S.D. Sartale

Preparation and characterization of nickel sulphide thin films using successive ionic layer adsorption and reaction (SILAR) method

Semiconducting nickel sulphide (NiS) thin films were deposited onto glass, fluorine doped tin oxide (FTO) coated glass and single crystal Si(1 1 1) wafer substrates using a new successive ionic layer adsorption and reaction (SILAR) method. The deposition conditions for obtaining good quality films such as concentration, pH and temperature of cationic and anionic precursor solutions, immersion and rinsing times and number of immersions were optimized. The XRD studies show that the crystallinity of NiS thin films depends on the nature of substrate. The optical band gap and activation energy were found to be 0.45 and 0.15 eV, respectively. Thermo-emf measurement revealed that the films are of p-type semiconductors.

Patterning Co nanoclusters on thin-film Al2O3/NiAl(100)

Self-organized patterning of supported nanoclusters by virtue of low cost and readiness for mass production is considered as one of the most promising methods; however, this approach is challenging, since the capability of controlling the patterns relies on a suitable combination of clusters and templates. In this paper we demonstrate that Co nanoclusters grown from vapour deposition over Al2O3 thin films on NiAl(100) substrate make a perfect combination for self-organized patterning. Uniform and sizeable Co nanoclusters are formed only on crystalline Al2O3 films and they are highly aligned by protrusion structures of the crystalline Al2O3. Through simple thermal treatments we can pattern the crystalline Al2O3 films and consequently the grown Co nanoclusters. The patterns are robust as they are sustained even when the Co nanoclusters are flashed to 750 K, exposed to atmosphere or the coverage is increased to coalescence. Moreover, the patterns can be further refined by using STM tips. The results imply potential applications in both fundamental and applied researches for electronic and magnetic nanodevices as well as catalysis.

Growth of Co clusters on thin films Al2O3∕NiAl(100)

We present a scanning tunnel microscopy study of Co clusters grown through vapor deposition on Al(2)O(3) thin films over NiAl(100) at different coverages and temperatures. Formation of Co clusters was observed at 90, 300, 450, and 570 K. At the three lower temperatures, we find narrow cluster size distributions and the mean sizes (with a diameter of 2.6 nm and a height of 0.7 nm) do not change significantly with the coverage and temperature, until the clusters start to coalesce. Even on 3-4-nm-wide crystalline Al(2)O(3) strips where the deposited Co atoms are confined, the same features sustain. Only at 570 K the normal growth mode where the cluster size increases with the deposition coverage is observed, although the data are less conclusive. A simple modeling of kinetic surface processes on a strip confirms the normal growth mode, but fails to show a favored size unless additional energetic constraints are applied on the cluster sizes. Increasing Co coverages to cluster coalescence, a larger preferable size (mean diameter of 3.5 nm and height of 1.4 nm) appears for growth at 450 K. These two sizes are corroborated by morphology evolution of high Co coverages deposited at 300 K and annealed to 750 K, in which the coalescence is eliminated and the two preferable geometries appear and coexist.

Engineering patterns of Co nanoclusters on thin film Al2O3∕NiAl(100) using scanning tunneling microscopy manipulation techniques

We present precise engineering of patterns of Co nanoclusters grown on ordered Al2O3∕NiAl(100) surface using the scanning tunneling microscopy (STM) manipulation technique. The clusters are attracted to the STM tip by lowering the bias below a threshold value and translated and relocated to another position by reversing the polarity. This facile manipulation technique in combination with the self-organized patterning on this system reported earlier might play a decisive role in nanotechnology for various applications where patterned nanoclusters are desired.

Deposition and Characterization Of Nanocrystalline Silver Thin Films By Using SILAR Method

Nanocrystalline silver thin films were deposited on glass substrate by using Successive Ionic Layer Adsorption and Reduction (SILAR) method. Silver nitrate and hydrazine hydrate (HyH) were used as precursors. The deposited silver thin films were characterized by using X–ray diffraction (XRD), UV‐visible‐NIR absorption spectroscopy and scanning electron microscopy (SEM) techniques. Effect of concentration of HyH on properties of SILAR grown silver thin films has been extensively studied.

Effect of ultrasonication on properties of sequential layer deposited nanocrystalline silver thin films

Nanocrystalline silver thin films were deposited by using sequential layer deposition (SLD) method with and without ultrasonication. Silver nitrate and hydrazine hydrate (HyH) were used as precursors. The deposited silver thin films were characterized by using X-ray diffraction (XRD), UV-visible-NIR absorption spectroscopy and scanning electron microscopy (SEM) techniques. XRD confirmed the formation of nanocrystalline silver with face centred cubic structure without any oxide presence. Absorption spectra reveal that for ultrasonication silver thin film dipole plasmon band get red shifted which can be assigned as increase in size. SEM and TEM images show particle size increases with ultrasonication due to increase in diffusion rate of particles onto the substrate.

Chemical Synthesis of Nanocrystalline Ceria

Chemical co‐precipitation method is modified, by addition of oxidizing agent, to get faster production of desired oxide phase. Nanocrystalline ceria (CeO2) is successfully synthesized by using this modified method. The formed powder is of nanograins of CeO2 having cubic phase. Calcination improves the crystallization and size of ceria nanograins; due to agglomerization. The synthesized powder were characterized by using X‐ray Diffraction (XRD) and Scanning Electron Microscope (SEM) techniques.