Dr. Bablu Mukherjee | National University of Singapore (original) (raw)
Uploads
Papers by Dr. Bablu Mukherjee
Japanese Journal of Applied Physics
The chemical nature of surface fluorination followed by ion bombardment has been explored to achi... more The chemical nature of surface fluorination followed by ion bombardment has been explored to achieve a topographically selective atomic layer etching of silicon dioxide at low temperature. In this work, a two-step low-pressure sulfur hexafluoride (SF6) remote plasma modification (without any ion bombardment) followed by argon (Ar) ion bombardment is presented. In-situ investigations of the surface bonding confirmed the modification during the half-reaction steps and spectroscopic ellipsometry data reveal the thickness change while suggesting an incubation period prior to obtaining a uniform etch per cycle (EPC) of 0.14 nm with a synergistic 30 s fluorination of the surface followed by a 60 s Ar bombardment. The etch profile of the trenched structured sample displays the isotropic etch for the two-step process, as well as the feasibility of a topo-selective top-and-bottom etch by bias application in the Ar bombardment step.
Solid State Devices and Materials, 2022
In the area of sub-10 nm fabrication, Atomic Layer Etching (ALE) has become one of the most promi... more In the area of sub-10 nm fabrication, Atomic Layer Etching (ALE) has become one of the most promising processes. Control of the etching rate and the tuning of etching selectivity among more than three different materials remains challenging. In this report, we discuss the etching mechanism of Ti-compounds (e.g. TiO2) and establish the etching selectivity between Ti-compounds (TiO2 & TiN) and Si-compounds (SiN, SiCN, SiO2). An ALE process consisting of reactive H-ion plasma modification followed by remote fluorine radical plasma-based removal is developed. Various control parameters i.e. bias power, temperature, process pressure, step duration and their effect on the etching rate are discussed. High etching selectivity between TiO2 as well as TiN and SiO2 is achieved. Additionally plasma treatments and/or controlling the substrate temperature can be used to control the selective etch of Ti-compounds film etching with respect to Si-compounds.
Advanced electronic materials, Nov 30, 2020
Journal of Crystal Growth, May 1, 2012
arXiv (Cornell University), Mar 7, 2015
Proceedings of SPIE, Mar 14, 2016
In order to protect optoelectronic and mechanical properties of atomically thin layered materials... more In order to protect optoelectronic and mechanical properties of atomically thin layered materials (ATLMs) fabricated over SiO2/Si substrates, a secondary oxide or nitride layer can be capped over. However, such protective capping might decrease ATLMs’ visibility dramatically. Similar to the early studies conducted for graphene, we numerically determine optimum thicknesses both for capping and underlying oxide layers for strongest visibility of monolayer MoS2, MoSe2, WS2, and WSe2 in different regions of visible spectrum. We find that the capping layer should not be thicker than 60 nm. Furthermore the optimum capping layer thickness value can be calculated as a function of underlying oxide thickness, and vice versa.
US Patent App. 18/143,652, 2023
The current disclosure relates to methods of selectively etching material from a first surface of... more The current disclosure relates to methods of selectively etching material from a first surface of a substrate relative to a second surface of the substrate. The method includes providing the substrate having a first surface comprising an etchable material, and a second surface comprising a non-etchable material in a reaction chamber, providing hydrogen-containing plasma into the reaction chamber to reduce the etchable material to a predetermined depth; and providing remotely-generated reactive halogen species and hydrogen into the reaction chamber to selectively etch the reduced etchable material. The disclosure further relates to methods of selectively etching at least two different etchable materials simultaneously from a surface of a substrate relative to a non-etchable material on the same substrate, to methods of simultaneous differential etching of three or more etchable materials on a substrate, as well as to assemblies for processing semiconductor substrates.
Extended Abstracts of the 2020 International Conference on Solid State Devices and Materials
The Japan Society of Applied Physics, 2018
Advanced Functional Materials, 2020
Japanese Journal of Applied Physics, 2020
We investigate the humidity sensing performance and mechanism of few-layer-thick rhenium disulfid... more We investigate the humidity sensing performance and mechanism of few-layer-thick rhenium disulfide (ReS2) field-effect transistors (FETs) under gate bias operation. Consequently, a negative gate bias exhibits the sensor response, exceeding 90% mainly in the low relative humidity (RH) range. Meanwhile, the threshold voltage change was discovered to be a superior sensing parameter to achieve a broad monitoring of RH range with high response and sensitivity. The approach obtained a practical sensitivity of 0.4 V per 1% RH, which exceed a majority of previous studies with the pristine 2D materials. Besides, our devices display reversible adsorption–desorption and long-term stability operations even after a one-month period. This suggests the sensor capacity to function in real-time applications with a short response and recovery times. These outcomes offer support in the development of adaptable tunable humidity sensors based on ReS2 FETs.
Advanced Electronic Materials, 2020
2018 IEEE Photonics Conference (IPC), 2018
Anisotropic optical constants of N-layer ReS2 are determined by angle resolved reflection measure... more Anisotropic optical constants of N-layer ReS2 are determined by angle resolved reflection measurements. Optimum parameters for a metal nanoparticle array leading to maximum light-matter interaction are determined using numerical simulations. Plasmonic enhancement in absorptance of the ReS2 layer and photocurrent are demonstrated experimentally.
ACS applied materials & interfaces, Jan 24, 2018
Rhenium disulfide (ReS) is an attractive candidate for photodetection applications owing to its t... more Rhenium disulfide (ReS) is an attractive candidate for photodetection applications owing to its thickness-independent direct band gap. Despite various photodetection studies using two-dimensional semiconductors, the trade-off between responsivity and response time under varying measurement conditions has not been studied in detail. This report presents a comprehensive study of the architectural, laser power and gate bias dependence of responsivity and speed in supported and suspended ReS phototransistors. Photocurrent scans show uniform photogeneration across the entire channel because of enhanced optical absorption and a direct band gap in multilayer ReS. A high responsivity of 4 A W (at 50 ms response time) and a low response time of 20 μs (at 4 mA W responsivity) make this one of the fastest reported transition-metal dichalcogenide photodetectors. Occupancy of intrinsic (bulk ReS) and extrinsic (ReS/SiO interface) traps is modulated using gate bias to demonstrate tunability of th...
Scientific reports, Jan 30, 2017
Modulation of photoluminescence of atomically thin transition metal dichalcogenide two-dimensiona... more Modulation of photoluminescence of atomically thin transition metal dichalcogenide two-dimensional materials is critical for their integration in optoelectronic and photonic device applications. By coupling with different plasmonic array geometries, we have shown that the photoluminescence intensity can be enhanced and quenched in comparison with pristine monolayer MoS2. The enhanced exciton emission intensity can be further tuned by varying the angle of polarized incident excitation. Through controlled variation of the structural parameters of the plasmonic array in our experiment, we demonstrate modulation of the photoluminescence intensity from nearly fourfold quenching to approximately threefold enhancement. Our data indicates that the plasmonic resonance couples to optical fields at both, excitation and emission bands, and increases the spontaneous emission rate in a double spacing plasmonic array structure as compared with an equal spacing array structure. Furthermore our expe...
Advanced Materials Letters, 2015
Optics Communications, 2016
Japanese Journal of Applied Physics
The chemical nature of surface fluorination followed by ion bombardment has been explored to achi... more The chemical nature of surface fluorination followed by ion bombardment has been explored to achieve a topographically selective atomic layer etching of silicon dioxide at low temperature. In this work, a two-step low-pressure sulfur hexafluoride (SF6) remote plasma modification (without any ion bombardment) followed by argon (Ar) ion bombardment is presented. In-situ investigations of the surface bonding confirmed the modification during the half-reaction steps and spectroscopic ellipsometry data reveal the thickness change while suggesting an incubation period prior to obtaining a uniform etch per cycle (EPC) of 0.14 nm with a synergistic 30 s fluorination of the surface followed by a 60 s Ar bombardment. The etch profile of the trenched structured sample displays the isotropic etch for the two-step process, as well as the feasibility of a topo-selective top-and-bottom etch by bias application in the Ar bombardment step.
Solid State Devices and Materials, 2022
In the area of sub-10 nm fabrication, Atomic Layer Etching (ALE) has become one of the most promi... more In the area of sub-10 nm fabrication, Atomic Layer Etching (ALE) has become one of the most promising processes. Control of the etching rate and the tuning of etching selectivity among more than three different materials remains challenging. In this report, we discuss the etching mechanism of Ti-compounds (e.g. TiO2) and establish the etching selectivity between Ti-compounds (TiO2 & TiN) and Si-compounds (SiN, SiCN, SiO2). An ALE process consisting of reactive H-ion plasma modification followed by remote fluorine radical plasma-based removal is developed. Various control parameters i.e. bias power, temperature, process pressure, step duration and their effect on the etching rate are discussed. High etching selectivity between TiO2 as well as TiN and SiO2 is achieved. Additionally plasma treatments and/or controlling the substrate temperature can be used to control the selective etch of Ti-compounds film etching with respect to Si-compounds.
Advanced electronic materials, Nov 30, 2020
Journal of Crystal Growth, May 1, 2012
arXiv (Cornell University), Mar 7, 2015
Proceedings of SPIE, Mar 14, 2016
In order to protect optoelectronic and mechanical properties of atomically thin layered materials... more In order to protect optoelectronic and mechanical properties of atomically thin layered materials (ATLMs) fabricated over SiO2/Si substrates, a secondary oxide or nitride layer can be capped over. However, such protective capping might decrease ATLMs’ visibility dramatically. Similar to the early studies conducted for graphene, we numerically determine optimum thicknesses both for capping and underlying oxide layers for strongest visibility of monolayer MoS2, MoSe2, WS2, and WSe2 in different regions of visible spectrum. We find that the capping layer should not be thicker than 60 nm. Furthermore the optimum capping layer thickness value can be calculated as a function of underlying oxide thickness, and vice versa.
US Patent App. 18/143,652, 2023
The current disclosure relates to methods of selectively etching material from a first surface of... more The current disclosure relates to methods of selectively etching material from a first surface of a substrate relative to a second surface of the substrate. The method includes providing the substrate having a first surface comprising an etchable material, and a second surface comprising a non-etchable material in a reaction chamber, providing hydrogen-containing plasma into the reaction chamber to reduce the etchable material to a predetermined depth; and providing remotely-generated reactive halogen species and hydrogen into the reaction chamber to selectively etch the reduced etchable material. The disclosure further relates to methods of selectively etching at least two different etchable materials simultaneously from a surface of a substrate relative to a non-etchable material on the same substrate, to methods of simultaneous differential etching of three or more etchable materials on a substrate, as well as to assemblies for processing semiconductor substrates.
Extended Abstracts of the 2020 International Conference on Solid State Devices and Materials
The Japan Society of Applied Physics, 2018
Advanced Functional Materials, 2020
Japanese Journal of Applied Physics, 2020
We investigate the humidity sensing performance and mechanism of few-layer-thick rhenium disulfid... more We investigate the humidity sensing performance and mechanism of few-layer-thick rhenium disulfide (ReS2) field-effect transistors (FETs) under gate bias operation. Consequently, a negative gate bias exhibits the sensor response, exceeding 90% mainly in the low relative humidity (RH) range. Meanwhile, the threshold voltage change was discovered to be a superior sensing parameter to achieve a broad monitoring of RH range with high response and sensitivity. The approach obtained a practical sensitivity of 0.4 V per 1% RH, which exceed a majority of previous studies with the pristine 2D materials. Besides, our devices display reversible adsorption–desorption and long-term stability operations even after a one-month period. This suggests the sensor capacity to function in real-time applications with a short response and recovery times. These outcomes offer support in the development of adaptable tunable humidity sensors based on ReS2 FETs.
Advanced Electronic Materials, 2020
2018 IEEE Photonics Conference (IPC), 2018
Anisotropic optical constants of N-layer ReS2 are determined by angle resolved reflection measure... more Anisotropic optical constants of N-layer ReS2 are determined by angle resolved reflection measurements. Optimum parameters for a metal nanoparticle array leading to maximum light-matter interaction are determined using numerical simulations. Plasmonic enhancement in absorptance of the ReS2 layer and photocurrent are demonstrated experimentally.
ACS applied materials & interfaces, Jan 24, 2018
Rhenium disulfide (ReS) is an attractive candidate for photodetection applications owing to its t... more Rhenium disulfide (ReS) is an attractive candidate for photodetection applications owing to its thickness-independent direct band gap. Despite various photodetection studies using two-dimensional semiconductors, the trade-off between responsivity and response time under varying measurement conditions has not been studied in detail. This report presents a comprehensive study of the architectural, laser power and gate bias dependence of responsivity and speed in supported and suspended ReS phototransistors. Photocurrent scans show uniform photogeneration across the entire channel because of enhanced optical absorption and a direct band gap in multilayer ReS. A high responsivity of 4 A W (at 50 ms response time) and a low response time of 20 μs (at 4 mA W responsivity) make this one of the fastest reported transition-metal dichalcogenide photodetectors. Occupancy of intrinsic (bulk ReS) and extrinsic (ReS/SiO interface) traps is modulated using gate bias to demonstrate tunability of th...
Scientific reports, Jan 30, 2017
Modulation of photoluminescence of atomically thin transition metal dichalcogenide two-dimensiona... more Modulation of photoluminescence of atomically thin transition metal dichalcogenide two-dimensional materials is critical for their integration in optoelectronic and photonic device applications. By coupling with different plasmonic array geometries, we have shown that the photoluminescence intensity can be enhanced and quenched in comparison with pristine monolayer MoS2. The enhanced exciton emission intensity can be further tuned by varying the angle of polarized incident excitation. Through controlled variation of the structural parameters of the plasmonic array in our experiment, we demonstrate modulation of the photoluminescence intensity from nearly fourfold quenching to approximately threefold enhancement. Our data indicates that the plasmonic resonance couples to optical fields at both, excitation and emission bands, and increases the spontaneous emission rate in a double spacing plasmonic array structure as compared with an equal spacing array structure. Furthermore our expe...
Advanced Materials Letters, 2015
Optics Communications, 2016
The main objective of this thesis is to study various morphological growth and optoelectrical pro... more The main objective of this thesis is to study various morphological growth and optoelectrical properties of individual Ge based layered chalcogenides nanostructures. This thesis essentially summarizes the synthesis of GeSe2 and GeSe nanostructures, as well as investigations on their electrical properties for photodetector applications. Photodetectors comprising of individually isolated GeSe2 nanobelts with different surface morphologies were fabricated to study their photodetection properties. The photoresponsivity of the devices were investigated at different excitation wavelengths. High-gain photoresponse of the single NB devices with the possible electronic conduction and photoconducting mechanism was illustrated. Furthermore, the thesis includes the controlled structural changes, which was investigated on micropatters created on GeSe2 nanostructures film using Raman spectroscopy. In addition, the electrical conductivity and near infrared (NIR) photosensing properties of individual GeSe nanosheet devices were investigated for promising potential application in future nanoelectronics applications.
