Non Gaussian noise in organic-inorganic structures

by Mr. Misha Chapsky

at Condensed Matter Seminar

Mon, 30 Mar 2020, 11:30
Sacta-Rashi Building for Physics (54), room 207


This seminar will be on Zoom *only* please see the details below.

Crackling noise in hybrid organic-inorganic, light sensitive structures has been investigated
using a test device consisting of a semiconducting field effect transistor (FET) with a light sensitive gate.
The gate is formed by nanocrystals (NCs) linked by organic self-assembled
monolayer (SAM) linkers to the surface of the FET. Non-Gaussian noise appears in
such a device in the form of series of avalanche-like events in the source-drain conductivity.
The measured noise shows hallmarks of crackling noise, such as self-similarity and power
law distributions of avalanches parameters. The origin of the crackling noise is attributed
to the phase transition in the SAM molecular structure between "all-trans" and "gauche"
structural configuration states of alkane molecules. Disordered gauche configuration in alkane
molecules is characterized by high potential barrier for electron transfer, while the ordered
all-trans configuration is characterized by relatively low barrier. The trigger that initiates
an avalanche is a spontaneous transition of a molecule from the gauche to all-trans state.
Avalanche propagation across the molecular layer is sustained by coupling between the adjacent
molecules and resulting subsequent transitions of neighboring molecules. The
avalanche-like structural transition results in FET conductivity changes due to photo-excited
charge carriers transfer from the illuminated NCs through the linkers to the transistor gate.
These charges are trapped in surface states, and released after some characteristic time back
to the NCs. In this work, we have investigated non-Gaussian component of FET conductivity
noise and found that crackling noise also appears in dark conditions after test device was
illuminated with high intensity laser. We have demonstrated that the relaxation crackling
noise properties in these conditions are almost identical to the previously observed crackling
noise under the illumination. We have proposed a plausible explanation for the crackling
mechanism in dark conditions. In addition, we have performed conductivity and noise measurements
of devices in which alkane molecular bridges were replaced by ones constituted of
aromatic benzene molecules, which are not known to undergo structural gauche to all-trans transition.
As expected, these devices did not show any crackling noise, further confirming
that crackling noise in the detector devices originates in the structural phase transition of
the self-assembled molecular layer.

Dganit Meidan is inviting you to a scheduled Zoom meeting.

Topic: Condensed matter seminar - Misha Chapsky
Time: Mar 30, 2020 11:30 AM Jerusalem

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Created on 20-02-2020 by Meidan, Dganit (dganit)
Updaded on 23-03-2020 by Meidan, Dganit (dganit)