Raman spectroscopy Archives – Institute of Nano Electronic Engineering

Formation of nanocrystalline GeSn thin film on Si substrate by sputtering and rapid thermal annealing

September 25, 2016 By Editor

Abstract – Nanocrystalline Ge1-xSnx thin films have been formed after rapid thermal annealing of sputtered GeSn layers. The alloy films were deposited onto the Silicon (100) substrate via low cost radio frequency magnetron sputtering. Then, the films were annealed by rapid thermal annealing at 350 °C, 400 °C, and 450 °C for 10 s. The morphological, structural, and optical properties of the layers were investigated with field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and high-resolution X-ray diffraction (HR-XRD). The Raman analysis showed that the only observed phonon mode is attributed to Ge-Ge vibrations. Raman phonon intensities of GeSn thin films were enhanced with increasing the annealing temperature. The results clearly revealed that by increasing the annealing temperature the crystalline quality of the films were improved. The XRD measurements revealed the nanocrystalline phase formation in the annealed films with (111) preferred orientation. The results showed the potentiality of using the sputtering technique and rapid thermal anneal to produce crystalline GeSn layer.

Keywords – Germanium-tin, HR-XRD, Nanocrystalline materials, Raman spectroscopy, Sputtering, Thin films

Corresponding Author: Uda Hashim
Corresponding Author’s Email: uda@unimap.edu.my

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Synthesis of single-walled carbon nanotubes by chemical vapor deposition using sodium chloride support

September 4, 2013 By Editor

Abstract – Bundled single-walled carbon nanotubes (SWCNTs) together with multi-walled carbon nanotubes (MWCNTs) were directly grown on a water-soluble support catalyst that was prepared via sublimation of ferrocene on sodium chloride. The synthesis of nanotubes was carried out at a growth temperature of 700 °C in a combined methane and nitrogen environment of 1:1 volumetric ratio at a total flowrate of 80 ml/min for 1 h in a vertical reactor. Characterization techniques such as scanning electron microscope, transmission electron microscope, thermogravimetric analysis, and Raman spectroscopy were employed to study the carbon deposits. Transmission electron microscope shows the presence of SWCNTs with an average diameter of ca. 1.18 nm on the catalyst. The radial breathing mode (RBM) of Raman for shifts below 350 ^-1cm further confirmed the presence of SWCNTs and the diameters were calculated to be 0.93, 1.36, 1.5 and 1.85nm.

Keywords – Single-walled carbon nanotubes, Multi-walled carbon nanotubes, Electron microscopy, Raman spectroscopy

Corresponding Author: Liu Wei Wen
Corresponding Author’s Email: wwliu@unimap.edu.my

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Preparation of iron oxide nanoparticles supported on magnesium oxide for producing high-quality single-walled carbon nanotubes

November 22, 2012 By Editor

Abstract – Fe3O4 nanoparticles with a narrow diameter distribution having an average diameter of 10.33 nm ± 2.99 nm (average diameter ± standard deviation) were prepared by a precipitation method. The Fe3O4 nanoparticles were supported on MgO by mixing the MgO nanopowder with the required amount of Fe3O4 nanoparticles in water under extensive sonication. Single-walled carbon nanotubes (SWCNTs) were synthesized by the chemical vapor deposition (CVD) of methane over the Fe3O4/MgO catalyst. Transmission electron microscopy showed that a large number of SWCNT bundles of nearly uniform diameter were produced by the CVD method. The average diameter of the produced SWCNTs was ca. 1.22 nm. Thermogravimetric analysis showed that the weight loss was approximately 19% by oxidation of carbon in the temperature range of 400-680 oC. The ratio of the intensity of the D-band to the G-band was 0.03, indicating that the SWCNTs were well-graphitized.

Keywords – Single-walled carbon nanotubes, Chemical vapor deposition, Electron microscopy, Raman spectroscopy

Corresponding Author: Liu Wei Wen
Corresponding Author’s Email: wwliu@unimap.edu.my

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Carbon nano dots scale by focused ion beam system for MIS diode nano devices

October 3, 2012 By Editor

Abstract – Metal-insulator-semiconductor (MIS) structures with a nanocrystal carbon (nc-C) embedded in SiO2 thin films were fabricated using a focused ion beam (FIB) system with a precursor of low-energy Ga+ ion and carbon source. The crystallinity of nc-C was investigated by Raman spectroscopy and atomic force microscopy (AFM). Raman spectra indicate the evidence of crystallization of nc-C after annealed at 600˚C by the sharp peak at 1565 cm-1 in graphite (sp2), while no peak of diamond (sp3) could be seen at 1333 cm-1. The AFM images showed the nc-C dots controlled with diameter of 100 nm, 200 nm and 300 nm, respectively. The above results revealed that the nc-C dots had sufficiently stuck onto SiO2 films. The hysterisis loop in the capacitance–voltage characteristics appeared in the MIS device with SiO2/nc-C/SiO2 structure in which voltage shift is 0.32 V for radical oxidation and 0.14 V for dry oxidation, respectively.

Keywords – Carbon; Nanocrystal; Memory device; Focused ion beam; Raman spectroscopy; Atomic force microscopy

Corresponding Author: Ruslinda Abdul Rahim
Corresponding Author’s Email: ruslinda@unimap.edu.my

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