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  • 1
    Electronic Resource
    Electronic Resource
    Optical characterization of bulk ZnSeTe solid solutions (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5148-5152 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical characterization was performed on wafers sliced from crystals of ZnSe, ZnTe, and ZnSe1−xTex(0〈x〈0.4) grown by physical vapor transport. Energy band gaps at room temperature were determined from optical transmission measurements on 11 wafers. A best fit curve to the band gap versus composition x data gives a bowing parameter of 1.45. This number lies between the value of 1.23 determined previously on ZnSeTe bulk crystals and the value of 1.621 reported on ZnSeTe epilayers. Low-temperature photoluminescence (PL) spectra were measured on six samples. The spectra of ZnSe and ZnTe were dominated by near band edge emissions and no deep donor-acceptor pairs were observed. The PL spectrum exhibited a broad emission for each of the ZnSe1−xTex samples, 0.09〈x〈0.39. For x=0.09, this emission energy is about 0.2 eV lower than the band gap energy measured at low temperature. As x increases the energy discrepancy gradually decreases and reduces to almost zero at x=0.4. The single broad PL emission spectra and the spectra measured as a function of temperature were interpreted as being associated with the exciton bound to Te clusters because of the high Te content in these samples. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1315330
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  • 2
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    Optical characterization of bulk ZnSeTe solid solutions (2000)
    American Institute of Physics
    Details
    Publication Date: 2000-11-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics
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  • 3
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    Transient torque method: A fast and nonintrusive technique to simultaneously determine viscosity and electrical conductivity of semiconducting and metallic melts (2004)
    American Institute of Physics
    Details
    Publication Date: 2004-09-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics
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  • 4
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    Vapor Growth and Characterization of ZnSeTe Solid Solutions (2000)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: Six ZnSe(1-x)Te(x) crystals were grown by the physical vapor transport technique. For each of the source material compositions, x = 0.10, 0.20 and 0.30, two crystals were grown - one under the horizontal and the other under the vertical stabilized configurations. The axial and radial compositional uniformity were measured by precision density measurements, wavelength dispersive X-ray spectroscopy (WDS) and optical transmission mappings. The measured radial ZnTe content was quite uniform for all the grown crystals except the horizontally grown crystal for x = 0.30. The WDS results on this crystal indicated a core with uniform ZnTe content, about 0.38, surrounded by a thin region of high ZnTe content with x = 0.8. This feature was confirmed by the SEM back scattering electron images. For the three source compositions the axial compositional variations for the vertically grown crystals were more uniform than that for the horizontally grown crystals. The measured compositions in the crystals grown from source composition of x = 0.10 suggest that the transport mechanism in the system can not be interpreted by a simple one-dimensional diffusion limited model.
    Keywords: Solid-State Physics
    Type: Journal of Crystal Growth (ISSN 0022-0248); Volume 216; 104-112
    Format: text
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  • 5
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    Photoluminescence Studies of ZnSe Starting Materials and Vapor Grown Bulk Crystals (2001)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: Low-temperature photoluminescence (PL) spectra were measured on ZnSe starting materials provided by various vendors and on bulk crystals grown from these starting materials by physical vapor transport (PVT) to study the effects of purification and contamination during PVT process. The impurity levels in one set of starting material/grown crystal were also measured by glow discharge mass spectroscopy (GDMS). The purification effect of pre-growth heat treatments and the PVT process is evidenced from the GDMS results which showed orders of magnitude reduction in the Li and Na concentration and a factor of 3 reduction in the O content after growth. The PL spectra showed that the strong emissions associated with Li (or Na) in one of the starting materials disappeared after growth. The GDMS results also showed increases in the At and Si contents by orders of magnitude after growth. To evaluate the contamination of the crystal during the high temperature growth process, three growth runs were processed using similar growth parameters but different furnace environments. The PL spectra suggest that the At contamination originated from the fused silica ampoule and that the Inconel cartridge might have been the cause of the broad Cu green and Cu red bands observed in one of the grown crystals.
    Keywords: Solid-State Physics
    Type: Journal of Crystal Growth (ISSN 0022-0248); Volume 224; 32-40
    Format: text
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  • 6
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    Transient Torque Method: A Fast and Nonintrusive Technique to Simultaneously Determine Viscosity and Electrical Conductivity of Semiconducting and Metallic Melts (2004)
    In:  Other Sources
    Details
    Publication Date: 2018-06-12
    Description: A transient torque method was developed to rapidly and simultaneously determine the viscosity and electrical conductivity of liquid metals and molten semiconductors. The experimental setup of the transient torque method is similar to that of the oscillation cup method. The melt sample is sealed inside a fused silica ampoule, and the ampoule is suspended by a long quartz fiber to form a torsional oscillation system. A rotating magnetic field is used to induce a rotating flow in the conductive melt, which causes the ampoule to rotate around its vertical axis. A sensitive angular detector is used to measure the deflection angle of the ampoule. Based on the transient behavior of the deflection angle as the rotating magnetic field is applied, the electrical conductivity and viscosity of the melt can be obtained simultaneously by numerically fitting the data to a set of governing equations. The transient torque viscometer was applied successfully to measure the viscosity and electrical conductivity of high purity mercury at 53.4 C. The results were in excellent agreement with published data. The method is nonintrusive; capable of rapid measurement of the viscosity of toxic, high vapor pressure melts at elevated temperatures. In addition, the transient torque viscometer can also be operated as an oscillation cup viscometer to measure just the viscosity of the melt or as a rotating magnetic field method to determine the electrical conductivity of a melt or a solid if desired.
    Keywords: Instrumentation and Photography
    Type: Review of Scientific Instruments (ISSN 0034-6748); Volume 75; No. 9; 2810-2816
    Format: text
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  • 7
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    Crystal Growth of HgZnTe Alloy by Directional Solidification in Low Gravity Environment (2002)
    In:  Other Sources
    Details
    Publication Date: 2018-06-12
    Description: An Hg(0.84)Zn(0.16)Te alloy crystal was back-melted and partially re-solidified during the first United States Microgravity Laboratory mission in the Marshall Space Flight Center's Crystal Growth Furnace. The experiment was inadvertently terminated at about 30% of planned completion. Nonetheless, it was successfully demonstrated that a HgZnTe alloy ingot partially grown and quenched on the ground can be back-melted and re-grown in space under nearly steady-state growth conditions. An identical "ground-truth" experiment was performed following the mission and a comparison between the properties of the crystals is described. The results indicate the importance of residual microgravity acceleration (less than or approx. equal to 0.4 micro-grams) even in the sub-microgravity range for the slow solidification velocities and large density gradients.
    Keywords: Geosciences (General)
    Type: Journal of Crystal Growth (ISSN 0022-0248); Volume 234; 487-497
    Format: text
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  • 8
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    Density, Electrical Conductivity and Viscosity of Hg(0.8)Cd(0.2)Te Melt (2004)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The density, viscosity, and electrical conductivity of Hg(0.8)Cd(0.2)Te melt were measured as a function of temperature. A pycnometric method was used to measure the melt density in the temperature range of 1072 to 1122 K. The viscosity and electrical conductivity were determined using a transient torque method from 1068 to 1132 K. The density result from this study is within 0.3% of the published data. However, the current viscosity result is approximately 30% lower than the existing data. The electrical conductivity of Hg(0.8)Cd(0.2)Te melt as a function of temperature, which is not available in the literature, is also determined. The analysis of the temperature dependent electrical conductivity and the relationship between the kinematic viscosity and density indicated that the structure of the melt appeared to be homogeneous when the temperature was above 1090 K. A structural transition occurred in the Hg(0.8)Cd(0.2)Te melt as the temperature was decreased to below 1090 K
    Keywords: Metals and Metallic Materials
    Type: 14th International Conference on Crystal Growth; Aug 10, 2004 - Aug 13, 2004; Grenoble; France
    Format: text
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  • 9
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    Characterizing Thermal Properties of Melting Te Semiconductor: Thermal Diffusivity Measurements and Simulation (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Tellurium is an element for many II-VI and I-III-VI(sub 2) compounds that are useful materials for fabricating many devises. In the melt growth techniques, the thermal properties of the molten phase are important parameter for controlling growth process to improve semiconducting crystal quality. In this study, thermal diffusivity of molten tellurium has been measured by a laser flash method in the temperature range from 500 C to 900 C. A pulsed laser with 1064 nm wavelength is focused on one side of the measured sample. The thermal diffusivity can be estimated from the temperature transient at the other side of the sample. A numerical simulation based on the thermal transport process has been also performed. By numerically fitting the experimental results, both the thermal conductivity and heat capacity can be derived. A relaxation phenomenon, which shows a slow drift of the measured thermal conductivity toward the equilibrium value after cooling of the sample, was observed for the first time. The error analysis and the comparison of the results to published data measured by other techniques will be discussed in the presentation.
    Keywords: Solid-State Physics
    Type: Fourteenth American Conference on Crystal Growth and Epitaxy; Aug 05, 2002; Seattle, WA; United States
    Format: text
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  • 10
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    Carbon Nanomaterials as Reinforcements for Composites (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Carbon nanomaterials including fellerenes, nanotubes (CNT) and nanofibers have been proposed for many applications. One of applications is to use the carbon nanomaterials as reinforcements for composites, especially for polymer matrices. Carbon nanotubes is a good reinforcement for lightweight composite applications due to its low mass density and high Young's modulus. Two obscures need to overcome for carbon nanotubes as reinforcements in composites, which are large quantity production and functioning the nanotubes. This presentation will discuss the carbon nanotube growth by chemical vapor deposition. In order to reduce the cost of producing carbon nanotubes as well as preventing the sliding problems, carbon nanotubes were also synthesized on carbon fibers. The synthesis process and characterization results of nanotubes and nanotubes/fibers will be discussed in the presentation.
    Keywords: Composite Materials
    Type: Aug 22, 2002; Tallahassee, FL; United States
    Format: text
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