Demiao Wang

Flexible surface acoustic wave resonators built on disposable plastic film for electronics and lab-on-a-chip applications

Flexible electronics are a very promising technology for various applications. Several types of flexible devices have been developed, but there has been limited research on flexible electromechanical systems (MEMS). Surface acoustic wave (SAW) devices are not only an essential electronic device, but also are the building blocks for sensors and MEMS. Here we report a method of making flexible SAW devices using ZnO nanocrystals deposited on a cheap and bendable plastic film. The flexible SAW devices exhibit two wave modes - the Rayleigh and Lamb waves with resonant frequencies of 198.1 MHz and 447.0 MHz respectively, and signal amplitudes of 18 dB. The flexible devices have a high temperature coefficient of frequency, and are thus useful as sensitive temperature sensors. Moreover, strong acoustic streaming with a velocity of 3.4 cm/s and particle concentration using the SAW have been achieved, demonstrating the great potential for applications in electronics and MEMS.

Crystalline structure effect on the performance of flexible ZnO/polyimide surface acoustic wave devices

This paper reports the fabrication of flexible surface acoustic wave (SAW) devices on ZnO/polyimide substrates and investigation of the effects of the deposition conditions, crystal quality, and film thickness of the ZnO films on the performance of the SAW devices. The deposition pressure has a significant effect on the crystal quality of the ZnO film, and which in turn affects the transmission of the SAW devices strongly. The device performance improves greatly and is mainly attributed to the better crystal quality of the film deposited at high pressure. The performance of the SAW devices also improves significantly with increase in ZnO film thickness, owing to the reduced defects and improved piezoelectric effect for the films with large grain sizes and better crystallinity as the film thickness increases. Flexible SAW devices with a resonant frequency of 153 MHz, a phase velocity of 1836 m/s, and a coupling coefficient of 0.79% were obtained on the ZnO film of 4 μm thickness, demonstrated its great pot...

Design of Balanced RF Filter for Wireless Applications Using FBAR Technology

We present a balanced RF filter based on thin film bulk acoustic resonator (FBAR) technology for wireless applications, and demonstrate its usage in the wide-band code division multiple access (WCDMA) front-end as post-LNA filter. The filter, which consists of two lattice sections and one symmetric ladder section, provides deep rejection at stop-band, particularly at transmitter band (1920-1980 MHz), steep roll-off at pass-band edges, and excellent common mode rejection ratio (CMRR). The typical broadband rejection is better than 60 dB. The small size, low in-band insertion loss, sharp roll-off, high stop-band rejection, good temperature stability, and compatibility with semiconductor processing make this FBAR filter an ideal choice for GHz wireless applications

Flexible surface acoustic wave device with AlN film on polymer substrate

Surface acoustic wave device with c-axis-oriented aluminum nitride (AlN) piezoelectric thin films on polymer substrates can be potentially used for development of flexible sensors, flexible microfluidic applications, microsystems, and lab-on-chip systems. In this work, the AlN films have been successfully deposited on polymer substrates using the DC reactive magnetron-sputtering method at room temperature, and the XRD, SEM, and AFM methods reveal that low deposition pressure is beneficial to the highly c-axis-oriented AlN film on polymer substrates. Studies toward the development of AlN thin film-based flexible surface acoustic wave devices on the polymer substrates are initiated and the experimental and simulated results demonstrate the devices showing the acoustic wave velocity of 9000-10000 m/s, which indicate the AlN lamb wave.

Effect of film thickness on properties of Al-doped ZnO film as transparent conducting electrodes in OLEDs

Al-doped ZnO (AZO) thin film is a promising alternative to an ITO electrode in organic light-emitting diodes applications due to its low price, non-toxicity and other promising properties. In this paper, AZO thin films of different thicknesses were deposited on glass substrates as transparent conducting films by sputtering. The effect of film thickness on the structural, electrical and optical properties of AZO films were investigated. Results show that with the increase of film thickness, the electrical conductivity increase but the optical transmittance decrease. The optimum properties were obtained in 874 nm film, which exhibited an excellent figure of merit (27.8 × 10-3Ω-1) with transmittance of 84.4% and resistance of 5.72 × 10-4Ωcm.

Influence of annealing temperature on properties of RF sputtered In x S y buffer layers in Cu(In,Ga)Se 2 solar cells

Sputtered InxSy layers were deposited on glass at post-annealing temperature ranging from 623 to 723K. Investigation of the properties indicated decreased optical band-gap and changes in microstructure with increasing annealing temperature.