Transcript esmaili_20070911.ppt

ENEE-698E
1st presentation by:
Saeed Esmaili Sardari
September 11, 2007
Piezoelectric Field Effect Transistor and
Nanoforce Sensor Based on a Single
ZnO Nanowire
Xudong Wang, Jun Zhou, Jinhui Song, Jin Liu, Ningsheng Xu,
and
Zhong L. Wang
School of Materials Science and Engineering, Georgia Institute of
Technology, Atlanta, Georgia 30332-0245, and
School of Physics and Engineering, State Key Lab
of 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 PEFET
 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
 Back
Energy Triangle
 Back
NW FET
Picture from ref#2
 Back
Nanowire
Picture from ref#1
 Back