Heated microcantilevers sensors

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Heated microcantilevers sensors
Heated microcantilever
IR image of the cantilever
Microcantilever with CNT sensing layers
The heated cantilever can be used as an excellent
sensor for (i) chemical analysis of trapped
molecules in the CNT layers, (ii) measuring
thermal properties of surrounding gases, and
(iii) various SPM probing methods, including
lithography
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Noise in piezoresistive microcantilever

• Electrical noise
• Johnson noise (Random thermal motion of carriers)
• 1/f low frequency noise (Carrier mobility
  fluctuation due to bulk defects or carrier number
  fluctuation due to surface traps)
• Vibration noise
• Thermo-mechanical noise (Random movement of
  molecular in air surrounding mechanical
  structures leads to random fluctuations in the
  energy transfer between structure and damping gas)

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Electrical noise
Johnson noise
SV Noise power spectrum density kB Boltzmann's
constant T Temperature R Resistance
R 1100 O Measurement bandwidth ?f 1 Hz
Deflection sensitivity 11e-5 per µm, Vbias
1.0 V
RMS noise JOHNSON 0.03 nm
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Electrical noise
1/f low frequency noise (Flicker noise)
SV noise power spectral density V2/Hz N
the number of carriers (depends on the
piezoresistor volume and implant dose) Vbias
bias voltage , f the frequency, n unity
(n1) a empirical coefficient depends on
annealing length
fmax 100 Hz fmin 1 Hz R 99.2 O Lr 54 µm Wr
14 µm Hr 2 µm Vbias 1 V µ 400 cm2/Vs kBT
0.026 eV a1.0e-6
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Vibration noise
Thermo-mechanical noise
L250 µm W140 µm H2 µm E 179GPa Q 69 w0
2pi 31.5 kHz KBT 0.026 eV k 3.11N/m B 1 Hz
Force noise spectrum density
At resonance
RMS noise TM 0.0013 nm
At resonance, Vac 5.0 sin (?t)

Minimum ?f 12 µV
P. G. Datskos, N. V. Lavrik, and S. Rajic,
Performance of uncooled microcantilever thermal
detectors, Rev. Sci. Intr., 75, 1134 (2004)
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Nanowire based chemical sensing
InN/In2O3 nano core/shell based FET sensor
Morphology
Probe current
SEM image
TEM image
Diffraction pattern
µ 150 cm2/Vs
J. Liu, Z. Cai, G. Koley, Charge transport and
trapping in InN nanowires investigated by
scanning probe microscopy, J. Appl. Phys. 106,
124907 (2009)
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Continued
TEM image of nano core/shell InN/In2O3 NWs
Vth shifted
SEM image of NanoFET
NO2 sensing
45 ppb (parts-per-billion) NO2 could be detected
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TMV nanofiber based sensor
TEM image of TMV nanofibers
Conductivity s 2.93 x10-5 O-1cm-1
Z. Niu, J. Liu, L. A. Lee, M. A. Bruckman, D.
Zhao, G. Koley, Q. Wang, Biological Templated
Synthesis of Water-Soluble Conductive Polymeric
Nanowires, Nano Lett. 7, 3729 (2007)
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Continued
Off
Methanol
On
Time (s)
Good selectivity toward Methanol and Ethanol
vapor
M. A. Bruckman, J. Liu, G. Koley, Y. Li, B.
Benicewicz, Z. Niu, and Q. Wang, Tobacco mosaic
virus based thin film sensor for detection of
volatile organic compounds, J. Mater. Chem. 20,
5715 (2010)