Study on A.C properties of tin selenidethin films

A.c properties of tin selenide thin films prepared by an encapsulated selenization method are investigated. The measurements obtained from al/snse/al sandwich structures showed strong indication of frequency and temperature dependence of capacitance, dielectric loss and conductance over the ranges of 5-200 khz and 228-373 k, respectively. Dielectric behaviour was expected to be due to space charge polarization which contributed to a.c conduction. This was generally explained in terms of hopping of the charge carriers between localized states with activation energies 0.03-0.08 ev. Parameters such as trap binding energy (0.94 ev) and minimum hopping distance (1.01 nm) were also predicte

Hydrophobic silica thin films by sol-gel processing and spin coating technique at low temperature

Hydrophobic silica thin films were prepared by sol-gel processing and self-assembly by chemical vapor reaction with Trimethylchlorosilane (TMCS) at low temperature. The sols were divided into Sol A with ethanol, Polyethylene glycol (PEG) and water (H2O) while Sol B were contain precursor of silica Tetraethylorthosilicate (TEOS) hydrolyze with ethanol which was stirred for 15 minutes. HCl was added into the mixture and stirred for another 10 minutes. After deposition on 1 x 1 cm corning glass using spin coating technique (two-step timer), the films were heated at 60˚C for 10 minutes and finally annealed at 150°C for 1 hour. The films were characterized by using Rudolph/Auto EL Ellipsometer, Shimadzu Spectrophotometer, Perkin Elmer Fourier Transform Infrared (FTIR) and Atomic Force Microscope (AFM). The results showed that the films thickness and refractive index were in the range of 105.2 to 112.4 nm and 1.35 to 1.38, respectively. The films were transmitted 70-80% of light (in visible range) with various bondings of C-H, Si-O-Si, Si-C and Si-OH. Surface roughness of the films was increased from 30.6 nm (silica thin film) to 140.5 nm (hydrophobic silica thin films) after modification have been done on the films by using TMCS (heated at 40˚C). It was found that the water contact angles increased when time of reaction increased from 109° to 124

Optical properties of diamond like carbon films prepared by DC-PECVD

Diamond-like carbon (DLC) thin films were deposited at different substrate temperatures using methane and hydrogen gas in DC-PECVD at 2x10-1Torr. From the light transmission using UV-VIS spectroscopy it was found that the optical transition had changed from allowed indirect transition to allowed direct transition as the substrate temperature increased. The Optical gap increased with temperature, highest of 3.034 eV was observed at 573 K, beyond which it dropped. Colour of the film changed from light brownish to a colourless transparent film in the higher temperature. The Urbach energy decreased from 1.25 eV to 0.75 eV with increasing substrate temperature till 573 K and a slight increase after it. This trend is attributed to change in sp3/sp2 ratio or change in structure. The cluster size decreases with temperature, resulting in larger band gap and the structure more ordered. Similar pattern is also witnessed in the emission spectrum of the photoluminescence

Structural and luminescent characteristic of Sm3+ doped magnesium sulfide borate orange-red phosphor for white LED

Polycrystalline compositions based on MgO, SO3 and B2O3 have both scientific and technological importance because of their useful applications. Doping with rare earth elements not only due to a rearrangement in the structure, but also to variation in the luminescence properties. Magnesium sulfide borate doped samarium oxide (MgSBO3:Sm3+) phosphors were prepared by solid state reaction and their structural and luminescence characteristic were studied and reported. IR and Raman spectral studies have been made to explore the presence of functional groups and various structural units in the prepared Polycrystalline. The formation of SO4, BO4, BO3, B-O-B and S-O-B structural units have been investigated. The emission and excitation properties were studied. And the results show that the emission and excitation spectra of these phosphors can be excited by ultraviolet (UV) 341, 370 and 403 nm light, and emit green, yellow and red light with intense peak at 601 nm, which are nicely in accordance with the widely applied near- UV LED chip. The emission spectral intensity of Sm3+ ions in the titled phosphors increases up to 1 mol% of Sm3+ ions and then decreases for 1.5 mol%. These results indicate that MgSBO3:Sm3+phosphor could be a potential suitable orange-red emitting phosphor candidate for white LEDs with excitation of a ~403 nm near UV LED chip

Photoluminescence characteristics of strontium titanate thin films prepared by spray pyrolysis

Strontium titanate, SrTiO3 thin films were successfully prepared by spray pyrolysis. The strontium titanate, STO precursor solid thin film were fabricated from an aqueous solution of Sr(NO3)2/[(CH3)2CHO]4Ti/HNO3 = 19:1:20 (molar ratio) at room temperature on a substrate. The as-deposited STO thin film with those annealed at different temperature were prepared. Photoluminescence spectra of thin films were obtained using Photoluminescence Spectrophotometer and optical properties were carried out by using Shimadzu Uv-Vis Spectrophotometer. In conclusion, the band gap energy and the bandwidth of thin films have been analysed

Hubungan Antara Kerja Rumah Dengan Pencapaian Akademik Dalam Kalangan Pelajar Dari Kelas Premier Di Dua Buah Sekolah Menengah

Kerja rumah telah menjadi komponen penting dalam sistem persekolahan di Malaysia. Kerja rumah memainkan peranan yang penting untuk membantu pelajar supaya lebih memahami pelajaran yang diajarkan di dalam kelas. Kerja rumah juga berperanan untuk menyumbangkan pencapaian yang tinggi terhadap sesuatu mata pelajaran. Kajian ini bertujuan untuk mengkaji hubungan antara kerja rumah dengan pencapaian mata pelajaran Matematik, Bahasa Inggeris dan Sejarah dalam kalangan pelajar tingkatan dua dari kelas premier di Sekolah Menengah Kebangsaan Taman Mutiara Rini dan Sekolah Menengah Kebangsaan Sri Skudai, Johor Bahru. Kajian ini menumpukan tiga faktor yang berkaitan dengan kerja rumah, iaitu peruntukan masa, jenis-jenis kerja rumah, dan cara pengelolaan guru terhadap kerja rumah. Seramai 106 orang pelajar telah dipilih sebagai sampel kajian: dua kelas tingkatan dua premier dari SMK Sri Skudai dan satu kelas tingkatan dua premier dari SMK Taman Mutiara Rini. Alat kajian yang digunakan ialah borang soal selidik. Borang ini terdiri daripada dua bahagian. Bahagian A mengandungi soalan yang berkaitan dengan demografi pelajar, pencapaian mata pelajaran dan faktor peruntukan masa. Manakala Bahagian B pula terdiri daripada 30 soalan berkaitan dengan faktor jenis kerja rumah dan faktor cara pengelolaan guru terhadap kerja rumah pelajar. Nilai kebolehpercayaan alat kajian ini ialah ? = 0.929. Keputusan peperiksaan akhir tahun dijadikan sebagai ukuran pencapaian pelajar dalam setiap mata pelajaran yang dikaji. Analisis deskriptif (kekerapan dan peratusan) dan inferensi (korelasi Pearson) digunakan dalam tatacara menganalisis data. Secara keseluruhannya, tahap pencapaian pelajar dalam setiap mata pelajaran berada pada tahap tinggi (60–79%). Hasil kajian ini menunjukkan bahawa terdapat hubungan signifikan tetapi sederhana antara faktor cara pengelolaan guru semasa dan selepas pemberian kerja rumah dengan pencapaian bagi mata pelajaran Matematik

X-ray diffraction study of evaporated cadmium telluride thin films

X-ray diffraction measurement was performed on evaporated CdTe thin films indicating a preferential orientation in (111) direction. The effect of the deposition rate, thickness and substrate temperature was investigated and the film quality was discussed. It was found that as the deposition rate was increased finer crystallite size was obtained, while at the same time the micro-strain decreased. The decrease in crystallite size at higher deposition rate can be interpreted according to the increased velocity and intensity of the vapour atoms during rapid film formation. The crystallite size increased as the substrate temperature was increased up to 200 oC, above which the crystallite size decreased again. As the thickness was increased the micro-strain decreased, while the crystallite size increased with thicknes

Excess silicon concentration dependence of the structural and optical properties of silicon nanocrystals embedded in silicon oxide matrix

Silicon (Si) nanocrystals embedded in Si oxide matrix have been formed by rapid thermal annealing of sub-stoichiometric Si oxide films (SiOx with x < 2). The SiOx films were deposited by co-sputtering of Si oxide and Si target using magnetron RF sputtering technique. The Si-to-SiO2 ratio was controlled by varying the number of Si chips being placed on the pure SiO2 target during sputtering. Rapid thermal anneal in nitrogen gas at 1100°C lead to the decomposition of SiOx into Si nanocrystals and SiO2. The structural (size of nanocrystals) and optical properties (absorption and luminescence) of Si nanocrystals embedded in oxide matrix, were found, strongly depend on the initial excess Si concentration in SiOx films

Infrared studies and determination of optical band gap of hydrophobic silica thin films

Hydrophobic silica is a form of silicon dioxide (commonly known as silica) that has hydrophobic groups chemically bonded to the surface

Relationship between precursor gas flow rate with the structural and morphology properties of diamond like carbon films

Diamond like carbon (DLC) thin films were grown onto glass substrates by using direct current plasma enhance chemical vapour deposition (DC-PECVD) system. Films were deposited under fixed deposition pressure (4 × 10-1 Torr), substrate temperature (500 °C) and deposition time (3 hours) but with different flow rate of precursor gas (methane, hydrogen and argon). The fabricated films were characterized by using x-ray diffraction (XRD) and atomic force microscopy (AFM). XRD has revealed that the DLC films were having amorphous phase as the XRD spectrum did not show any obvious sharp peak. From AFM, it was discovered that the precursor gas flow rate has inversely relationship with the grain size and surface roughness of films