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effect is observed in low pressure large area 024 UDDIN, A.H.M.Z. (Research and
microwave discharge helium plasmas. Probe Receiving Centre, Bangladesh Betar, Shabag,
characteristics measured in helium plasmas have Dhaka) & HOSSAIN, M. (Dept. of Physics,
been analyzed in order to study the spatial plasma Bangladesh University of Engineering and
properties and to explore the cause of dips found Technology, Dhaka). THEORETICAL MODEL
in the probe characteristics. The results show that STUDY OF LIQUID PHASE EPITAXIAL
the dips observed in the probe characteristics are GROWTH KINETICS OF InGaP
believed to be by the secondary electron emission SEMICONDUCTOR. J. Bang. Acad. Sci., 2007,
from the probe surface due to the interaction of 31 (2), 155-162.
metastable atoms with the metal probe. The
density of helium metastable atoms has been A one-dimensional diffusion limited equation
determined from the metastable induced for Liquid Phase Epitaxial growth of InGaP is
secondary electron emission current and studied using numerical method and
compared with the model calculation. Density of crystallization path. Concentration profiles, solid
mhetastables increases with increasing pressure mole fraction, layer thickness as a function of
because of increasing electron-neutral collision time and temperature are constructed. A good
frequency to metastable level with pressure. But agreement is found when the theoretical findings
it is decreased with distance because of are compared with the reported values.
decreasing energy of microwave field. Electron
temperature decreases due to increasing electron- 025 ULLAH, A.K.M.S. (Dept. of
neutral collision frequency with pressure. The Mathematics and Natural Sciences, BRAC
density of electrons increases with increasing University, 66 Mohakhali, Dhaka); AHSAN,
pressure because of increasing ionizing events. M. H. (Dept. of Physics, Shahjalal University
Measured and calculated values of electron
temperature and metastable density are found in of Science and Technology, Sylhet); AHMED,
approximate agreement. F. U. (Bangladesh Atomic Energy Commission,
Dhaka) & KAMAL, I. (Institute of Nuclear
023 UDDIN, M.A.; MORTUZA, M.G. & Science & Technology, Bangladesh Atomic
BASAK, A.K. (Dept. of Physics, University of Energy Commission, Dhaka). STUDY OF
Rajshahi, Rajshahi). STUDY OF ELECTRON SANS DISTRIBUTION FUNCTION FOR
IMPACT SINGLE IONIZATION OF IONS WITH DIFFERENT PARTICLES AT DIFFERENT
CHARGE q > 2. J. Bang. Acad. Sci., 2006, 30 (1), CONDITIONS. BRAC Univ. J., 2008, V (1), 9-
101-109. 17.
The total electron impact single ionization cross- The size and shape of a particle can he found out
sections of light ionic targets (q > 2) are by the analysis of form factor distributions in
evaluated employing a simpler version of the small angle neutron scattering. In the present
modified binary-encounter dipole (MBED) work, the form factors were calculated
model. The proposed model, referred to as theoretically by computer program and their
QBED, also embodies the modification of the plots were analyzed to find out the size and
Burgess denominator and an ionic correction. The shape of the particles. The structure factor, on
analytic fit procedure is used to obtain the the other hand was found to be very useful to
differential continuum oscillator strength as done find out the particle separation and concentration
in MBED. They report here the application of the of the particles. The structure factors were
3+
4+
QBED model to various targets e.g., C , N , calculated for three potentials (i) Screened
6+
5+
7+
3+
4+
O , Ne , Ne , Ar , and Cu and our theoretical Coulomb Potential (ii) Hard Sphere Repulsion
results are compared with other available and (iii) Baxter Hard Sphere Model and their
theoretical and experimental findings. The QBED plots were analyzed to see the effects of
model is found to work much better than its structure factor on particle separation,
parent BED and perform at least as good as its concertration particle charge, potential height,
sister MBED model. potential width and temperature.
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