Presentation Outline Introduction

ZnO properties Piezoelectricity

FET NW FET

PEFET Structure Experimental results Theoretical explanations

Nanoforce sensor Conclusions and summary

Introduction ZnO is a II-VI compound semiconductor

Wurtzite crystal structure Hegzagonal closed pack ( HCP )

Direct wide band gap ~ 3.4 eV Conduction is primarily thru electrons Among the tetrahedrally bonded

semiconductors; highest piezoelectric tensor [or at least comparable to GaN, AlN ] The electromechanical coupling is high

FET Applied electric filed on the channel,

controls the current between source and drain

Nanowire FETs use a nanowire—a quasi 1 dimensional structure, as the channel NW might be exposed as the gate

or It can be attached to a gate contact

PEFET An FET without

gate electrode

A PEFET exploits the piezoelectric property of the NW to create the current controlling field

Structure “ZnO NWs were synthesized by the well-established

technique of thermal evaporation in a tube furnace. A single NW sample was prepared by aligning the NW

on the edge of a silicon substrate using a probe station. The extended length of the NW was 100 um, while the other side of the NW was fixed onto the silicon substrate by conductive sliver paint, through which the NW was connected to the negative electrode of the power source.

The silicon substrate was placed on the sample stage of an SEM with the NW pointing at the tungsten needle tip.”

Structure

Experimental Results

Theoretical Explanation

The drop in current can be attributed to the following 2 reasons:

Carrier Trapping due to induced charges Due to the compression and the stretch of the

ZnO NW, positively and negatively charged surfaces are produced

Channel narrowing due to depletion region expansion

Theoretical Explanation

Nanoforce Sensor

Nanoforce Sensor

Conclusions and Summary A new type of FETs are suggested Semiconducting and piezoelectric

properties of ZnO are key parameters of the new PE-FET

Nanoforce sensors can be fabricated using PE-FETs The major limitation is that the sensor should

work in linear region of the NW It can be used for forces <17 nN

PEFET can also be used in biosensros

References

1 Nano Letters, 2005, 5, 1954-1958

2 Science, 2001. 293, 1289-1292

Thanks

ZnO crystal structure

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Energy Triangle

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NW FET

Picture from ref#2

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Nanowire

Picture from ref#1 Back