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  • 1
    Electronic Resource
    Electronic Resource
    The influence of ion energy, ion flux, and etch temperature on the electrical and material quality of GaAs etched with an electron cyclotron resonance source (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2712-2715 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The residual damage incurred to GaAs via etching with a Cl2/Ar plasma generated by an electron cyclotron resonance (ECR) source was investigated as a function of variations in ion energy, ion flux, and etching temperature. The residual damage and electrical properties of GaAs were strongly influenced by changes in these etching parameters. Lattice damage was incurred in all processing situations in the form of small dislocation loops. GaAs etched at high ion energies with 200 W rf power, exhibited a defect density five times higher than GaAs etched at lower ion energies with 20 W rf power. This enhanced residual damage at the higher rf powers was paralleled by a degradation in the unannealed contact resistance. Higher etch rates, which accompany the higher rf power levels, caused the width of the disordered region to contract as the rf power was elevated. Therefore, the residual etch damage is influenced by both the generation and removal of defects. Increasing the microwave power or ion flux resulted in elevating the residual defect density, surface roughness, and unannealed contact resistance. GaAs etched at high temperatures, ∼350 °C, resulted in a lower contact resistance than GaAs etched at 25 °C. The high temperature etching augmented the defect diffusion which in turn lowered the near surface defect density. This decrease in residual damage was deemed responsible for improving the electrical performance at 350 °C. The electrical measurements were found to be more sensitive to the density of defects than the vertical extent of disorder beneath the etched surface. Results of this investigation demonstrate that in order to minimize material damage and improve electrical performance, etching with an ECR source should be performed at low rf and microwave powers with a high substrate temperature. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360067
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  • 2
    Electronic Resource
    Electronic Resource
    Temporal relationship between air pollution and hospital admissions for asthmatic children in Hong Kong (2001)
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 31 (2001), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Many epidemiological studies have shown positive association between respiratory health and current levels of outdoor air pollution in Europe and America.Objective The aim of this study was to investigate the association between air pollution and the number of childhood admissions for asthma in Hong Kong.Methods Daily counts of childhood admission for asthma to a large teaching Hospital were obtained from the computerized database for the period 1993–1994. A Poisson regression allowing for seasonal patterns and meteorological conditions was used to assess the associations between the number of Hospital admissions and the three pollutants: nitrogen dioxide, sulphur dioxide and inhalable particles (measured as PM10, particles 〈 10 µm in aerodynamic diameter).Results A total of 1217 children under 15 years of age were admitted for asthma during the study period. The calculated annual hospitalization rates were 283 and 178 per 100 000 for boys and girls, respectively. The mean PM10, NO2 and SO2 levels were 44.1 µg/m3, 43.3 µg/m3, and 12.2 µg/m3, respectively. Daily admission for asthma increased significantly with increasing ambient level of nitrogen dioxide (relative risk (RR) = 1.08 per 10 µg/m3 increase), sulphur dioxide (RR = 1.06) and inhalable particles (RR = 1.03). No association was found between hospital admission and humidity, temperature or atmospheric pressure.Conclusion This is the first daily time series study of childhood admissions for asthma and air pollution in Hong Kong. The results support that current levels of air pollution contribute to the respiratory morbidity in asthmatic children in Hong Kong.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2222.2001.01063.x
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  • 3
    Electronic Resource
    Electronic Resource
    Investigation of reactive-ion-etch-induced damage of InP/InGaAs multiple quantum wells by photoluminescence (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1528-1532 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of CH4/H2 reactive ion etching (RIE) on the optical properties of an InP/InGaAs multiple-quantum-well structure have been investigated by low-temperature photoluminescence (PL). The structure consisted of eight InGaAs quantum wells, lattice matched to InP, with nominal thicknesses of 0.5, 1, 2, 3, 5, 10, 20, and 70 monolayers, respectively, on top of a 200-nm-thick layer of InGaAs for calibration. The design of this structure allowed etch-induced damage depth to be obtained from the PL spectra due to the different confinement energies of the quantum wells. The samples showed no significant decrease of luminescence intensity after RIE. However, the observed shift and broadening of the PL peaks from the quantum wells indicate that intermixing of well and barrier material increased with etch time. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360245
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  • 4
    Electronic Resource
    Electronic Resource
    Si nanostructures fabricated by anodic oxidation with an atomic force microscope and etching with an electron cyclotron resonance source (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1729-1731 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanometer-scale Si structures have been fabricated by anodic oxidation with an atomic force microscope (AFM) and dry etching using an electron cyclotron resonance (ECR) source. The AFM is used to anodically oxidize a thin surface layer on a H-passivated (100) Si surface. This oxide is used as a mask for etching in a Cl2 plasma generated by the ECR source. An etch selectivity (approximately-greater-than)20 was obtained by adding 20% O2 to the Cl2 plasma. The AFM-defined mask withstands a 70 nm deep etch, and linewidths∼10 nm have been obtained with a 30 nm etch depth. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113348
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  • 5
    Electronic Resource
    Electronic Resource
    Nanometer-scale columns in GaAs fabricated by angled chlorine ion-beam-assisted etching (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1726-1728 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Angled chlorine ion-beam-assisted etching has been used in combination with masked ion beam lithography to produce columns in GaAs with widths of less than 10 nm and height-to-width ratios greater than 25. This technique allows the highly controllable fabrication of structures with dimensions smaller than initially defined by the lithography. It can be applied to the fabrication of ultrasmall GaAs/AlGaAs quantum well structures having quantized energy states in two or three dimensions while at the same time being compatible with full-wafer processing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98557
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  • 6
    Electronic Resource
    Electronic Resource
    Photoluminescence and electro-optic properties of small (25–35 nm diameter) quantum boxes (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2766-2768 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The luminescence and electro-optic properties of buried 25–35 nm quantum boxes have been measured. The quantum boxes were defined by a combination of molecular beam epitaxial growth and regrowth, electron beam lithography, and dry etching. The photoluminescence from 35 nm boxes shows a blue shift of ∼15 meV compared to the bulk luminescence and an enhancement, taking into account the fill factor. An enhanced effective linear electro-optic coefficient, rl, is observed for the quantum boxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109254
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  • 7
    Electronic Resource
    Electronic Resource
    Photolithographic micromolding of ceramics using plasma etched polyimide patterns (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3379-3381 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Features as fine as 4 μm with high aspect ratio were produced from ceria-zirconia ceramic using a thick plasma-etched polyimide layer as a micromold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110151
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  • 8
    Electronic Resource
    Electronic Resource
    Relative fluorine concentrations in radio frequency/electron cyclotron resonance hybrid glow discharges (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 818-820 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relative concentration of atomic fluorine was measured in a radio frequency (rf) glow discharge and a modified electron cyclotron resonance microwave/rf hybrid discharge in CF4 using an actinometric technique. The dependence of fluorine concentration on rf and microwave power, pressure, flow, and excitation source are presented. Anomalous behavior with rf power at constant microwave power was observed when using the Ar 750-nm line as the actinometric species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107428
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of electron cyclotron resonance etching on the ambient (100) GaAs surface (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3054-3055 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance has been used to study the electronic behavior of the ambient (100) GaAs surface and its modification by etching in a Cl2/Ar plasma generated by an electron-cyclotron resonance (ECR) source. We observed two pinning positions for ambient (100) GaAs, with n-GaAs pinning near midgap and p-GaAs pinning near the valance band. ECR etching shifts the Fermi level of p-GaAs toward midgap, but has little effect on n-GaAs. The surface modification is most influenced by the rf power. Auger electron spectroscopy indicates that the etching increases As at the GaAs/oxide interface. We suggest that the Ga/As ratio controls the position of the Fermi level. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114275
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  • 10
    Electronic Resource
    Electronic Resource
    Nasopharyngeal intraepithelial lesion: latent Epstein–Barr virus infection with malignant potential (2004)
    Oxford, UK : Blackwell Science Ltd
    Histopathology 45 (2004), S. 0 
    Details
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Aims:  To study the morphology and immunohistochemical expression of nasopharyngeal intraepithelial lesions and to understand their place in nasopharyngeal carcinogenesis.Methods and results:  Nine cases of nasopharyngeal intraepithelial lesion (NPIL) were diagnosed during nasopharyngeal biopsy screening for nasopharyngeal carcinoma (NPC). Two cases were associated with early invasion. All cases demonstrated specific histological features and consistent positivity on in-situ hybridization for Epstein–Barr virus (EBV)-encoded RNA. Pure NPIL lesions showed low-grade morphology while lesions associated with early invasion were high grade. Immunohistochemical studies showed increased expression of bcl-2 and essentially negative findings for BZLF1 and LMP1. High-grade lesions had relatively stronger expression of bcl-2 and p53.Conclusions:  NPIL harbours latent EBV infection and has malignant potential. Multiple steps are involved in its occurrence and progression. Low-grade and high-grade lesions should be managed differently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2559.2004.01935.x
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