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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
    Distribution mechanism of voids in Si-implanted GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 656-660 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Voids, formed by the condensation of an excess of implantation-induced vacancies, have been recently identified as the defect directly responsible for dopant diffusion and electrical activation anomalies in Si-implanted and annealed GaAs and GaAs/AlGaAs superlattice materials. Depending on the implanted dose, voids can be distributed either throughout the implanted region or in two bands. We have examined the origin of this void distribution difference. In the as-implanted sample associated with the latter case, a buried continuous band of amorphous GaAs has formed. GaAs formed by the recrystallization of amorphous GaAs does not contain excess vacancies and therefore cannot form voids. However, on either side of the amorphous layer, the excess vacancies can condense to form the observed banded distribution of voids. In the as-implanted sample associated with the former case, a continuous amorphous GaAs layer did not form, and therefore, upon annealing, voids are seen throughout the implanted region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349669
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  • 3
    Electronic Resource
    Electronic Resource
    Erratum: "Gettering of donor impurities by V in GaAs and the growth of semi-insulating crystals'' [J. Appl. Phys. 66, 3309 (1989)] (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 1621-1621 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346112
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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    An immunomodulating protein, Ling Zhi-8 (LZ-8) prevents insulitis in non-obese diabetic mice (1990)
    Springer
    Diabetologia 33 (1990), S. 713-718 
    Details
    ISSN: 1432-0428
    Keywords: LZ-8 ; immunomodulator ; NOD mouse ; Type 1 (insulin-dependent) diabetes ; insulitis ; autoimmunity ; T cell subset
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ling Zhi-8 (LZ-8), a novel and recently discovered immunomodulatory protein having in vivo immunosuppressive activity, was tested for in vivo effect against Type 1 (insulin-dependent) diabetes mellitus in the non-obese diabetic mouse, the disease having immunologically mediated aetiology in this animal. LZ-8 had mitogenic activity in vitro towards spleen cells of the non-obese diabetic mice as previously shown towards those of DBA/2 mice. Intraperitoneal administration of LZ-8 twice weekly into the mice (10.3–12.6 mg/kg body weight) from 4 weeks of age prevented insulitis and an almost normal number of insulin producing cells were observed. Extreme insulitis and reduction of the number of insulin producing cells were observed in the pancreata of the untreated non-obese diabetic mouse. No cumulative incidence of diabetes mellitus was observed in the LZ-8 treated group, while cumulative incidences of 70% and 60% were observed in an untreated group followed up to 42 weeks of age when the incidence of diabetes was defined as a plasma glucose level of greater than 11 mmol/l and as a urine glucose level of greater than 2 +, respectively. T cell subset population analysis was performed to further investigate the action of LZ-8 on the non-obese diabetic mouse which revealed that LZ-8 treatment increased in L3T4+/Lyt-2+ ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00400340
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  • 7
    Electronic Resource
    Electronic Resource
    An adaptive mesh refinement technique for the analysis of shear bands in plane strain compression of a thermoviscoplastic solid (1992)
    Springer
    Computational mechanics 10 (1992), S. 369-379 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have developed an adaptive mesh refinement technique that generates elements such that the integral of the second invariant of the deviatoric strain-rate tensor over an element is nearly the same for all elements in the mesh. It is shown that the finite element meshes so generated are effective in resolving shear bands, which are narrow regions of intense plastic deformation that form in high strain-rate deformation of thermally softening viscoplastic materials. Here we assume that the body is deformed in plane strain compression at a nominal strain-rate of 5000 sec-1, and model a material defect by introducing a temperature perturbation at the center of the block.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00363993
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  • 8
    Electronic Resource
    Electronic Resource
    The epidemiology and surveillance of blood lead in Taiwan (R.O.C.): A report on the PRESS-BLL project (1997)
    Springer
    International archives of occupational and environmental health 69 (1997), S. 386-391 
    Details
    ISSN: 1432-1246
    Keywords: Key words Blood lead level (BLL) ; Surveillance ; Occupational health ; Field survey ; PRESS-BLLs project
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  To monitor the lead hazards in industries and to investigate the prevalence of elevated blood lead levels (BLLs) in lead-exposed workers, a lead surveillance system (PRESS-BLLs) has been established and operated in Taiwan, Republic of China, since July 1993. A cohort of lead-exposed workers who received a periodic annual health examination at 55 accredited hospital laboratories was constructed. A total of 9807 separate BLL measurements were reported to the system in 1994. The mean BLL was 15.8 μg/dl in male workers and 11.6 μg/dl in female workers. The mean BLL of lead-exposed workers was significantly (P〈0.05, z-test) higher than that of the general Taiwanese population (8.6 μg/dl for males and 6.7 μg/dl for females). In addition, the BLLs of 983 (10.0%) workers exceeded the regulatory action level (40 μg/dl for males; 30 μg/dl for females). The workplaces and homes of 57% of the workers with elevated BLLs were thoroughly investigated to determine the sources of lead contamination. These actions identified the causes of elevated BLLs and set up strategies to reduce workers’ lead exposure. The establishment of this occupational lead surveillance system represents a method for monitoring of lead hazards from occupational and environmental settings to prevent lead poisoning. The information acquired from the system can help in the setting up of a priority of prevention and the development of control measures. It is also useful for further monitoring of changes in the BLLs of the lead-exposed-worker cohort. The Health Department of Taiwan can use this information to evaluate the effectiveness of current industrial hygiene practice. Subjects with elevated BLLs have been medically treated and placed on long-term follow-up for sequelae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004200050165
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  • 9
    Electronic Resource
    Electronic Resource
    Pump-energy-dependent photo-ionization and collisional ionization in two-photon-resonant- and three-photon-ionization processes (1998)
    Springer
    Applied physics 66 (1998), S. 617-620 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 32.80.Rm; 34.50.Fa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003400050446
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  • 10
    Electronic Resource
    Electronic Resource
    Risk factors for high blood lead levels among the general populationin Taiwan (1998)
    Springer
    European journal of epidemiology 14 (1998), S. 775-781 
    Details
    ISSN: 1573-7284
    Keywords: High blood lead ; Risk factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: Environmental and occupational lead pollution is a common problem in both developing and industrialized countries. The purpose of this study is to evaluate the risk factors for high blood lead levels among the general population in Taiwan. Methods: After multi-stage sampling, we randomly selected 2803 subjects (1471 males and 1332 females) for this study. Univariate and multivariate logistic regression analyses were conducted to evaluate the risk of high blood lead. To control for differences in age and gender, all analyses were with age-adjusted and gender-stratified. Results: Among males, the mean age is 46 years (15 to 85 years), mean and median blood lead levels is 7.3 and 6.3μg/dl, respectively. Among females, the mean age is 43 years (15 to 84 years), mean and median blood lead level is 5.7 and 4.8μg/dl, respectively. Among males, the history of herbal drug use, drinking water from well or spring sources, and occupational lead exposure are significantly different between relatively high and normal blood lead level subjects. The history of occupational lead exposure, history of herbal drug use, and well or spring sources of drinking water are the major risk factors for high blood lead with odds ratio of 4.62 (95% CI: 2.82–7.55), 3.09 (95% CI: 1.60–5.97), 2.06 (95% CI: 1.13–3.76), and 2.37 (95% CI: 1.39–4.04), respectively. Among females, these characteristics remain important except the sources of drinking water. The history of herbal drug use and occupational lead exposure become the major risk factors for high blood lead with odds ratio of 2.94 (95% CI: 1.26–6.88) and 7.72 (95% CI: 3.51–16.99), respectively. In multivariate logistic regression analyses, we find that the risk factors for high blood lead in both genders include a history of herbal drug use and occupational lead exposure. Among males, the drinking water sources and factories in the neighboring areas are also significant factors for high blood lead. Conclusions: For the goal of reducing prevalence of high blood lead by the year 2000, the improvement and monitoring of the working environment, the careful attention to herbal drug use and the lead-free drinking water sources should be executed as thoroughly as possible to reduce the probability of lead pollution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007544205378
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