K. N. Tripathi

Effect of laser irradiation on structural, electrical and optical properties of SnO2 films

Thin films of SnO2 were prepared using a spray pyrolysis technique. Films were irradiated with Nd:YAG laser pulses of various energy densities (2–50 mJ cm−2) with varying number of pulses from 1–50. X-ray diffraction studies were made to investigate the structural changes due to laser irradiation. An improvement in crystallinity and an increase in grain size were observed in laser-irradiated films. Hall coefficient and Hall mobility studies were made in the temperature range 77–300 K for the as-grown as well as laser-irradiated films. An increase in mobility and a decrease in carrier concentration were observed in the films after laser irradiation. Optical transmission studies revealed that the refractive index increased as a result of laser irradiation.

A method for the calculation of the characteristic impedance of microstrip

A simple method has been reported for the estimation of the characteristic impedance of microstrip by evaluating the associated capacitances. These results are in good agreement with the experimental data.

Effect of laser irradiation on the electrical properties of amorphous germanium films

Amorphous films of germanium were grown using a vacuum evaporation technique, on glass substrates kept at room temperature. As-grown films were irradiated with Q-Switched Nd-YAG laser pulses (λ=1.06 μm, 20nsec, 10 to 50Jcm−2). The d.c. conductivity measurements were made in the temperature range 77 to 300 K. It was observed that the effect of laser irradiation was similar to the effect caused by the thermal annealing of the films. The d.c. conductivity data were analysed in the light of Motts theory of a variable range hopping conduction process.

The influence of transverse magnetic field on Gunn effect threshold

Abstract The effect of magnetic field has been studied on the Gunn effect threshold electric field for short planar Gunn devices. For low magnetic fields, experimental results are in good agreement with the theoretical results but a large increase in threshold electric field has been observed for higher magnetic fields.

The effect of transverse magnetic field on resistively loaded Gunn diodes

Abstract The effect of transverse magnetic field has been studied on a resistively loaded diode. The peak to valley ratio of the current and transit time of the domains is found to increase with the magnetic field.

Study of an impedance step in a microstrip line

The additional discontinuity capacitance associated with an abrupt impedance step in a microstrip line is calculated using Schwartz Chirstofell transformation technique under static assumptions. The computed results are compared with the other available data.

A study of gaps in microstrip transmission lines

An analytical method and numerical results for gap capacitance in microstrip transmission lines and an abruptly ended strip conductor have been described using Schwarz-Christofell transformation. The numerical results are compared with the published experimental data.

The temperature variation of low field electron mobility in n-GaAs

Abstract We have studied the effect of low temperatures on low field electron mobility, threshold electric field and peak to valley ratio for Gunn oscillations. The low field electron mobility increases slightly while the threshold field decreases with the lowering of the temperature. The peak to valley ratio of the current is found to increase with a decrease in temperature.

Losses in microstrip resonators

The effects of radiation losses on the microstrip resonator have been investigated in detail. The ratio of the power radiated to power loss in the microstrip has been theoretically calculated using a modified relation for the characteristic impedance and effective dielectric constant. The results have been found to be in good agreement with available experimental data.

Calculation of the characteristic impedance of coupled microstrip lines

A simple method is presented whereby the characteristic impedance of the coupled microstrip lines may be calculated with reasonable accuracy. The technique uses single microstrip-line geometry as an intermediate step. The results obtained are in good agreement with the experimental data.