Sanjeev Kumar Srivastava | IIT Kharagpur (original) (raw)

Papers by Sanjeev Kumar Srivastava

AIP Conference Proceedings, 2017

We investigate the interface mixing across Pd0.60 Ni0.40 (∼20 nm)/SiO2 interface on irradiation b... more We investigate the interface mixing across Pd0.60 Ni0.40 (∼20 nm)/SiO2 interface on irradiation by 100 MeV Au ions at a fluence 1 × 1014 ions/cm2. The samples were characterized using Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy (XPS). From RBS results, a weak but significant intermixing is observed at the interface. The XPS spectra suggest that the irradiation first homogenizes the alloy film and then causes an interdiffusion of Pd and Ni atoms in SiO2.

Journal of Applied Physics, 2003

Solid acidity was found to be generated in methylsiloxane-based inorganic/organic hybrids by inco... more Solid acidity was found to be generated in methylsiloxane-based inorganic/organic hybrids by incorporating inorganic components other than Si, such as Al and Nb, into methylsiloxane networks by combining theoretical first-principles calculations based on the density functional theory (DFT) with experimental synthesis and characterization. First-principles calculations based on the DFT indicated that the dissociation energy of protons at the surface followed the order Si<Al<Nb. The calculation led to the conclusion that methylsiloxane-based inorganic/organic hybrids were synthesized from metal alkoxides. The solid acidity followed the same order: Si<Al<Nb. The Fourier-transform infrared measurements of pyridine adsorbed on the methylsiloxane-based inorganic/organic hybrids showed that the solid acidity can be attributed to Bronsted acid sites.

Physical Review B, 2005

The recently proposed hypothesis that swift-heavy-ion induced mixing is a consequence of a transi... more The recently proposed hypothesis that swift-heavy-ion induced mixing is a consequence of a transient molten state diffusion is tested by studying 230 MeV Au ion induced mixing at an Fe/ Si interface monitored online by elastic recoil detection analysis. An extensive data analysis has been made to determine the experimental intrinsic diffusivities of Fe in Si, and vice versa. The required size and duration of the transient melt phase have been calculated theoretically from the thermal spike model. The close resemblance of the experimental diffusivities to the liquid state diffusivities reported in the literature is a verification of the hypothesis.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002

The potential device application of semiconductor heterostructures and strained layer superlattic... more The potential device application of semiconductor heterostructures and strained layer superlattices has been highlighted. Metal organic chemical vapour deposition grown In 0:53 Ga 0:47 As/InP lattice-matched structure has been irradiated by 130 MeV Ag 13þ and studied by RBS/Channelling using 3.5 MeV He 2þ ions. Ion irradiation seems to have induced a finite tensile strain in the InGaAs layer, indicating thereby that ion beam mixing occurs at this energy. Other complementary techniques like high resolution XRD and STM are needed to conclude the structural modifications in the sample.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014

Pulsed laser deposited 60 nm thin film of homogeneous Mn 0.82 Bi 0.18 composite has been irradiat... more Pulsed laser deposited 60 nm thin film of homogeneous Mn 0.82 Bi 0.18 composite has been irradiated by 100 MeV Au ions at fluence 1 Â 10 13 ions/cm 2 , and investigated by field emission scanning electron microscopy, X-ray diffraction, magnetic hysteresis, X-ray photoelectron spectroscopy, and nanoindentation measurements. Dispersed nanostructures of soft Bi-rich phase of about 20 nm diameter emerged in a hard Mn-rich matrix on irradiation. Such structures, as synthesized by the present novel swift heavy ion irradiation approach, are usable as self-lubricating thin films.

Physical Chemistry Chemical Physics

Thermal spike model (TSM), a widely accepted mechanism of swift heavy ion (SHI) - matter interact... more Thermal spike model (TSM), a widely accepted mechanism of swift heavy ion (SHI) - matter interaction, provides explanation to various SHI induced effects, including mixing across interfaces. We assess the...

ACS Applied Materials & Interfaces

The Journal of Physical Chemistry C

Understanding the radiation tolerance of ceramics against low energy heavy ions is important for ... more Understanding the radiation tolerance of ceramics against low energy heavy ions is important for evaluating their stability against alpha recoils, which are a significant source of damage for their...

Two dimensional (2D) van der Waals heterostructures (vdWHs) have their unique potential in facili... more Two dimensional (2D) van der Waals heterostructures (vdWHs) have their unique potential in facilitating the stacking of layers of different 2D materials for optoelectronic devices with superior characteristics at a reduced cost. However, the fabrication of large area all-2D heterostructures is still challenging towards realizing practical devices. In the present work, we have demonstrated a rapid yet simple, impurity free and highly efficient sonication-assisted chemical exfoliation approach to synthesize hybrid vdWHs based on 2D molybdenum disulphide (MoS$_2$) and tungsten disulphide (WS$_2$), with high yield. Microscopic and spectroscopic studies have confirmed the successful exfoliation of layered 2D materials and formation of their hybrid heterostructure. The co-existence of 2D MoS2 and WS2 in the vdW hybrid is established by optical absorption and Raman shift measurements along with their chemical stiochiometry determined by X-ray photoelectron spectroscopy. The spectral respon...

Journal of Materials Engineering and Performance

In the present work, nanostructured functionalized silica is coated on an aluminum (Al) substrate... more In the present work, nanostructured functionalized silica is coated on an aluminum (Al) substrate by the spray pyrolysis method to create a stable and effective super-hydrophobic substrate for water harvesting via moist air. Substrate characterization reveals that (1) major diffraction peaks corresponding to crystoballite SiO2 (C-SiO2), quartz (Q-SiO2), Al2O3, and Al2SiO5 are to be found at SiO2/Al interface; (2) strong chemically bonded methyl functionalized silica is confirmed on the Al surface by Fourier-transform infrared spectroscopy (FT-IR) and x-ray photoelectron spectrometry (XPS) shows the presence of Al-O-Si bond at the interface; and (3) the equilibrium contact angle of the water droplet on the coated substrate is measured to be 156° ± 5° with a hysteresis of 10° ± 3°. The coating is found to be stable for more than 365 days in a humid atmosphere. Finally, moist air condensation experiments confirm substantial augmentation of condensate collected ranging from 188 ml/m2-h over an untreated aluminum substrate to 750 ml/m2-h over the coated substrate. Hence, it is concluded that nanostructured silica-coated Al substrate is highly effective for enhancing the condensation of water vapor from a moist air environment.

Environmental Science and Pollution Research

An ecofriendly and solar light-responsive graphene oxide wrapped zinc oxide nanohybrid has been s... more An ecofriendly and solar light-responsive graphene oxide wrapped zinc oxide nanohybrid has been synthesized hydrothermally using lemon and honey respectively as chelating and complexing agents. By tuning the reaction conditions, a heterostructure between GO and ZnO has been formed during synthesis. The photocatalytic activity of the synthesized nanohybrid was investigated by degradation of hazardous organic textile dye (methylene blue) as well as wastewater under natural solar light. The nanohybrid exhibited excellent photocatalytic activity towards degradation (~ 89%) of methylene blue (MeB). Furthermore, along with decolorization, 71% of mineralization was also achieved. Interestingly, the nanohybrid has been found to be reusable up to 4 cycles without significant loss of photocatalytic activity. Along with this, the physicochemical parameters of the wastewater generated from textile industry have been also monitored before and after exposure to nanohybrid. The results revealed significant reduction in chemical oxygen demand (COD) (96.33%), biochemical oxygen demand (BOD) (96.23%), and total dissolved solids (TDS) (20.85%), suggesting its potential applicability in textile wastewater treatment.

Advanced Energy Materials

Body weight, lipid profile, atherogenic index and coronary risk index were determined in rats fed... more Body weight, lipid profile, atherogenic index and coronary risk index were determined in rats fed commercial chicken salad with dressing. Twenty four weaning albino rats were divided into three groups of eight animals, baseline, rat chow (control) and chicken salad with dressing and fed respective diets, for five weeks. Body weights, serum cholesterol, serum triglycerides, HDL cholesterol and LDL cholesterol were determined using standard methods. Atherogenic and coronary risk indices were also calculated. Body weights and lipids profiles of animals on regular rat chow and chicken salad groups increased with age. Weight gain in rats fed chicken salad with dressing increased significantly (P<0.05) and had higher serum cholesterol, triglyceride, HDL cholesterol and LDL cholesterol values compared with the rat chow group. The observed increases in parameters evaluated might be due to the chicken component and salad dressing comprising of both mayonnaise and salad cream. Despite the observed absolute increase in the lipid profile values of the chicken salad with dressing group, the coronary risk index, atherogenic index, HDL cholesterol/total cholesterol ratio and triglyceride/HDL cholesterol ratios were within normal range and not significantly (P>0.05) different from the corresponding values for the rat chow fed group. It is however desirable that a similar study be carried out with human subjects.

Solar Energy

Abstract In thin film photovoltaics, antimony selenide (Sb2Se3) is making a mark as an important ... more Abstract In thin film photovoltaics, antimony selenide (Sb2Se3) is making a mark as an important absorber layer for its attractive structural, optical, and electrical properties. Several deposition techniques are used to grow Sb2Se3 films, albeit growth angle-dependent physical properties of Sb2Se3 films are yet to be explored in a systematic manner. In this work, we investigate the roles of growth angle (in the range of 0°-87°) and thickness (250 and 1000 nm) in governing optoelectronic properties of Sb2Se3 films grown by radio frequency sputter deposition technique. It is interesting to note that upon increasing the growth angle, a systematic enhancement in the optical band-gap takes place. This is accompanied by a systematic reduction in the work function of these amorphous films with increasing growth angle. Subsequently, after postgrowth annealing at 573 K for 180 s (in vacuum) all Sb2Se3 films undergo a structural phase transition from amorphous to crystalline one. Following this, the band-gap and work function of these films also get modified. This study paves the way to fabricate Sb2Se3 films having tunable optoelectronic properties like absorption coefficient, band-gap, and work function. Thus, it should be extremely useful to select Sb2Se3 films having optimal thickness and optoelectronic properties to fabricate Sb2Se3 absorber layer-based multi-junction hole-blocking solar cells having improved cell efficiencies.

Journal of Magnetism and Magnetic Materials

The generalized gradient approximation (GGA) scheme in the first-principles calculations are used... more The generalized gradient approximation (GGA) scheme in the first-principles calculations are used to study the effect of L21 and XA ordering on the phase stability, halfmetallicity and magnetism of Co2FeAl (CFA) Heusler alloy. Various possible hypothetical structures: L21-I, L21-II, XA-I, and XA-II were prepared under the conventional L21 and inverse XA phases by altering the atomic occupancies at their Wyckoff sites. It is found that the XA-II phase of CFA is the most stable phase energetically among all the structures. The electronic structure calculations without U show the presence of half-metallic (HM) ground state only in L21-1 structure and the other structures are found to be metallic. However, the electronic structures of CFA are significantly modified in the presence of U, although the total magnetic moments per cell remained the same and consistent with the Slater-Pauling (SP) rule. The metallic ground states of CFA in L21-II and XA-II structures are converted into the half-metallic ground states in presence of U but remained the same (metallic) in XA-I structure. The results indicate that the electronic structures are not only dependent on the L21 and XA ordering of the atoms but also depend on the choice of U values. So experiments may only verify the superiority of GGA+U to GGA.

Journal of Physics D: Applied Physics

Physical Chemistry Chemical Physics

Thermal spike model (TSM), a widely accepted mechanism of swift heavy ion (SHI) - matter interact... more Thermal spike model (TSM), a widely accepted mechanism of swift heavy ion (SHI) - matter interaction, provides explanation to various SHI induced effects, including mixing across interfaces. We assess the...

Journal of Science: Advanced Materials and Devices

In this paper, we have presented the comparative study of mechanical, electrical and magnetic pro... more In this paper, we have presented the comparative study of mechanical, electrical and magnetic properties of Co 2 MnAl 1Àx Z x Heusler alloy with Z ¼ Si, Ge and Ga and x ¼ 0, 0.25, 0.75 and 1 using electronegativity (EN) model. We employed density functional theory for numerical calculations. It is found that Co 2 M-nAl 1Àx Z x with Z ¼ Ga, Ge follow the Vegard's law while Co 2 MnAl 1Àx Si x does not follow the same trend. Among all composition Co 2 MnAl .25 Si .75 alloy is found to be more compressible. Electronic density distribution depicts the ionic nature of Co 2 MnAl 1Àx Z x alloy systems. The Co 2 MnAl 1Àx Z x with Z ¼ Si, Ge possess larger magnetic moment and band gap with respect to Co 2 MnAl 1Àx Ga x system which results from the EN difference, degree of delocalization of valence electron, atomic size and atomic number, respectively.

Materials Letters

Abstract Effect of Si substitution at Al site of Co 2 MnSi 1 - x Al x Heusler alloy for compositi... more Abstract Effect of Si substitution at Al site of Co 2 MnSi 1 - x Al x Heusler alloy for composition x = 0.25 on its structural and magnetic properties, prepared by the arc melting method, was studied. The alloy was characterized by X-ray diffraction (XRD), X-ray photo electron spectroscopy (XPS), energy dispersive X-ray analysis (EDAX) and magnetic measurements. Our findings revealed the soft ferromagnetic nature of alloy, crystallizes in the L21 structure of lattice parameter a = 5.671 A. However, the presence of some antisite disorder (B2/A2) destroyed the half metallicity of alloy as computed by full-potential linearized augmented plane wave (FLAPW) method of density functional theory (DFT), indicates the traditional ferromagnetic behavior of Co2MnAl.25Si.75 alloy. Theoretical magnetic moment of Co2MnAl.25Si.75 alloy was found 4.29 μ B /formula unit (f.u.) in contrast to experimentally obtained moment 3.91 μ B /f.u., with good agreements with literature.

Phys. Chem. Chem. Phys., 2014

To investigate the variation in the radiation stability of ceria with microstructure under the el... more To investigate the variation in the radiation stability of ceria with microstructure under the electronic excitation regime, ceria samples sintered under different conditions were irradiated with high energy 100 MeV Ag ions. The ceria nanopowders were synthesized and sintered at 800 1C (S800), 1000 1C (S1000) and 1300 1C (S1300), respectively. The samples with widely varying grain size, densities and microstructure were obtained. The pristine and irradiated samples were studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). None of the samples amorphized up to the highest fluence of 1 Â 10 14 ions per cm 2 employed in this study. XRD and Raman studies showed that the sample with lowest grain size suffered maximum damage while the sample with largest grain size was most stable and showed little change in crystallinity. Raman spectroscopy indicated the enhanced formation of Ce 3+ and related defects in the sample with larger grain size after irradiation. The most intriguing result was the absence of Ce 3+-related defects in the sample with lowest grain size which actually showed maximum damage upon irradiation. The XPS studies on S800 and S1300 provided concrete evidence for the presence of Ce 3+ and oxygen ion vacancies in S1300. The grain boundaries and grain size dependent stability have been discussed.

AIP Conference Proceedings, 2017

We investigate the interface mixing across Pd0.60 Ni0.40 (∼20 nm)/SiO2 interface on irradiation b... more We investigate the interface mixing across Pd0.60 Ni0.40 (∼20 nm)/SiO2 interface on irradiation by 100 MeV Au ions at a fluence 1 × 1014 ions/cm2. The samples were characterized using Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy (XPS). From RBS results, a weak but significant intermixing is observed at the interface. The XPS spectra suggest that the irradiation first homogenizes the alloy film and then causes an interdiffusion of Pd and Ni atoms in SiO2.

Journal of Applied Physics, 2003

Solid acidity was found to be generated in methylsiloxane-based inorganic/organic hybrids by inco... more Solid acidity was found to be generated in methylsiloxane-based inorganic/organic hybrids by incorporating inorganic components other than Si, such as Al and Nb, into methylsiloxane networks by combining theoretical first-principles calculations based on the density functional theory (DFT) with experimental synthesis and characterization. First-principles calculations based on the DFT indicated that the dissociation energy of protons at the surface followed the order Si<Al<Nb. The calculation led to the conclusion that methylsiloxane-based inorganic/organic hybrids were synthesized from metal alkoxides. The solid acidity followed the same order: Si<Al<Nb. The Fourier-transform infrared measurements of pyridine adsorbed on the methylsiloxane-based inorganic/organic hybrids showed that the solid acidity can be attributed to Bronsted acid sites.

Physical Review B, 2005

The recently proposed hypothesis that swift-heavy-ion induced mixing is a consequence of a transi... more The recently proposed hypothesis that swift-heavy-ion induced mixing is a consequence of a transient molten state diffusion is tested by studying 230 MeV Au ion induced mixing at an Fe/ Si interface monitored online by elastic recoil detection analysis. An extensive data analysis has been made to determine the experimental intrinsic diffusivities of Fe in Si, and vice versa. The required size and duration of the transient melt phase have been calculated theoretically from the thermal spike model. The close resemblance of the experimental diffusivities to the liquid state diffusivities reported in the literature is a verification of the hypothesis.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002

The potential device application of semiconductor heterostructures and strained layer superlattic... more The potential device application of semiconductor heterostructures and strained layer superlattices has been highlighted. Metal organic chemical vapour deposition grown In 0:53 Ga 0:47 As/InP lattice-matched structure has been irradiated by 130 MeV Ag 13þ and studied by RBS/Channelling using 3.5 MeV He 2þ ions. Ion irradiation seems to have induced a finite tensile strain in the InGaAs layer, indicating thereby that ion beam mixing occurs at this energy. Other complementary techniques like high resolution XRD and STM are needed to conclude the structural modifications in the sample.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014

Pulsed laser deposited 60 nm thin film of homogeneous Mn 0.82 Bi 0.18 composite has been irradiat... more Pulsed laser deposited 60 nm thin film of homogeneous Mn 0.82 Bi 0.18 composite has been irradiated by 100 MeV Au ions at fluence 1 Â 10 13 ions/cm 2 , and investigated by field emission scanning electron microscopy, X-ray diffraction, magnetic hysteresis, X-ray photoelectron spectroscopy, and nanoindentation measurements. Dispersed nanostructures of soft Bi-rich phase of about 20 nm diameter emerged in a hard Mn-rich matrix on irradiation. Such structures, as synthesized by the present novel swift heavy ion irradiation approach, are usable as self-lubricating thin films.

Physical Chemistry Chemical Physics

Thermal spike model (TSM), a widely accepted mechanism of swift heavy ion (SHI) - matter interact... more Thermal spike model (TSM), a widely accepted mechanism of swift heavy ion (SHI) - matter interaction, provides explanation to various SHI induced effects, including mixing across interfaces. We assess the...

ACS Applied Materials & Interfaces

The Journal of Physical Chemistry C

Understanding the radiation tolerance of ceramics against low energy heavy ions is important for ... more Understanding the radiation tolerance of ceramics against low energy heavy ions is important for evaluating their stability against alpha recoils, which are a significant source of damage for their...

Two dimensional (2D) van der Waals heterostructures (vdWHs) have their unique potential in facili... more Two dimensional (2D) van der Waals heterostructures (vdWHs) have their unique potential in facilitating the stacking of layers of different 2D materials for optoelectronic devices with superior characteristics at a reduced cost. However, the fabrication of large area all-2D heterostructures is still challenging towards realizing practical devices. In the present work, we have demonstrated a rapid yet simple, impurity free and highly efficient sonication-assisted chemical exfoliation approach to synthesize hybrid vdWHs based on 2D molybdenum disulphide (MoS$_2$) and tungsten disulphide (WS$_2$), with high yield. Microscopic and spectroscopic studies have confirmed the successful exfoliation of layered 2D materials and formation of their hybrid heterostructure. The co-existence of 2D MoS2 and WS2 in the vdW hybrid is established by optical absorption and Raman shift measurements along with their chemical stiochiometry determined by X-ray photoelectron spectroscopy. The spectral respon...

Journal of Materials Engineering and Performance

In the present work, nanostructured functionalized silica is coated on an aluminum (Al) substrate... more In the present work, nanostructured functionalized silica is coated on an aluminum (Al) substrate by the spray pyrolysis method to create a stable and effective super-hydrophobic substrate for water harvesting via moist air. Substrate characterization reveals that (1) major diffraction peaks corresponding to crystoballite SiO2 (C-SiO2), quartz (Q-SiO2), Al2O3, and Al2SiO5 are to be found at SiO2/Al interface; (2) strong chemically bonded methyl functionalized silica is confirmed on the Al surface by Fourier-transform infrared spectroscopy (FT-IR) and x-ray photoelectron spectrometry (XPS) shows the presence of Al-O-Si bond at the interface; and (3) the equilibrium contact angle of the water droplet on the coated substrate is measured to be 156° ± 5° with a hysteresis of 10° ± 3°. The coating is found to be stable for more than 365 days in a humid atmosphere. Finally, moist air condensation experiments confirm substantial augmentation of condensate collected ranging from 188 ml/m2-h over an untreated aluminum substrate to 750 ml/m2-h over the coated substrate. Hence, it is concluded that nanostructured silica-coated Al substrate is highly effective for enhancing the condensation of water vapor from a moist air environment.

Environmental Science and Pollution Research

An ecofriendly and solar light-responsive graphene oxide wrapped zinc oxide nanohybrid has been s... more An ecofriendly and solar light-responsive graphene oxide wrapped zinc oxide nanohybrid has been synthesized hydrothermally using lemon and honey respectively as chelating and complexing agents. By tuning the reaction conditions, a heterostructure between GO and ZnO has been formed during synthesis. The photocatalytic activity of the synthesized nanohybrid was investigated by degradation of hazardous organic textile dye (methylene blue) as well as wastewater under natural solar light. The nanohybrid exhibited excellent photocatalytic activity towards degradation (~ 89%) of methylene blue (MeB). Furthermore, along with decolorization, 71% of mineralization was also achieved. Interestingly, the nanohybrid has been found to be reusable up to 4 cycles without significant loss of photocatalytic activity. Along with this, the physicochemical parameters of the wastewater generated from textile industry have been also monitored before and after exposure to nanohybrid. The results revealed significant reduction in chemical oxygen demand (COD) (96.33%), biochemical oxygen demand (BOD) (96.23%), and total dissolved solids (TDS) (20.85%), suggesting its potential applicability in textile wastewater treatment.

Advanced Energy Materials

Body weight, lipid profile, atherogenic index and coronary risk index were determined in rats fed... more Body weight, lipid profile, atherogenic index and coronary risk index were determined in rats fed commercial chicken salad with dressing. Twenty four weaning albino rats were divided into three groups of eight animals, baseline, rat chow (control) and chicken salad with dressing and fed respective diets, for five weeks. Body weights, serum cholesterol, serum triglycerides, HDL cholesterol and LDL cholesterol were determined using standard methods. Atherogenic and coronary risk indices were also calculated. Body weights and lipids profiles of animals on regular rat chow and chicken salad groups increased with age. Weight gain in rats fed chicken salad with dressing increased significantly (P<0.05) and had higher serum cholesterol, triglyceride, HDL cholesterol and LDL cholesterol values compared with the rat chow group. The observed increases in parameters evaluated might be due to the chicken component and salad dressing comprising of both mayonnaise and salad cream. Despite the observed absolute increase in the lipid profile values of the chicken salad with dressing group, the coronary risk index, atherogenic index, HDL cholesterol/total cholesterol ratio and triglyceride/HDL cholesterol ratios were within normal range and not significantly (P>0.05) different from the corresponding values for the rat chow fed group. It is however desirable that a similar study be carried out with human subjects.

Solar Energy

Abstract In thin film photovoltaics, antimony selenide (Sb2Se3) is making a mark as an important ... more Abstract In thin film photovoltaics, antimony selenide (Sb2Se3) is making a mark as an important absorber layer for its attractive structural, optical, and electrical properties. Several deposition techniques are used to grow Sb2Se3 films, albeit growth angle-dependent physical properties of Sb2Se3 films are yet to be explored in a systematic manner. In this work, we investigate the roles of growth angle (in the range of 0°-87°) and thickness (250 and 1000 nm) in governing optoelectronic properties of Sb2Se3 films grown by radio frequency sputter deposition technique. It is interesting to note that upon increasing the growth angle, a systematic enhancement in the optical band-gap takes place. This is accompanied by a systematic reduction in the work function of these amorphous films with increasing growth angle. Subsequently, after postgrowth annealing at 573 K for 180 s (in vacuum) all Sb2Se3 films undergo a structural phase transition from amorphous to crystalline one. Following this, the band-gap and work function of these films also get modified. This study paves the way to fabricate Sb2Se3 films having tunable optoelectronic properties like absorption coefficient, band-gap, and work function. Thus, it should be extremely useful to select Sb2Se3 films having optimal thickness and optoelectronic properties to fabricate Sb2Se3 absorber layer-based multi-junction hole-blocking solar cells having improved cell efficiencies.

Journal of Magnetism and Magnetic Materials

The generalized gradient approximation (GGA) scheme in the first-principles calculations are used... more The generalized gradient approximation (GGA) scheme in the first-principles calculations are used to study the effect of L21 and XA ordering on the phase stability, halfmetallicity and magnetism of Co2FeAl (CFA) Heusler alloy. Various possible hypothetical structures: L21-I, L21-II, XA-I, and XA-II were prepared under the conventional L21 and inverse XA phases by altering the atomic occupancies at their Wyckoff sites. It is found that the XA-II phase of CFA is the most stable phase energetically among all the structures. The electronic structure calculations without U show the presence of half-metallic (HM) ground state only in L21-1 structure and the other structures are found to be metallic. However, the electronic structures of CFA are significantly modified in the presence of U, although the total magnetic moments per cell remained the same and consistent with the Slater-Pauling (SP) rule. The metallic ground states of CFA in L21-II and XA-II structures are converted into the half-metallic ground states in presence of U but remained the same (metallic) in XA-I structure. The results indicate that the electronic structures are not only dependent on the L21 and XA ordering of the atoms but also depend on the choice of U values. So experiments may only verify the superiority of GGA+U to GGA.

Journal of Physics D: Applied Physics

Physical Chemistry Chemical Physics

Thermal spike model (TSM), a widely accepted mechanism of swift heavy ion (SHI) - matter interact... more Thermal spike model (TSM), a widely accepted mechanism of swift heavy ion (SHI) - matter interaction, provides explanation to various SHI induced effects, including mixing across interfaces. We assess the...

Journal of Science: Advanced Materials and Devices

In this paper, we have presented the comparative study of mechanical, electrical and magnetic pro... more In this paper, we have presented the comparative study of mechanical, electrical and magnetic properties of Co 2 MnAl 1Àx Z x Heusler alloy with Z ¼ Si, Ge and Ga and x ¼ 0, 0.25, 0.75 and 1 using electronegativity (EN) model. We employed density functional theory for numerical calculations. It is found that Co 2 M-nAl 1Àx Z x with Z ¼ Ga, Ge follow the Vegard's law while Co 2 MnAl 1Àx Si x does not follow the same trend. Among all composition Co 2 MnAl .25 Si .75 alloy is found to be more compressible. Electronic density distribution depicts the ionic nature of Co 2 MnAl 1Àx Z x alloy systems. The Co 2 MnAl 1Àx Z x with Z ¼ Si, Ge possess larger magnetic moment and band gap with respect to Co 2 MnAl 1Àx Ga x system which results from the EN difference, degree of delocalization of valence electron, atomic size and atomic number, respectively.

Materials Letters

Abstract Effect of Si substitution at Al site of Co 2 MnSi 1 - x Al x Heusler alloy for compositi... more Abstract Effect of Si substitution at Al site of Co 2 MnSi 1 - x Al x Heusler alloy for composition x = 0.25 on its structural and magnetic properties, prepared by the arc melting method, was studied. The alloy was characterized by X-ray diffraction (XRD), X-ray photo electron spectroscopy (XPS), energy dispersive X-ray analysis (EDAX) and magnetic measurements. Our findings revealed the soft ferromagnetic nature of alloy, crystallizes in the L21 structure of lattice parameter a = 5.671 A. However, the presence of some antisite disorder (B2/A2) destroyed the half metallicity of alloy as computed by full-potential linearized augmented plane wave (FLAPW) method of density functional theory (DFT), indicates the traditional ferromagnetic behavior of Co2MnAl.25Si.75 alloy. Theoretical magnetic moment of Co2MnAl.25Si.75 alloy was found 4.29 μ B /formula unit (f.u.) in contrast to experimentally obtained moment 3.91 μ B /f.u., with good agreements with literature.

Phys. Chem. Chem. Phys., 2014

To investigate the variation in the radiation stability of ceria with microstructure under the el... more To investigate the variation in the radiation stability of ceria with microstructure under the electronic excitation regime, ceria samples sintered under different conditions were irradiated with high energy 100 MeV Ag ions. The ceria nanopowders were synthesized and sintered at 800 1C (S800), 1000 1C (S1000) and 1300 1C (S1300), respectively. The samples with widely varying grain size, densities and microstructure were obtained. The pristine and irradiated samples were studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). None of the samples amorphized up to the highest fluence of 1 Â 10 14 ions per cm 2 employed in this study. XRD and Raman studies showed that the sample with lowest grain size suffered maximum damage while the sample with largest grain size was most stable and showed little change in crystallinity. Raman spectroscopy indicated the enhanced formation of Ce 3+ and related defects in the sample with larger grain size after irradiation. The most intriguing result was the absence of Ce 3+-related defects in the sample with lowest grain size which actually showed maximum damage upon irradiation. The XPS studies on S800 and S1300 provided concrete evidence for the presence of Ce 3+ and oxygen ion vacancies in S1300. The grain boundaries and grain size dependent stability have been discussed.