Narrow band UV emission from direct band gap Si nanoclusters embedded in bulk Si
This paper has been withdrawn keeping in view of publication elsewhere with some appropriate modifications.
cond-mat.mtrl-sci↗
arXiv subjects
G. Sahu
Publications and source records attributed to G. Sahu.
Observation of a Universal Aggregation Mechanism and a Possible Phase Transition in Au Sputtered by Swift Heavy Ions
Two exponents, $δ$, for size distribution of $n$-atom clusters, $Y(n)\sim n^{-δ}$, have been found in Au clusters sputtered from embedded Au nanoparticles under swift heavy ion irradiation. For small clusters, below 12.5 nm in size, $δ$ has been found to be 3/2, which can be rationalized as occurring from a steady state aggregation process with size independent aggregation. For larger clusters, a $δ$ value of 7/2 is suggested, which might come from a dynamical transition to another steady state where aggregation and evaporation rates are size dependent. In the present case, the observed decay exponents do not support any possibility of a thermodynamic liquid-gas type phase transition taking place, resulting in cluster formation.
cond-mat.mtrl-sci↗
The mechanism of ion induced amorphization in Si
Some results on damage build up in, and amorphization of, Si, induced by 25-30 keV Al$_5^-$, Si$_5^-$ and Cs$^-$ ions, at room temperature, are reported. We show that at low energy, amorphization is a nucleation and growth process, based on the direct impact mechanism. With an Avrami exponent $\sim 1.6$, the growth towards amorphization seems to be diffusion limited. A transition to a completely amorphized state is indicated at a dose exceeding 17 eV/atom, which is higher than 6-12 eV/atom as predicted by simulations. The observed higher threshold could be due to temperature effects although an underestimation of keV-energy recoils, in simulation, may not be ruled out.
cond-mat.mtrl-sci↗
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↗