Ramphal Sharma

Engineering of nanocrystalline cadmium sulfide thin films by using swift heavy ions

Swift heavy ion (SHI) irradiation experiments have been performed on as-deposited nanocrystalline cadmium sulfide (CdS) thin films by using 100 MeV Au8+ ions with 5 × 1012 ions cm−2. In addition, the as-deposited films were annealed at 300 °C in air for 1 h. Structural, optical and electrical properties of pristine (as-deposited), annealed and irradiated thin films were carried out by using x-ray diffraction (XRD), energy dispersive spectra, scanning electron microscopy, atomic force microscopy, UV-VIS spectroscopy and Arrhenius plots for resistivity and thermoemf, respectively. XRD shows the intrinsic peak of (0 0 2) for the hexagonal phase of CdS. After annealing and SHI irradiation this peak was enhanced drastically and dramatically, showing the dominant orientation in this plane. The grain growth observed in these two post-deposition processes was different. This resulted in a decrease in resistivity of the annealed and the irradiated samples by one and two orders from the pristine sample, respectively.

Enhancement in sensitivity of copper sulfide thin film ammonia gas sensor: Effect of swift heavy ion irradiation

The studies are carried out on the effect of swift heavy ion (SHI) irradiation on surface morphology and electrical properties of copper sulfide (CuxS) thin films with three different chemical compositions (x values). The irradiation experiments have been carried out on CuxS films with x=1.4, 1.8, and 2 by 100 MeV gold heavy ions at room temperature. These as-deposited and irradiated thin films have been used to detect ammonia gas at room temperature (300 K). The SHI irradiation treatment on x=1.4 and 1.8 copper sulfide films enhances the sensitivity of the gas sensor. The results are discussed considering high electronic energy deposition by 100 MeV gold heavy ions in a matrix of copper sulfide.

Bio-green synthesis of Ni-doped tin oxide nanoparticles and its influence on gas sensing properties

Considering the potential applications of transition metal doped nanostructured materials and the advantages of novel, cost-effective and environmentally friendly biosynthesis methods, Ni-doped SnO2 nanomaterials have been synthesized using remnant water (ideally kitchen waste) collected from soaked Bengal gram bean (Cicer arietinum L.) extract. The structural and optical properties of the Ni-doped SnO2 nanostructures were studied using various techniques such as UV/visible spectroscopy, FT-IR spectroscopy, X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The SEM and TEM images and the XRD results of the biosynthesized Ni–SnO2 nanoparticles reveal a uniform size distribution with an average size of 6 nm and confirmed the formation of a rutile structure with the space group (P42/mnm) and the nanocrystalline nature of the products with a spherical morphology. Subsequently, Ni-doped biosynthesized SnO2 nanoparticles were coated onto a glass substrate using the doctor blade method to form thin films. The NO2 sensing properties of the materials have been studied in comparison with other gases. The reported gas sensing results are promising, which suggest that the Ni-dopant is a promising noble metal additive to fabricate low cost SnO2 based sensors.

Study of room temperature LPG sensing behavior of polyaniline thin film synthesized by cost effective oxidative polymerization technique

Polyaniline thin films doped with an inorganic acid were deposited on glass substrate using simple and cost effective oxidative polymerization technique. As-synthesized thin film of polyaniline was studied with different characterization techniques. The formation of polyaniline on glass substrate was confirmed by X-ray diffraction and UV spectroscopy. Surface morphological investigation was performed using scanning electron microscopy. Gas sensing behavior of polyaniline thin film was studied by I–V measurements before and after liquefied petroleum gas (LPG) exposure at room temperature, based on change in electrical resistance. The observed result shows polyaniline thin film sensor is efficient for LPG detection at room temperature.

Annealing-Induced Modifications in Physicochemical and Optoelectronic Properties of Ag-Doped Nanostructured CdS Thin Films

The Ag-doped nanostructured CdS thin films are grown by simple, cost effective chemical ion exchange technique at room temperature on ITO-coated glass substrate. These as grown thin films are annealed at 100, 200, 300, and 400°C in air atmosphere for 1 hour. To study the effect of annealing on physicochemical and optoelectronic properties, these as grown and annealed thin films are characterized for structural, compositional, morphological, optical, and electrical properties. X-ray diffraction (XRD) pattern reveals polycrystalline nature of these thin films with increase in crystallite size from 6.4 to 11.2 nm, from XRD the direct identification of Ag doping in CdS thin films cannot be judged, while shift in characteristics peak position of CdS is observed. The Raman spectrum represents increase in full width at half maxima and intensity of characteristic peak, confirming the material modification upon annealing treatment. Presence of Cd, Ag, and S in energy dispersive X-ray analysis spectra (EDAX) confirms expected elemental composition in thin films. Scanning electron microscopy (SEM) images represent grain growth and agglomeration upon annealing. Red shift in optical absorbance strength and energy band gap values from 2.28 to 2.14 eV is obtained. I-V response obtained from as grown and annealed thin films shows an enhancement in photosensitivity from 72% to 96% upon illumination to 100 mW/cm2 light source.

Study of Opto-Electronic Properties of Copper Sulphide Thin Film Grown by Chemical Bath Deposition Technique for Electronic Device Application

Cu2S Thin Film have been synthesized by simple and economic solution growth technique onto silica glass substrate with bath temperature at 40°C for an hour. Optical, properties of the prepared Thin Films were investigated by UV-Visible Spectrophotometer and Electrical properties of the prepared Thin Films were investigated by I-V Measurement System. The optical band gap was calculated by plotting Energy (hν) versus (αhν)2 and it was found to be 2.315 eV which is in very good agreement with the reported values. The semiconducting nature of the film has been confirmed from I-V Measurement curve which has shown ohmic nature in dark condition. Surface morphology have been studied by Scanning Electron Microscopy which revealed entire substrate surface was covered with uniform deposition which contains irregular shaped grains are uniformly distributed.

Studies on high electronic energy deposition in transparent conducting indium tin oxide thin films

We have examined the effect of swift heavy ions using 100 MeV Au8+ ions on the electrical properties of transparent, conducting indium tin oxide polycrystalline films with resistivity of 0.58 × 10−4 Ω cm and optical transmission greater than 78% (pristine). We report on the modifications occurring after high electronic energy deposition. With the increase in fluency, x-ray line intensity of the peaks corresponding to the planes (1 1 0), (4 0 0), (4 4 1) increased, while (3 3 1) remained constant. Surface morphological studies showed a pomegranate structure of pristine samples, which was highly disturbed with a high dose of irradiation. For the high dose, there was a formation of small spherical domes uniformly distributed over the entire surface. The transmittance was seen to be decreasing with the increase in ion fluency. At higher doses, the resistivity and photoluminescence intensity was seen to be decreased. In addition, the carrier concentration was seen to be increased, which was in accordance with the decrease in resistivity. The observed modifications after high electronic energy deposition in these films may lead to fruitful device applications.

Room Temperature Ammonia Gas Sensing Properties of Biosynthesized tin Oxide Nanoparticle Thin Films

The authors are thankful to UGC-DAE Consortium for Scientific Research, Indore (Project Ref. No.: CSR-I/CRS-48/48) and UGC, New Delhi (F. No. 41-370/2012 (SR)) for the financial support. We are also thankful to the Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad for providing the laboratory facility.

Effect of Cu doping on LPG sensing properties of soft chemically grown nano-structured ZnO thin film

Zinc oxide (ZnO) thin film was grown by soft chemical route. Structural studies of ZnO thin film reveal hexagonal structure. The c/a ratio increase as the concentration of Cu (dopant) enhanced. Elemental analysis reveals the presence of Cu ions into ZnO matrix, which substitute at Zn site into the nano-structured ZnO crystal as it was presented in ball and stick model. Successful tailoring of band gap by doping was found in optical study and presented in band diagram model. The gas response was found to be 1.15 for 200ppm of gas concentration. The response and recovery times were found to be ~ 10 and 8 sec respectively.

Room temperature synthesis of nanostructured mixed-ordered-vacancy compounds (OVCs) and chalcopyrite CuInSe2 (CIS) thin films in alkaline chemical bath

Room temperature synthesis of ordered-vacancy-compounds (OVCs) and copper indium diselenide (CuInSe2, CIS) by cation and anion exchange reactions of solid CdS thin films with CIS ionic solution in an alkaline chemical bath is reported. The growth parameters such as pH, deposition time and concentration of the solutions were optimized to achieve uniform thin films. Nanostructured CdS thin films (150 nm thick) prepared by chemical bath deposition are used for the deposition of OVC and CIS thin films. The ion exchange reaction between the CdS thin film and the CIS ionic solutions transforms the yellow colour CdS film into faint black, indicating the formation of OVC and CIS film. The resultant films were annealed in air at 200 °C for 1 h and further subjected to characterization using the x-ray diffraction, transmission electron microscopy, energy dispersive x-ray analysis, x-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, optical absorption and electrical measurement techniques. The OVC and CuIn3Se5 nanodomains are observed in chalcopyrite CIS thin films and these films have nanostructured morphology onto amorphous/nanocrystalline phase of CdS. The OVC–CIS films are p-type with a band gap energy of 1.453 eV.