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D. Ghose

Publications and source records attributed to D. Ghose.

5 recordsLinked to original sources
arXiv2009

Formation of ripple pattern on silicon surface by grazing incidence ion beam sputtering

Off-normal low energy ion beam sputtering of solid surfaces often leads to morphological instabilities resulting in the spontaneous formation of ripple structures in nanometer length scales. In the case of Si surfaces at ambient temperature, ripple formation is found to take place normally at lower incident angles with the wave vector parallel to the ion beam direction. The absence of ripple pattern on Si surface at larger angles is due to the dominance of ion beam polishing effect. We have shown that a gentle chemical roughening of the starting surface morphology can initiate ripple pattern under grazing incidence ion beam sputtering, where the ripple wave vector is perpendicular to the ion beam direction. The characteristics of the perpendicular mode ripples are studied as a function of pristine surface roughness and ion fluence. The quality of the morphological structure is assessed from the analysis of ion induced topological defects.

cond-mat.mtrl-sci↗
arXiv2008

Study of low energy Si$_5^-$ and Cs$^-$ implantation induced amorphization effects in Si(100)

The damage growth and surface modifications in Si(100), induced by 25 keV Si$_5^-$ cluster ions, as a function of fluence, $ϕ$, has been studied using atomic force microscopy (AFM) and channeling Rutherford backscattering spectrometry (CRBS). CRBS results indicate a nonlinear growth in damage from which it has been possible to get a threshold fluence, $ϕ_0$, for amorphization as $2.5\times 10^{13}$ ions-cm$^{-2}$. For $ϕ$ below $ϕ_0$, a growth in damage as well as surface roughness has been observed. At a $ϕ$ of $1\times 10^{14}$ ions-cm$^{-2}$, damage saturation coupled with a much reduced surface roughness has been found. In this case a power spectrum analysis of AFM data showed a significant drop, in spectral density, as compared to the same obtained for a fluence, $ϕ< ϕ_0$. This drop, together with damage saturation, can be correlated with a transition to a stress relaxed amorphous phase. Irradiation with similar mass Cs$^-$ ions, at the same energy and fluence, has been found to result in a reduced accumulation of defects in the near surface region leading to reduced surface features.

cond-mat.mtrl-sci↗
arXiv2003

Ion beam sputtering induced ripple formation in thin metal films

We have observed the formation of ripples in a number of thin metal films, e.g. Au, Pt, Ag, Cu and Co under Ar^{+} ion beam sputtering at grazing incidence. The structures are found to be quite stable under ambient conditions. The results show that the ripple formation in polycrystalline metallic films relies on the erosion-induced surface instability similar to that in amorphous materials.

cond-mat.mtrl-sci↗
arXiv2002

Low energy Ar$^{+}$ ion beam induced kinetic roughening of thin Pt films on a Si substrate

A 30 nm Pt thin film evaporated onto a Si wafer was sputtered by 8 keV Ar$^{+}$ ions at various ion doses. The evolution of the modified sputtered films was monitored by atomic force microscopy (AFM), high resolution scanning electron microscopy (HRSEM) and Rutherford backscattering spectrometry (RBS). The most interesting observation was the formation of mound-like structures on the metal surface. Morphological data were quantitatively analysed within the framework of the dynamic scaling theory. Analyses of the height-height correlation function for different doses yield roughness exponents $α$ in the range 0.65 - 0.87, while the root-mean-square roughness amplitude $w$ evolves with the dose $ϕ$ as a power law $w\propto ϕ^β$, with the growth exponent, $β$ $\approx $ 0.3. The results are discussed.

cond-mat.mtrl-sci↗