Maskless etching of silicon using patterned microdischarges

Microdischarges in flexible copper-polyimide structures with hole diameters of 200 µm have been used as stencil masks to pattern bare silicon in CF4/Ar chemistry. The discharges were operated at 20 Torr using the substrate as the cathode, achieving etch rates greater than 7 µm/min. Optical emission spectroscopy provides evidence of excited fluorine atoms. The etch profiles show a peculiar shape attributed to plasma expansion into the etched void. Forming discharges in multiple hole and line shapes permits direct pattern transfer in silicon and could be an alternative to ultrasonic milling and laser drilling

Hollow cathode sustained plasma microjets: Characterization and application to diamond deposition

Extending the principle of operation of hollow cathode microdischarges to a tube geometry has allowed the formation of stable, high-pressure plasma microjets in a variety of gases including Ar, He, and H2. Direct current discharges are ignited between stainless steel capillary tubes (d = 178 µm) which are operated as the cathode and a metal grid or plate that serves as the anode. Argon plasma microjets can be sustained in ambient air with plasma voltages as low as 260 V for cathode-anode gaps of 0.5 mm. At larger operating voltage, this gap can be extended up to several millimeters. Using a heated molybdenum substrate as the anode, plasma microjets in CH4/H2 mixtures have been used to deposit diamond crystals and polycrystalline films. Micro-Raman spectroscopy of these films shows mainly sp3 carbon content with slight shifting of the diamond peak due to internal stresses. Optical emission spectroscopy of the discharges used in the diamond growth experiments confirms the presence of atomic hydrogen and CH radicals

High-pressure micro-discharges in etching and deposition applications

High-pressure micro-discharges are promising sources of light, ions, and radicals and offer some advantages in materials processing applications as compared to other more conventional discharges. We review here results from etching experiments using stencil masks where the discharge is formed only in the pattern cutout. The mask consists of a thin metal-dielectric structure and is pressed against a Si wafer, which becomes part of the electric circuit. Pattern transfer takes place, albeit the profile shape appears to be limited by the expansion of the plasma into the etched hole at long etch times. We also review experiments on using micro-discharges as sources of radicals for materials deposition applications. In the latter case, the micro-discharges form in metal capillary tubes permitting incorporation of gas flow and a short reaction zone that can be controlled to favour production of specific radicals. We demonstrate these concepts by using CH4/H2 chemistry for diamond deposition on a heated Mo substrate. Good quality micro- and nano-diamond crystals could be produced

Argon excimer emission from high-pressure microdischarges in metal capillaries

We report on argon excimer emission from high-pressure microdischarges formed inside metal capillaries with or without gas flow. Excimer emission intensity from a single tube increases linearly with gas pressure between 400 and 1000 Torr. Higher discharge current also results in initial intensity gains until gas heating causes saturation or intensity drop. Argon flow through the discharge intensifies emission perhaps by gas cooling. Emission intensity was found to be additive in prealigned dual microdischarges, suggesting that an array of microdischarges could produce a high-intensity excimer source

Characterization of lower respiratory tract inflammation in patients with smear negative pulmonary tuberculosis

Bronchoalveolar lavage (BAL) studies were carried out in 27 sputum smear negative but radiographic probable pulmonary tuberculosis patients to characterize the inflammatory and Immune effector cells in the lower respiratory tract and in 17 normal subjects. The diagnosis of active pulmonary tuberculosis was confirmed by isolation of Mycobacterium tuberculosis in culture from sputum and/or lavage specimens. BAL was done first from radiologically normal lobe and then from radiologically abnormal lobe prior to treatment and the BAL fluids were analyzed separately. Two groups were identified based on lavage results. One group (macrophage predominant) had significantly elevated total cells and alveolar macrophages in both radiologically normal (p<0.01) and abnormal lobes (p<0.001) compared to normal controls. The other group (lymphocyte predominant) had expanded numbers of total cells (p<0.01), lymphocytes (p<0.01), neutrophlls (p<0.05) and eosinophils (p<0.01) in radiologically abnormal lobe. The cell profile in radiologically normal lobe in lymphocyte predominant group was within normal limits. These results suggest that two distinct cell profiles, in one group an increase in alveolar macrophages and in the other an increase in lymphocytes can occur In the lower respiratory tract of patients with sputum smear negative, but radiographic probable pulmonary tuberculosis

Damping in Torsional Vibrations of Embedded Footings

The existing theoretical models to explain the dynamic behavior of embedded footings, overestimate the real response by neglecting damping forces which are inevitable as a result of slip at the interface of the embedded footing and soil. Many researchers in the field of Soil Dynamics have suggested that the inclusion of friction damping and internal damping in the mathematical model is necessary to improve the reliability of theoretical predictions. In this paper, results of the experimental investigations on full scale model embedded footings subjected to torsional mode of vibration have been presented. The results have been analyzed making use of three theoretical models, as developed by, Novak and Sachs (1973); Sankaran et al (1978) and Sankaran et al (1980). The importance of d-ping in predicting the dynamic response is brought out by a comparison of field vibratory test data with the corresponding values predicted by each of the above mentioned theoretical models

Association between Obesity and Hypertension in South Indian Patients

Two hundred and forty four newly diagnosed hypertensives (cases) of age 40 years and above, attending the hypertensive clinic of the Government General Hospital during one year and three hundred and twelve normotensives (controls) belonging to the same age group and attending the outpatient department during the same period for other minor ailments formed the subjects for this case control study. There were 18 (7.4%) obese subjects among hypertensives and 6 (1.9%) among controls. Inspite of these low proportions, there was a strong association between obesity and hypertension with an overall odds ratio of 4 and there appeared to be a significant increasing trend in the proportion of cases of hypertension (37%, 63%, 75%) observed according to the different grades (underweight or normal. overweight, obese) of nutrition

Cellular profile of bronchoalveolar lavage fluid in pulmonary tuberculosis

Bronchoalveolar lavage (BAL) has been used to study the immunopathogenesis of several respiratory diseases. The aim of our study was to determine the inflammatory changes occurring at the site of a tuberculous lesion in the lung in children

Synthesis of Blue Luminescent Si Nanoparticles Using Atmospheric-Pressure Microdischarges

Silicon nanoparticles are synthesized from a mixture of argon/silane in a continuous flow atmospheric-pressure microdischarge reactor. Particles nucleate and grow to a few nanometers (1−3 nm) in diameter before their growth is abruptly terminated in the short residence time microreactor. Narrow size distributions are obtained as inferred from size classification and imaging. As-grown Si nanoparticles collected in solution exhibit room-temperature photoluminescence that peaks at 420 nm with a quantum efficiency of 30%; the emission is stable for months in ambient air

Extraction Characteristics of Alumina from Gujrat Bauxites

ALUMINIUM has been termed the versatile metal of the 20th century since it finds applications right from the kitchen to the spaceship. The growing popularity of this metal has been attributed to its outstanding physical and chemical properties, viz. lightness, high strength of its alloys, high electrical and thermal conductivity, good workability and the most important of all-its resistance to corrosion. Aluminium and its alloys find extensive applications in road transport, railways and aviation due to their good strength for relatively low weight. Aluminium also finds applications in chemical & food processing plants. Owing to its good electrical conductivity it finds use in electrical industries . Its strength, brightness, durab-ility and capacity to take anodic coatings and colours are the most important properties for its use for archite-ctural purposes