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1

Interface Engineering in Heteroepitaxy

100%

Hong S., Chen Y., Ko H., Yao T.

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issue 4-5

541-554

EN

We report the importance of interface engineering in heteroepitaxy with examples of plasma-assisted molecular beam epitaxial ZnO growths on (0001) sapphire substrates and on (0001) GaN/sapphire templates, whose interfaces are engineered to improve and to control properties of ZnO films. The growth of rocksalt structure MgO buffer on Al_2O_3 (0001) is developed for ZnO epitaxy. By employing the MgO buffer layer, the formation of 30^o rotated mixed domains is prohibited and two-dimensional layer-by-layer growth of ZnO on sapphire substrate is achieved. High-resolution X-ray diffraction reveals the superior improvement in a crystal quality of ZnO films with an MgO buffer. Polarity of wurtzite structure ZnO films on Ga-polar GaN/sapphire templates is controlled by changing interface structures. By forming a single crystalline, monoclinic Ga_2O_3 interfacial layer between GaN and ZnO through O-plasma pre-exposure on the Ga-polar GaN surface, O-polar ZnO films are grown. By forming the ZnO/GaN heterointerface without an interfacial layer through the Zn pre-exposure on the Ga-polar GaN surface, Zn-polar ZnO films are grown.

2

Effect of Milling Time Parameter on the Microstructure and the Thermoelectric Properties of n-Type BI2TE2.7SE0.3 Alloys

76%

Sharief P., Madavali B., Koo J. M., Kim H. J., Hong S., Hong S.-J.

Archives of Metallurgy and Materials

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2019

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vol. 64

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issue 2

3

Impedance and Scattering Variance Ratios of Complicated Wave Scattering Systems in the Low Loss Regime

64%

Yeh J., Drikas Z., Gil Gil J., Hong S., Taddese B., Ott E., Antonsen T., Andreadis T., Anlage S.

Acta Physica Polonica A

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2013

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vol. 124

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issue 6

1045-1052

EN

Random matrix theory successfully predicts universal statistical properties of complicated wave scattering systems in the semiclassical limit, while the random coupling model offers a complete statistical model with a simple additive formula in terms of impedance to combine the predictions of random matrix theory and nonuniversal system-specific features. The statistics of measured wave properties generally have nonuniversal features. However, ratios of the variances of elements of the impedance matrix are predicted to be independent of such nonuniversal features and thus should be universal functions of the overall system loss. In contrast with impedance variance ratios, scattering variance ratios depend on nonuniversal features unless the system is in the high loss regime. In this paper, we present numerical tests of the predicted universal impedance variance ratios and show that an insufficient sample size can lead to apparent deviation from the theory, particularly in the low loss regime. Experimental tests are carried out in three two-port microwave cavities with varied loss parameters, including a novel experimental system with a superconducting microwave billiard, to test the variance-ratio predictions in the low loss time-reversal-invariant regime. It is found that the experimental results agree with the theoretical predictions to the extent permitted by the finite sample size.

4

Effect of Trace Elements (Co, Cr) on the Microstructure and Physical Properties of Al-Si-Cu-Mg-Fe Extruded Alloy

64%

Ahn S. S., Sharief P., Lee C. H., Son H. T., Kim Y. H., Kim Y. C., Hong S., Hong S. J.

Archives of Metallurgy and Materials

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2019

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vol. 64

|

issue 3

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Interface Engineering in Heteroepitaxy

Effect of Milling Time Parameter on the Microstructure and the Thermoelectric Properties of n-Type BI2TE2.7SE0.3 Alloys

Impedance and Scattering Variance Ratios of Complicated Wave Scattering Systems in the Low Loss Regime

Effect of Trace Elements (Co, Cr) on the Microstructure and Physical Properties of Al-Si-Cu-Mg-Fe Extruded Alloy