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- 2019
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Song, Yuxin, 1981, et al.
(författare)
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Growth of GaSb1-xBix by molecular beam epitaxy
- 2012
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Ingår i: Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures. - : American Vacuum Society. - 2166-2754 .- 2166-2746. ; 30:2, s. 02B114-
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Tidskriftsartikel (refereegranskat)abstract
- Molecular beam epitaxy for GaSb1-xBix is investigated in this article. The growth window for incorporation of Bi in GaSb was found. Strategies of avoiding formation of Bi droplets and enhancing Bi incorporation were studied. The Bi incorporation was confirmed by SIMS and RBS measurements. The Bi concentration in the samples was found to increase with increasing growth temperature and Bi flux. The position of GaSb1-xBix layer peak in XRD rocking curves is found to be correlated to Bi composition. Surface and structural properties of the samples were also investigated. Samples grown on GaSb and GaAs substrates were compared and no apparent difference for Bi incorporation was found.
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| 4. |
- Song, Yuxin, 1981, et al.
(författare)
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Molecular beam epitaxy growth of InSb1-xBix thin films
- 2013
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 378, s. 323-328
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Tidskriftsartikel (refereegranskat)abstract
- Molecular beam epitaxy growth for InSb1-xBix thin films on (100) GaAs substrates is reported. Successful Bi incorporation for 2% is achieved, and up to 70% of the incorporated Bi atoms are at substitutional sites. The effects of growth parameters on Bi incorporation and surface morphology are studied. Strong In and Ga inter-diffusion induced by Bi incorporation is observed and discussed.
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| 5. |
- Wang, Yuchen, et al.
(författare)
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Field observations of C2 and C3 organosulfates and insights into their formation mechanisms at a suburban site in Hong Kong
- 2023
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Ingår i: SCIENCE OF THE TOTAL ENVIRONMENT. - 0048-9697 .- 1879-1026. ; 904
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Tidskriftsartikel (refereegranskat)abstract
- Organosulfates (OSs) are formed from volatile organic compounds (VOCs) and their oxidation products in the presence of sulfate particles. While OSs represent an important component in secondary organic aerosol, the knowledge of their formation driving force, mechanisms, and environmental impact remain inadequately understood. In this study, we report ambient observations of C2-3 oxygenated VOCs derived OSs (C2-3 OSs) at a suburban location of Hong Kong during autumn 2016. The C2-3 OSs, including glycolaldehyde sulfate (GS), hydroxyacetone sulfate (HAS), glycolic acid sulfate (GAS), and lactic acid sulfate (LAS), were quantified/semiquantified using offline liquid chromatography-mass spectrometry analysis of aerosol filter samples. The average sum concentration of C2-3 OSs was 36 ng/m3. Correlation analysis revealed that sulfate, surface area, and liquid water content were important factors influencing C2-3 OS formation. Online measurement with an iodide High-Resolution Time-of-Flight Chemical-Ionization Mass Spectrometer (HR-ToF-CIMS) coupled with the Filter Inlet for Gases and AEROsols (FIGAERO) was also conducted to monitor C2-3 OSs, and their potential oxygenated VOC precursors in both gas-and particle-phase, and aerosol acidity tracer simultaneously. Our measurements support that glycolaldehyde/glyoxal, hydroxyacetone, glycolic acid/glyoxal, and lactic acid/ methylglyoxal are likely precursors for GS, HAS, GAS, and LAS, respectively. Additionally, we found strong correlation between C2-3 OSs and H3S2O8 , a marker for aerosol acidity, providing field observational evidence for acid-catalyzed formation of small OSs. Based on both online and offline measurements, acid-catalyzed formation mechanisms in particle/aqueous phase are proposed. Specifically, the unique structure of adjacent carbonyl and hydroxyl groups in the C2-3 oxygenated VOC precursors can facilitate the formation of (1) a five member ring intermediate via intramolecular hydrogen bond to react with sulfur trioxide through heterogenous reaction or (2) cyclic sulfate intermediate via particle-phase reaction with sulfuric acid to generate C2-3 OSs. These proposed mechanisms provide an alternative pathway for the liquid-phase production of C2-3 OSs.
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| 6. |
- Guina, M., et al.
(författare)
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Molecular Beam Epitaxy of Dilute Nitride Optoelectronic Devices
- 2018
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Ingår i: Molecular Beam Epitaxy: from Research to Mass Production. - 9780128121368 ; , s. 73-94
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Molecular beam epitaxy of dilute nitride materials has progressed a long way toward claiming its unique place as a technology that enables the development of new types of optoelectronics devices. This chapter starts by reviewing the particularities related to epitaxial incorporation of nitrogen into III–V materials using plasma-assisted molecular beam epitaxy. We then focus on describing the interplay between the growth parameters and nitrogen incorporation processes in dilute nitride arsenides (III-N-As). Emphasis is put on nitrogen-related growth kinetics that are accompanied by various bonding configurations and formation of several types of defects. Then we review the basics of MBE for dilute nitride antimonides (III-N-Sb) and dilute nitride phosphides (III-N-P). Finally, we review the growth optimization and properties of several classes of dilute nitride heterostructures for optoelectronics. These include uncooled long-wavelength laser diodes, ultrafast nonlinear devices, high power lasers enabling yellow-orange emission by frequency doubling, and high-efficiency multijunction solar cells, for which dilute nitride MBE technology is rapidly evolving and provides development opportunities.
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| 7. |
- Jung, Seungyoun, et al.
(författare)
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Alcohol consumption and breast cancer risk by estrogen receptor status : in a pooled analysis of 20 studies.
- 2016
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Ingår i: International Journal of Epidemiology. - : Oxford University Press (OUP). - 0300-5771 .- 1464-3685. ; 45:3, s. 916-928
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Breast cancer aetiology may differ by estrogen receptor (ER) status. Associations of alcohol and folate intakes with risk of breast cancer defined by ER status were examined in pooled analyses of the primary data from 20 cohorts.METHODS: During a maximum of 6-18 years of follow-up of 1 089 273 women, 21 624 ER+ and 5113 ER- breast cancers were identified. Study-specific multivariable relative risks (RRs) were calculated using Cox proportional hazards regression models and then combined using a random-effects model.RESULTS: Alcohol consumption was positively associated with risk of ER+ and ER- breast cancer. The pooled multivariable RRs (95% confidence intervals) comparing ≥ 30 g/d with 0 g/day of alcohol consumption were 1.35 (1.23-1.48) for ER+ and 1.28 (1.10-1.49) for ER- breast cancer (Ptrend ≤ 0.001; Pcommon-effects by ER status: 0.57). Associations were similar for alcohol intake from beer, wine and liquor. The associations with alcohol intake did not vary significantly by total (from foods and supplements) folate intake (Pinteraction ≥ 0.26). Dietary (from foods only) and total folate intakes were not associated with risk of overall, ER+ and ER- breast cancer; pooled multivariable RRs ranged from 0.98 to 1.02 comparing extreme quintiles. Following-up US studies through only the period before mandatory folic acid fortification did not change the results. The alcohol and folate associations did not vary by tumour subtypes defined by progesterone receptor status.CONCLUSIONS: Alcohol consumption was positively associated with risk of both ER+ and ER- breast cancer, even among women with high folate intake. Folate intake was not associated with breast cancer risk.
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| 8. |
- Kini Manjeshwar, Sushanth, 1990, et al.
(författare)
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Integrated microcavity optomechanics with a suspended photonic crystal mirror above a distributed Bragg reflector
- 2023
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 31:19, s. 30212-30226
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Tidskriftsartikel (refereegranskat)abstract
- Increasing the interaction between light and mechanical resonators is an ongoing endeavor in the field of cavity optomechanics. Optical microcavities allow for boosting the interaction strength through their strong spatial confinement of the optical field. In this work, we follow this approach by realizing a sub-wavelength-long, free-space optomechanical microcavity on-chip fabricated from an (Al,Ga)As heterostructure. A suspended GaAs photonic crystal mirror is acting as a highly reflective mechanical resonator, which together with a distributed Bragg (DBR) reflector forms an optomechanical microcavity. We demonstrate precise control over the microcavity resonance by change of the photonic crystal parameters. We find that the microcavity mode can strongly couple to the transmissive modes of the DBR. The interplay between the microcavity mode and a guided resonance of the photonic crystal modifies the cavity response and results in a stronger dynamical backaction on the mechanical resonator compared to conventional optomechanical dynamics.
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| 9. |
- Liao, Chunyang, et al.
(författare)
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Changes in synaptic transmission, calcium current, and neurite growth by perfluorinated compounds are dependent on the chain length and functional group
- 2009
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:6, s. 2099-2104
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Tidskriftsartikel (refereegranskat)abstract
- Scientific and public concerns on perfluorinated compounds (PFCs) are increasingly growing because of their environmental persistency, bioaccumulation, and extensive distribution throughout the world. Little is known about the effects of PFCs on neural function and the underlying mechanisms. Recent evidence suggests that the toxicological effects of PFCs are closely correlated with their carbon chain lengths. In this present work, the actions of PFCs with varying chain length on cultured rat hippocampal neurons and possible action patterns were examined. Increases in the frequencies of spontaneous miniature postsynaptic current (mPSC) were commonly found in cultured neurons when perfused with PFCs. The increase of mPSC frequency was in proportion to the carbon chain length, and the potency of perfluorinated carboxylates was less pronounced than that of perfluorinated sulfonates. A comparable but less perceptible trend was also found for the amplitudes of voltage-dependent calcium current (ICa). No regular change in pattern was observed for the effects of PFCs on activation and inactivation kinetics of ICa. Furthermore, prolonged treatment of PFCs inhibited the neurite growth of neuronsto various degrees. Comparisons between nonfluorinated and perfluorinated analogues demonstrated thatthefluorination in alkyl chain exerts stronger actions on neurons as compared to the surfactant activity. This study shows that PFCs exhibit adverse effects on cultured neurons to various extents, which is dependent on the carbon chain length and functional group attached to the fully fluorinated alkyl chain.
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| 10. |
- Shi, Zhangyong, et al.
(författare)
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Photoluminescence mapping of mid-wave infrared InAs/GaSb type II superlattice: Influence of materials and processes on spatial uniformity
- 2023
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 947
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Tidskriftsartikel (refereegranskat)abstract
- The imaging performance of infrared focal plane array (FPA) is limited by the non-uniformity of the in-plane response of InAs/GaSb type II superlattices (T2SL) consisting of a few hundred or more thin layers. Fundamentally, the non-uniformity results from the materials’ property variation and process fluctuations over an area of a square centimeter. Thus, the influence of materials and processes on the uniformity of internal response is necessary to accurately detect and evaluate to improve the imaging performance of an FPA detector. In this work, spatially resolved photoluminescence (PL) was implemented to detect the microscale mesa pixels, and the effects of materials and processes on spatial uniformity were studied for the first time. Modulated PL-mapping technology based on step-scan Fourier transform infrared spectrometry was used to extract parameters from each test spectrum, such as PL peak energy, linewidth, and integral intensity, which were then analyzed by 2D spatial mapping. Results showed that the variation of T2SL material properties accounted for 29% of the non-uniformity, and the remaining 71% resulted from the process fluctuation. In particular, the etching process had a great influence on the uniformity. The non-uniformity of the integral intensity of the sample after etching increased by 2.44 times compared with that before etching. Thereafter, a layer of SiO2 film was deposited to passivate the surface. The results showed that the non-uniformity returned to the level before etching, which directly proves that the passivation process can improve the response uniformity of the infrared FPA detector.
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