Effects of rapid thermal annealing on GaAs 1-x

The effects of rapid thermal annealing on the optical and structural properties of GaAs1-xBix alloys for x ranging from 0.022 to 0.065 were investigated. At room temperature, the annealed GaAs1-xBix showed modest improvement (∼3 times) in photoluminescence (PL) while the PL peak wavelength remained relatively unchanged. It was found that bismuth related defects are not easily removed by annealing and the PL improvement may be dominated by the reduction of other types of defects including arsenic and gallium related defects. Also, the optimum annealing temperature is Bi composition dependent. For samples with x < 0.048, the optimum annealing temperature is 700 °C but reduces to 600 °C for higher compositions

Photoluminescence investigation of high quality GaAs1−xBix on GaAs

Photoluminescence (PL) of GaAs0.97Bi0.03 alloy was measured over a wide range of temperatures and excitation powers. Room temperature PL with peak wavelength of 1038 nm and full-width-half-maximum of 75 meV was observed which is relatively low for this composition. The improved quality is believed due to reduced alloy fluctuations by growing at relatively high temperature. The temperature dependence of PL peak energy indicated significant exciton localization at low temperatures. Furthermore, the band gap temperature dependence was found to be weaker than GaAs. An analysis of dominant carrier recombination mechanism(s) was also carried out indicating that radiative recombination is dominant at low temperature

The effect of Bi composition to the optical quality of GaAs 1−x

GaAs1−xBix alloys grown by molecular beam epitaxy for x up to 0.06 were studied by photoluminescence (PL). The results indicate that dilute fractions of bismuth (Bi) with x < 0.025 improve the material quality of this low temperature growth alloys by reducing the density of gallium (Ga) and/or arsenic related defects. The crystal quality starts to degrade at higher Bi concentration probably due to significant amount of Bi-related defects, BiGa. However, the room temperature PL intensity continues to increase with Bi content for the range studied due to greater band-gap offset between GaAs and GaAs1−xBix. Analysis carried out shows no correlation between localization effects and the room temperature PL enhancement

Photoluminescence and raman scattering of GaAs1-xBix alloy

Photoluminescence (PL) and Raman spectra of GaAs1-xBix samples grown at different rates (0.09 to 0.5 µm/h) were investigated. The PL peak wavelength initially redshifted with the increase of growth rate and reached the longest wavelength (1158 nm) for sample grown at 0.23 µm/h. This is followed by PL peak wavelength blueshift for higher growth rates. The Raman data show peaks at 162, 228, 270, and 295 cm-1 which can be attributed to GaAs like phonons. GaBi like vibrational modes were also observed at 183 and 213 cm-1. However, the intensity of Bi induced phonons is significantly weaker compared to GaAs due to low concentration of Bi compared to As and thin GaAs1-xBix epilayer. The PL data and GaAs transverse optical (TO) to longitudinal optical (LO) phonons intensity ratio indicate that Bi concentration is highly dependent on the growth rate and the highest Bi concentration was obtained by sample grown at 0.23 µm/h. It is found that the full-width-at-half-maximum (FWHM) of GaAs LO mode increases significantly for samples grown at high growth rates suggesting crystal quality degradation due to lack of surfactant effects

Karsinoma buah dada dan faktor-faktor yang mempengaruhi dikalangan pesakit di Hospital Kuala Lumpur

Suatu kajian kes kontrol telah dilakukan untuk menentukan samada faktor-faktor seperti sejarah keluarga karsinoma buah dada, pariti, penyusuan anak dan pengambilan pil perancang keluarga dapat mempengaruhi prevalens karsinoma buah dada. Dalam kajian ini 40 kes pesakit karsinoma buah dada yang mendapatkan rawatan di Hospital Kuala Lumpur bagi tahun 1992 dan 1993 telah diambil secara rawak dari Unit Rekod, Fakulti Perubatan UKM. Manakala 40 kontrol yang berpadanan dari segi umur dan bangsa telah ditemuduga pada pesakit dari wad-wad di Hospital Kuala Lumpur. Daripada 40 pesakit karsinoma buah dada yang dipilih 65% adalah berbangsa Melayu diikuti Cina 20.0% dan India 15.0%. Daripada kajian ini, didapati bahawa terdapat hubungan yang bererti (p0.05). Sejarah keluarga karsinoma buah dada merupakan faktor risiko yang terpenting dengan nisbah ods sebanyak 6.31 (95%Selang Keyakinan (SK) : 1.2, 45.5). Pariti juga adalah faktor yang penting dengan nisbah ods sebanyak 4.7. Sementara penyususan ibu merupakan faktor pelindung dengan nisbah ods 0.34 (SK 0.1, 0.9). Dengan pengetahuan faktor risiko ia dapat membantu mengesan karsinoma buah dada diperingkat awal

Strategies to revitalize urban markets as active public space that foster social interaction

Urban markets located in the city act as a nodal point which is able to gather people from different demographics to sell and buy. It also provides a platform for social interaction for the surrounding neighbourhood. Thus, the market is a place where a sense of community can be developed. However, the role of the urban market to serve as an unofficial social hub has lost due to the rapid modernisation and the rise of modern retails. The previous studies only focused on the factors that caused the issues and still lacked the architectural criteria to create social spaces to enhance social function of the urban market. Hence, this study is to identify the strategies to revitalize the urban market in order to stimulate social aspects in the city. In this research, case study on the existing urban market will be used as the research inquiry and interview will be conducted with the users of the marketplace. This research will explore the design criteria to revitalize urban markets to foster social interaction across different groups of people. This research will contribute to the enhancement of the sense of community and stimulate the social aspect in urban areas by revitalizing the urban marketplace. It will benefit the local community or urban dweller to ensure their social well-being. Future research can add more variables to the existing study, for instance, the political and economic aspects that influence the social role of the urban markets

Preliminary thermal evaluation of actuator for steer-by-wire vehicle

Automotive industry is moving towards electrification of steering system due to efficiency and active safety integration concerns. Studies on actuators for Steer-by-Wire (SBW) application is very limited, and no thermal effects on the actuator related to utilization in SBW have yet been looked into. Using a valid thermal model, and steer torque data collected from a journey mapping, a temperature profile of a prototype Synchronous Reluctance machine (Syncrel) has been established as if it was utilized as SBW actuator to verify the thermal robustness of the machine in that particular application. The maximum temperature in the winding is shown to not exceed the limit temperature for the winding insulation if the winding resistance can be divided by half of the current resistance in the prototype machine, thus, allowing us to consider Syncrel as another actuator solution for SBW