Xiao Tao Zu

Annealing effect on the generation of dual mode acoustic waves in inclined ZnO films.

ZnO films with different inclined angles on steel substrates were sputter-deposited by changing the substrate tilt angle during deposition and then used to fabricate ZnO film ultrasonic transducers. The ultrasonic performance of those devices was characterized using a standard pulse-echo method. A dual mode wave with both longitudinal and shear wave components was detected from the ZnO device at 0° inclined angle. At a columnar inclined angle of 31°, longitudinal wave excitation was suppressed with a nearly pure shear wave detected. Post annealing of the ZnO film improved the crystallinity and decreased the film stress. The dispersion of the received echoes was observed when the grain sizes of ZnO films were increased after annealing. The frequency components of the waveforms were analyzed and identified using a short time Fourier transform. Post-annealing of the ZnO films changed the primary frequency and enhanced the propagation of the relative high-frequency acoustic wave.

The Effect of Oxygen in ∑3(114) CulnSe2 Grain Boundary

Using density functional theory calculation, we show that oxygen (O) exhibits an interesting effect in CuInSe2. The Se atoms with dangling bonds in a Se-rich ∑3 (114) grain boundary (GB) create deep gap states due to strong interaction between Se atoms. However, when such a Se atom is substituted by an O atom, due to their smaller atomic size and stronger electronegativity, the deep gap states are shifted to lower energy regions close or even below the top of the valence band, which is beneficial to CuInSe2 solar cell.

First-Principles Study of the Elastic Properties of Hexagonal Phase ScAx (A=H, He)

First-principles calculations are performed to investigate the Young’s modulus, bulk modulus, shear modulus and Poisson’s ratio of hexagonal phase ScAx (A=H, He), where x=0, 0.0313, 0.125 and 0.25, represent the ratio of interstitial atoms A (A=H, He) to Sc atoms. The influences of hydrogen concentrations and helium concentrations on elastic modulus and Poisson’s ratio of ScAx (A=H, He) have been studied. The results indicate that hydrogen and helium have different effects on the elastic modulus of hexagonal phase scandium. The change mechanism of the Poisson’s ratio with the variation of the x ranging from 0 to 0.25 has also been studied in hexagonal phase ScAx (A=H, He). In addition, the changes in the charge densities of ScAx due to the presence of hydrogen and helium have been calculated.

Droplet Streaming and Nebulization Induced by the Shear Horizontal Surface Acoustic Wave

Droplet streaming and nebulization on a shear horizontal surface acoustic wave device made of 36o Y-cut LiTaO3 have been reported. The streaming pattern inside the droplet is sensitive to the droplet shape, the position to the interdigital transducer, and the aperture size. Droplet nebulization was enhanced with the increased aperture size of the driven IDTs and mainly occurred in horizontal direction along two lateral sides of the droplet, which is perpendicular to the designed SAW propagation direction. The atomization duration increases with the droplet size and decreases with the driven power at a given droplet size. The maximum rate of the atomization is ~0.2 μL/s at an applied power of 6.7 W. This provides a simple and effective method of the integration of both bio-liquid sensing and fluid manipulation on a single substrate for lab-on-chip biosensing platform.