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Sep 19 2006 Condensed Matter Seminar Department of Physics / NTHU. Metal-stable excited states in closed quantum dot probed by Al-SET. Jeng-Chung Chen. Metal-stable excited states in closed Device characterization Excited electronic states in closed QD Discussion Conclusion - PowerPoint PPT Presentation
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Metal-stable excited states in closed quantum dot probed by Al-SET
Jeng-Chung Chen
Sep 19 2006Condensed Matter SeminarDepartment of Physics / NTHU
Outline
Metal-stable excited states in closed
• Device characterization
• Excited electronic states in closed QD
• Discussion
• Conclusion
On-chip optical-coupled QH devices
• Passive THz scanning microscopes
• Emitter: Hot spots
• Detector QH detector
• Device design
• Future perspective
Introduction: Technological and biological length scales
Single Electron Transistor - Introduction
Lateral Confinement Technique
Shadow Evaporation Technique
Al
SEM picture
100nm
Eg. diameter ~ 0.5-0.2mCg ~100-10 aFC ~2-0.9 fF
Capacitive Charging Model
Lithographic size of QD : 570nm560nm
Device Characterization
(a)
Temperature: 70-100mK
)(20)(800
groundedin source/dra :
ACVDCVV
QD
SDSET
Meta-stable states of QD observed by Al-SET
F0
Qualitative Discussion
V1=-1.18V
V1=-1.18V fixedIn closed QD, regime 2-6
QDQDQD
QDQD
QDQD
NC
eVeU
NC
eVeU
NC
eVeU
2
2,
2
,12,1
2
,22,2
2
21
22
2,12,2,2 QD
Discussion: Emperical Model
QDcsg
SET Ue
CV
e
CN
2
12 2)(
Cc~58.8aF, C1sg2=3.12aF
U1U2
UQD
e
UVeU
e
UVeU
QDQDQDQD
QDQDQDQD
,12,,12,1
,22,,22,2
2)(1
2)(2
233.0 ,0122.0
885.0 ,33.0
,12,,12,11
,22,,22,22
QDQDQD
QDQDQD
Quantitative discussion
1. Kinetics of charging and discharging of closed quantum dots (QD) in a GaAs/AlGaAs heterostructure crystal are studied by an Aluminum single electron transistor (Al-SET) electrostatically coupled to the quantum dot.
2. The period and conductance of CB peaks of Al-SET associated with different gating conditions reveal several distinct regimes, strongly depending on the tunneling barriers of QD.
3. A lift-up and an uncovered sinking electron excited state with long life time are realized in the completely closed dot.
4. An empirical model is proposed to explain the physical origins of these transitions.
Conclusion – First part
Ref: J.C. Chen, et al. Phys. Rev. B, 74, 045321 (2006).
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