Micro-morphological investigations on wettability of Al-incorporated c-Si thin films using statistical surface roughness parameters

The tunable surface properties of Al-incorporated c-Si and/or homogeneous c-Si (i.e., absorber layer) thin films are investigated with the help of 3D surface topography, statistical analysis, and contact angle measurement. The absorber layers are developed by ion irradiation on c-Al/a-Si films, which results the crystallization of Si in bilayer films, and the top unreacted Al layers were chemically etched off by wet selective etching. The 3D surface topography and statistical analysis is performed on the atomic force microscopy images of the absorber film surface. The analyses suggest that the surfaces are highly complex and irregular isotropic. The surface roughness and irregularity is found to be decreasing with increasing ion fluence. Variation of contact angle with statistical parameters suggest that the wettability of the absorber surface strongly depends on the surface statistical parameters. The surfaces are hydrophobic in nature, and hydrophobicity is found to decrease with increasing ion fluence. The hydrophobic nature of low reflective absorber surface suggests that the film may be useful as a photon absorber layer for advance solar cell applications.     

Phase transformation in Ni–Mn–Sn ferromagnetic shape memory alloy thin films induced by dense ionization

The effects of 200 MeV Au ions irradiation on the structural and magnetic properties of Ni–Mn–Sn ferromagnetic shape memory alloy (FSMA) thin films have been systematically investigated. In order to understand the role of initial microstructure and phase of the film with respect to high energy irradiation, the two types of Ni–Mn–Sn FSMA films having different phases at room temperature were irradiated, one in martensite phase (Ni_58.9Mn_28.0Sn_13.1) and other in austenite phase (Ni₅₀Mn_35.6Sn_14.4). Transmission electron microscope (TEM) and scanning electron microscope (SEM) images along with the diffraction patterns of X-rays and electrons confirm that martensite phase transforms to austenite phase at a fluence of 6×10¹² ions/cm² and a complete amorphization occurs at a fluence of 3×10¹³ ions/cm², whereas ion irradiation has a minimal effect on the austenitic structure (Ni₅₀Mn_35.6Sn_14.4). Thermo-magnetic measurements also support the above mentioned behaviour of Ni–Mn–Sn FSMA films with increasing fluence of 200 MeV Au ions. The results are explained on the basis of thermal spike model considering the core and halo regions of ion tracks in FSMA materials.     

Bilinear Hardy–Steklov Operators

Mathematical Notes - The weighted inequality in Lebesgue norms with bilinear Hardy–Steklov operators is characterized.     

Study on the ferromagnetism in Co and N doped ZnO thin films

Present investigation reports the structural, optical and magnetic properties of co-doping of Co and N ions in ZnO samples, prepared by two distinct methods. In the first method, samples are synthesized by Sol–gel technique in which the Co and N are co-doped simultaneously during the growth process itself. In the second case, N ions are implanted in the Co doped ZnO thin films grown by Pulsed Laser Deposition (PLD). Structural studies showed that the nitrogen implantation on Co doped ZnO samples developed compressive stress in the films. X-ray photoelectron spectroscopy confirmed the doping of Co and N in ZnO matrix. In the Resonant Raman scattering multiple LO phonons up to fifth order are observed in the (Co, N) co-doped ZnO. Photoluminescence spectra showed that there is reduction in the bandgap due to the presence of Co in the lattice and also the presence of Zn vacancies in the films. All samples showed ferromagnetic behavior at room temperature. The magnetic moment observed in the implanted films is found to be varied with the different dosages of the implanted N ions. First principle calculations have been carried out to study the possible magnetic interaction in the co-doped system. Present study shows that the ferromagnetic interaction is due to the hybridization between N 2p and Co 3d states in the (Co, N) co-doped ZnO and is very sensitive to the geometrical configurations of dopants and the vacancy in the ZnO host lattice.     

Ion irradiation induced nano pattern formation on TiO2 single crystal

Nanodots have been fabricated on rutile TiO₂(1 1 0) single crystals using Ar ion beam. Ion beam sputtering creates oxygen vacancies, leading to a 45 nm thick Ti rich layer, on the surface. Post-sputtering, rutile TiO₂ also exhibits a decrease in the inter planar separation along [1 1 0] direction. Additionally, blueshift in the E_g Raman mode, representing the vibrations of oxygen atoms along c-axis, is also observed. Both these results suggest the development of a compressive stress along c-axis upon sputtering. Enhancement in intensity of A_1g Raman mode also indicates modification in TiO vibrational influence.     

Nano/micro structure synthesis on semiconducting substrate and their characterization

In this paper electrical and field emission properties of the randomly distributed copper, iron and nickel nanowires on GaAs substrate are presented. Semiconducting (GaAs) wafers, spin coated with thin polymeric films were irradiated with 50 MeV Li (+3) ions at a fluence of 8 × 10⁷ ions/cm², followed by UV irradiation and chemically etching in aqueous NaOH (6N, at room temperature). The wires have been deposited potentiostatically into the pores of the track-etch polycarbonate membrane spin coated onto the GaAs substrate. The size, shape and morphology of the deposits are strongly dependent of the preparation conditions such as deposition potential, current density, electrolyte and etching conditions. Later, morphological, electrical and field emission properties of the so deposited nano-/micro-structures were studied.     

10Be measurements at IUAC-AMS facility

An accelerator mass spectrometry (AMS) facility for measurements of ¹⁰Be has been developed by upgrading the 15UD Pelletron accelerator at Inter-University Accelerator Centre (IUAC), New Delhi. Details of the up gradation of the facilities and the measurement procedure are described briefly. Chemical processing for the separation of ¹⁰Be from manganese nodules and results of recent experiments on ¹⁰Be are presented.     

An exercise concerning the selfdual cusp forms on GL(3)

Using L-functions and various known results, we provide a proof of the following Let F be a number field and II a cuspidal automorphic form on GL(3)/F which is selfdual. Then, up to replacing II by a quadratic twist, it can be realized as the adjoint of a cusp form π on GL(2)/F, with π unramified at any prime where II is. We also investigate the properties of π when II is regular and algebraic.     

Composition dependent structural modification in relaxed Si1−xGex films by 100 MeV Au beam

We report the modification of molecular beam epitaxy grown strain-relaxed single crystalline Si_1−xGe_x layers for x=0.5 and 0.7 as a result of irradiation with 100 MeV Au ions at 80 K. The samples were structurally characterized by Rutherford backscattering spectrometry/channeling, transmission electron microscopy (TEM) and high-resolution X-ray diffraction before and after irradiation with fluences of 5×10¹⁰, 1×10¹¹ and 1×10¹² ions/cm², respectively. No track formation was detected in both the samples from TEM studies and finally, the crystalline to amorphous phase transformation at 1×10¹² ions/cm² was examined to be higher for Si_0.3Ge_0.7 layers compared to Si_0.5Ge_0.5 layers.