Arshad Mahmood

Optical diagnosis of malaria infection in human plasma using Raman spectroscopy

Abstract. We present the prediction of malaria infection in human plasma using Raman spectroscopy. Raman spectra of malaria-infected samples are compared with those of healthy and dengue virus infected ones for disease recognition. Raman spectra were acquired using a laser at 532 nm as an excitation source and 10 distinct spectral signatures that statistically differentiated malaria from healthy and dengue-infected cases were found. A multivariate regression model has been developed that utilized Raman spectra of 20 malaria-infected, 10 non-malarial with fever, 10 healthy, and 6 dengue-infected samples to optically predict the malaria infection. The model yields the correlation coefficient r2 value of 0.981 between the predicted values and clinically known results of trainee samples, and the root mean square error in cross validation was found to be 0.09; both these parameters validated the model. The model was further blindly tested for 30 unknown suspected samples and found to be 86% accurate compared with the clinical results, with the inaccuracy due to three samples which were predicted in the gray region. Standard deviation and root mean square error in prediction for unknown samples were found to be 0.150 and 0.149, which are accepted for the clinical validation of the model.

Optical Characterization of rf-Magnetron Sputtered Nanostructured SnO2 Thin Films *

Tin oxide (SnO2) thin films are deposited by rf-magnetron sputtering and annealed at various temperatures in the range of 100–500 °C for 15 min. Raman spectra of the annealed films depict the formation of a small amount of SnO phase in the tetragonal SnO2 matrix, which is verified by x-ray diffraction. The average particle size is found to be about 20–30 nm, as calculated from x-ray peak broadening and SEM images. Various optical parameters such as optical band gap energy, refractive index, optical conductivity, carrier mobility, carrier concentration etc. are determined from the optical transmittance and reflectance data recorded in the wavelength range 250–2500 nm. The results are analyzed and compared with the data in the literature.

Structural and optical analysis of Cr2N thin films prepared by DC magnetron sputtering

Chromium nitride (Cr2N) thin films were prepared by a DC magnetron sputtering technique. The deposition temperature was raised from 50 to 300°C, and its influence on the film structure and refractive index was investigated. X-ray diffraction analysis shows that the crystalline structure of the films transforms from the (101) to (002) oriented hexagonal Cr2N phase as the increase of substrate temperature above 50°C, and a highly textured film grows at 100°C. An empirical relation between the crystalline orientation and infrared active modes of the films is obtained, i.e., the Fourier transform infrared (FTIR) spectrum of the film prepared at 50°C exhibits only A1 (TO) mode. The prominent peak in the FTIR spectra of the film prepared above 50°C is assigned to the E1 (TO) mode and is correlated with the (002) or c-axis oriented hexagonal wurtzite phase of Cr2N. In the surface analysis of atomic force microscopy, a transformation from the featureless surface to columnar-type morphology is observed with the increase of substrate temperature from 50 to 100°C, exhibiting c-axis oriented crystallite growth. A further increase in substrate temperature to 200°C causes the c-axis crystallites to merge, resulting in the formation of voids. The refractive index (n) of the deposited films is obtained using spectroscopic ellipsometry.

Cu IONS IRRADIATION IMPACT ON STRUCTURAL AND OPTICAL PROPERTIES OF GaN THIN FILM

Epitaxial grown Gallium nitride (GaN) thin film on sapphire was irradiated with Cu ions at various fluences (5×1014, 1 ×1015 and 5×1015cm-2). The level of lattice disorder, as measured by Rutherford backscattering spectrometry and channeling (RBS/C), gradually increases with the increasing of ions fluence. Lattice amorphization is observed for the sample irradiated with fluence of 5×1015cm-2 which is also confirmed by X-ray diffractometer (XRD) analysis. It was found that both Raman modes of GaN layer clearly shifted with Cu+ fluences. Both Raman and X-ray analyses explore that Cu atom substituted into Ga sites. Atomic force microscopy (AFM) images show the irradiated GaN surface roughness increases with the increasing ions fluence. The UV-visible transmittance spectrum and ellipsometric measurements show a decrease in the band gap value after irradiation of Cu ions in the GaN film. Moreover, the optical constants (n and k) of the films vary with the increasing of Cu ion fluences.

Photoluminescence and structural analysis of wurtzite (ZnO)1−x(V2O5)x composite

This paper demonstrates the structural, vibrational and photoluminescence characteristics of (ZnO) 1− x (V 2 O 5 ) x ( x = 0, 3, 6 and 9 mol%) composites semiconductor synthesized by using the solid state reaction method. X-ray diffraction (XRD) studies show that (ZnO) 1− x (V 2 O 5 ) x composites have the poly crystalline wurtzite structure of hexagonal ZnO. It is found from the XRD results that the lattice constants and the crystallite size increase while the dislocation density decreases with increase in doping concentration. The existence of E 1 (TO) and E 2 (high) Raman modes show that the ZnO still preserve wurtzite structure after doping vanadium oxide, which is in agreement with XRD results. Room temperature photoluminescence (PL) exhibit near band edge and broad deep level emission while indicating the suppression of deep level emission with the incorporation of V 2 O 5 up to a certain concentration ( x < 9). Moreover, the optical band gap increase with doping, which is accompanied by the blue shift of the NBE emission.

Modification in surface properties of poly-allyl-diglycol-carbonate (CR-39) implanted by Au+ ions at different fluences

Abstract Ion implantation has a potential to modify the surface properties and to produce thin conductive layers in insulating polymers. For this purpose, poly-allyl-diglycol-carbonate (CR-39) was implanted by 400 keV Au+ ions with ion fluences ranging from 5 × 1013 ions/cm2 to 5 × 1015 ions/cm2. The chemical, morphological and optical properties of implanted CR-39 were analyzed using Raman, Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM) and UV-Vis spectroscopy. The electrical conductivity of implanted samples was determined through four-point probe technique. Raman spectroscopy revealed the formation of carbonaceous structures in the implanted layer of CR-39. From FT-IR spectroscopy analysis, changes in functional groups of CR-39 after ion implantation were observed. AFM studies revealed that morphology and surface roughness of implanted samples depend on the fluence of Au ions. The optical band gap of implanted samples decreased from 3.15 eV (for pristine) to 1.05 eV (for sample implanted at 5 × 1015 ions/cm2). The electrical conductivity was observed to increase with the ion fluence. It is suggested that due to an increase in ion fluence, the carbonaceous structures formed in the implanted region are responsible for the increase in electrical conductivity.

Optical spectroscopic analysis of annealed Cd1−xZnxSe thin films deposited by close space sublimation technique

Abstract Cd1−xZnxSe (x = 0, 0.40 and 1) thin films were deposited on a glass substrate at room temperature by closed space sublimation method. Optical investigation has been performed using spectrophotometry and ellipsometry. It has been found that for as deposited films the optical band gap increased and the optical constants decreased with increasing Zn content. To improve the optical properties of Cd1−xZnxSe thin films annealing effect at 400 °C was taken into consideration for various Zn contents. It was observed that the optical transmittance and band gap decreased while optical constants increased with increasing Zn content after annealing. The effects of composition and annealing on the optical dispersion parameters Eo and Ed were investigated using a single effective oscillator model. The calculated value of the average excitation energy Eo obeys the empirical relation (Eo = Eg/2) obtained from the single oscillator model.

Exploration of optical behavior of Cd1−xNixTe thin films by spectroscopic ellipsometry

We report on the tunability over the optical behavior of e-beam evaporated nanocrystalline thin films of Cd1−xNixTe (0 ≤ x ≤ 0.15). X-ray diffraction analysis reveals the polycrystalline nature of the film having zinc blend structure with a preferred growth direction along (111) plane parallel to the substrate. X-ray diffraction results also indicate that the grain size of the films decreases from 27.13 nm to 16.23 nm with an increase in Ni concentration from 0 to 15 at%. The compositional analysis of the film was carried out by energy dispersive x-ray analysis (EDX) which confirms the successful inclusion of Ni in CdTe matrix. Spectroscopic ellipsometery (SE) results demonstrate that the band gap of the grown films increases from 1.48 eV to 1.86 eV while refractive index (n) and extinction coefficient (k) decrease with the increasing Ni concentration. The increase in band gap energy of Cd1−xNixTe films as a function of Ni concentration was confirmed by spectrophotometric analysis.