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Electrical connectors can get static charges during handling and discharge on a printed circuit board when assembled. The rise time and shape of the discharge current waveform is studied with simulation and measurement methods. Results show that the ESD current rise time can be less than 10 ps. • The rise time of an ESD discharge current can be below 10 ps close to the discharge point. • CDM testers or transmission line pulse tools are not designed to qualify ICs with below 50 ps rise time pulses. • A few centimeter long PCB traces do not give full safety against high frequency ESD current pulses. • FEM simulation methods can be used accurately to predict ESD events with tens of GHz bandwidth. • A test method to test rise time sensitivity of high-speed interfaces should be created. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO 2) thin films were deposited on silicon (100), quartz, and r-cut sapphire substrates by DC magnetron sputtering at 650 °C. The thin films were characterized by Raman spectroscopy and imaging, scanning electron microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDS), and Transmission Electron Microscopy (TEM). The optical transmittance and hence the insulator-to-metal transition (IMT) and metal-to-insulator transition (MIT) were characterized as a function of temperature. The effects of substrate material on VO 2 thin film's growth, microstructure, stoichiometry and optical properties were investigated. The results show that the as-deposited VO 2 thin films on Si, quartz, and sapphire all show a near-zero IR transmission in switched metallic state; especially VO 2 thin film grown on sapphire shows superior IMT characteristics compared with previously published works on thin VO 2 films, and very close to its bulk single crystal form, which is probably due to the significantly reduced imperfections in the film and the interface, and especially the highly preferred growth with similar paralleled grain orientation of VO 2 on sapphire arising from both the high deposition temperature and epitaxial growth. The spectral transmittance of the films on quartz and sapphire substrates was analyzed to extract the optical constants n and k as a function of wavelength. No significant difference between optical properties could be observed for films deposited on quartz and sapphire substrates indicating that the differences in microstructure of these films play a minor role in their optical properties. n and k spectra are, in general, in agreement with previously reported works. The absorption coefficient versus photon energy characteristics indicate that VO 2 in the insulating phase possesses a direct bandgap at 2.6 eV and an indirect bandgap of 0.52 eV. Raman imaging was used to map the phase mixture of various regions of the film at micron scale (1.2 μm × 1.2 μm) during heating and cooling scans through the IMT and MIT. The dependence of the integrated Raman intensities at 220 cm−1 and 600 cm−1 on the temperature shows an excellent correlation with the optical transmittance through the IMT and MIT, both during heating and cooling scans. It is shown that the transformation occurs by the growth of one phase at the expense of the other and, in the IMT/MIT region, both phases coexist. Image 1 • Effects of substrate material (quartz, silicon and sapphire) on the microstructure and optical properties of sputtered VO2 films are investigated. • High quality, epitaxial VO2 film growth on sapphire is demonstrated by RF magnetron sputtering with a hysteresis matching the single crystal. • The VO2/sapphire interface has been studied by HRTEM and EDS. • Optical constants n, k and two bandgaps have been determined in near-epitaxial film. • Phase mapping by Raman imaging demonstrates non-uniform structural transformation though the formation and growth of domains during insulator-metal and metal-insulator transition. [ABSTRACT FROM AUTHOR]

VO 2 microrods (MRs) have been successfully synthesized by the reduction of V 2 O 5 thin films. The effects of reduction temperature and thickness of the precursor V 2 O 5 thin films on the stochiometry and morphology of the resulting VO 2 MRs have been studied in this work. Results show that size of the VO 2 MRs increases with increasing precursor thickness due to the enlargement of the droplets during the melting of V 2 O 5 thin films. Further, the growth of VO 2 MRs from V 2 O 5 droplets on a sapphire substrate form a unique angle between each other, which is probably due to epitaxial growth. Reduction temperatures between 600 °C and 650 °C are preferred for the growth of VO 2 MRs, while temperatures lower or higher than this range produce V 2 O 5 nanostructures or VO 2 nanoparticles, respectively. HRTEM shows that during VO 2 MR's growth, the (110) plane remains parallel to the Si substrate, and a 10 nm amorphous interface was formed between the VO 2 MR and the Si substrate. Optical properties of the MRs were examined by carrying out light scattering experiments as a function of temperature to identify the temperature range of insulator-to-metal (IM) and metal-to-insulator (MI) transition characteristics. The optical scattering experiments show the large influence of microrod (MR) size and distribution on the characteristics of MI and IM transitions. The transition behavior can range from polycrystalline film type transition to new unique features. Image 1 • The size of the VO 2 microrods has been successfully controlled by the precursor V 2 O 5 film thickness. • Temperature range for producing VO 2 microrods was found to be between 600 °C and 650 °C. • Microrods growth is aligned along two directions on the sapphire crystal surface. • Optical properties have been studied by light scattering through metal-insulator transition (MIT). • The MIT characteristics depend on the microrod size and distribution, and exhibits memory-like behavior during cooling. [ABSTRACT FROM AUTHOR]