SSL Seminar Series 2006 No. 2

Date: 11 April (Tuesday), 2006
Time: 11:00am-12:00pm
Venue: Physics Resource Room (Blk S13 # 02-16)

Speaker I: Mr Sunil Singh Kushvaha
Title: In-situ STM study of growth of Mn, Sb and MnSb graphite

The surface morphology of Mn, Sb and MnSb on highly-oriented pyrolytic graphite (HOPG) has been studied in detail with in-situ scanning tunneling microscopy (STM) in ultrahigh vacuum. It has been found that the initial stage of growth three dimensional (3D) clusters and islands of Mn and Sb are formed at step edges and defect sites. In middle stage, single- and double-layer clusters chains of Mn are obtained at room temperature (RT). We observed three different types of Sb structures on HOPG such as crystalline spherical 3D, 2D thin film and 1D nanorods. The shape of these Sb nanostructures can be controlled in self-assembly by tuning flux and substrate temperature. The allotropic modification of Sb at nano-scale is obtained in case of 1D nanorods formation which show a simple cubic crystal structure instead of rhombohedral bulk Sb lattice. MnSb crystallites were obtained on HOPG surface after deposition of Sb and Mn at different temperature followed by post-annealing at 475 K in presence of Sb flux. We mostly got atomic planes in hexagonal shape and the step heights of these structures reveal (0001) phase of MnSb. The ex-situ x-ray photoemission spectroscopy measurement reveals the formation of MnSb compound on graphite surface. Also the excellent magnetic property of the 100-nm thick MnSb films was observed by vibrating sample magnetometer.

Speaker II: Mr Arpan Roy
Title: Fabrication and Field Emission Properties of Vanadium Nanowires

Title: V2O5 nanowires are fabricated on a silicon substrate by heating the pre-sputtered substrate in air on a hotplate. Various temperatures and various sputtering times were investigated to find optimal conditions for nanowires growth. Once the growth of the nanowires was perfected, their field emission properties were studied. Surface studies were also done using SEM, XRD and XPS.