The Role of Dopant Concentration on Conductivity and Mobility of CdTe Thin Films

Films of CdTe pure and doped with various atomic percentages of Al and Sb (0.5, 1.5 & 2.5) were prepared, and their electrical properties were investigated. The films were prepared by thermal evaporation on glass substrates at two substrate temperatures (Ts=RT & 423 K). The results showed that the conduction phenomena of all the investigated CdTe thin films on glass substrates are caused by two distinct mechanisms. Room temperature DC conductivity increases by a factor of four for undoped CdTe thin films as Ts increases and by 1-2 orders of magnitude with increasing dopant percentage of Al and Sb. In general, films doped with Sb are more efficient than Al-doped films. The activation energy (Ea2) decreases with increasing Ts and dopant percentage for both Al and Sb. Undoped CdTe films deposited at RT are p-type convert to n-type with increasing Ts and upon doping with Al at more than 0.5%. The carrier concentration decreases as Ts increases while it increases with increasing dopant percentage. Hall mobility decreases more than three times as Al increases whereas it increases about one order of magnitude with increasing Sb percentage in CdTe thin films deposited at 423 K and RT, respectively

Identifying rail asset maintenance processes: a human-centric and sensemaking approach

Efficient asset maintenance is key for delivering services such as transport. Current rail maintenance processes have been mostly reactive with a recent shift towards exploring proactive modes. The introduction of new ubiquitous technologies and advanced data analytics facilitates the embedding of a ‘predict-and-prevent’ approach to managing assets. Successful, user-centred integration of such technology is still, however, a sparsely understood area. This study reports results from a set of interviews, based on Critical Decision Method, with rail asset maintenance and management experts regarding current procedural aspects of asset management and maintenance. We analyse and present the results from a human-centric sensemaking timeline perspective. We found that within a complex sociotechnical environment such as rail transport, asset maintenance processes apply not just at local levels, but also to broader, strategic levels that involve different stakeholders and necessitate different levels of expertise. This is a particularly interesting aspect within maintenance that has not been discussed as of yet within a process-based and timeline-based models of asset maintenance. We argue that it is important to consider asset maintenance activities within both micro (local) and macro (broader) levels to ensure reliability and stability in transport services. We also propose that the traditionally distinct notions of individual, collaborative and artefact-based sensemaking are in fact all in evidence in this sensemaking context, and argue that a more holistic view of sensemaking is therefore appropriate by placing these results within an amended Recogntion Primed Decsion making model

The Analytical and Alternatives Generation Phases in Urban Design Practice in US Cities. The Case Study of Pittsburgh Development Plan 2001

According to some experts, urban design plans adopted in US cities are often developed without being underpinned by relevant analytical content, or are not based on in-depth analysis for the specific problem of the study area. There may be need to examine current urban design plans to provide local authorities with new processes that would improve urban design and implementation. This paper examines the analysis and alternatives generation methods used in a selected case of urban design practice in Pittsburgh and compares them against various theoretical conceptions. It attempts to establish gaps in its methodology and to explore the extent with which the analytical content underpinned the design solutions. It has been found that the plan's content has emphasized the role of research and analysis in its methodological framework and had a significant impact on the development plan yet with various degrees of success. The paper identifies the methodology and techniques adopted in both phases, and highlights the gaps in each phase as well as gaps between both phases. The paper found that the analysis phase and the analytical content have had significant impact on the general and the specific levels of the development plan yet with different degrees of success. In sum, the policies were generally good at expressing the analytical content and consultative bases of policies

Optical Properties of Al- and Sb-Doped CdTe Thin Films

Nondoped and (Al, Sb)-doped CdTe thin films with 0.5, 1.5, and 2.5  wt.%, respectively, were deposited by thermal evaporation technique under vacuum onto Corning 7059 glass at substrate temperatures () of room temperature (RT) and 423 K. The optical properties of deposited CdTe films such as band gap, refractive index (n), extinction coefficient (), and dielectric coefficients were investigated as function of Al and Sb wt.% doping, respectively. The results showed that films have direct optical transition. Increasing and the wt.% of both types of dopant, the band gap decrease but the optical is constant as n, and real and imaginary parts of the dielectric coefficient increase

Compositional Dependence of Structural Properties of Prepared Alloys and Films

Results of a study of PbS1− alloys and films with various Pb content have been reported and discussed. Films of PbS1− of thickness 1.5 μm have been deposited on glass substrates by flash thermal evaporation method at room temperature, under vacuum at constant deposition rate. These films were annealed under vacuum around 10−6 Torr at different temperatures up to 523 K. The composition of the elements in PbS1− alloys was determined by standard surfaces techniques such as atomic absorption spectroscopy (AAS) and X-ray fluorescence (XRF), and the results were found of high accuracy and in very good agreement with the theoretical values. The structure for alloys and films is determined by using X-ray diffraction. This measurement reveals that the structure is polycrystalline with cubic structure and there are strong peaks at the direction (200) and (111). The effect of heat treatment on the crystalline orientation, relative intensity, and grain size of PbS1− films is presented

Electrical and Optical Properties of :H Thin Films Prepared by Thermal Evaporation Method

Thin a-GeSi1−:H films were grown successfully by fabrication of designated ingot followed by evaporation onto glass slides. A range of growth conditions, Ge contents, dopant concentration (Al and As), and substrate temperature, were employed. Stoichiometry of the thin films composition was confirmed using standard surface techniques. The structure of all films was amorphous. Film composition and deposition parameters were investigated for their bearing on film electrical and optical properties. More than one transport mechanism is indicated. It was observed that increasing substrate temperature, Ge contents, and dopant concentration lead to a decrease in the optical energy gap of those films. The role of the deposition conditions on values of the optical constants was determined. Accordingly, models of the density of states for the Ge0.5Si0.5:H thin films as pure, doped with 3.5% of Al (p-type) and that doped with 3.5% As (n-type), were proposed