R. K. Tripathi

Influence of silver incorporation on the structural and electrical properties of diamond-like carbon thin films.

A simple approach is proposed for obtaining low threshold field electron emission from large area diamond-like carbon (DLC) thin films by sandwiching either Ag dots or a thin Ag layer between DLC and nitrogen-containing DLC films. The introduction of silver and nitrogen is found to reduce the threshold field for emission to under 6 V/μm representing a near 46% reduction when compared with unmodified films. The reduction in the threshold field is correlated with the morphology, microstructure, interface, and bonding environment of the films. We find modifications to the structure of the DLC films through promotion of metal-induced sp2 bonding and the introduction of surface asperities, which significantly reduce the value of the threshold field. This can lead to the next-generation, large-area simple and inexpensive field emission devices.

Structural and Electronic Characterization of Nanocrystalline Diamondlike Carbon Thin Films

The origin of low threshold field-emission (threshold field 1.25 V/μm) in nanocrystalline diamond-like carbon (nc-DLC) thin films is examined. The introduction of nitrogen and thermal annealing are both observed to change the threshold field and these changes are correlated with changes to the film microstructure. A range of different techniques including micro-Raman and infrared spectroscopy, X-ray diffraction, electron microscopy, energy-dispersive X-ray analysis and time-of-flight-secondary ion mass spectroscopy are used to examine the properties of the films. A comparison of the field emission properties of nc-DLC films with atomically smooth amorphous DLC (a-DLC) films reveals that nc-DLC films have lower threshold fields. Our results show that nc-DLC can be a good candidate for large area field emission display panels and cold cathode emission devices.

Structural, nanomechanical, field emission and ammonia gas sensing properties of nitrogenated amorphous carbon films deposited by filtered anodic jet carbon arc technique

This paper reports the effect of substrate bias on the structural, nanomechanical, field emission and ammonia gas sensing properties of nitrogenated amorphous carbon films embedded with nanocrystallites (a-C: N: nc) deposited by a filtered anodic jet carbon arc (FAJCA) technique. The films are characterized by X-ray diffraction, high resolution transmission electron microscopy, energy dispersive X-ray spectroscopic analysis, Raman spectroscopy, nanoindentation, field emission and ammonia gas sensing measurements. The properties of the films obtained are found to depend on the substrate bias. The maximum hardness (H)=42.7 GPa, elastic modulus (E)=330.4 GPa, plastic index parameter (H/E)=0.129 and elastic recovery (% ER)=74.4% have been obtained in a-C: N: nc films deposited at -60 V substrate bias which show the lowest ID/IG=0.43, emission threshold (ET)=4.9 V/µm accompanied with the largest emission current density (Jmax)=1 mA/cm(2) and field enhancement factor (β)=1805.6. The gas sensing behavior of the a-C: N: nc film has been tested by measuring the change in electrical resistance of the sample in ammonia environment at room temperature with the fast response and recovery time as 29 and 66.9s, respectively.

Study of inter-relationship of depression, seizure frequency and quality of life of people with epilepsy in India

Epilepsy is a chronic neurological disorder that can have profound physical, social and psychological consequences. We aimed to assess the clinical predictors of quality of life of people with epilepsy. We recruited 31 patients suffering from epilepsy in this cross-sectional study. Their clinical profile was recorded. Quality Of Life in Epilepsy (QOLIE-31) was used to assess quality of life of our patients. Depression was screened by Neurological Disorders Depression Inventory in Epilepsy (NDDI-E). Among all the clinical variables, only seizure frequency significantly correlated with seizure worry (P=0.002), emotional well-being (P=0.026) and social functions (P=0.013) subscales of QOLIE-31. NDDIE score showed a significant negative correlation with all the subscales of QOLIE-31 except medication effects (P=0.993). A significant positive correlation was also noted between seizure frequency and NDDI-E score (r=0.417, P=0.020). Seizure frequency and depression are the most important predictors of quality of life in epilepsy patients. The management of patients with epilepsy should not only be aimed at just preventing seizures but the treating clinicians should also be cognizant about depression which itself can significantly affect the quality of life of patients.

Structural, Nanomechanical, and Field Emission Properties of Amorphous Carbon Films Having Embedded Nanocrystallites Deposited by Filtered Anodic Jet Carbon Arc Technique

This paper reports the effect of substrate bias on the structural, nanomechanical, and field emission properties of amorphous carbon films having embedded nanocrystallites (a-C:nc films) deposited by filtered anodic jet carbon arc technique. X-ray diffraction results exhibit predominantly an amorphous nature of the films. High-resolution transmission electron microscope images showed the amorphous nature of the films with nanocrystallites embedded in the amorphous matrix. Ultrafine nanograined microstructures with average grain size between 20 and 30 nm are observed throughout the film with a majority of the grains of single crystallites. A strong influence of substrate bias has been observed on the structural, nanomechanical, and field emission properties. Maximum nanohardness (H) of 58.3 GPa, elastic modulus (E) of 426.2 GPa, and H/E of 0.136 have been observed in a-C:nc films deposited at −60 V substrate bias which showed 82.6% sp3 content.

Synthesis and Characterization of Phosphorus Doped Hydrogenated Silicon Films by Filtered Cathodic Vacuum Arc Technique

Phosphorous doped hydrogenated silicon thin film has been deposited by filtered cathodic vacuum arc technique at different substrate temperatures at a fixed hydrogen gas pressure. X-ray diffraction, electrical conductivity and optical band gap and scanning electron microscopy have been used to characterize the properties of films.

Study of Phosphorus Doped Micro/Nano Crystalline Silicon Films Deposited by Filtered Cathodic Vacuum Arc Technique

Phosphorus doped micro/nano crystalline silicon thin films have been deposited by the filtered cathodic vacuum arc technique at different substrate temperatures (Ts) ranging from room temperature (RT) to 350 ∘C. The films have been characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, secondary ion mass spectroscopy, dark conductivity ( σD), activation energy ( ΔE) and optical band gap (E g). The XRD patterns show that the RT grown film is amorphous in nature but high Ts (225 and 350 ∘C) deposited films have a crystalline structure with (111) and (220) crystal orientation. The crystallite size of the higher Ts grown silicon films evaluated was between 17 to 31 nm. Raman spectra reveal the amorphous nature of the film deposited at RT whereas higher Ts deposited films show a higher crystalline nature. The crystalline volume fraction of the silicon film deposited at higher Ts was estimated as 65.7 % and 74.4 %. The values of σD, ΔE and E g of the silicon films deposited at different Ts were found to be in the range of 8.84 x 10 −4− 0.98 ohm −1cm−1, 0.06 - 0.31 eV and 1.31-1.93 eV, respectively. A n-type nc-Si/p-type c-Si heterojunction diode was fabricated which showed the diode ideality factor between 1.1 to 1.5.

Growth and Characterization of Nitrogen Incorporated Amorphous Carbon Films Having Embedded Nanocrystallies

This paper reports the growth and characterization of nitrogen incorporated amorphous carbon films having embedded nanocrystallites deposited by filtered anodic jet carbon arc technique. The films are characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman, residual stress and nanoindentation. The properties are found to depend on the substrate bias. The film deposited at −60 V substrate bias shows maximum hardness of 24 GPa and elastic modulus of 215 GPa.

Nanoindentation Study of Mechanical Properties of Diamond Like Carbon Coatings

Nanoindentation is a depth sensing indentation technique to probe the mechanical properties of small volume. In this contribution, the results of nanoindentation response of diamond like carbon (DLC) coatings on SiAlON ceramics are presented. Indentation measurements were performed with an applied load of 3 mN in order to examine the pressure induced deformation of the structure. The DLC coated SiAlON ceramics exhibited increased elastic modulus and hardness compared to uncoated samples. The other mechanical parameters estimated from nanoindentation measurements are elastic recovery, stiffness and plastic deformation energy.

Phosphorous Doped Hydrogenated Amorphous Silicon Carbide Films Deposited by Filtered Cathodic Vacuum Arc Technique

In the present work, we report the growth and characterization of phosphorous doped hydrogenated amorphous silicon carbide (a-SiC: H) films deposited by filtered cathodic vacuum arc technique using solid silicon target as cathode in presence of acetylene gas. The films have been characterized by x-ray diffraction, dark conductivity, activation energy, optical band gap, scanning electron microscopy, energy dispersive x-ray analysis and residual stress. The effect of arc current on the properties of P doped a-SiC: H films have been studied.