Manu Mohan - Academia.edu (original) (raw)
Papers by Manu Mohan
IOP conference series, Mar 1, 2022
Abstarct. Two dimensional (2D) derivatives of tin (Sn) have obtained special deliberations recent... more Abstarct. Two dimensional (2D) derivatives of tin (Sn) have obtained special deliberations recently due to practical realization of planar, as well as, buckled hexagonal lattice of Sn called stanene. However, it has been observed that proper choice of substrate is very important for growth of stanene like films owing to large core size of Sn that prefers sp 3 hybridization over sp 2. Transition metal dichalcogenides (TMDs) like MoS2 or WS2 with honey comb lattice structure seem to be promising substrate candidates for 2D growth of Sn. In the present work, we report mechanical exfoliation of few layers of WS2 under ultra-high vacuum (UHV) conditions and investigations of growth and local electronic structure by in-situ scanning tunneling microscopy (STM) and spectroscopy (STS) studies. Flat WS2 surface with honeycomb lattice structure in the atomic scale with a lattice constant of 0.34 nm is evident in the STM investigations, whereas, STS measurements reveal local density of states (LDOS) of WS2 with a bandgap of approximately 1.34 eV. Density functional theory (DFT) calculations performed by considering bulk WS2 reveal conduction and valence band states comprised of S p and W d at both sides of the Fermi energy (EF) and an indirect bandgap of 1.38 eV. Experimental observations upon Sn adsorption, reveal commensurate growth of Sn atoms on the sulfur `S’ sites with a buckling height of 40 ±10 pm. STS measurements exhibit local electronic structure of the Sn adsorbed surface with clear evidence of in-gap states. DFT calculations quantify the experimental results demonstrating `S’ sites as the most stable sites for the atomic adsorption of Sn with a buckling height of around 80 pm and reveal signature of in-gap hybridized states comprised of Sn p and W d orbitals.
ACS Omega, 2021
We investigate here the strain-induced growth of Cu at 600°C and its interactions with a thermall... more We investigate here the strain-induced growth of Cu at 600°C and its interactions with a thermally grown, 270 nm-thick SiO 2 layer on the Si(111) substrate. Our results show clear evidence of triangular voids and formation of triangular islands on the surface via a void-filling mechanism upon Cu deposition, even on a 270 nm-thick dielectric. Different coordination states, oxidation numbers, and chemical compositions of the Cu-grown film are estimated from the core level X-ray photoelectron spectroscopy (XPS) measurements. We find evidence of different compound phases including an intermediate mixed-state of Cu−O−Si at the interface. Emergence of a mixed Cu−O−Si intermediate state is attributed to the new chemical states of Cu x+ , O x , and Si x+ observed in the highresolution XPS spectra. This intermediate state, which is supposed to be highly catalytic, is found in the sample with a concentration as high as ∼41%. Within the Cu−O−Si phase, the atomic percentages of Cu, O, and Si are ∼1, ∼86, and ∼13%, respectively. The electrical measurements carried out on the sample reveal different resistive channels across the film and an overall n-type semiconducting nature with a sheet resistance of the order of 10 6 Ω.
DAE SOLID STATE PHYSICS SYMPOSIUM 2019, 2020
DAE SOLID STATE PHYSICS SYMPOSIUM 2019, 2020
IOP Conference Series: Materials Science and Engineering, 2019
We try to understand the photocurrent generated in the tailored Molybdenum disulphide (MoS2) nano... more We try to understand the photocurrent generated in the tailored Molybdenum disulphide (MoS2) nanostructures which were exfoliated from bulk MoS2 powder by a simple liquid phase exfoliation followed by microwave treatment. Sonication and microwave treatment led to the formation of mostly hollow tailored MoS2 nano-rods and nano-spheres which consist of more metallic 1T phase than semiconducting 2H phase. In this paper the interaction of light with these nanostructures and the generation of photocurrent is of peer interest. Confinement of photon in the hollow nanostructures could be very promising to derive photocurrent which can have applications in various optoelectronic devices.
Materials Today: Proceedings, 2019
Optical transmittance measurements of MoS 2 nanostructures with varying film thickness are report... more Optical transmittance measurements of MoS 2 nanostructures with varying film thickness are reported here. Optical transmittance value of the films containing assorted MoS 2 nanostructures (revealed by SEM studies) was obtained from optical microscope images taken under white light with 100Â magnification and also from the images acquired under an ordinary lens-laser combination. The relationship between the light exposed on the sample and the pixel intensities of the images are being exploited to establish a correspondence between average pixel intensity and the transmittance obtained by numerical coding. Our measurements show a transmittance variation in the range of 0.92-0.68 with sample thickness.
DAE SOLID STATE PHYSICS SYMPOSIUM 2018, 2019
Transition metal dichalcogenides (TMDs) have drawn immense interest recently owing to their exoti... more Transition metal dichalcogenides (TMDs) have drawn immense interest recently owing to their exotic electronic and optoelectronic properties. We report here our work on highly pure WS 2 crystal which was cleaved under ultra-high vacuum (UHV) conditions and was investigated by in-situ low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) measurements. LEED and STM measurements clearly indicate atomic configuration of the surface and the hexagonal arrangement of the WS 2 crystal, whereas, STS measurements reveal the local electronic structure of the surface via tunneling of electrons through conduction and valence bands. From the STS studies performed on WS 2 surface at different points, we estimate the band gap which is around 2.0 eV.
Surface Science, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
IOP conference series, Mar 1, 2022
Abstarct. Two dimensional (2D) derivatives of tin (Sn) have obtained special deliberations recent... more Abstarct. Two dimensional (2D) derivatives of tin (Sn) have obtained special deliberations recently due to practical realization of planar, as well as, buckled hexagonal lattice of Sn called stanene. However, it has been observed that proper choice of substrate is very important for growth of stanene like films owing to large core size of Sn that prefers sp 3 hybridization over sp 2. Transition metal dichalcogenides (TMDs) like MoS2 or WS2 with honey comb lattice structure seem to be promising substrate candidates for 2D growth of Sn. In the present work, we report mechanical exfoliation of few layers of WS2 under ultra-high vacuum (UHV) conditions and investigations of growth and local electronic structure by in-situ scanning tunneling microscopy (STM) and spectroscopy (STS) studies. Flat WS2 surface with honeycomb lattice structure in the atomic scale with a lattice constant of 0.34 nm is evident in the STM investigations, whereas, STS measurements reveal local density of states (LDOS) of WS2 with a bandgap of approximately 1.34 eV. Density functional theory (DFT) calculations performed by considering bulk WS2 reveal conduction and valence band states comprised of S p and W d at both sides of the Fermi energy (EF) and an indirect bandgap of 1.38 eV. Experimental observations upon Sn adsorption, reveal commensurate growth of Sn atoms on the sulfur `S’ sites with a buckling height of 40 ±10 pm. STS measurements exhibit local electronic structure of the Sn adsorbed surface with clear evidence of in-gap states. DFT calculations quantify the experimental results demonstrating `S’ sites as the most stable sites for the atomic adsorption of Sn with a buckling height of around 80 pm and reveal signature of in-gap hybridized states comprised of Sn p and W d orbitals.
ACS Omega, 2021
We investigate here the strain-induced growth of Cu at 600°C and its interactions with a thermall... more We investigate here the strain-induced growth of Cu at 600°C and its interactions with a thermally grown, 270 nm-thick SiO 2 layer on the Si(111) substrate. Our results show clear evidence of triangular voids and formation of triangular islands on the surface via a void-filling mechanism upon Cu deposition, even on a 270 nm-thick dielectric. Different coordination states, oxidation numbers, and chemical compositions of the Cu-grown film are estimated from the core level X-ray photoelectron spectroscopy (XPS) measurements. We find evidence of different compound phases including an intermediate mixed-state of Cu−O−Si at the interface. Emergence of a mixed Cu−O−Si intermediate state is attributed to the new chemical states of Cu x+ , O x , and Si x+ observed in the highresolution XPS spectra. This intermediate state, which is supposed to be highly catalytic, is found in the sample with a concentration as high as ∼41%. Within the Cu−O−Si phase, the atomic percentages of Cu, O, and Si are ∼1, ∼86, and ∼13%, respectively. The electrical measurements carried out on the sample reveal different resistive channels across the film and an overall n-type semiconducting nature with a sheet resistance of the order of 10 6 Ω.
DAE SOLID STATE PHYSICS SYMPOSIUM 2019, 2020
DAE SOLID STATE PHYSICS SYMPOSIUM 2019, 2020
IOP Conference Series: Materials Science and Engineering, 2019
We try to understand the photocurrent generated in the tailored Molybdenum disulphide (MoS2) nano... more We try to understand the photocurrent generated in the tailored Molybdenum disulphide (MoS2) nanostructures which were exfoliated from bulk MoS2 powder by a simple liquid phase exfoliation followed by microwave treatment. Sonication and microwave treatment led to the formation of mostly hollow tailored MoS2 nano-rods and nano-spheres which consist of more metallic 1T phase than semiconducting 2H phase. In this paper the interaction of light with these nanostructures and the generation of photocurrent is of peer interest. Confinement of photon in the hollow nanostructures could be very promising to derive photocurrent which can have applications in various optoelectronic devices.
Materials Today: Proceedings, 2019
Optical transmittance measurements of MoS 2 nanostructures with varying film thickness are report... more Optical transmittance measurements of MoS 2 nanostructures with varying film thickness are reported here. Optical transmittance value of the films containing assorted MoS 2 nanostructures (revealed by SEM studies) was obtained from optical microscope images taken under white light with 100Â magnification and also from the images acquired under an ordinary lens-laser combination. The relationship between the light exposed on the sample and the pixel intensities of the images are being exploited to establish a correspondence between average pixel intensity and the transmittance obtained by numerical coding. Our measurements show a transmittance variation in the range of 0.92-0.68 with sample thickness.
DAE SOLID STATE PHYSICS SYMPOSIUM 2018, 2019
Transition metal dichalcogenides (TMDs) have drawn immense interest recently owing to their exoti... more Transition metal dichalcogenides (TMDs) have drawn immense interest recently owing to their exotic electronic and optoelectronic properties. We report here our work on highly pure WS 2 crystal which was cleaved under ultra-high vacuum (UHV) conditions and was investigated by in-situ low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) measurements. LEED and STM measurements clearly indicate atomic configuration of the surface and the hexagonal arrangement of the WS 2 crystal, whereas, STS measurements reveal the local electronic structure of the surface via tunneling of electrons through conduction and valence bands. From the STS studies performed on WS 2 surface at different points, we estimate the band gap which is around 2.0 eV.
Surface Science, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.