Articles you may be interested inRecombination dynamics of excitons in Mg 0.11 Zn 0.89 O alloy films grown using the high-temperatureannealed self-buffer layer by laser-assisted molecular-beam epitaxy Growth of zinc blende MgS/ZnSe single quantum wells by molecular-beam epitaxy using ZnS as a sulphur source Appl.ZnS and ZnMgS layers have been grown onto GaP substrates by molecular beam epitaxy ͑MBE͒.The key parameters of the growth are a high substrate temperature and a high sulfur ͑S͒ beam pressure. The S beam pressure was typically 1ϫ10 Ϫ2 Pa, which was more than one order of magnitude larger than in conventional MBE of ZnS. Using the high S beam pressure, large ZnS growth rate of 0.3-1.0 m/h could be obtained even at 490°C. The growth rate was limited by the Zn supply. Optimization of the S beam pressure reduces the full width at half maximum ͑FWHM͒ of the ͑400͒ double-crystal x-ray rocking curve ͑DCXRC͒. For a 2.1-m-thick ZnS layer the width can be reduced to 400 arcsec. The low temperature photoluminescence ͑PL͒ spectra show sharp excitonic emissions including the free exciton emission. ZnMgS layers were grown onto ZnS buffer layers. The ZnMgS layers as well show good crystal and optical qualities. The FWHM of DCXRC of the 1.5-m-thick Zn 0.83 Mg 0.17 S layer is 650 arcsec, which is comparable to the FWHM of a ZnS layer of similar thickness. The low temperature PL of the ZnMgS layer is dominated by a strong excitonic emission. The band gap of Zn 1Ϫx Mg x S is estimated from reflection spectra. For x ϭ0.20, the band gap is 3.974 eV.

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We report a photoluminescence (PL) study of ZnS/ZnMgS strained-layer single quantum wells. The main PL peak from ZnS is attributed to light-hole free excitons. Quantum confinement causes it to shift from 3.76 eV to higher energy, 3.84 eV, with decreasing well width. Hydrostatic and shear deformation potentials are determined from energies of light- and heavy-hole exciton emission, to be a=−6.4 eV and b=−1.0 eV, respectively.

A propagation model of cigarette static burn at the cigarette periphery is proposed. Propagation of cigarette static burn is characterized by intermittent burn of the cigarette paper. The burning rate depends on the period of flash burn of the paper and is independent of the burning width. By measuring the local temperature near the front line of the burning propagation, the rate-determining step was identified as the time required to ignite the paper. A mathematical analysis was performed by calculating the heat transfer at the periphery during the paper heating period, and it was revealed that the thermal properties of the cigarette are the dominant factors of cigarette static burn. Modeling results showed good agreement with measured data.