Low defect, high purity crystalline layers grown by selective deposition

The purity and perfection of a semiconductor is improved by depositing a patterned mask of a material impervious to impurities of the semiconductor on a surface of a blank. When a layer of semiconductor is grown on the mask, the semiconductor will first grow from the surface portions exposed by the openings in the mask and will bridge the connecting portions of the mask to form a continuous layer having improved purity, since only the portions overlying the openings are exposed to defects and impurities

Advanced Czochralski silicon growth technology for photovoltaic modules

Several economic analyses had indicated that large-diameter, multiple ingot growth using a single crucible with melt replenishment would be required for Cz growth to be economically viable. Based on the results of these analyses, two liquid and two solid feed melt replenishment approaches were initiated. The sequential solid feed melt replenishment approach, which demonstrated elements of technical feasibility is described in detail in this paper. Growth results of multiple ingots (10-cm-diameter, totaling 100 kg; and 15-cm-diameter, totaling 150 kg weight per crucible) are presented. Solar cells were fabricated and analyzed to evaluate the effects of structure and chemical purities as a result of multiple growth. The results indicate that, with semiconductor-grade silicon, feedstock impurity build-up does not seem to degrade cell performance. For polycrystalline cells, the average efficiencies are 15 to 25% lower than those of single crystalline cells. Concerns regarding single crystal yields, crucible quality and growth speed are indicated, and present status and future research thrusts are also discussed

Corrosion at Sulphide Inclusions in Stainless Steel

Auger analysis was performed using a high resolution scanning auger electron microscope and auger electron spectroscopy. Elemental auger contour maps for corroded sulphide inclusions in stainless steel were presented. It was found that the copper enriched-manganese sulphide inclusions were uniformly corroded, which might be due to CU2S deposition on the surface of corroding inclusions. In contrast, manganese sulphide inclusions containing less copper were non-uniformly attacked, resulting in the formation of deep microcrevices at their edges

Factors Influencing the Achievement in Mathematics of Malay Secondary School Students

The present situation of many secondary school students having difficulty in learning mathematics needs to be thoroughly investigated. Various factors need to be studied in order to determine why these students failed to perform satisfactorily in mathematics. For this research, a group of three hundred secondary school students were studied in order to determine the influence of students' internal characteristics on achievements in mathematics. This research focused on the following seven internal characteristics: Attitudes towards mathematics, mathematics anxiety, motivation to study mathematics, personality and behavioural characteristics, cognitive readiness, learning strategies, and learning styles.For learning styles, Kolb's Learning Style Inventory (1985) was used. Cognitive readiness test consisted of questions involving abstract reasoning, logical thinking, and numerical computation. For the other variables. the tests consisted of questionnaires using likert scale from one to five. Mathematics achievements were determined by the scores that the students got for mathematics in the Trial SPM Examination, 1999. The research findings showed that mathematics achievements were significantly and positively correlated with attitudes towards mathematics. motivation to study mathematics, and personality and behavioural characteristics. Mathematics anxiety, on the other hand, had negative influence on achievements in mathematics. The result suggested that efforts must be made to reduce the level of mathematics anxiety in order to raise the students' performance in mathematics. Mathematics achievements were found to correl ate strongly with abstract reasoning, logical thinking, and numerical computational abilities. As for learning strategies, higher achievers were found to be more oriented towards meaningful learning, as opposed to rote memorising. The findings for learning styles indicated that higher achievers were more oriented towards abstract conceptualisation and active experimentation modes of learning. Convergence was found to be the dominant learning style of students who were excellent in mathematics.In the inter-groups comparison analyses, the findings showed that weak students did not have positive attitudes and strong motivation to succeed in learning mathematics. Their levels of mathematics anxiety were relatively high, and their personality and behavioural characteristics1 were relatively unfavourable. Weak students also had a relatively lower level of ability in abstract reasoning, logical thinking, and numerical computation. Weak students were more oriented towards rote memorising and concrete experiencing mode of learning

Fibre bragg grating sensor system for temperature application

A practical pass-through type fibre Bragg grating (FBG) temperature sensor system have been designed and experimentally investigated. The performance of FBG was evaluated with the varying of focusing elements in harsh environments, under direct sunlight. The sensor head of FBG was designed to be focused with convex and hand lens. Results shows that the Bragg wavelength shift, ΔλB increase proportionally with the temperature for both systems. The sensitivities of FBG were recorded to be 0.0107 and 0.0122 nm °C-1 for the system where convex and hand lens applied to the FBG’s sensor head respectively

Kajian Bioekologi Lamun di Perairan Sofifi Kota Tidore Kepulauan, Provinsi Maluku Utara

Lamun merupakan salah satu ekosistem pesisir dan laut yang memiliki peran, fungsi dan manfaat yang besar bagi kelangsungan berbagai organism pesisir dan laut. Di perairan sofifi, terdapat ekosistem lamun namun belum diteliti. Dengan demikian maka penelitian ini sangat penting dilakukan. Penelitian ini menggunakan metode kuadran yang ditempatkan secara teratur pada lima lintasan. Data yang terkumpul selanjutnya dianalisis untuk mencari tingkat keanekaragaman jenis, indeks dominansi dan kerapatan jenisnya. Penelitian ini dilakukan di perairan Sofifi, kota Tidore Kepulauan. Berdasarkan hasil analisis ditemukan bahwa lamun jenis Enhalus acroides memiliki persentase tutupan yang tinggi dan indeks dominansi yang tinggi, sedangkan lamun jenis Syringodium isoitifolium memiliki nilai keanekaragaman jenis yang tinggi yakni sebesar 0.368. kondisi ekologi atau hidrooseanogafi baik suhu, salinitas maupun pH sangat baik dan cocok untuk pertumbuhan lamun. Terdapat substrat pasir berlumpur dan lumpur berpasir yang di temukan di kelima lintasan penelitian. Secara umum kondisi ekosistem lamun sangat baik dan kondisi ekologi sangat mendukung pertumbuhan lamun. Kedepan perlu adanya penelitian untuk mengidentifikasi jenis-jenis lamun di Maluku Utara

Tests on the centrifugal flotation technique and its use in estimating the prevalence of Toxocara in soil samples from urban and suburban areas of Malaysia

The influence of soil texture (silt, sand and laterite) and flotation solutions (saturated NaCl, sucrose, NaNO3 and ZnSO4) upon the recovery of Toxocara ova from seeded soil samples with the centrifugal flotation technique was investigated. Soil samples of different texture were artificially seeded with Toxocara spp. ova and subjected to a centrifugal flotation technique which used various flotation solutions. The results showed significant (P<0.001) interactions between the soil types and the flotation solutions. The highest percentage of ova recovery was obtained with silty soil (34.9−100.8%) with saturated NaC1 as the flotation solution (45.3−100.8%). A combination of washing of soil samples with 0.1% Tween 80, and flotation using saturated NaCl and a 30 min coverslip recovery period was used to study the prevalence of contamination of soil samples. Forty-six soil samples were collected from up to 24 public parks/playgrounds in urban areas of Petaling Jaya and suburban areas of Serdang. The prevalence of Toxocara species in the urban and suburban areas was 54.5% and 45.8% respectively