R. Damle

Analysis of generation and annihilation of deep level defects in a silicon-irradiated bipolar junction transistor

A commercial bipolar junction transistor (2 N 2219 A, npn), irradiated with 120 MeV Si9+ ions with a fluence of the order of 1012 ions cm−2, is studied for radiation-induced gain degradation and deep level defects. I–V measurements are made to study the gain degradation as a function of ion fluence. Properties such as activation energy, trap concentration and capture cross section of deep levels are studied by deep level transient spectroscopy (DLTS). Minority carrier trap energy levels with energies ranging from EC − 0.160 eV to EC − 0.581 eV are observed in the base-collector junction of the transistor. Majority carrier trap levels are also observed with energies ranging from EV + 0.182 eV to EV + 0.401 eV. The identification of the defect type is made on the basis of its finger prints such as activation energy, annealing temperature and capture cross section by comparing with those reported in the literature. New energy levels for the defects A-center, di-vacancy and Si-interstitial are also observed. The irradiated transistor is subjected to isothermal and isochronal annealing. The defects are seen to anneal above 250 °C. The defects generated in the base region of the transistor by displacement damage appear to be responsible for transistor gain degradation.

Simulation of energy and fluence dependence of heavy ion induced displacement damage factor in bipolar junction transistor

This article presents the theoretical calculation of the variation of displacement damage factors as a function of energy and rad equivalent fluence in bipolar junction transistor for various particulate radiation viz., He, Si, Cl, Ti, Ni, Br, Ag, I, and Au. The calculation is based on the experimental data on γ-ray induced gain degradation in a commercial space borne BJT (2N3019). The method involves the calculation of γ-ray dose (rad(Si)) equivalent of effective particle fluence. The linear energy transfer (LET) in silicon for different particle radiation obtained from TRIM calculation has been used for the conversion of γ-dose into fluence of various particles. The estimation predicts a smooth increase in the displacement damage factor as the mass of the ion increases. Further, the displacement damage factor reaches a maximum at the same value of energy, which corresponds to maximum LET for all heavy ions. The maximum value of damage factor marginally decreases with increasing ion fluence for an ion of given energy. The results are compared with the data available in the literature for proton, deuteron, and helium induced displacement damage.

I-V and DLTS study of generation and annihilation of deep-level defects in an oxygen-ion irradiated bipolar junction transistor

A commercial bipolar junction transistor (2N 2219A, npn) irradiated with 84 MeV O6+-ions with fluence of the order of 1013 ions cm−2 is studied for radiation-induced gain degradation and deep-level defects or recombination centers. I-V measurements are made to study the gain degradation as a function of ion fluence. Properties such as activation energy, trap concentration and capture cross section of deep levels are studied by deep-level transient spectroscopy. Minority carrier trap energy levels with energies ranging from E C −0.17 eV to E C −0.55 eV are observed in the base–collector junction of the transistor. Majority carrier defect levels are also observed with energies ranging from E V +0.26 eV to E V +0.44 eV. The irradiated device is subjected to isothermal and isochronal annealing. The defects are seen to anneal above 250 °C. The defects generated in the base region of the transistor by displacement damage appear to be responsible for an increase in base current through Shockley-Read-Hall or multi-phonon recombination and consequent transistor gain degradation.

NMR study of molecular dynamics in hydrazinium phosphates

Abstract The proton spin-lattice relaxation time T 1 (at 5.4, 10 and 15 MHz) and second moment M 2 (at 9.8 MHz) were measured in the temperature range 77–300 K in hydrazinium dihydrogen phosphate N 2 H 5 H 2 PO 4 and dihydrazinium hydrogen phosphate (N 2 H 5 ) 2 HPO 4 . In N 2 H 5 H 2 PO 4 a well-defined single proton T 1 , minimum and three M 2 transitions have been observed. The T 1 minimum has been interpreted in terms of the NH 3 group reorientation with activation energy of 7.69 kcal mol −1 , relaxing all protons by spin-diffusion. In (N 2 H 5 ) 2 HPO 4 a single T 1 minimum and a small hysteresis behaviour have been observed in the temperature dependence of T 1 . Two M 2 transitions were observed. The T 1 minimum has been interpreted in terms of the NH 3 group reorientation with an activation energy of 4.4 kcal mol −1 . The M 2 behaviour in both phosphates is explained in terms of NH 3 /NH 2 motions.

Long-term optical flux and colour variability in quasars

We have used optical V and R band observations from the Massive Compact Halo Object (MACHO) project on a sample of 59 quasars behind the Magellanic clouds to study their long term optical flux and colour variations. These quasars lying in the redshift range of 0.2 < z < 2.8 and having apparent V band magnitudes between 16.6 and 20.1 mag have observations ranging from 49 to 1353 epochs spanning over 7.5 years with frequency of sampling between 2 to 10 days. All the quasars show variability during the observing period. The normalized excess variance (Fvar) in V and R bands are in the range 0.2% < Fvar < 1.6% and 0.1% < Fvar < 1.5%. In a large fraction of the sources, Fvar is larger in the V-band compared to the R-band. From the z-transformed discrete cross correlation function analysis, we find that there is no lag between the V and R-band variations. Adopting the Markov Chain Monte Carlo (MCMC) approach, and properly taking into account the correlation between the errors in colours and magnitudes, it is found that majority of the sources show a bluer when brighter trend, while a minor fraction of quasars show the opposite behaviour. This is similar to the results obtained from other two independent algorithms namely the weighted linear least squares fit (FITEXY) and the bivariate correlated errors and intrinsic scatter regression (BCES). However, the ordinary least squares (OLS) fit normally used in the colour variability studies of quasars, indicates that all the quasars studied here show a bluer when brighter trend. It is therefore very clear that OLS algorithm cannot be used for the study of colour variability in quasars.

1H NMR study of molecular dynamics in dihydrazinium sulphate

The proton spin-lattice relaxation time

Investigation of deep level defects in copper irradiated bipolar junction transistor

T_1

High-energy electron induced gain degradation in bipolar junction transistors

and second moment

DLTS study of deep level defects in Li-ion irradiated bipolar junction transistor

M_2

I-V, C-V and deep level transient spectroscopy study of 24 MeV proton-irradiated bipolar junction transistor

have been measured in dihydrazinium sulphate