Effect of Fe ion implantation on the thermoelectric properties and electronic structures of CoSb3 thin films

In the present study, thin films of single-phase CoSb₃ were deposited onto Si(100) substrates via pulsed laser deposition (PLD) method using a polycrystalline target of CoSb₃. These films were implanted by 120 keV Fe-ions with three different fluences: 1 × 10¹⁵, 2.5 × 10¹⁵ and 5 × 10¹⁵ ions per cm². All films were characterised by X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), Rutherford backscattering (RBS) spectrometry and X-ray absorption spectroscopy (XAS). XRD data revealed that the ion implantation decreased the crystalline nature of these films, which are recovered after the rapid thermal annealing process. The Seebeck coefficient S vary with the fluences in the temperature range of 300 K to 420 K, and is found to be highest (i.e., 254 μV K⁻¹) at 420 K for the film implanted with 1 × 10¹⁵ ions per cm². The high S and low resistivity lead to the highest power factor for the film implanted with 1 × 10¹⁵ ions per cm² (i.e., 700 μW m⁻¹ K⁻²) at 420 K. The changing of the sign of S from negative for the pristine film to positive for the Fe-implanted samples confirm that the Fe ions are electrically active and act as electron acceptors by replacing the Co atoms. XAS measurements confirm that the Fe ions occupied the Co site in the cubic frame of the skutterudite and exist in the 3+ oxidation state in this structure.

The power factor for the Fe ion-implanted samples is greater than that of the pristine sample with a value of 700 mW m⁻¹ K⁻² at 420 K for the I_1E15A sample.     

Hepatitis C risk factors in Iranian volunteer blood donors: a case-control study

BACKGROUND: In order to evaluate some possible risk factors for the spread of hepatitis C infection a case-control study was undertaken. METHODS: The study population consisted of first time blood donors referred to the Iranian Blood Transfusion Organization. Enzyme-linked immunosorbent assay and recombinant immunoblot assay anti-hepatitis C virus (HCV) tests were performed for all samples. Risk factors were evaluated using a questionnaire. A stepwise forward logistic regression analysis was used. RESULTS: The case group consisted of 193 HCV-positive donors, and 196 HCV-negative donors comprised the control group. Transfusion, undergoing endoscopy, extramarital sexual activities, non-intravenous (i.v.) drug abuse, i.v. drug abuse, and receiving wounds at war were found to be independent risk factors of being HCV-positive (Odds ratio: 17, 4, 42.2, 34.4, 52.8 and 5.2, respectively). No apparent risk factors could be demonstrated in 24.5% of the positive cases. CONCLUSION: This study could be of particular interest because of the low seroprevalence of hepatitis C and the religious culture of the study population. There are certain medical procedures, lifestyle patterns, and customs and cultural matters in Iran that predispose people to a number of HCV risk factors.