CIRCULAR TEST STRUCTURES FOR DETERMINING THE SPECIFIC CONTACT RESISTANCE OF OHMIC CONTACTS

Though the transport of charge carriers across a metal-semiconductor ohmic interface is a complex process in the realm of electron wave mechanics, such an interface is practically characterised by its specific contact resistance. Error correction has been a major concern in regard to specific contact resistance test structures and investigations by finite element modeling demonstrate that test structures utilising circular contacts can be more reliable than those designed to have square shaped contacts as test contacts become necessarily smaller. Finite element modeling software NASTRAN can be used effectively for designing and modeling ohmic contact test structures and can be used to show that circular contacts are efficient in minimising error in determining specific contact resistance from such test structures. Full semiconductor modeling software is expensive and for ohmic contact investigations is not required when the approach used is to investigate test structures considering the ohmic interface as effectively resistive

Simulation of graphitic contacts to p-type Si using a metal-resistor-semiconductor (M-R-S) model implemented in TCAD

In this paper, we describe simulations of highly rectifying carbon/p-Si junctions using Sentaurus TCAD from Synopsys. 2-D and 3-D models were constructed and optimized to fit I-V characteristics measured from these junctions. The TCAD models included a resistive interface layer, previously observed experimentally. From the model, the interface resistance was determined to be 0.04 ?·cm2, and the work function of the graphitic contacts was determined to be 4.43 eV. The latter is the work function at the interface, which cannot be measured experimentally. Schottky barrier lowering was implemented in the model to provide agreement with the measurements. The modeling provided information that could not be obtained from measurements and suggested a path to improved devices

Medical students’ perception of the learning environment at King Saud University Medical College, Saudi Arabia, using DREEM Inventory

Mona M Soliman,1,2 Kamran Sattar,2 Sami Alnassar,3 Faisal Alsaif,4 Khalid Alswat,5 Mohamed Alghonaim,6 Maysoon Alhaizan,7 Nawaf Al-furaih7 1Department of Physiology, 2Department of Medical Education, 3Department of Surgery, College of Medicine, King Saud University, 4Department of Surgery, King Saud University Medical City, 5Department of Internal Medicine, 6Department of Medicine, 7College of Medicine, King Saud University, Riyadh, Saudi Arabia Background: The students’ perception of the learning environment is an important aspect for evaluation and improvement of the educational program. The College of Medicine at King Saud University (KSU) reformed its curriculum in 2009 from a traditional to a system-oriented hybrid curriculum.Objective: The objective of the present study was to determine the perception of the second batch (reformed curriculum) of medical graduates about the educational environment at the College of Medicine, KSU, using the Dundee Ready Education Environment Measure (DREEM) scale.Methods: The fifth year medical students were asked to evaluate the educational program after graduation in May 2014. The questionnaire was distributed to the graduate students electronically. The DREEM questionnaire consisted of 50 items based on Likert’s scale; and five domains, namely, students’ perceptions of learning, perceptions of teachers, academic self-perceptions, perceptions of atmosphere, and social self-perceptions. Data were analyzed using SPSS.Results: A total of 62 students participated in the study. The score for students’ perception of learning among medical students ranged from 2.93 to 3.64 (overall mean score: 40.17). The score for students’ perception of teachers ranged from 2.85 to 4.01 (overall mean score: 33.35). The score for students’ academic self-perceptions ranged from 3.15 to 4.06 (overall mean score: 28.4). The score for students’ perception of atmosphere ranged from 2.27 to 3.91 (overall mean score: 41.32). The score for students’ social self-perceptions ranged from 2.85 to 4.33 (overall mean score: 24.33). The general perceptions of the students in all five sub-scales were positive.Conclusion: The overall student’s perception about the educational environment was satisfactory. This study was important to evaluate the students’ perception of the learning environment among medical graduates of the reformed curriculum and provided guidance on areas of improvement in the curriculum. Keywords: medical students, perception, learning environment, DREEM inventory, Saudi Arabi

Gastrointestinal angiodysplasia in three Saudi children

Angiodysplasia is a term used to describe distinct gastrointestinal mucosal ectasias that are not associated with cutaneous lesions, systemic vascular disease or a familial syndrome. Seventy-seven percent of angiodysplasia are located in the cecum and/or ascending colon. Fifteen percent are located in the jejunum and/or ileum and the remainder are distributed throughout the alimentary tract. Most commonly, the angiodysplastic lesions are typically seen in elderly patients of both genders, although gastric and duodenal lesions have been reported occasionally in subjects within the third decade of life. However, data on infants and children are scarce. We describe three cases (ages 7 days, 2 years, and 5 years) who presented to our unit with gastrointestinal bleeding. One of these patients developed moderate-to-severe symptoms and was blood-transfusion dependent. She was misdiagnosed as having inflammatory bowel disease and underwent a total colectomy and ileoanal anastomosis. The other two patients were managed conservatively for up to 5 years with no further bleeding