Abstract Details


Siv Sachin Shaji Deepa

Ph.D. student, Electrical and Electronic Engineering at University of Manchester

Siv Sachin Shaji Deepa

Ph.D. student, Electrical and Electronic Engineering at University of Manchester

Abstract Name:

Characterization of static water filled 2D-nanochannels via s-SNOM

Symposium:

Symposium B: Materials Discovery, Modification & Functionalisation

Topic:

B2: 2D Materials

Abstract Contributing Authors:

Siv Sachin S D1, Ravalika Sajja2, Radha Boya2, Ashok Keerthi3, Jessica L Boland1 1. Photon Science Institute, Department of EEE, University of Manchester, Oxford Road, Manchester, M13 9PL, UK. 2. Department of Physics and Astronomy, The University of Manchester, Schuster Building, Oxford Road, Manchester, M13 9PL, UK 3. Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK

Abstract Body:

Nano-FTIR has evolved into a platform for non-invasive nanoscale spectroscopy, owing to its ability to resolve unto tens of nanometres.  In this work, we investigate the layered behaviour of water and its isotopes (H2O and D2O) in 2D- nanochannels via infrared s-SNOM.
 
Nanometre-scale pores and capillaries have been studied extensively in recent years, owing to its importance in various natural phenomena and their numerous applications. The ability to artificially fabricate capillaries has enabled new research on molecular transport and led to the emergence of nanofluidics.

The 2D-nanochannel device consisted of SiN membrane on a Si substrate in which a hole of dimension 3 μm × 20 μm was made. A thin layer crystal MoS2 was exfoliated onto this to serve as the bottom layer. The second spacer layer was again which was etched into stripes with spacer width 130 nm and periodicity approximately the same and transferred onto the bottom layer. Lastly, a relatively thicker MoS2 crystal was transferred as the top layer for the device.

The Mid IR s-SNOM system uses difference frequency generation to output Mid Infrared pulses with a repetition rate of 80 MHz and a pulse duration of ∼ 100 fs. The ‘C’ and ‘D’ Sources with ranges 1020-1710 cm−1, 1175-2050 cm−1 and centre frequencies approximately 1333 cm-1 and 1666 cm-1 were chosen for our measurements such that it covers the bend modes of H2O and D2O. The optical images and mechanical phase images were used to identify the spacers and channels.

We observed peaks in the phase component corresponding to the bend mode of D2O (1029.4 cm-1) whilst observing at 1001 cm-1 which corresponding to plasmon polaritons using source C, although we couldn’t find a response from H2O with source D. The latter could possibly be because of lower probing depth or due to gold reference used which could have subsided the H2O response.

We performed s-SNOM measurements on 2D-nanochannels in its ‘dry’ and ‘wet’ states in the hopes of exploring the physical properties of static H2O and D2O. Although preliminary results, we observe prominent spectral signatures near the bend mode of D2O and a response from MoS2. By applying a finite dipole model to simulate the scattered amplitude and phase arising from the dielectric function of H2O and D2O layer, we further explore the dependence of our measured response with respect to the variation in the properties such as channel width, height and periodicity.

Attached Figure:

s-SNOM nanochannels.pdf

Submission Type:

Poster

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