Academic

Published scientific research:

Title: Fabrication and Application of Atomic-scale Silicon Structures

Authors: Achal, R.

Description: PhD Thesis, 2020. Nominated for Faculty of Science dissertation award.


Title: Detecting and Directing Single Molecule Binding Events on H-Si(100) with Application to Ultra-dense Data Storage

Authors: Achal, R., Rashidi, M., Croshaw, J., Huff, T., Wolkow, R.A.

Description: In this work we demonstrate the ability to electronically detect changes of charge at the atomic scale down to one electron. We use this sensitivity to illustrate the detection of single molecule reactions on a silicon wafer. We then show that we can direct the reaction of single molecules of hydrogen, letting us use them as molecular erasers to improve the speed of atomic-scale fabrication. We then demonstrate the writing and erasure of a small atomic-scale memory with this new technique.

Journal: ACS Nano, 2019. This article was selected and featured as an ACS Editors’ Choice article.


Title: Electrostatic Landscape of a Hydrogen-Terminated Silicon Surface Probed by a Moveable Quantum Dot

Authors: Huff, T., Dienel, T., Rashidi, M., Achal, R., Livadaru, L., Croshaw, J., Wolkow, R.A.

Description: In this work we show that a moveable quantum dot probe on a hydrogen-terminated silicon surface can be used to map the electrostatic potential in local nanometer-sized regions. This technique can help us determine the effects of the fields caused by subsurface dopant atoms on the behaviour of atomic-scale devices.

Journal: ACS Nano, 2019


Title: Binary Atomic Silicon Logic

Authors: Huff, T., Labidi, H., Rashidi, M., Livadaru, L., Dienel, T., Achal, R., Vine, W., Pitters, J., Wolkow, R.A.

Description: In this work we demonstrate the first realization of binary computer logic at the atomic scale using dangling bonds on the hydrogen-terminated silicon surface. With the new computational architecture, Binary Atomic Silicon Logic (BASiL), we were able to move just six atoms to create a field controlled logical ‘OR’ gate. This work lays the foundation for ultra-low power atomic-scale circuits.

Journal: Nature Electronics, 2018


Title: Lithography for robust and editable atomic-scale silicon devices and memories

Authors: Achal, R., Rashidi, M., Croshaw, J., Churchill, D., Taucer, M., Huff, T., Cloutier, M., Pitters, J., Wolkow, R.A.

Description: In this work we present a complete lithography process for the fabrication of devices and memories on the hydrogen-terminated silicon surface. A hydrogen removal procedure for scanned probe microscopes is outlined, along with the demonstration of a new hydrogen replacement/repassivation procedure that does not require an atomic force microscope. Additionally, the largest perfect structures created on this surface were showcased in the form of an ultra-dense rewritable atomic memory, highlighting important aspects of scalability.

Journal: Nature Communications, 2018. This article was placed in the Top 50 Physics Collection 2018, ranking 18th most popular.


Title: All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics

Authors: Rashidi, M., Vine, W., Burgess, J. A., Taucer, M., Achal, R., Pitters, J. L., Loth, S., Wolkow, R.A.

Description: In this work we present a detailed overview of the experimental techniques behind fast time-resolved charge dynamic measurements using a scanned probe microscope.

Journal: Journal of Visualized Experiments, 2018


Title: Resolving and Tuning Carrier Captures Rates at a Single Silicon Atom Gap State

Authors: Rashidi, M., Lloyd, E., Huff, T., Achal, R., Taucer, M., Croshaw, J., Wolkow, R.A.

Description: In this work we present measurements that systematically explore factors that alter dynamic rates related to the movement of charge within a dangling bond on a hydrogen-terminated silicon surface. These factors include dopant type, density, and temperature.

Journal: ACS Nano, 2017


Title: Atomic White-Out: Enabling Atomic Circuitry through Mechanically Induced Bonding of Single Hydrogen Atoms to a Silicon Surface

Authors: Huff, T., Labidi, H., Rashidi, M., Koleini, M., Achal, R., Salomons, M.H., Wolkow, R.A.

Description: In this work we present the first demonstration of a controlled procedure to cap/repassivate dangling bonds on the surface of hydrogen-terminated silicon. This technique uses an atomic force microscope with a hydrogen functionalized tip. It is an important step towards the scalable production of atomic-scale devices.

Journal: ACS Nano, 2017


Title: Time-Resolved Single Dopant Charge Dynamics in Silicon

Authors: Rashidi, M., Burgess, J., Taucer, M., Achal, R., Pitters, J.L., Loth, S., Wolkow, R.A.

Description: In this work we present the first implementation of an all-electronic pump-probe experiment in a scanning tunneling microscope to study fast time dynamics, which typically cannot be resolved. In particular, how quickly a dopant atom in silicon (As) could gain/lose charge.

Journal: Nature Communications, 2016


Title: Detailed Study of Atomic Silicon Dangling Bond Charge State Dynamics on the Surface of Hydrogen Terminated Silicon (100)–2 × 1

Authors: Achal, R.

Description: MSc Thesis, 2015


Title: Single Electron Dynamics of an Atomic Silicon Quantum Dot on the H-Si(100) 2 × 1 Surface

Authors: Taucer, M., Livadaru, L., Piva, P., Achal, R., Labidi, H., Pitters, J.L., Wolkow, R.A.

Description: In this work we present the first experimental measurements of single electron charge dynamics in a dangling bond on hydrogen-terminated silicon.

Journal: Physical Review Letters, 2014


Title: Generation of Arbitrary Quantum States from Atomic Ensembles

Authors: MacRae, A., Brannan, T., Achal, R., Lvovsky, A.I.

Description: In this work we present a general overview of the generation of single photons in a particular quantum state from an excited gas.

Journal: Physics in Canada, 2012 Prize article


Title: Exploring the Mysteries of the Human Brain with Physics

Authors: Achal, R., Davidsen, J.

Description: In this work we present the exploration of algorithms to detect the causal/structural connections of neurons in a network based upon their firing patterns. The algorithms were able to successfully detect all connections except for inhibitory connections in simulated neural networks.

Journal: Physics in Canada, 2012 Prize article


Title: Tomography of a High-Purity Narrowband Photon from a Transient Atomic Collective Excitation

Authors: MacRae, A., Brannan, T., Achal, R., Lvovsky, A.I.

Description: In this work we present the generation of a narrow band of single photons from a laser excited gas of hot vapours. Such narrow band photons have direct applications in select quantum memory designs, and other systems that require precise control over photon-atom interactions.

Journal: Physical Review Letters, 2012


Patents

Intellectual property:

Title: Lithography for Editable Atomic-Scale Devices and Memories

Authors: Achal, R., Wolkow, R.A., Pitters, J., Cloutier, M., Rashidi, M., Taucer, M., Huff, T.


Title: Multiple Silicon Atom Quantum Dot and Devices Inclusive Thereof

Authors: Wolkow, R.A., Achal, R., Huff, T., Labidi, H., Livadaru, L., Piva, P., Rashidi, M.