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Sebastián Caicedo Dávila 
José Ferney Rivera Miranda 
Jaime Velasco Medina
Taken from: www.vernier.com 
James, D., Scott S. M., Zulfiqur Ali, O’Hare, W. Chemical 
Sensors for Electronic Nose System...
Taken from: Ilia A. Solov'yov,. “Vibrationally assisted 
electron transfer mechanism of olfaction: myth or 
reality?” Phys...
Taken from 1995 BBC Horizon documentary “A Code in the Nose” about Luca Turin's vibration theory of olfaction.
Very sharp energy levels can be used as allowed states, lessing the effect of 
thermionic excitation’s current. Such level...
Bias applied accross the TBH shifts the energy profile (and the QB states). 
Vibrational modes of an adsorbate at the midd...
InP Barriers 
Cu Electrode Cu Electrode 
InAs Wells 
InAs 
Wire 
InAs 
Wire 
Right 
Well 
Left 
Well 
Source Drain
En 
E4 
E3 
E2 
E1 
H 
... 
{Ψ} 
Stationary QM system: closed 
system represented WF 
doesn’t change in time. 
En 
E4 
E3 ...
e +i 
g 
2 
æ 
è 
ç 
ö 
ø 
÷F = EF 
E -e -i 
g 
2 
æ 
è 
ç 
ö 
ø 
÷F= 0 
E -e -i 
g 
2 
æ 
è 
ç 
ö 
ø 
÷F= S 
Homogeneous ...
Spectral function 
A(E) = i G(E) -G(E)é + 
ë 
In the Eigenstates Basis 
ù 
û 
Non-equilibrium density of States
Current as change in Electron Density 
Remember 
{F} = [EI -H - S]-1 
{S} 
i 
¶ 
¶t 
{F} = E{F} 
Equivalent to the Landaue...
Potential profile (dashed blue), LDOS in the wells regions (solid red and 
magenta) and transmission (solid black), showin...
Transmission coefficient vs. Energy for the system at thermal equilibrium. The 
transmission peaks (double due to bonding-...
I-V characteristic curve showing peaks and valleys (resonant device). The 
latter are the regions most suitable for gas se...
• A gas nanosensor, based on an InAs/InP triple-barrier 
heterostructure, devised to achieve high selectivity and detect 
...
• Consider a self-consistent potential in order to include space-charge 
effects. 
• Build and simulate a 3D model with fi...
Questions?
Electronic Transport Calculation of a Selective Gas Sensor Based on an InAs/InP Triple-Barrier Heterostructure
Electronic Transport Calculation of a Selective Gas Sensor Based on an InAs/InP Triple-Barrier Heterostructure
Electronic Transport Calculation of a Selective Gas Sensor Based on an InAs/InP Triple-Barrier Heterostructure
Electronic Transport Calculation of a Selective Gas Sensor Based on an InAs/InP Triple-Barrier Heterostructure
Electronic Transport Calculation of a Selective Gas Sensor Based on an InAs/InP Triple-Barrier Heterostructure
Electronic Transport Calculation of a Selective Gas Sensor Based on an InAs/InP Triple-Barrier Heterostructure
Electronic Transport Calculation of a Selective Gas Sensor Based on an InAs/InP Triple-Barrier Heterostructure
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Electronic Transport Calculation of a Selective Gas Sensor Based on an InAs/InP Triple-Barrier Heterostructure

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Slides of the oral presentation at the 9th Iberoamericano Congress on Sensors. Bogotá, October 2014

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Electronic Transport Calculation of a Selective Gas Sensor Based on an InAs/InP Triple-Barrier Heterostructure

  1. 1. Sebastián Caicedo Dávila José Ferney Rivera Miranda Jaime Velasco Medina
  2. 2. Taken from: www.vernier.com James, D., Scott S. M., Zulfiqur Ali, O’Hare, W. Chemical Sensors for Electronic Nose Systems. Microchimica Acta, 2005 Yi Cui, Qingqiao Wei Hongkun Park, Charles M. Lieber. Nanowire Nanosensors for Highly Sensitive and Selective Detection of Biological and Chemical Species. Science 2001 Larry Senesac and Thomas G. Thundat. Nanosensors for trace explosives Detection. Mat. Today 2008
  3. 3. Taken from: Ilia A. Solov'yov,. “Vibrationally assisted electron transfer mechanism of olfaction: myth or reality?” Phys. Chem. Chem. Phys., 2012,14 Vibration of protein alpha helix, taken from Wikipedia
  4. 4. Taken from 1995 BBC Horizon documentary “A Code in the Nose” about Luca Turin's vibration theory of olfaction.
  5. 5. Very sharp energy levels can be used as allowed states, lessing the effect of thermionic excitation’s current. Such levels (QB-states) can be created by confinement in 1D. Heterostructures are suitable candidates for the job. Semiconductor sensors are very effective and easily integrated with conventional electronics. A. P. Horsfield, L. Tong, Y.-A. Soh, and P. A. Warburton, “How to use a nanowire to measure vibrational frequencies: Device simulator results,” Journal of Applied Physics, vol. 108, no. 1, 2010.
  6. 6. Bias applied accross the TBH shifts the energy profile (and the QB states). Vibrational modes of an adsorbate at the middle PB can be excited by electrons that will lose energy and tunnel through the device, just as Turin’s theory proposes.
  7. 7. InP Barriers Cu Electrode Cu Electrode InAs Wells InAs Wire InAs Wire Right Well Left Well Source Drain
  8. 8. En E4 E3 E2 E1 H ... {Ψ} Stationary QM system: closed system represented WF doesn’t change in time. En E4 E3 E2 E1 H ... {Ψ} μ HR {ΦR} [τ] Coupling to the contacts broadens the discrete energy states.
  9. 9. e +i g 2 æ è ç ö ø ÷F = EF E -e -i g 2 æ è ç ö ø ÷F= 0 E -e -i g 2 æ è ç ö ø ÷F= S Homogeneous equation Non-homogeneous equation G = E -e -i g 2 æ è ç -1 ö ø ÷ Green’s Function {F} = [EI -H - S]-1 {S} G = i S- Sé * ë ù û
  10. 10. Spectral function A(E) = i G(E) -G(E)é + ë In the Eigenstates Basis ù û Non-equilibrium density of States
  11. 11. Current as change in Electron Density Remember {F} = [EI -H - S]-1 {S} i ¶ ¶t {F} = E{F} Equivalent to the Landauer Formula T (E) = Trace G1G G2G+ { }
  12. 12. Potential profile (dashed blue), LDOS in the wells regions (solid red and magenta) and transmission (solid black), showing the whole energy picture of the system at thermal equilibrium.
  13. 13. Transmission coefficient vs. Energy for the system at thermal equilibrium. The transmission peaks (double due to bonding-antibonding combinations) arise due to the alignment of quasi-bound states of the wells. The red dashed line shows the bottom of the conduction band.
  14. 14. I-V characteristic curve showing peaks and valleys (resonant device). The latter are the regions most suitable for gas sensing.
  15. 15. • A gas nanosensor, based on an InAs/InP triple-barrier heterostructure, devised to achieve high selectivity and detect vibrational modes of molecules was simulated at room temperature. • We proposed a simplified 1D model and used NEGF, and a single-band effective-mass Hamiltonian, to calculate the I-V characteristic curve of the semiconductor triple-barrier heterostructure at low computational expense. • We were able to demonstrate the plausibility of the device, by analyzing the LDOS in the wells regions, which showed that our model device would be able to sense different vibrational modes of SO2. • NEGF lets us include all kind of interactions between the system and external stimuli. We can include electron-phonon interactions and the interaction with vibrating molecules adsorbed at the device region, only by adding extra self-energy matrices.
  16. 16. • Consider a self-consistent potential in order to include space-charge effects. • Build and simulate a 3D model with finite cross-section, attached to metallic contacts. • Analyze the phonons of the simplified model, and build a self-energy matrix describing the electron-phonon interaction. • Calculate the Hamiltonian and self-energy matrices using self-consistent DFT. • Build additional self-energy matrices that describe the interaction of vibrating molecules with the device. • Determine the selectivity of the device by performing calculations of the interaction with several molecules.
  17. 17. Questions?

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