Shyamal Mondal

Performance of a size-selected nanocluster deposition facility and in situ characterization of grown films by x-ray photoelectron spectroscopy.

We report here on a newly installed gas aggregation type nanocluster deposition unit based on magnetron sputtering ion source with mass selection of the clusters by quadrupole mass filter. The system is ultra high vacuum compatible and is equipped with an in situ X-ray Photoelectron Spectroscopy facility, giving compositional information of the films formed by nanoclusters deposition on a substrate. Detailed descriptions and working of the components of the system are presented. For the characterization of the nanocluster source and associated mass filter for size selected clusters, the dependence of output performance as a function of aggregation length, sputter gas flow and magnetron power of the cluster source have been studied. Copper nanoclusters deposited on Silicon (100) surface and on transmission electron microscope grids are, respectively, studied with scanning electron microscopy and transmission electron microscopy for the morphology.

Oxidation behaviour of copper nanofractals produced by soft-landing of size-selected nanoclusters

We report the oxidation dynamics of a copper nanocluster assembled film, containing fractal islands, fabricated by the soft-landing of size-selected copper nanoclusters with an average diameter of 3 nm. The time evolution of the spontaneous oxidation of the prepared film in air at room temperature (RT) was studied. A compositional analysis of the film was carried out in an ultra-high vacuum (UHV) deposition chamber using an in situ X-ray photoelectron spectroscopy (XPS) system. The morphological aspects of the deposited film were studied with a high resolution scanning electron microscope (SEM) and an atomic force microscope (AFM). We report the spontaneous production of highly pure (∼95%) and technologically appealing nano-crystalline Cu2O within 300 seconds of air exposure. The crystalline structure was probed using high resolution transmission electron microscopy (HRTEM) and the optical properties were studied using a cathodoluminescence (CL) device attached to a SEM.

Pattern formation on ion-irradiated Si surface at energies where sputtering is negligible

The effect of low energy irradiation, where the sputtering is imperceptible, has not been deeply studied in the pattern formation. In this work, we want to address this question by analyzing the nanoscale topography formation on a Si surface, which is irradiated at room temperature by Ar+ ions near the displacement threshold energy, for incidence angles ranging from 0° to 85°. The transition from the smooth to ripple patterned surface, i.e., the stability/instability bifurcation angle is observed at 55°, whereas the ripples with their wave-vector is parallel to the ion beam projection in the angular window of 60°–70°, and with 90° rotation with respect to the ion beam projection at the grazing angles of incidence. A similar irradiation setup has been simulated by means of molecular dynamics, which made it possible, first, to quantify the effect of the irradiation in terms of erosion and redistribution using sequential irradiation and, second, to evaluate the ripple wavelength using the crater function formalism. The ripple formation results can be solely attributed to the mass redistribution based mechanism, as erosion due to ion sputtering near or above the threshold energy is practically negligible.The effect of low energy irradiation, where the sputtering is imperceptible, has not been deeply studied in the pattern formation. In this work, we want to address this question by analyzing the nanoscale topography formation on a Si surface, which is irradiated at room temperature by Ar+ ions near the displacement threshold energy, for incidence angles ranging from 0° to 85°. The transition from the smooth to ripple patterned surface, i.e., the stability/instability bifurcation angle is observed at 55°, whereas the ripples with their wave-vector is parallel to the ion beam projection in the angular window of 60°–70°, and with 90° rotation with respect to the ion beam projection at the grazing angles of incidence. A similar irradiation setup has been simulated by means of molecular dynamics, which made it possible, first, to quantify the effect of the irradiation in terms of erosion and redistribution using sequential irradiation and, second, to evaluate the ripple wavelength using the crater function for...

Evolution of nano-structures of silver due to rapid thermal annealing

This report deals with rapid thermal annealing (RTA) effect on continuous silver film on Si(100) substrate. For this purpose silver films of different thicknesses were deposited and subsequently annealed at 500 and 800 °C. The as-deposited and annealed samples were investigated by scanning electron microscope (SEM). Formations of different nano-structures have been observed. Fragmentation of formed nanoislands also observed at temperature below melting temperature.

Size-selected copper nanolclusters for fabrication of isolated size-controlled nanostructures

Here we report formation of isolated and mono-dispersed Copper islands of predicted size on Silicon substrate with native oxide and amorphous carbon film by soft landing of size selected nanoclusters using magnetron based gas aggregation type source. Transmission electron microscopy (TEM) and Atomic Force Microscopy (AFM) are done to characterize the structures formed on different substrates. Effect of larger AFM tip-size compared to feature size is discussed.

Characterization of submonolayer film composed of soft-landed copper nanoclusters on HOPG

Preformed Copper nanoclusters are deposited on highly oriented pyrolytic graphite (HOPG) at very low energy. For the study of chemical composition X-ray Photoelectron Spectroscopy (XPS) is performed for a wide range of binding energy without exposing the sample in the ambient. Morphological aspects of the supported clusters are characterized employing high resolution scanning electron microscope (SEM). Different types of morphology are observed depending on the nature of the substrate surface. Big fractal islands are formed on terraces while at the step edges small islands are found to form. Ex-situ cathodoluminescence (CL) measurement shows peak at 558 nm wavelength which corresponds to the band gap of 2.22 eV which is due to Cu2O nanocrystals formed due to oxidation of the deposited film in ambient.

Morphology of size-selected copper nanocluster film

We report a preliminary study of the morphology of size-selected Copper nanocluster film grown on Si substrate using a state of the art nanocluster deposition system. The clusters are produced in a dc magnetron and gasaggregation type cluster source at room temperature. The size or mass of the nanoclusters are analysed by a quadrupole mass filter. The morphology of cluster assembled surface has been investigated by Scanning electron microscopy (SEM) and atomic force microscopy (AFM).