Carbon superatom thin films

Assembling clusters on surfaces has emerged as a novel way to grow thin films with targeted properties. In particular, it has been proposed from experimental findings that fullerenes deposited on surfaces could give rise to thin films retaining the bonding properties of the incident clusters. However the microscopic structure of such films is still unclear. By performing quantum molecular dynamics simulations, we show that C_28 fullerenes can be deposited on a surface to form a thin film of nearly defect free molecules, which act as carbon superatoms. Our findings help clarify the structure of disordered small fullerene films and also support the recently proposed hyperdiamond model for solid C_28.Comment: 13 pages, RevTeX, 2 figures available as black and white PostScript files; color PostScript and/or gif files available upon reques

Home media and science performance:A cross-national study

This study examines the effects of media resources in the parental home on the science performance of 15-year-old students. It employs data from the 2006 Programme for International Student Assessment (PISA) containing information on 345,967 respondents from 53 countries. Results show that media assets in the family home are indeed meaningful for children’s science performance, as a beneficial resource but also as a disadvantage. A positive reading climate in the parental home and the availability of computers benefits science performance. However, a television-rich home seems to hinder children’s school success. Furthermore, results indicate that, compared to less developed countries, in more modernized societies parental reading investments are even more beneficial to their children’s science performance, whereas a television-rich parental home is even more disadvantageous

Amorphous thin films for solar-cell applications. Quarterly report No. 2, 11 December 1979-10 March 1980

Measurements of both primary and secondary photocurrents for photon energies between 0.58 and 2.0 eV in a-Si:H solar-cell structures have been used to provide information about the density of states above the valence band as well as show that holes are mobile deep in the bandgap. The drift mobility is independent of excitation energy, indicating that the majority carriers are excited to the same states, irrespective of the excitation energy. Deposition studies in the dc proximity system have shown that the conductivity and photoconductivity of doped films (both boron- and phosphorus-doped) increase with substrate temperature. Mass spectroscopy studies have shown that the larger Si/sub x/H/sub y//sup +/ clusters are favored by operating rf discharges at low rf powers and high pressures. The Hall mobility is roughly constant below 360 K but exhibits a thermal activation energy of approx. 0.13 eV at higher temperatures. These observations rule out simple extended-state transport as the conduction mechanism. The photoelectromagnetic effect has been used to estimate the hole lifetime (approx. 3.4 x 10/sup -7/s) in undoped a-Si:H; the electron lifetime is approx. 1.7 x 10/sup -6/s. An a-Si:H monolithic solar panel consisting of 16 cells in series has been fabricated on a 4'' x 4'' glass substrate (63 cm/sup 2/ of active area), and the panel exhibits a conversion efficiency of 3.6%. In another series of experiments, the thicknesses and doping levels of p-i-n cells made in a dc(P) discharge were optimized. The best cell made in these experiments had an efficiency of 5.3% with an area of 1.19 cm/sup 2/