TY  - JOUR
A1  - Pietsch, Ullrich
A1  - Bhattacharya, M. K.
A1  - Mukherjee, M.
A1  - Sanyal, M. K.
A1  - Geue, Thomas
A1  - Grenzer, Jörg
T1  - Energy dispersive x-ray reflectivity technique to study thermal properties of polymer films
Y1  - 2003
ER  - 
TY  - JOUR
A1  - Pietsch, Ullrich
A1  - Bhattacharya, M. K.
A1  - Sanyal, M. K.
A1  - Geue, Thomas
T1  - Glass transition in Ultrathin Polymer Films : a Thermal Expansion Study
N2  - The glass transition process gets affected in ultrathin films having thickness comparable to the size of the molecules. We observe systematic broadening of the glass transition temperature (T-g) as the thickness of an ultrathin polymer film reduces below the radius of gyration but the change in the average T-g was found to be very small. The existence of reversible negative and positive thermal expansion below and above T-g increased the sensitivity of our thickness measurements performed using energy-dispersive x-ray reflectivity. A simple model of the T-g variation as a function of depth expected from sliding motion could explain the results
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Pietsch, Ullrich
A1  - Hazra, S.
A1  - Chini, T. K.
A1  - Sanyal, M. K.
A1  - Grenzer, Jörg
T1  - Ripple structure of crystalline layers in ion beam induced Si wafers
N2  - Ion-beam-induced ripple formation in Si wafers was studied by two complementary surface sensitive techniques, namely atomic force microscopy (AFM) and depth-resolved x-ray grazing incidence diffraction (GID). The formation of ripple structure at high doses (similar to7x10(17) ions/cm(2)), starting from initiation at low doses (similar to1x10(17) ions/cm(2)) of ion beam, is evident from AFM, while that in the buried crystalline region below a partially crystalline top layer is evident from GID study. Such ripple structure of crystalline layers in a large area formed in the subsurface region of Si wafers is probed through a nondestructive technique. The GID technique reveals that these periodically modulated wavelike buried crystalline features become highly regular and strongly correlated as one increases the Ar ion-beam energy from 60 to 100 keV. The vertical density profile obtained from the analysis of a Vineyard profile shows that the density in the upper top part of ripples is decreased to about 15% of the crystalline density. The partially crystalline top layer at low dose transforms to a completely amorphous layer for high doses, and the top morphology was found to be conformal with the underlying crystalline ripple
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Mukhopadhyay, M. K.
A1  - Datta, A.
A1  - Sanyal, M. K.
A1  - Geue, Thomas
A1  - Pietsch, Ullrich
T1  - Synchrotron Studies of Melting of Langmuir-Blodgett Films
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Mukherjee, M.
A1  - Bhattacharya, M. K.
A1  - Sanyal, M. K.
A1  - Geue, Thomas
A1  - Grenzer, Jörg
A1  - Pietsch, Ullrich
T1  - Temperature dependent thickness and surface tension of polymer films
Y1  - 2000
SN  - 81-7371295-6
ER  - 
TY  - JOUR
A1  - Pietsch, Ullrich
A1  - Mukhopadhyay, M. K.
A1  - Sanyal, M. K.
A1  - Datta, A.
A1  - Mukherjee, M.
A1  - Geue, Thomas
A1  - Grenzer, Jörg
T1  - Transition from two-dimensional to three-dimensional melting in Langmuir-Blodgett films
N2  - Results of energy-dispersive x-ray reflectivity and grazing incidence diffraction studies of Langmuir-Blodgett films exhibited evolution of conventional three-dimensional melting from continuous melting, characteristic of two- dimensional systems, as a function of deposited monolayers. Continuous expansion followed by a sharp phase transition of the in-plane lattice was observed before the melting point and found to be independent of number of deposited layers. Evolution of conventional melting with an increase in the number of monolayers could be quantified by measuring stiffness against tilting of the vertical stack of molecules, which are kept together by an internal field. The internal field as defined in this model reduces as the in-plane lattice expands and the sample temperature approaches melting point. The sharpness of the melting transition, which has been approximated by a Langevin function, increases with the number of deposited monolayers
Y1  - 2004
ER  -