Electron-Electron Interactions in Sb-Doped SnO2 Thin Films

WOS: 000279504900005Electrical conductivity and Hall-effect measurements on undoped and Sb-doped SnO2 thin films prepared by the sol-gel technique were carried out as a function of temperature (55 K to 300 K). Structural characterizations of the films were performed by atomic force microscopy (AFM) and x-ray diffraction (XRD). A doping-induced metal-insulator transition (MIT) was observed. On the metallic side of the transition, the experimental data were interpreted in terms of electron-electron interactions (EEI). The existence of EEI was confirmed by excellent agreement between theoretical and experimental data. The experimental data on the insulator side of the transition were analyzed in terms of variable-range hopping (VRH) conduction. A complete set of parameters describing the properties of the localized electrons, including hopping energy, hopping distance, and the value of the density of states at the Fermi level, was determined.State of Planning Organization of TurkeyTurkiye Cumhuriyeti Kalkinma Bakanligi [2001K120590]; Ankara University BAPAnkara University [2007-07-45-054]This work is supported by the State of Planning Organization of Turkey under Grant No. 2001K120590 and the Ankara University BAP under Project Number 2007-07-45-054. We would also like to thank Prof. Dr. Yusuf Kagan Kadioglu and Ms. Murat Yavuz for providing XRD and AFM measurements

Electrical Properties of Polycrystalline SnO2 Thin Films

WOS: 000298290500001The electrical properties of polycrystalline SnO2 films are investigated by conductivity measurements with respect to the deposition temperature over a temperature range from 60 to 200 K. The electrical conduction is found to be governed by the thermionic emission and tunneling in high temperatures (T > 100 K) and low temperatures (T < 100 K), respectively. (C) 2011 The Japan Society of Applied PhysicsState of Planning Organization of TurkeyTurkiye Cumhuriyeti Kalkinma Bakanligi [2001K120590]; Ankara University BAPAnkara University [2007-07-45-054]This work is supported by the State of Planning Organization of Turkey under Grant No. 2001K120590 and the Ankara University BAP under Project No. 2007-07-45-054. We would also like to thank Professor Dr. Yusuf Kagan Kadioglu and Ms. Murat Yavuz for carriying out XRD and AFM measurements

The effects of film thickness on the optical properties of TiO2-SnO2 compound thin films

WOS:000298181300026In this work, TiO2-SnO2 compound thin films was synthesized by the sol-gel technique, and the effects of film thickness on the optical and structural properties of these thin films were investigated. Optical constants such as the refractive index, extinction coefficient, dielectric constant and third-order optical nonlinear susceptibility were determined from the measured transmittance spectra in the wavelength range 300-1500 nm using the envelope method. Meanwhile, the dispersion behavior of the refractive index was studied in terms of the single-oscillator Wemple-DiDomenico (W-D) model, and the physical parameters of the refractive index dispersion parameter and the dispersion energy were found. Furthermore, the optical band gap values were calculated by the W-D model and the Tauc model, respectively. It is observed that the values obtained from the W-D model are in quite good agreement with those determined from the Tauc model. Important changes in optical and dielectric constants were observed by means of variation in film thickness. To examine the structure of the thin films, x-ray diffraction (XRD) methods were used. Combined with XRD analysis, the observed variations in both the refractive index and optical band gap are directly correlated with the structural evolution of the composite TiO2-SnO2 thin films. The most significant results of the present study are that the thickness of the film can be used to modify the optical, structural and dielectric properties of TiO2-SnO2 thin films

Crossover from Nearest-Neighbor Hopping Conduction to Efros-Shklovskii Variable-Range Hopping Conduction in Hydrogenated Amorphous Silicon Films

WOS: 000272265300017We presented the results of optical and electrical studies of the properties of hydrogenated amorphous silicon (a-Si H) film which was prepared by hot wire method. Using transmittance measurements, the dielectric constant of the a-Si H was determined. The temperature-dependent conductivity was measured using the two-point probe method in the temperature range 115-326 K. It was shown that the temperature-dependent conductivity can be well explained by the nearest-neighbor hopping conduction and the Efros-Shklovskii variable-range hopping conduction models A clear transition from the nearest-neighbor hopping conduction mechanism to the Efros-Shklovskii variable-range hopping conduction mechanism was also observed The transition between two conduction regimes and characteristic hopping temperatures, as well as the complete set of parameters describing the properties of the localized electrons (the localization length, the hopping energy, the hopping distance, the width of the Coulomb gap, and the value of the density of states at the Fermi level) were determined (C) 2009 The Japan Society of Applied Physic

Phase transformation of nanostructured titanium dioxide thin films grown by sol-gel method

WOS:000302642400035Nanostructured TiO2 thin films were deposited on quartz glass at room temperature by sol-gel dip coating method. The effects of annealing temperature between 200 degrees C to 1100 degrees C were investigated on the structural, morphological, and optical properties of these films. The X-ray diffraction results showed that nanostructured TiO2 thin film annealed at between 200 degrees C to 600 degrees C was amorphous transformed into the anatase phase at 700 degrees C, and further into rutile phase at 1000 degrees C. The crystallite size of TiO2 thin films was increased with increasing annealing temperature. From atomic force microscopy images it was confirmed that the microstructure of annealed thin films changed from column to nubbly. Besides, surface roughness of the thin films increases from 1.82 to 5.20 nm, and at the same time, average grain size as well grows up from about 39 to 313 nm with increase of the annealing temperature. The transmittance of the thin films annealed at 1000 and 1100 degrees C was reduced significantly in the wavelength range of about 300-700 nm due to the change of crystallite phase. Refractive index and optical high dielectric constant of the n-TiO2 thin films were increased with increasing annealing temperature, and the film thickness and the optical band gap of nanostructured TiO2 thin films were decreased

Polimeraz zincir reaksiyonu (PCR) ile tüberküloz meninjitin hızlı tanısı

Tüberküloz meninjitin (TBM) erken tanı ve tedavisi nörolojik sekelleri ve mortaliteyi azaltır. Konvansıyonel yöntemlerle TBM tanısı koymak zaman alıcı ve zordur. Bu nedenle, TBM'li 24, akut bakteriyel meninjitli 18 ve aseptik meninjitli 16 hastanın beyin-omurilik sıvıları polimeraz zincir reaksiyonu (PCR) yöntemi ile incelendi. TBM tanısı alan hastalarda PCR % 91.6 pozitif bulunurken, tüberküloz dışı diğer meninjitli hastaların biri dışında tümünde negatif bulundu.Early diagnosis and specific treatment of tuberculous meningitis (TBM) reduce the occurrence of neurologic sequela and mortality. It is very difficult and time consuming to diagnose TBM by conventional methods. For this reason, the cerebrospinal fluid samples (CSF) of 24 patients with TBM, 18 patients with acute bacterial meningitis, and 16 patients with acute aseptic meningitis were analyzed by polymerase chain reaction (PCR). PCR was found to be positive in 91.6 % of patients with TBM, however, was negative in all but one patient with meningitis other than tuberculosis

Prevalence of GB virus C / hepatitis G virus infection in pediatric patients receiving multiple transfusions in Southern Turkey

The aim of this study was to determine the prevalence of GB virus C (GBV-C) infection in pediatric patients receiving multiple blood transfusions in Turkey where HBV and HCV infections are common. Sera of a total of 148 children, of whom 85 had cancer and 63 hemoglobinopathies, were tested for GBV-C RNA and HCV RNA by RT-PCR and for antibodies to HBV and HCV. Demographic and clinical information as well as laboratory results were recorded for the patients (81 boys, 67 girls, aged 1-19 years). HBsAg positivity was found in 23 (15.5%) patients, HBV DNA positivity in 12 (8.1%), HCV RNA positivity in 9 (6.7%), and GBV-C RNA positivity in 4 (2.7%). There was no significant difference in the GBV-C RNA positivity between patients with cancer (3.2%) and patients with hemoglobinopathies (2.4%) (p > 0.05). GBV-C RNA was found in 4 (3.1%) out of 127 patients who had received transfusions, but it was not found in any of 21 patients who had not received transfusions. However, there was no relationship between GBV-C RNA positivity and the number of transfusions. Two of the patients with GBV-C RNA had high levels of ALT (ALT > 40 IU). In these two patients, neither HBV DNA nor HCV RNA were detected by PCR, and serological tests were also negative for these agents. We concluded that pediatric patients who had multiple transfusions in Turkey are at risk of being infected with GBV-C, in addition to HBV and HCV. Investigation of GBV-C RNA in patients with high ALT levels in the absence of other viral markers may be useful.The aim of this study was to determine the prevalence of GB virus C (GBV-C) infection in pediatric patients receiving multiple blood transfusions in Turkey where HBV and HCV infections are common. Sera of a total of 148 children, of whom 85 had cancer and 63 hemoglobinopathies, were tested for GBV-C RNA and HCV RNA by RT-PCR and for antibodies to HBV and HCV. Demographic and clinical information as well as laboratory results were recorded for the patients (81 boys, 67 girls, aged 1-19 years). HBsAg positivity was found in 23 (15.5%) patients, HBV DNA positivity in 12 (8.1%), HCV RNA positivity in 9 (6.7%), and GBV-C RNA positivity in 4 (2.7%). There was no significant difference in the GBV-C RNA positivity between patients with cancer (3.2%) and patients with hemoglobinopathies (2.4%) (p > 0.05). GBV-C RNA was found in 4 (3.1%) out of 127 patients who had received transfusions, but it was not found in any of 21 patients who had not received transfusions. However, there was no relationship between GBV-C RNA positivity and the number of transfusions. Two of the patients with GBV-C RNA had high levels of ALT (ALT > 40 IU). In these two patients, neither HBV DNA nor HCV RNA were detected by PCR, and serological tests were also negative for these agents. We concluded that pediatric patients who had multiple transfusions in Turkey are at risk of being infected with GBV-C, in addition to HBV and HCV. Investigation of GBV-C RNA in patients with high ALT levels in the absence of other viral markers may be useful