Event calendar file
Department of Nuclear and Atomic Physics Seminars
Clustering In Thin Films on Silicon Surfaces
by Dr. Milind Rundhe (IIT, Madras)
Thursday, April 26, 2012
from
to
(Asia/Kolkata)
at Colaba Campus ( P 305 )
at Colaba Campus ( P 305 )
| Description |
In this talk he will present three different clustering phenomena on silicon surfaces. Thin Pb films, deposited on clean Si surfaces at room temperature (RT), show spectral broadening in ion backscattering spectra due to clustering of Pb, when annealed [Nucl. Instr. and Meth. B 190 (2002) 641]. In order to study the dynamics of clustering on bromine-passivated Si(1 1 1) substrates, Pb thin films (1–3 nm) were deposited from a Knudsen cell under ultrahigh vacuum conditions. Each film was deposited at RT and subsequently annealed at 100, 150 and 260 0C for about 4 h. Five Rutherford backscattering spectrometry (RBS) measurements were made at different time intervals for each annealing. Analysis of RBS spectra of as-deposited and annealed Pb films does not show any significant spectral broadening in annealed Pb films. However, island formation has been confirmed by transmission electron microscopy on a 100 0C-annealed sample. Clustering has apparently occurred in the as-deposited film due to lower surface free energy of the passivated substrate and further detectable growth in cluster height has not occurred in annealing. We have used Auger electron spectroscopy (AES) to investigate the effect of electron beam exposure on growth modes of fullerene (C60) on substrates like Ag and hydrogen-passivated Si(1 1 1). The electron beam comprises of 3.4 keV electrons, which are used in the AES study. To investigate the effect, Auger signal (AS) vs. deposition time (t) measurements were conducted in a sequential mode, i.e., alternating deposition of C60 and analysis using the electron beam. Duration of AES data collection after each deposition was the duration of exposure to electron beam in this experiment. For the growth study of C60 on Ag, three AS–t plots were recorded for three different durations of exposure to electron beam. Changes in the AS–t plot, depending on the duration of exposure to the electron beam, reflect the electron beam-induced damage. Electron beam induced damages of C60 produce carbon materials of different densities and consequently transmission coefficient (alpha) of Auger electron through this material changes. In order to fit the AES (AS vs. t) data a model has been used which simultaneously provides the growth mode and the transmission coefficient (alpha). Observation of an increasing transmission coefficient with the increasing duration of exposure to the electron beam from a alpha= 0.34 to 0.60 indicates the change of the nature of the carbon material due to the partial damage of C60. SiC films were grown by exposing hydrogen-passivated Si(100) substrates to a C60 flux, at a substrate temperature of 950 oC. The samples were investigated ex-situ utilizing different techniques like Rutherford backscattering spectroscopy (RBS), X- ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. A combination of the results enables us to discuss structure, orientation, the crystalline quality, and stress in the SiC film grown. |
| Organised by | Dr. Vaibhav Prabhudesai |
