time-correlated single photon counting (tcspc)
DESCRIPTION
Time-Correlated Single Photon Counting (TCSPC). Scott Thalman Brigham Young University Advisor: Dr. John Colton Dr Haeyeon Yang USU Physics Help from Mitch Jones, Steve Brown, Dallas Smith. Overview. Time-correlated single photon counting (TCSPC) measures photoluminescence (PL) lifetimes - PowerPoint PPT PresentationTRANSCRIPT
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Time-Correlated Single Photon Counting (TCSPC)
Scott Thalman Brigham Young University
Advisor: Dr. John ColtonDr Haeyeon Yang USU Physics
Help from Mitch Jones, Steve Brown, Dallas Smith
![Page 2: Time-Correlated Single Photon Counting (TCSPC)](https://reader033.vdocument.in/reader033/viewer/2022061602/56816156550346895dd0e003/html5/thumbnails/2.jpg)
Overview Time-correlated single photon counting
(TCSPC) measures photoluminescence (PL) lifetimes Pulsed laser illumination source Single-photon detectors Very fast timing module
100 picosecond time resolution with deconvolution
InGaAs Quantum Dots Optical properties are an indicator of
sample quality
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Photoluminescence
e-
e-
e-
Excitation Relaxation
Ground State(valence band)
Excited States(conduction band)
PhotonEnergy Gap
e-
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GaAs
Quantum Dots
Scanning tunneling micrograph of InGaAs
Quantum Dots on GaAs substrate
Dong Jun Kim et al 2008 Nanotechnology 19 47560
GaAs
QD
40 nm
InGaAs
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Quantum Dots Confined electrons must occupy
energy states that fulfill the Schroedinger equation
Results:• Discrete energy
levels• Discrete
luminescence wavelengths
http://www.vectorsite.net/tpqm_02.html
Ene
rgy
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QD Photoluminescence
1000 1200 1400
1E-12
1E-11
1E-10
1E-9
P
ower
(Abi
trary
Uni
ts)
Wavelength(nm)
120mW (889.5W/cm^2)180mW (1334.3W/cm^2)270mW (2001.5W/cm^2)
405mW (3002.2W/cm^2)
Sample 032607A, 3K, 780nm, .3s Tau, 8% Duty, Files 3-6, 2010-07-09
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Time Correlated Single Photon Counting
QDSample
Pulsed Laser~30 fs, center wavelength 800 nm
Si-APDDetector
Fast Photodiod
e Detector
Ortec Fast DigitizerTiming Module
Start
Stop
60 70 80 90 100 110 120
10000
100000
Laser: 1.6 mW (Focus 3.5in in front of sample)25-30fs pulse 4.5 minCard Thresh: Start Falling -0.3mV Stop Rising +0.34mVAOM: 300 ns delay 200 ns widthRef: 300 ns delay 30 ns width
File 314 Apr 2010 Haeyon Sample 032607-A
Cou
nts
Time (ns)
Lenses and Filters
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QD Fluorescence Lifetime Expected
Results
Mazur et al 2006 Journal Of Applied Physics 100 054313
Fluorescence lifetime of InGaAs Quantum Dot (fig 1) and Quantum Well (fig 2) samples measured by a streak camera.
Fig 2Fig 1
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70 75 80 85 90 95 1001E-3
0.01
0.1
1
Laser: 9 mW approximately 0.2W/cm^225-30fs pulse 2 min 3.7 K 510K countsCard Thresh: Start Falling -0.3mV Stop Rising +0.34mVAOM: 300 ns delay 200 ns widthRef: 300 ns delay 30 ns width
19 Apr 2010 All Samples Unfocused (normalized) Files 3-6
Cou
nts
Time (ns)
032607-B:t1= 1.56nst2= 3.7ns
032607-A:t1= 1.54nst2= 3.5ns
032907:t1= 1.77nst2= 3.7ns
IRF: t= 1.00ns
InGaAs QD Results
60 70 80 90 100 110 120
10000
100000
Laser: 1.6 mW (Focus 3.5in in front of sample)25-30fs pulse 4.5 minCard Thresh: Start Falling -0.3mV Stop Rising +0.34mVAOM: 300 ns delay 200 ns widthRef: 300 ns delay 30 ns width
File 314 Apr 2010 Haeyon Sample 032607-A
Cou
nts
Time (ns)
Instrument Response
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InGaAs QD Results:Convolution
( ) ( ) ( ) ( ) ( )f t g t h t f t g t t dt
Definition of Convolution
( ) ( ) 2 ( ) ( )FT f g FT h FT f FT g
Convolution Theorem
-4 -2 0 2 4 6 8 10
0.0
0.3
0.6
Apr 19 2010 Sample 032607-A (Focused) File 9
Data: g9_BModel: ExpDec1Equation: y = A1*exp(-x/t1) + y0Weighting: y No weighting Chi^2/DoF = 0.00004R^2 = 0.99916 y0 -0.00163 ±0.00177A1 0.74229 ±0.00585t1 0.64574 ±0.0106
Nor
mal
ized
Cou
nts
Time(ns)0 10
0.0
0.3
0.6
0.9
Nor
mal
ized
Cou
nts
Time(ns)
DeconvolutionIRFMeasured Data
Example Of Deconvolution using Sample 032607-A File 9
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Summary of Results
Sample Number
Photoluminescent Lifetime (ns)
Unfocused Laser
Focused Laser
032607-A 0.86 0.65
032607-B 0.78 0.78
032907 0.96 0.60
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Conclusion Using TCSPC we were able to measure
the photoluminescent lifetimes of self-assembled InGas QDs to help determine their quality.
Our samples had lifetimes of 0.6-1.0 ns. Using deconvolution we were able to
enhance our results. Future studies will determine if
quantum structures such as QD chains can be formed by this growth method.Thank
You