Yashika Gupta | University of Delhi (original) (raw)

Papers by Yashika Gupta

Research paper thumbnail of Grain Size and Lattice Parameter's Influence on Band Gap of SnS Thin Nano-crystalline Films

The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been inv... more The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been investigated. Both grain size and lattice parameters are known to influence the band gap. The present study initially investigates each contribution individually. The experimentally determined dependency on lattice parameter is verified by theoretical calculations. We also suggest how to treat the variation of band gap as a two variable problem. The results allow us to show dependency of effective mass (reduced) on lattice unit volume.

Research paper thumbnail of Tailoring the mechanical response of Ruddlesden Popper lead halide perovskites

Journal of Alloys and Compounds

Research paper thumbnail of Gate tunable light-matter interaction in natural biaxial hyperbolic van der Waals heterostructures

The recent discovery of natural biaxial hyperbolicity in van der Waals crystals, such as α-MoO3, ... more The recent discovery of natural biaxial hyperbolicity in van der Waals crystals, such as α-MoO3, has opened up new avenues for nanophotonics due to their deep subwavelength phonon-polaritons. However, a significant challenge is the lack of active tunability of these hyperbolic phonon polaritons. In this work, we investigate heterostructures of graphene and α-MoO3 for actively tunable hybrid plasmon phonon polariton modes via electrostatic gating in the mid-infrared spectral region. We observe a unique propagation direction dependent hybridization of graphene plasmon polaritons with hyperbolic phonon polaritons for experimentally feasible values of graphene chemical potential. We further report for the first time tunable anisotropic Purcell factors in this system larger than 10 with a broad operational bandwidth due to the formation of these hybrid modes. This work presents a lithography-free alternative for actively tunable, anisotropic spontaneous emission enhancmenet using a sub-w...

Research paper thumbnail of Mechanical response of butylamine based Ruddlesden Popper organic-inorganic lead halide perovskites

2D Ruddlesden Popper perovskites have been extensively studied for their exceptional optical and ... more 2D Ruddlesden Popper perovskites have been extensively studied for their exceptional optical and electronic characteristics while only a few studies have shed light on their mechanical properties. The existing literature mainly discusses the mechanical strength of single crystal perovskites, however a systematic study towards structure tunability of 2D perovskite thin films is still missing. In this study, we report the effect of number of inorganic layers ‘n’ on elastic modulus of Butylammonium based 2D, quasi-2D perovskites and 3D perovskite using nanoindentation technique. The experimental results have also been substantiated using first principle density functional theory calculations. Understanding the mechanical behaviour of 2D Ruddlesden Popper perovskites thin films in comparison with conventional 3D perovskite offers intriguing insights into the atomic layer dependent properties and paves the path for next generation mechanically durable novel devices.

Research paper thumbnail of Development of a Novel Embedded Board: CANduino

This paper proposes the analysis of a self-designed embedded system based on the controller area ... more This paper proposes the analysis of a self-designed embedded system based on the controller area network. Most automotive industries utilize CAN bus to reduce the intricacies of wiring in an automobile. To overcome the shortcoming and compatibility of different sensors in a particular communication network and its applicability in different fields for the current real-time monitoring system, we have developed a communication module CANduino, which creates a gateway linking different communication protocols in a single network. CANduino is an integration of a microcontroller and the CAN protocol leading to an ordered, secured, and a faster medium with higher capacity messages, thus increasing flexibility of the system. With this module, the user does not need to understand the aspects of CAN protocol, controller, and transceivers, thereby making it an optimum solution for innovators.

Research paper thumbnail of Grain size and lattice parameter's influence on band gap of SnS thin nano-crystalline films

Thin Solid Films, 2016

The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been inv... more The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been investigated. Both grain size and lattice parameters are known to influence the band gap. The present study initially investigates each contribution individually. The experimentally determined dependency on lattice parameter is verified by theoretical calculations. We also suggest how to treat the variation of band gap as a two variable problem. The results allow us to show dependency of effective mass (reduced) on lattice unit volume.

Research paper thumbnail of Mitigating Reasons for the Poor Performance of n-CdS/p-SnS Solar Cells

Research paper thumbnail of Optimization of SnS active layer thickness for solar cell application

Journal of Semiconductors

Research paper thumbnail of Contribution of lattice parameter and vacancies on anisotropic optical properties of tin sulphide

Journal of Alloys and Compounds

Research paper thumbnail of Influence of Urbach tail on the refractive index of p-SnS thin films

physica status solidi (c), 2016

Tin sulphide thin films of p-type conductivity were grown on glass substrates. The refractive ind... more Tin sulphide thin films of p-type conductivity were grown on glass substrates. The refractive index of the as grown films were calculated using both transmission and spectroscopic ellipsometry (SE) data. The SE data was fit using Tauc Lorentz model which showed that the films did not absorb for λ > 700 nm. The variation in all the films refractive index with respect to wavelength, i.e. the dispersion behaviour of the films in region 700 < λ < 1000 nm were found to follow the Wemple-Dedomenico (WDD) single oscillator model. The optical properties of the films were found to be closely related to the structural properties of the films. Intrinsic crystal disorders, tin vacancies in p-SnS thin films leads to appearance of defect levels (Urbach tail) within the bandgap. The band-gap and the band tail's spread, intimately controls the refractive index of the films.

Research paper thumbnail of A study of SnS thin films and its suitability for photovoltaic application based on the existence of persistent photocurrent

Tin Sulphide is a layered compound which retains its structure when deposited as thin films by th... more Tin Sulphide is a layered compound which retains its structure when deposited as thin films by thermal evaporation. The films were found to have oriented growth with the direction of orientation changing with film thickness. The film's morphology was found to change with orientation. The poor conductivity of the thicker samples made it difficult to make photocunductivity characterisation. However, unlike reported the thinner samples showed photo-sensitivity to be independent of film thickness and grain size with a high persistent photocurrent. With their absorption, photosensitivty, optimum band-gap and traps within the band-gap giving the charge carriers a longer life-time, thin samples of tin sulphide gives adequate scope designing efficient photovoltaics. The refractive index was modeled using Sellmeir's model, while most of the previous studies talk of Wemple-DiDomenico single oscillator model or Cauchy's dispersion relation. The Sellmeir's fitting parameters are...

Research paper thumbnail of Influence of Urbach tail on the refractive index of p-SnS thin films

physica status solidi (c), Nov 14, 2016

Tin sulphide thin films of p-type conductivity were grown on glass substrates. The refractive ind... more Tin sulphide thin films of p-type conductivity were grown on glass substrates. The refractive index of the as grown films were calculated using both transmission and spectroscopic ellipsometry (SE) data. The SE data was fit using Tauc Lorentz model which showed that the films did not absorb for λ > 700 nm. The variation in all the films refractive index with respect to wavelength, i.e. the dispersion behaviour of the films in region 700 < λ < 1000 nm were found to follow the Wemple-Dedomenico (WDD) single oscillator model. The optical properties of the films were found to be closely related to the structural properties of the films. Intrinsic crystal disorders, tin vacancies in p-SnS thin films leads to appearance of defect levels (Urbach tail) within the bandgap. The band-gap and the band tail's spread, intimately controls the refractive index of the films.

Research paper thumbnail of Zener behaviour of p-SnS/ZnO and p-SnS/ZnS heterojunctions

Materials Research Express

Research paper thumbnail of A Novel Route for Fabrication of Stable CsPbI 3 Perovskite Thin Film by Thermal Evaporation

Research paper thumbnail of A comment on the dependence of LED’s efficiency on the junction ideality factor

Research paper thumbnail of Influence of strain on the sensitivity of tin sulphide films

Materials Chemistry and Physics, 2017

Research paper thumbnail of Suitability of SnS thin films for photovoltaic application due to the existence of persistent photocurrent

physica status solidi (b), 2015

Research paper thumbnail of Grain Size and Lattice Parameter's Influence on Band Gap of SnS Thin Nano-crystalline Films

The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been inv... more The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been investigated. Both grain size and lattice parameters are known to influence the band gap. The present study initially investigates each contribution individually. The experimentally determined dependency on lattice parameter is verified by theoretical calculations. We also suggest how to treat the variation of band gap as a two variable problem. The results allow us to show dependency of effective mass (reduced) on lattice unit volume.

Research paper thumbnail of A study of SnS thin films and its suitability for photovoltaic application based on the existence of persistent photocurrent

Tin Sulphide is a layered compound which retains its structure when deposited as thin films by th... more Tin Sulphide is a layered compound which retains its structure when deposited as thin films by thermal evaporation. The films were found to have oriented growth with the direction of orientation changing with film thickness. The film's morphology was found to change with orientation. The poor conductivity of the thicker samples made it difficult to make photocunductivity characterisation. However, unlike reported the thinner samples showed photo-sensitivity to be independent of film thickness and grain size with a high persistent photocurrent. With their absorption, photosensitivty, optimum band-gap and traps within the band-gap giving the charge carriers a longer life-time, thin samples of tin sulphide gives adequate scope designing efficient photovoltaics. The refractive index was modeled using Sellmeir's model, while most of the previous studies talk of Wemple-DiDomenico single oscillator model or Cauchy's dispersion relation. The Sellmeir's fitting parameters are...

Research paper thumbnail of First Step to Ellipsometry

International Journal of Physics, 2014

Ellipsometry is a non-destructive, fast and accurate characterization technique used for determin... more Ellipsometry is a non-destructive, fast and accurate characterization technique used for determining the thickness and the optical constants of a material. However, this method has a drawback considering that the experimentally measured data are not meaningful in itself and one has to interpret the data based on modelling making ellipsometry dependent on the model selection, computation power/time and fitting. This makes ellipsometry, a difficult characterization method. However, it also presents a wonderful opportunity to apply the various topics taught in physics classes at undergraduate level. This paper provides the detailed insight into the selfstanding film, the simplest case possible and hence the first step of ellipsometry experimentation which can be useful for substrate analysis in complex systems if the nature of the substrate is not known.

Research paper thumbnail of Grain Size and Lattice Parameter's Influence on Band Gap of SnS Thin Nano-crystalline Films

The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been inv... more The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been investigated. Both grain size and lattice parameters are known to influence the band gap. The present study initially investigates each contribution individually. The experimentally determined dependency on lattice parameter is verified by theoretical calculations. We also suggest how to treat the variation of band gap as a two variable problem. The results allow us to show dependency of effective mass (reduced) on lattice unit volume.

Research paper thumbnail of Tailoring the mechanical response of Ruddlesden Popper lead halide perovskites

Journal of Alloys and Compounds

Research paper thumbnail of Gate tunable light-matter interaction in natural biaxial hyperbolic van der Waals heterostructures

The recent discovery of natural biaxial hyperbolicity in van der Waals crystals, such as α-MoO3, ... more The recent discovery of natural biaxial hyperbolicity in van der Waals crystals, such as α-MoO3, has opened up new avenues for nanophotonics due to their deep subwavelength phonon-polaritons. However, a significant challenge is the lack of active tunability of these hyperbolic phonon polaritons. In this work, we investigate heterostructures of graphene and α-MoO3 for actively tunable hybrid plasmon phonon polariton modes via electrostatic gating in the mid-infrared spectral region. We observe a unique propagation direction dependent hybridization of graphene plasmon polaritons with hyperbolic phonon polaritons for experimentally feasible values of graphene chemical potential. We further report for the first time tunable anisotropic Purcell factors in this system larger than 10 with a broad operational bandwidth due to the formation of these hybrid modes. This work presents a lithography-free alternative for actively tunable, anisotropic spontaneous emission enhancmenet using a sub-w...

Research paper thumbnail of Mechanical response of butylamine based Ruddlesden Popper organic-inorganic lead halide perovskites

2D Ruddlesden Popper perovskites have been extensively studied for their exceptional optical and ... more 2D Ruddlesden Popper perovskites have been extensively studied for their exceptional optical and electronic characteristics while only a few studies have shed light on their mechanical properties. The existing literature mainly discusses the mechanical strength of single crystal perovskites, however a systematic study towards structure tunability of 2D perovskite thin films is still missing. In this study, we report the effect of number of inorganic layers ‘n’ on elastic modulus of Butylammonium based 2D, quasi-2D perovskites and 3D perovskite using nanoindentation technique. The experimental results have also been substantiated using first principle density functional theory calculations. Understanding the mechanical behaviour of 2D Ruddlesden Popper perovskites thin films in comparison with conventional 3D perovskite offers intriguing insights into the atomic layer dependent properties and paves the path for next generation mechanically durable novel devices.

Research paper thumbnail of Development of a Novel Embedded Board: CANduino

This paper proposes the analysis of a self-designed embedded system based on the controller area ... more This paper proposes the analysis of a self-designed embedded system based on the controller area network. Most automotive industries utilize CAN bus to reduce the intricacies of wiring in an automobile. To overcome the shortcoming and compatibility of different sensors in a particular communication network and its applicability in different fields for the current real-time monitoring system, we have developed a communication module CANduino, which creates a gateway linking different communication protocols in a single network. CANduino is an integration of a microcontroller and the CAN protocol leading to an ordered, secured, and a faster medium with higher capacity messages, thus increasing flexibility of the system. With this module, the user does not need to understand the aspects of CAN protocol, controller, and transceivers, thereby making it an optimum solution for innovators.

Research paper thumbnail of Grain size and lattice parameter's influence on band gap of SnS thin nano-crystalline films

Thin Solid Films, 2016

The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been inv... more The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been investigated. Both grain size and lattice parameters are known to influence the band gap. The present study initially investigates each contribution individually. The experimentally determined dependency on lattice parameter is verified by theoretical calculations. We also suggest how to treat the variation of band gap as a two variable problem. The results allow us to show dependency of effective mass (reduced) on lattice unit volume.

Research paper thumbnail of Mitigating Reasons for the Poor Performance of n-CdS/p-SnS Solar Cells

Research paper thumbnail of Optimization of SnS active layer thickness for solar cell application

Journal of Semiconductors

Research paper thumbnail of Contribution of lattice parameter and vacancies on anisotropic optical properties of tin sulphide

Journal of Alloys and Compounds

Research paper thumbnail of Influence of Urbach tail on the refractive index of p-SnS thin films

physica status solidi (c), 2016

Tin sulphide thin films of p-type conductivity were grown on glass substrates. The refractive ind... more Tin sulphide thin films of p-type conductivity were grown on glass substrates. The refractive index of the as grown films were calculated using both transmission and spectroscopic ellipsometry (SE) data. The SE data was fit using Tauc Lorentz model which showed that the films did not absorb for λ > 700 nm. The variation in all the films refractive index with respect to wavelength, i.e. the dispersion behaviour of the films in region 700 < λ < 1000 nm were found to follow the Wemple-Dedomenico (WDD) single oscillator model. The optical properties of the films were found to be closely related to the structural properties of the films. Intrinsic crystal disorders, tin vacancies in p-SnS thin films leads to appearance of defect levels (Urbach tail) within the bandgap. The band-gap and the band tail's spread, intimately controls the refractive index of the films.

Research paper thumbnail of A study of SnS thin films and its suitability for photovoltaic application based on the existence of persistent photocurrent

Tin Sulphide is a layered compound which retains its structure when deposited as thin films by th... more Tin Sulphide is a layered compound which retains its structure when deposited as thin films by thermal evaporation. The films were found to have oriented growth with the direction of orientation changing with film thickness. The film's morphology was found to change with orientation. The poor conductivity of the thicker samples made it difficult to make photocunductivity characterisation. However, unlike reported the thinner samples showed photo-sensitivity to be independent of film thickness and grain size with a high persistent photocurrent. With their absorption, photosensitivty, optimum band-gap and traps within the band-gap giving the charge carriers a longer life-time, thin samples of tin sulphide gives adequate scope designing efficient photovoltaics. The refractive index was modeled using Sellmeir's model, while most of the previous studies talk of Wemple-DiDomenico single oscillator model or Cauchy's dispersion relation. The Sellmeir's fitting parameters are...

Research paper thumbnail of Influence of Urbach tail on the refractive index of p-SnS thin films

physica status solidi (c), Nov 14, 2016

Tin sulphide thin films of p-type conductivity were grown on glass substrates. The refractive ind... more Tin sulphide thin films of p-type conductivity were grown on glass substrates. The refractive index of the as grown films were calculated using both transmission and spectroscopic ellipsometry (SE) data. The SE data was fit using Tauc Lorentz model which showed that the films did not absorb for λ > 700 nm. The variation in all the films refractive index with respect to wavelength, i.e. the dispersion behaviour of the films in region 700 < λ < 1000 nm were found to follow the Wemple-Dedomenico (WDD) single oscillator model. The optical properties of the films were found to be closely related to the structural properties of the films. Intrinsic crystal disorders, tin vacancies in p-SnS thin films leads to appearance of defect levels (Urbach tail) within the bandgap. The band-gap and the band tail's spread, intimately controls the refractive index of the films.

Research paper thumbnail of Zener behaviour of p-SnS/ZnO and p-SnS/ZnS heterojunctions

Materials Research Express

Research paper thumbnail of A Novel Route for Fabrication of Stable CsPbI 3 Perovskite Thin Film by Thermal Evaporation

Research paper thumbnail of A comment on the dependence of LED’s efficiency on the junction ideality factor

Research paper thumbnail of Influence of strain on the sensitivity of tin sulphide films

Materials Chemistry and Physics, 2017

Research paper thumbnail of Suitability of SnS thin films for photovoltaic application due to the existence of persistent photocurrent

physica status solidi (b), 2015

Research paper thumbnail of Grain Size and Lattice Parameter's Influence on Band Gap of SnS Thin Nano-crystalline Films

The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been inv... more The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been investigated. Both grain size and lattice parameters are known to influence the band gap. The present study initially investigates each contribution individually. The experimentally determined dependency on lattice parameter is verified by theoretical calculations. We also suggest how to treat the variation of band gap as a two variable problem. The results allow us to show dependency of effective mass (reduced) on lattice unit volume.

Research paper thumbnail of A study of SnS thin films and its suitability for photovoltaic application based on the existence of persistent photocurrent

Tin Sulphide is a layered compound which retains its structure when deposited as thin films by th... more Tin Sulphide is a layered compound which retains its structure when deposited as thin films by thermal evaporation. The films were found to have oriented growth with the direction of orientation changing with film thickness. The film's morphology was found to change with orientation. The poor conductivity of the thicker samples made it difficult to make photocunductivity characterisation. However, unlike reported the thinner samples showed photo-sensitivity to be independent of film thickness and grain size with a high persistent photocurrent. With their absorption, photosensitivty, optimum band-gap and traps within the band-gap giving the charge carriers a longer life-time, thin samples of tin sulphide gives adequate scope designing efficient photovoltaics. The refractive index was modeled using Sellmeir's model, while most of the previous studies talk of Wemple-DiDomenico single oscillator model or Cauchy's dispersion relation. The Sellmeir's fitting parameters are...

Research paper thumbnail of First Step to Ellipsometry

International Journal of Physics, 2014

Ellipsometry is a non-destructive, fast and accurate characterization technique used for determin... more Ellipsometry is a non-destructive, fast and accurate characterization technique used for determining the thickness and the optical constants of a material. However, this method has a drawback considering that the experimentally measured data are not meaningful in itself and one has to interpret the data based on modelling making ellipsometry dependent on the model selection, computation power/time and fitting. This makes ellipsometry, a difficult characterization method. However, it also presents a wonderful opportunity to apply the various topics taught in physics classes at undergraduate level. This paper provides the detailed insight into the selfstanding film, the simplest case possible and hence the first step of ellipsometry experimentation which can be useful for substrate analysis in complex systems if the nature of the substrate is not known.