P. K. Goyal

Effect of temperature on the electrical transport properties of p-type polycrystalline indium antimonide

Measurements of Hall coefficient (RH), dc conductivity and Hall mobility have been made on p-type polycrystalline indium antimonide in the temperature range ∼ 77–450K. The average size of the grains in the sample was ∼0. 15 μm. It is found that Hall coefficient in the low temperature range is determined by the carrier concentration in the crystallites and n-type conduction predominates over p-type conduction above room temperature. Conductivity and Hall mobility were found to be thermally activated above 120K while the conduction near liquid nitrogen temperature is predominated by the variable range hopping. The effect of grain boundaries is found to be removed above ∼ 370K. The experimental results were used to calculate the grain size, intrinsic carrier density, energy band gap of the sample and the concentration of trap states.

Study of Electrical Conductivity of Kr+ Ion implanted Polycarbonate in Relation to Carbon Structure

Polycarbonate films were irradiated to 100 keV Kr+ ions under high vacuum at room temperature with the fluences ranging from 1×1015 to 1×1016 ions/cm2. The surface conductivity measurements of these samples were carried out by two probe method using pressure contacts. The surface conductivity was found to be increased from 3.64E‐14 S in virgin sample to 1.88E‐10 S for the sample implanted at the dose of 1×1016 ions/cm2. The formation of a three dimensional carbonaceous network, consisting of disordered bonds, emerges in the implanted region of the polycarbonate, as confirmed through Raman spectroscopy, is considered responsible for increased surface conductivity as a result of implantation.

Study of Dielectric Behavior and Charge Conduction Mechanism of Poly(Vinyl Alcohol) (PVA)-Copper (Cu) and Gold (Au) Nanocomposites as a Bio-resorbable Material for Organic Electronics

Poly(vinyl alcohol) (PVA) embedded with varying concentrations of chemically synthesized copper (Cu) and gold (Au) nanoparticles (NPs) were prepared using ex situ sol–gel casting method. The addition of almost the same concentration of CuNPs in PVA improves the conducting properties, while that of AuNPs improves the dielectric nature of composite films. It has been found that addition of AuNPs up to ∼0.4 wt.% concentration enhaneces the capacitive nature due to the formation of small Coulomb tunneling knots as internal capacitors. The dielectric studies suggest the Maxwell–Wagner interfacial polarization as the dominant dielectric relaxation process, whereas the I–V characteristics indicate bulk limited Poole–Frenkel emission at high voltages as the dominant charge transport mechanism operating at room temperature in all specimens. These novel features lead to the conclusion that addition of a small quantity of metal nanoparticles can help tune the properties of PVA for desired applications in bio-compatible polymer-based organic electronic devices.

Study of the structure, dielectric and ferroelectric behavior of BaBi4+δTi4O15 ceramics

The structure and ferroelectric properties of excess bismuth doped barium bismuth titanate BaBi4+δTi4O15 (δ = 2 - 10 wt.%)) ceramics prepared by solid-state reaction method have been investigated. X-ray diffraction (XRD) confirms the formation of a single phase material with a change in the orthorhombic distortion with varying excess of bismuth content. There is no change in the phase transition temperature (Tm) while the relaxor behaviour has been modified significantly with excess of bismuth doping. Saturated hysteresis loops with high remnant polarization (Pr ~ 12.5  µC/cm2), low coercive fields (Ec ~ 26 kV/cm) are measured and a high piezoelectric coefficient (d33 ~ 29 pC/N) is achieved in poled BaBi4Ti4O15 ceramics prepared with up to 8 wt.% of excess bismuth oxide. The improvement in the ferroelectric properties with increase in the excess bismuth content in BaBi4Ti4O15 ceramics has been explained in terms of changing oxygen vacancy concentration and structural relaxation. Tunable ferroelectric mate...

Study of the structure and ferroelectric behavior of BaBi4-xLaxTi4O15 ceramics

The structure and ferroelectric properties of Lanthanum substituted barium bismuth titanate BaBi4-xLaxTi4O15 (0 ≤ x ≤ 0.5) ceramics prepared by solid-state reaction method have been investigated. X-ray diffraction (XRD) confirms the formation of a single phase material. The distribution of lanthanum into the perovskite layers and (Bi2O2)2+ layers of BaBi4Ti4O15 ceramics have been revealed through Raman spectroscopy. At lower value of x, it is seen that La3+ ions prefer to substitute A-site Bi3+ ions in the perovskite layers while for higher x values, La3+ ions get incorporated into the (Bi2O2)2+ layers. A critical La content of x ∼ 0.2 in BaBi4-xLaxTi4O15 is seen to exhibit a large remnant polarization (Pr) with low coercive field (Ec). The improvement in the ferroelectric properties of La substituted BaBi4Ti4O15 ceramics has been explained in terms of changing oxygen vacancy concentration and structural relaxation. Tunable ferroelectric materials can be obtained by manipulating the doping amount of lanth...

Electrical conduction in 100 keV Kr+ ion implanted poly (ethylene terephthalate)

Polyethylene terephthalate (PET) samples have been implanted to 100 keV Kr+ ions at the fluences 1×1015−- 1×1016 cm−2. From I-V characteristics, the conduction mechanism was found to be shifted from ohmic to space charge limited conduction (SCLC) after implantation. The surface conductivity of these implanted samples was found to increase with increasing implantation dose. The structural alterations in the Raman spectra of implanted PET samples indicate that such an increase in the conductivity may be attributed to the formation of conjugated double bonded carbonaceous structure in the implanted layer of PET.

Optical Behaviour of N+ Ion Implanted CR‐39 Polymer

The 100 keV N+ ion implanted samples of CR‐39 polymer at different doses from 5×1015 to 2×1016 ions/cm2 were subjected to UV‐Visible transmission and reflection spectroscopy. After applying necessary corrections for reflection losses at the front and back surfaces, the true value of absorption coefficient and reflectance from the implanted surface have been determined. From these corrected values of absorbance and reflectance, the values of optical energy gap and refractive index have been deduced. A drastic decrease in the values of optical energy gap while a significant increase in refractive index have been observed after implantation.