Self-consistent model of unipolar transport in organic semiconductor diodes: accounting for a realistic density-of-states distribution

A self-consistent, mean-field model of charge-carrier injection and unipolar transport in an organic semiconductor diode is developed utilizing the effective transport energy concept and taking into account a realistic density-of-states distribution as well as the presence of trap states in an organic material. The consequences resulting from the model are discussed exemplarily on the basis of an indium tin oxide/organic semiconductor/metallic conductor structure. A comparison of the theory to experimental data of a unipolar indium tin oxide/poly-3-hexyl-thiophene/Al device is presented.Comment: 6 pages, 2 figures; to be published in Journal of Applied Physic

Nature of Chemisorption on Titanium Carbide and Nitride

Extensive density-functional calculations are performed to understand atomic chemisorption on the TiC(111) and TiN(111) surfaces, in particular the calculated pyramid-shaped trends in the adsorption energies for second- and third-period adatoms. Our previously proposed concerted-coupling model for chemisorption on TiC(111) is tested against new results for adsorption on TiN(111) and found to apply on this surface as well, thus reflecting both similarities and differences in electronic structure between the two compounds.Comment: 7 pages, 4 figures, conference proceeding presented at IWSP-2005 (Polanica Zdoj, Poland, 2005), submitted to Surf. Sci. (2005

Lithiation of Tin Oxide: A Computational Study

We suggest that the lithiation of pristine SnO forms a layered Li$_\text{X}$O structure while the expelled tin atoms agglomerate into 'surface' planes separating the Li$_\text{X}$O layers. The proposed lithiation model widely differs from the common assumption that tin segregates into nano-clusters embedded in the lithia matrix. With this model we are able to account for the various tin bonds that are seen experimentally and explain the three volume expansion phases that occur when SnO undergoes lithiation: (i) at low concentrations Li behaves as an intercalated species inducing small volume increases; (ii) for intermediate concentrations SnO transforms into lithia causing a large expansion; (iii) finally, as the Li concentration further increases a saturation of the lithia takes place until a layered Li$_2$O is formed. A moderate volume expansion results from this last process. We also report a 'zipper' nucleation mechanism that could provide the seed for the transformation from tin oxide to lithium oxide.Comment: 21 pages, 6 figure

Investigation of interface properties of sputter deposited TiN/CrN superlattices by low-angle X-ray reflectivity

Approximately 1.8 m thick nanolayered multilayer coatings of TiN/CrN (also known as superlattices) were deposited on silicon (100) substrates at different modulation wavelengths (4.6–12.8 nm), substrate temperatures (50-400 °C) and substrate bias voltages (-50 to -200 V) using a reactive direct current magnetron sputtering system. X-ray reflectivity (XRR) technique was employed to determine various properties of the multilayers such as interface roughness, surface roughness, electron density, critical angle and individual layer thicknesses. The modulation wavelengths of the TiN/CrN superlattice coatings were calculated using modified Bragg’s law. Furthermore, the experimental X-ray reflectivity patterns were simulated using theoretically generated patterns and a good fit was obtained for a three layer model, i.e., (1) top surface roughness layer, (2) TiN/CrN multilayer coating (approximately 1.8 m) and (3) Ti interlayer (~ 0.5 m) at the film-substrate interface. For the superlattice coatings prepared at a modulation wavelength of 9.7 nm, a substrate bias of -200 V and a substrate temperature of 400 C the XRR patterns showed Bragg reflections up to 5th order, indicating well-defined periodicity of the constituent layers and relatively sharp interfaces. The simulation showed that the superlattice coatings prepared under the above conditions exhibited low surface and interface roughnesses. We also present the effect of substrate temperature and substrate bias, which are critical parameters for controlling the superlattice properties, onto the various interface properties of TiN/CrN superlattices

Comments on the Refractive Index of Tin Sulphide Nano-crystalline Thin Films

The refractive indices of nano-crystalline thin films of Tin (IV) Sulphide (SnS) were investigated here. The experimental data conformed well with the single oscillator model for refractive indices. Based on the this, we explain the increasing trend of refractive index to the improvement in crystal ordering with increasing grain size.Comment: Nine figure

Cluster formation probability in the trans-tin and trans-lead nuclei

Within our fission model, the Coulomb and proximity potential model (CPPM) cluster formation probabilities are calculated for different clusters ranging from carbon to silicon for the parents in the trans-tin and trans- lead regions. It is found that in trans-tin region the 12^C, 16^O, 20^Ne and 24^Mg clusters have maximum cluster formation probability and lowest half lives as compared to other clusters. In trans-lead region the 14^C, 18, 20^O, 23^F, 24,26^Ne, 28,30^Mg and 34^Si clusters have the maximum cluster formation probability and minimum half life, which show that alpha like clusters are most probable for emission from trans-tin region while non-alpha clusters are probable from trans-lead region. These results stress the role of neutron proton symmetry and asymmetry of daughter nuclei in these two cases.Comment: 20 pages, 6 figure

Volatilitas Harga Komoditas Timah

. The aim of this research is to analyse the factors which influence the pricevolatility of tin commodity. Monthly basis data were collected from 1990 to 2015. Weemployed ARCH-GARCH models and verified by interview with tin expert. Theresults showed that model EGARCH (1,1,1) is the best model to explain the pricevolatility of tin commodity. Changing factors from crude oil price, copper price, leadprice and T-Bill 3M were significantly affecting volatility in tin price. Experts believethe high volatility from 2001 to 2015 led to the difficulties in developing ofdownstream tin industry in Indonesia

An Empirical Model for Estimating the Probability of Electrical Short Circuits from Tin Whiskers

In this experiment, an empirical model to quantify the probability of occurrence of an electrical short circuit from tin whiskers as a function of voltage was developed. This empirical model can be used to improve existing risk simulation models. FIB and TEM images of a tin whisker confirm the rare polycrystalline structure on one of the three whiskers studied. FIB cross-section of the card guides verified that the tin finish was bright tin