Raman Spectroscopy

The band gap of Cd1-xMgxTe can be easily tuned from 1.48 to 3.5 eV (x = 0 to 1), and hence this material is a potential candidate for developing the wide band gap top cell in tandem solar cells. In this paper, we present an all-sputtered Cd1-xMgxTe/CdS top cell developed on commercial SnO2:F-coated (Tec-7) glass substrates with sheet resistance of

The roméite-group [1,2] is part of the pyrochlore supergroup and comprises some cubic oxides of A2-mB2X6-wY1-n formula in which Sb 5+ predominates in the B-site. Indices m, w and n indicate vacancies in A, X and Y crystallographic sites, respectively. A-site is typically occupied by cations with ionic radii greater than 1.0Å or H2O, whereas X-site is usually occupied by O 2-, but smaller amounts of OHor Fare also commonly found. Finally, Y-site is typically occupied by anions O 2-, OHor F-; however, large ionic radii monovalent cations (>1.0Å) such as K + , Cs + and Rb + , or even H2O can occupy it. Since the predominance of Sb 5+ for B site is already known, the correct A and Y main occupants determine different minerals in the group and are important for the discovery of new mineral species [3]. As a source of Sb, the roméite-group minerals are economically relevant, since Sb is present in different applications, from cosmetic industry to the metal alloy production. However, only five roméite-group mineral species, namely fluorcalcioroméite, hydroxycalcioroméite, hydroxyferroroméite, oxycalcioroméite, and oxyplumboroméite have been approved by IMA. Many others can probably be discovered from possible chemical substitutions at crystallographic sites. This study analysed three different samples and determined their chemical composition by electron microprobe analysis and Raman spectra and crystal structure obtained from single-crystal X-ray diffraction. The first sample occurs in Kalugeri Hill, Babuna Valley, Jakupica Mountains, Nezilovo,Veles, Macedonia, whereas the other two occur in Prabornaz Mine, Saint Marcel, Valle d'Aosta, Italy. Sample 1 was identified as fluorcalcioroméite, and samples 2 and 3 as hydroxycalcioroméite. These are the first descriptions of these mineral species at the mentioned occurrences.

GaAs, GaAs:Si and GaAs:C films were deposited on GaAs substrates by Metal Organic Chemical Vapor Deposition( MOCVD) technique. The vibrational study of the heterostructures was performed by mu-Raman technique, and measurements were made at different temperatures using a sample holder with a micro-heater included within it. The spectral information was used to determine the strain caused in GaAs heterostructure because

In this paper we report on the formation of nickel silicide by electroless process. The nickel plating solution was composed of a mixture of NiSO4·6H2O, NaH2PO2·H2O, Na3C6H5O7, and NH4Cl, where NiSO4·6H2O is the main nickel source and NaH2PO2·H2O is the reducing agent. The nickel silicide formation was carried out by heating the deposited samples in vacuum at temperatures from 100 °C to 800 °C. The evolution of NiSi phase from the nickel film was verified using the X-ray diffraction technique and Raman spectroscopy. The surface morphology was studied using AFM technique. The electroless plating technique can provide a cheap and easy process for forming nickel silicide, and has potentiality of application for the electronic device industries.

Potential applications of diamond-like carbon (DLC) coatings range from precision tools and biomedical implants to micro mechanical devices and engine components. Where uniform coatings are required on substrates with complex geometries, plasma enhanced chemical vapour deposition (PECVD) is often a preferred deposition method. As a non-line of sight process, the geometry of the substrate is often considered negligible. For this reason analysis of PECVD coatings, such as amorphous carbon, has mostly been concerned with reactor deposition variables, such as bias voltage, pressure and gas ratios. Samples are therefore usually prepared and positioned to minimise the influence of other variables. By depositing nominally similar DLC films on silicon samples positioned horizontally and vertically on the reactor cathode plate it was possible to examine the variations in the coating characteristics and mechanical properties that occur due to the geometry of the substrate being coated. Topographic measurements and analysis of bonding structures revealed significant heterogeneity in the coatings. Electron microscopy showed variation in surface structure as well as thickness disparities of up to 50% in the vertical sample. Atomic force microscopy showed roughness, Ra, varied from 0.37 nm to 15.4 nm between samples. Raman spectroscopy highlighted variations in the sp2/sp3 bonding ratios whilst micro wear tests demonstrated how these variations reduce the critical load performance. These effects are explained in terms of the deposition mechanisms involved and are related to variation in deposition species and geometrical field enhancements within the deposition chamber. Improved understanding of these local variations will aid in the optimization of coatings for complex substrate geometries.