arXiv subjects

Geetika Bhardwaj

Publications and source records attributed to Geetika Bhardwaj.

3 recordsLinked to original sources

arXiv2023

A compact and highly collimated atomic/molecular beam source

We describe the design, characterization and application of a simple, highly collimated and compact atomic/molecular beam source. This source is based on a segmented capillary design, constructed using a syringe needle. Angular width measurements and free molecular flow simulations show that the segmented structure effectively suppresses atoms travelling in off-axis directions, resulting in a narrow beam of Helium atoms having a width of 7 mrad (full width half maximum). We demonstrate an application of this source by using it for monitoring real-time changes in surface coverage on a clean Cu(110) surface exposed to oxygen, by measuring specular reflectivity of the Helium beam generated using this source.

physics.chem-ph↗

arXiv2022

Contrast inversion in neutral atom microscopy using atomic cluster beams

This work explores the possibility of atomic cluster beams as a probe for neutral atom microscopy (NAM) measurements. Using a beam of Kr clusters with mean size $\sim$ 10$^4$ atoms/cluster we demonstrate that topographical contrast can be obtained, similar to that in the case of monoatomic beams. Further, using atomically thin films of MoS$_2$ grown on SiO$_2$/Si substrate we show that NAM imaging using Kr clusters is also possible in domains where topographical contrast is not expected. Surprisingly, these images show an inverted contrast pattern when compared to the case of monoatomic beams. We attempt to understand these observations on the basis of angular distributions resulting from cluster-surface scattering. Finally, we discuss the implications of these results towards achieving a high lateral resolution neutral atom microscope using atomic cluster beams.

physics.chem-ph↗

arXiv2022

Neutral atom scattering based mapping of atomically thin layers

Imaging surfaces using low energy neutral atom scattering is a relatively recent development in the field of microscopy. In this work we demonstrate that this technique is sensitive enough to distinguish films as thin as a single monolayer from the underlying substrate. Using collimated beams of He and Kr atoms as an incident probe on MoS$_2$ films grown on SiO$_2$/Si substrate, we observe systematic changes in the scattered atom flux which allows us to map the thin MoS$_2$ films. Measurements carried out by varying incidence energy using both He and Kr provides insights into the details of atom-surface collision dynamics and its role in contrast generation.

physics.chem-ph↗