The Effect of Air-Exposed Layer on Electrical Properties of Cu/n-Si/Al Schottky Diodes

In this work, we studied the effect of air-exposed layer on the current-voltage (I-V) capacitance versus voltage (C-V) and capacitance versus frequency (C-f) characteristics of Cu/n-Si/Al Schottky diodes. We fabricated with and without thin oxide layer Cu/n-Si/Al diodes. Firstly, n-Si wafer having (100) oriented and 15 Ω.cm resistivity was cut into eight pieces labeled Diode 1 (D1) to Diode 8 (D8). We formed the referents Cu/n-Si/Al Schottky diode (D1) which has not exposed to air. Rest of the samples, before formation of Schottky contact, was exposed to clean air at the room temperature for 2, 4, 8, 16, 32, 48 and 64 days. Therefore, Schottky contact with native oxide layer on the polished n-Si surface was obtained. From ln(I)-V plot of the Cu/n-Si/Al diodes, ideality factor (n), barrier height (eb), the interface state density of the Schottky junctions (Ns), saturation current (I0) and serial resistor (RS) were calculated. In addition, same parameters were verified using both Cheung functions and C-2-V characteristics. Moreover, the interface state densities of the Schottky junctions versus energy Ns-(Ec-Es) also was calculated and plotted. What causes to excess capacity of the space charge have also been investigated. While the value of ideality factor and series resistance increased with increasing exposure time to air, the barrier height Φb value of the Schottky diode with oxide layer is smaller than those without oxide layer. This is attributed to formation oxide layer occurring between interfaces of metal and semiconductor surface

A Mean Field Approximation to the Worldsheet Model of Planar phi^3 Field Theory

We develop an approximation scheme for our worldsheet model of the sum of planar diagrams based on mean field theory. At finite coupling the mean field equations show a weak coupling solution that resembles the perturbative diagrams and a strong coupling solution that seems to represent a tensionless soup of field quanta. With a certain amount of fine-tuning, we find a solution of the mean field equations that seems to support string formation.Comment: 27 pages, 10 figures, typos corrected, appendix on slowly varying mean fields adde

New applications and developments in the neutron shielding

Shielding neutrons involve three steps that are slowing neutrons, absorption of neutrons, and impregnation of gamma rays. Neutrons slow down with thermal energy by hydrogen, water, paraffin, plastic. Hydrogenated materials are also very effective for the absorption of neutrons. Gamma rays are produced by neutron (radiation) retention on the neutron shield, inelastic scattering, and degradation of activation products. If a source emits gamma rays at various energies, high-energy gamma rays sometimes specify shielding requirements. Multipurpose Materials for Neutron Shields; Concrete, especially with barium mixed in, can slow and absorb the neutrons, and shield the gamma rays. Plastic with boron is also a good multipurpose shielding material. In this study; new applications and developments in the area of neutron shielding will be discussed in terms of different materials

Trakya University Güllapoğlu Arboretum Landscape Planning Studies

Bu çalışma Edirne İli, Trakya Üniversitesi Güllapoğlu Yerleşkesi içinde tesis edilecek olan arboretumun planlama ilkelerini belirlemek ve öneri bir peyzaj projesi sunmak amacıyla yapılmıştır. Bu amaçla, öncelikle arboretum kavramı, işlevleri, planlama ve uygulama kriterleri, Dünyadaki ve Türkiye’deki özel ve kamu kuruşlarına ait arboretumların özellikleri araştırılmıştır. T.Ü. Güllapoğlu Arboretumunun bulunduğu Edirne İli’nin sosyo-kültürel özellikleri araştırılmış ve bu arboretumun kurulmasını gerekli kılan nedenler belirlenmiştir. Daha sonra çalışma alanında gözlem, inceleme ve veri toplama işlemleri yapılmış, elde edilen veriler değerlendirilmeye çalışılmıştır. Tüm verilerin ışığında, alana ilişkin öneri peyzaj projesi hazırlanmıştır.The aim of this study is to determine the planning rules of the arboretum to be established in Trakya University Güllapoğlu Campus and propose landscape plan. In thıs study, several researches are made on Trakya University Güllapoğlu Arboretum in Trakya University Campus in Edirne. First of all the concept of “Arboretum”, functions, planning and application criteria and the properties of arboretums in Turkey and other countries are studied. The socio-economical structure of Edirne where Güllapoğlu arboretum will be established is studied and the establishg reasons of arboretum in Edirne were determined. Afterwords the natural properties [slop, soil, flora] of the arboretum are collected and the results are analysed

More On The Connection Between Planar Field Theory And String Theory

We continue work on the connection between world sheet representation of the planar phi^3 theory and string formation. The present article, like the earlier work, is based on the existence of a solitonic solution on the world sheet, and on the zero mode fluctuations around this solution. The main advance made in this paper is the removal of the cutoff and the transition to the continuum limit on the world sheet. The result is an action for the modes whose energies remain finite in this limit (light modes). The expansion of this action about a dense background of graphs on the world sheet leads to the formation of a string.Comment: 27 pages, 3 figure

Field Theory On The World Sheet: Improvements And Generalizations

This article is the continuation of a project of investigating planar phi^3 model in various dimensions. The idea is to reformulate them on the world sheet, and then to apply the classical (meanfield) approximation, with two goals: To show that the ground state of the model is a solitonic configuration on the world sheet, and the quantum fluctuations around the soliton lead to the formation of a transverse string. After a review of some of the earlier work, we introduce and discuss several generalizations and new results. In 1+2 dimensions, a rigorous upper bound on the solitonic energy is established. A phi^4 interaction is added to stabilize the original phi^3 model. In 1+3 and 1+5 dimensions, an improved treatment of the ultraviolet divergences is given. And significantly, we show that our approximation scheme can be imbedded into a systematic strong coupling expansion. Finally, the spectrum of quantum fluctuations around the soliton confirms earlier results: In 1+2 and 1+3 dimensions, a transverse string is formed on the world sheet.Comment: 29 pages, 5 figures, several typos and eqs.(74) and (75) are corrected, a comment added to section

Kinematic modelling of a 3-axis NC machine tool in linear and circular interpolation

Machining time is a major performance criterion when it comes to high-speed machining. CAM software can help in estimating that time for a given strategy. But in practice, CAM-programmed feed rates are rarely achieved, especially where complex surface finishing is concerned. This means that machining time forecasts are often more than one step removed from reality. The reason behind this is that CAM routines do not take either the dynamic performances of the machines or their specific machining tolerances into account. The present article seeks to improve simulation of high-speed NC machine dynamic behaviour and machining time prediction, offering two models. The first contributes through enhanced simulation of three-axis paths in linear and circular interpolation, taking high-speed machine accelerations and jerks into account. The second model allows transition passages between blocks to be integrated in the simulation by adding in a polynomial transition path that caters for the true machining environment tolerances. Models are based on respect for path monitoring. Experimental validation shows the contribution of polynomial modelling of the transition passage due to the absence of a leap in acceleration. Simulation error on the machining time prediction remains below 1%

A Worldsheet Description of Large N_c Quantum Field Theory

The N_c to infinity limit of a matrix quantum field theory is equivalent to summing only planar Feynman diagrams. The possibility of interpreting this sum as some kind world-sheet theory has been in the air ever since 't Hooft's original paper. We establish here just such a world sheet description for a scalar quantum field with interaction term g\Tr\phi^3, and we indicate how the approach might be extended to more general field theories.Comment: 16 pages, 3 figures, latex, typos corrected, references added, interpretation of ghost determinant clarifie