In order to begin to evaluate and model the suitability of high temperature ceramic composites, such as AlN:Mo, as susceptor materials for power beaming applications, the electromagnetic, thermal, and mechanical properties of the material must be known at elevated temperatures. Work reported here focuses on the development of thermal property datasets for AlN:Mo composites ranging from 0.25% to 4.0% Mo by volume. To calculate thermal conductivity of the AlN:Mo composite series, specific heat capacity, thermal diffusivity, and density data were acquired. The calculated specific heat capacity, Cp, of the set of AlN:Mo composites was, on average, found to be approximately 803 J/kgK at 100 °C and to increase to approximately 1133 J/kgK at 1000 °C, with all values to be within +/- 32 J/kgK of the average at a given temperature. These calculated specific heat capacity values matched values derived from DSC measurements to within the expected error of the measurements. Measured thermal diffusivity, α, of the set of AlN:Mo composites was, on average, found to be approximately 3.93 x 10-1 cm2/s at 100 °C and to increase to approximately 9.80 x 10-2 cm2/s at 1000 °C, with all values within +/- 1.84 x 10-2 cm2/s of the average at a given temperature. Thermal conductivity, k, for the set of AlN:Mo composites was found to be approximately 108 W/mK at 100 °C and to decrease to approximately 38 W/mK at 1000 °C, with all values within +/- 5.3 W/mK of the average at a given temperature. Data trends show that increasing Mo content correlates to lower values of of Cp, α, and k at a given temperature.

Electrohydrodynamic (EHD) instabilities can be induced in polymers by placing a polymer film above its Tg in a strong electric field between two capacitor plates or electrodes. The polymer experiences an electrostatic stress at the interface between the polymer and air due to a mismatch in their dielectric constants. This stress, along with thermal fluctuations, induces small magnitude capillary waves in the polymer film, and the minima and maxima of those waves experience slightly different electric field strengths. In a sufficiently strong electric field, the capillary wave maxima, where the distances between the polymer film and the top electrode(s) are the smallest, are eventually drawn up to the top electrode. The wavelength of the instabilities in the film and the ability of the polymer to be drawn upward is a dependent on the competition between surface tension forces and the electrostatic stress imparted on the polymer. While EHD instabilities are typically used to pattern polymer surfaces on a nanometer-scale, instabilities have been induced in polymer films with air gaps up to 500 μm. Upper electrodes with non-planar structures have also been used to induce instabilities in polymer films, resulting in patterned polymer surfaces without contact. Size, shape, arrangement, and placement of the upper electrode relative to the polymer film and lower electrode, as well as the processing conditions such as temperature and applied voltage, can all be modified to produce a desired array of structures with tailored performance characteristics. Patterned polymer surfaces can provide high-index contrast over a periodic matrix with 3-dimensional element shapes. The dielectric contrast and array pitch and height can be tuned to control specular reflection and achieve specific scattering characteristics. Surfaces with tailored scattering characteristics in the aforementioned ranges could be useful in producing frequency-selective windows for glare reduction, anti-reflective solar cells with enhanced efficiency, surface waveguides and whispering gallery-mode resonator arrays for integrated photonics and sensors, and surfaces with controlled emissivity for directed heat dissipation.

We have recently developed a novel semiconductor, (ZnO)x(InN)1-x (abbreviated to ZION). In this study, we have succeeded in direct epitaxial growth of ZION films on 19–21%-lattice-mismatched c-plane sapphire by radio-frequency (RF) magnetron sputtering. X-ray diffraction analysis showed that there is no epitaxial relationship between ZION films fabricated at room-temperature (RT) and the sapphire substrates, while the films fabricated at 450oC grow epitaxially on the sapphire substrates. From the analysis of time evolution of the surface morphology, the process for the epitaxial growth of ZION on sapphire is found to consist of three stages. They are (i) initial nucleation of ZION crystallites with crystal axis aligned to the sapphire substrate, (ii) island growth from the initially formed nuclei and subsequent nucleation (secondary nucleation) of ZION crystallites, and (iii) lateral growth of ZION islands originated from initially formed nuclei. On the other hand, non-epitaxial ZION films fabricated at RT just grow in 3D mode. From these results, we conclude that the substrate temperature is the key to control of nucleation and subsequent epitaxial growth of ZION films on the lattice-mismatched substrate.

Effects of nitrogen impurity on ZnO crystal growth on Si substrates have been investigated. The quantitative analysis on the surface morphology deriving height-height correlation function indicates that adsorbed nitrogen atoms suppress the secondary nucleation and enhance adatom migration. The resultant films have smooth surface as well as large grain size up to 24 nm even for small thickness of 10 nm. ZnO films fabricated by using such films as buffer layers possess high crystal quality, where the full width at half maximum of (002) rocking curve is 0.68°, one-fourth of that for films fabricated without nitrogen.

In this paper, the effect of TiN metal gate deposition conditions on the crystal orientation and size of TiN grains has been investigated. We have focused on process conditions that reduce the grain size or provide a unique orientation, which might impact CMOS threshold voltage variability. We have shown that the grain size can be significantly modulated by the RF power and pressure, with grain size as low as 5.2 nm. Further it has been shown that for a few optimized conditions, a unique grain orientation can be obtained. Then, the impact of these process conditions on TiN gate mechanical stress and electrical properties has been investigated. Mechanical stress and sheet resistance are modulated by pressure and RF power and have been correlated to the deposition rate and TiN grain size respectively. The effect of TiN process conditions on MOS capacitor effective workfunction (WFeff) has been investigated, and the trend is opposite to the expected modulation of the intrinsic TiN metal gate workfunction with grain orientation. On the contrary, WFeff variation is well correlated to the Ti/N ratio, suggesting an effect related to dipole at the SiO2/high-k interface.

Photochromic (PC) ZnO nanoparticles are synthesized for the first time by using a VHF plasma enhanced CVD apparatus. The prepared ZnO film changes from transparent to PC state under UV irradiation; on being subjected to heat treatment, it changes back to transparent state. There is a threshold temperature for attaining the PC phase. The Debye-Waller factor of Zn atoms is specifically large for the PC ZnO. The ZnO nanoparticles contain carbon as impurity. The effects of C-O bonds on the ZnO crystal structure and density of states (DOS) are simulated based on density-functional theory. The results reveal that the crystal structure is slightly distorted and a sufficient DOS for PC light absorption is formed in the band gap.

AlN etching with chloride plasmas is studied. The experimental results show that the etching of AlN under a low pressure Cl2/Ar plasma mixture in moderate DC bias is not possible. The addition of BCl3 gas to Cl2/Ar mixture allows the etching of AlN materials. However the obtained properties of etched AlN is still not in conformity with the technological specification especially for the condition which the etched AlN must be kept only along the sidewall of the InP laser cavity and be removed elsewhere (selective etching). To know more about the effect of the BCl3 addition to the Cl2/Ar plasma mixture, global model of BCl3/Cl2/Ar is developed to quantify the neutral and ion densities as well as the electron density and temperature. The simulation results show that the electron density and low pressure linearly varies with the RF power. The negative ion density decreases with the percentage of BCl3 leading to the diminution of the electronegativity which is represented by negative ion to electron density ratio. The simulation shows that the positive ion to atomic chlorine flux ratio increases with the %BCl3. Such parameters could play an important role in the ion neutral synergy during the etching process.

This work describes exploration of mitigating the parasitic amorphous alumina (Al2O3) shell of aluminum nanoparticles (n-Al) and modifying the surface using different plasmas, leading to n-Al with thinner shell and different coatings including carbons and oxidizing salt called aluminum iodate hexahydrate (AIH), respectively. The approach exploits a prototype atmospheric non-thermal plasma reactor with dielectric barrier discharge (DBD) configuration for nanoparticle surface modifications using n-Al of 80 nm average diameter as an example. Preliminary results indicate that the amorphous Al2O3 shell surrounding the active aluminum core can be mitigated with inert plasmas by as much as 40% using either helium (He) or argon (Ar). The particle surface becomes carbon-rich with carbon monoxide (CO) / He plasmas. By immersing the plasma-treated n-Al in an iodic acid (HIO3) solution, AIH crystals can be formed on the n-Al surface. Transmission electron microscopy (TEM) is used as a major tool to study the details of the modified surface morphologies, diffraction patterns, and chemical composition of the modified n-Al. The results demonstrate effective surface passivation of n-Al via atmospheric plasma techniques.