In the present study, the structural, morphological, compositional, nanomechanical, and surface wetting properties of Bi2Se3 thin films prepared using a stoichiometric Bi2Se3 target and a Se-rich Bi2Se5 target are investigated. The Bi2Se3 films were grown on InP(111) substrates by using pulsed laser deposition. X-ray diffraction results revealed that all the as-grown thin films exhibited were highly c-axis-oriented Bi2Se3 phase with slight shift in diffraction angles, presumably due to slight stoichiometry changes. The energy dispersive X-ray spectroscopy analyses indicated that the Se-rich target gives rise to a nearly stoichiometric Bi2Se3 films, while the stoichiometric target only resulted in Se-deficient and Bi-rich films. Atomic force microscopy images showed that the films’ surfaces mainly consist of triangular pyramids with step-and-terrace structures with average roughness, Ra, being ~2.41 nm and ~1.65 nm for films grown with Bi2Se3 and Bi2Se5 targets, respectively. The hardness (Young’s modulus) of the Bi2Se3 thin films grown from the Bi2Se3 and Bi2Se5 targets were 5.4 GPa (110.2 GPa) and 10.3 GPa (186.5 GPa), respectively. The contact angle measurements of water droplets gave the results that the contact angle (surface energy) of the Bi2Se3 films obtained from the Bi2Se3 and Bi2Se5 targets were 80° (21.4 mJ/m2) and 110° (11.9 mJ/m2), respectively.
With advancement of technology, package sizes and products are becoming smaller due to miniaturization. Separate light-emitting diode (LED) chips and control integrated circuits with through silicon via (TSV) structurescan be combined to achieve reduced size. LED chipswithFlip Chip structureare capable of higher optical efficiency and heat dissipation. Analysis of LED chip structure after heat-related destruction of the chip indicated that the chip suffered stress from heating and cooling. The material used for TSV structures is copper, sincethis provides good electrical conductivity and high thermal conductivity. However, the thermal expansion coefficient of copper is higher than for other materials and can result in thermal expansion coefficient mismatch. Hence, the use of this material is likely to cause stress concentration and thus cause damage. In this study, molybdenum and tungsten were tested as replacements for copper in TSV, and the modified TSV was subjected to simulation analysis.The results indicate that replacement of TSV materials can reduce thermal expansion coefficient mismatch and consequent stress fracture and that the performance of different materials can be simulated by Fatigue Analysis and Load.
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