Theoretical study of work function modification by organic molecule-derived linear nanostructure on H-silicon(100)-2 7 1

Tuning of the electronic properties of semiconductors can be achieved by surface modification with organic molecules. In this work, we study, by periodic density functional theory, the change in work function that occurs upon the modification of nominally hydrogen-terminated Si(100)-2 x 1 by chemisorption of substituted styrene molecules. Our results show that monolayers derived from 4-X-styrene molecules, with X being electron donating groups or hydrogen, decrease the work function of the system. Conversely, monolayers derived from 4-X-styrene molecules, with X being electron withdrawing groups, increase the work function of the system. For the molecules used in the modeling, the calculations indicate that the work function can be substantially modified from -1.4 eV (X=N(CH3)2) to +1.9 (X=NO2) eV relative to H-Si(100)-2 x 1. Because the direction and magnitude of charge transferred upon chemisorption is the same for all molecules, the work function changes are not the result of band bending. The work function modification comes exclusively from the inherent dipoles of the molecules chemisorbed on the surface. The computed dipoles for the monolayers range from -1.3 (X=N(CH3)2) to +1.4 (X=NO2) Debye. We conclude that substantial local control over some of the electronic properties of silicon can be achieved by the chemisorption of dipole-containing molecules.Peer reviewed: YesNRC publication: Ye

Sero-prevalence of hepatitis B virus infection and associated factors among health care workers and medical waste handlers in primary hospitals of North-west Ethiopia

Abstract Objective The aim of this cross-sectional study was to determined the sero-prevalence of HBV infection and associated factors among health care workers and medical waste handlers in primary hospitals of North-west Ethiopia. Results A total of 388 study participants were included in this study. Of which, 268 (69%) were health care workers and 120 (31%) were medical waste handlers. Males accounted 54.9% and the mean age for all study participants was 28.3 (standard deviation = 6.9). Hepatitis B virus surface antigen (HBsAg) was detected in 2.6% health care workers and 2.5% medical waste handlers and the overall hepatitis B virus infection was 10 (2.6%). High rate of hepatitis B virus infection was detected in single participants and those in the age group of 30–40 years were more infected (6.6%). History of contact with HBV infected case (8.3%) (AOR = 6.8, 95% CI = 1.6–28.5, P = 0.009) and history of jaundice (15.4%) (AOR = 10.5, 95% CI = 2.1–12.2, P = 0.03) were statistically associated factors for HBV infection. More than half (54.4%) of the study participants did not take training on infection and 9 (4.3%) of them were positive for HBsAg (COR = 1.3, 95% CI = 0.0.02–1.02, P = 0.052)