Theoretical considerations regarding pulsed CO2 laser annealing of silicon

We present a calculation of the surface temperature and investigate the “thermal runaway” phenomenon during pulsed CO₂ laser (λ = 10.6 μm) annealing of silicon. In calculating the temperature variation of free carrier absorption in n-Si, we have taken into account acoustic deformation potential scattering, optical deformation potential scattering, and ionized impurity scattering. The deformation potentials are adjusted to fit the experimentally observed values at 300°K. Also, we discuss the contribution of free carrier absorption during annealing with a Nd:glass laser (λ = 1.06 μm).     

Flavour physics and CP violation

It is well known that the study of flavour physics and CP violation is very important to critically test the Standard Model and to look for possible signature of new physics beyond it. The observation of CP violation in kaon system in 1964 has ignited a lot of experimental and theoretical efforts to understand its origin and to look for CP violation effects in other systems besides the neutral kaons. The two B-factories BABAR and BELLE, along with other experiments, in the last decade or so made studies in flavour physics and CP violation a very interesting one. In this article we discuss the status and prospectives of the flavour physics associated with the strange, charm and bottom sectors of the Standard Model. The important results in kaon sector will be briefly discussed. Recently, mixing in the charm system has been observed, which was being pursued for quite some time without any success. The smallness of the mixing parameters in the charm system is due to the hierarchical structure of the CKM matrix. Interestingly, so far we have not found CP violation in the charm system but in the future, with more dedicated experiments at charm threshold, the situation could change. Many interesting observations have been made in the case of bottom mesons and some of them show some kind of deviations from that of the Standard Model expectations which are mainly associated with the b → s flavour changing neutral current transitions. It is long believed that the B _s system could be the harbinger of new physics since it is a system in which both bottom and strange quarks are the constituents. Recently, D0 and CDF announced their result for the B _s mixing which is claimed to be the first possible new physics signature in the flavour sector. We plan to touch upon all important issues pointing out both theoretical and experimental developments and future prospects in this review article.     

Design of medium energy beam transport line between the RFQ and the Linac in the radioactive ion beam facility at VECC,Kolkata

The design of a medium energy beam transport (MEBT) line comprising of a re-buncher and four quadrupoles, two upstream and the other two downstream of the re-buncher, has been presented. The design was done to ensure almost 100% transport of heavy-ion beams of about 99 keV/u energy from RFQ having a q/A not less than 1/14 through the re-buncher and then through IH Linac of about 0.6 m length in which beam would be accelerated to about 185 keV/u. The re-buncher has been designed to operate at 37.8 MHz, the resonating frequency of both the RFQ and the IH Linac. The entire beam line has been installed and recently O⁵⁺ beam from RFQ has been transported through the re-buncher and subsequently accelerated in the IH Linac successfully.     

Effect of progressive annealing on Silicon Nanostructures grown by Hot Wire Chemical Vapor Deposition

In this work, the evolution of Silicon Nanostructures with progressive annealing has been studied. Hot Wire CVD (HWCVD) process was used to deposit a Si_xN_y/a-Si structure on an n-type 〈100〉$〈100〉$ Silicon substrate with the Nitride acting as the buffer layer. The depositions were carried out at a low substrate temperature (250 °C) which is precisely why HWCVD was chosen over other processes for this work. The as-deposited sample was then annealed at 800 °C and 900 °C respectively. AFM studies revealed promising results hinting at the presence of Silicon Nanostructures. With progressive annealing the Nanostructures began to evolve, eventually turning into sharp Nanopillars upon annealing at 900 °C. In this paper, a growth model has been proposed which attempts to validate the experimental results. Though a lot of work is currently underway in this field, study of Silicon Nanostructures grown by HWCVD technique is relatively new.     

1-Soliton solution of the generalized KP equation with generalized evolution

This paper obtains the 1-soliton solution of three variants of the generalized KP equation with generalized evolution. The solitary wave ansatz is used to carry out the integration of such equations. The parameter domain is also identified in the process. The numerical simulations are also obtained in this paper.     

1-Soliton solution and conservation laws for nonlinear wave equation in semiconductors

This paper obtains the 1-soliton solution of a nonlinear wave equation that arises in the study of semiconductors. The conserved quantities are also calculated from this equation. Furthermore, additional non-trivial conserved quantities are computed using the invariance and multiplier approach based on the well known result that the Euler-Lagrange operator annihilates the total divergence.