Zhuanghao Zheng

The high performance of a thin film thermoelectric generator with heat flow running parallel to film surface

In conventional thin film thermoelectric generators, heat flow running vertical to film surface is used. The hot side and the cold side are just separated by the thickness of the films and to maintain the temperature difference between both sides remains a key challenge. Here, we demonstrate the properties of our designed thin film thermoelectric generators with heat flow running parallel to film surface, where a larger temperature difference between both sides is maintained. The maximum output power of our generator can reach 19.13 μW at the temperature difference of 85 K.

A new type of glucose biosensor based on surface acoustic wave resonator using Mn-doped ZnO multilayer structure.

This work reports a high-performance Mn-doped ZnO multilayer structure Love mode surface acoustic wave (SAW) biosensor for the detection of blood sugar. The biosensor was functionalized via immobilizing glucose oxidase onto a pH-sensitive polymer which was attached on Mn-doped ZnO biosensor. The fabricated SAW glucose biosensor is highly sensitive, accurate and fast with good anti-interference. The sensitivity of the SAW glucose biosensor is 7.184 MHz/mM and the accuracy is 6.96 × 10(-3)mM, which is sensitive and accurate enough for glucose monitoring. A good degree of reversibility and stability of the glucose sensor is also demonstrated, which keeps a constant differential frequency shift up to 32 days. Concerning the time response to human serum, the glucose sensor shows a value of 4.6 ± 0.4 min when increasing glucose concentrations and 7.1 ± 0.6 min when decreasing, which is less than 10 min and reach the fast response requirement for medical applications. The Mn-doped ZnO Love mode SAW biosensor can be fully integrated with CMOS Si chips and developed as a portable, passive and wireless real time detection system for blood sugar monitoring in human serum.

Low-cost flexible thin film thermoelectric generator on zinc based thermoelectric materials

The high cost and complex production technique restrict the use of the conventional thermoelectric generators. In this work, we demonstrate a promising flexible thin film thermoelectric generator using the N-type Al-doped ZnO and P-type Zn-Sb based thin film. By using the cost-effective zinc based thermoelectric materials and flexible substrate, we greatly reduce the cost production of thin film thermoelectric generator. The maximum output power of our device with 10 couples is 246.3 μW when the temperature difference is 180 K. The maximum output power of the flexible thin film thermoelectric generator produced per couple and per unit temperature difference was 0.14 μW per K-couple, which is about several times that of other thin film reported. The thin film thermoelectric generator with low cost and excellent output power was fabricated on flexible substrate, which is can be made into various shapes for micro- and nano-energy application.

High-performance perovskite CH3NH3PbI3 thin films for solar cells prepared by single-source physical vapour deposition

In this work, an alternative route to fabricating high-quality CH3NH3PbI3 thin films is proposed. Single-source physical vapour deposition (SSPVD) without a post-heat-treating process was used to prepare CH3NH3PbI3 thin films at room temperature. This new process enabled complete surface coverage and moisture stability in a non-vacuum solution. Moreover, the challenges of simultaneously controlling evaporation processes of the organic and inorganic sources via dual-source vapour evaporation and the heating process required to obtain high crystallization were avoided. Excellent composition with stoichiometry transferred from the powder material, a high level of tetragonal phase-purity, full surface coverage, well-defined grain structure, high crystallization and reproducibility were obtained. A PCE of approximately 10.90% was obtained with a device based on SSPVD CH3NH3PbI3. These initial results suggest that SSPVD is a promising method to significantly optimize perovskite CH3NH3PbI3 solar cell efficiency.

The n-type conduction of indium-doped Cu2O thin films fabricated by direct current magnetron co-sputtering

Indium-doped Cu2O thin films were fabricated on K9 glass substrates by direct current magnetron co-sputtering in an atmosphere of Ar and O2. Metallic copper and indium disks were used as the targets. X-ray diffraction showed that the diffraction peaks could only be indexed to simple cubic Cu2O, with no other phases detected. Indium atoms exist as In3+ in Cu2O. Ultraviolet-visible spectroscopy showed that the transmittance of the samples was relatively high and that indium doping increased the optical band gaps. The Hall effect measurement showed that the samples were n-type semiconductors at room temperature. The Seebeck effect test showed that the films were n-type semiconductors near or over room temperature (<400 K), changing to p-type at relatively high temperatures. The conduction by the samples in the temperature range of the n-type was due to thermal band conduction and the donor energy level was estimated to be 620.2–713.8 meV below the conduction band. The theoretical calculation showed that indi...

Influence of plasma treatment on laser-induced damage characters of HfO 2 thin films at 355nm

HfO(2) thin films were deposited by e-beam evaporation, and were post-treated with plasma under different flow rate ratios of argon to oxygen. By measuring the surface defect density, weak absorption, laser-induced damage threshold (LIDT) and damage morphology, the influence of the flow rate ratio of argon to oxygen on the laser-induced damage characters of HfO(2) thin films were analyzed. The experimental results show that plasma treatment is effective in reducing the surface defect density of thin films. Compared with the as-grown sample, the absorption reduction is obvious after plasma treatment when argon and oxygen flow rate ratio is 5:25, but the absorption increases gradually with the continued increase of argon and oxygen flow rate ratio. LIDT measurements in 1-on-1 mode demonstrate that plasma treatment is not effective in improving LIDT of the samples at 355 nm. Damage morphologies reveal that the LIDT is dominated by nanoscale absorbing defects in subsurface layers, which agrees well with our numerical simulation result based on a spherical absorber model.

Cost-effective and high frequency surface acoustic wave filters on ZnO:Fe/Si for low-loss and wideband application

ZnO:Fe films with various piezoelectric coefficient d33 were employed to fabricate high frequency surface acoustic wave (SAW) filters on Si by conventional photolithography technology. Comparing with the SAW filters on undoped ZnO films, the electromechanical coupling factor and bandwidth, respectively, increases 75.7% and 14.8%, while the insertion loss decreases 20.3% when using Zn0.988Fe0.012O films with a d33 of ∼127 pC/N. Through annealing demonstration, d33 is considered as the intrinsic factor determining the SAW properties of filters, and the properties are improved by O2 annealing. ZnO:Fe films with enhanced d33 is promising for high frequency, low-loss, and wideband SAW applications.

Thermoelectric Properties of Cobalt Antimony Thin Films Deposited on Flexible Substrates by Radio Frequency Magnetron Sputtering

Cobalt antimony thin films were deposited on flexible substrates at room temperature by radio frequency magnetron sputtering with different sputtering power. The atomic ratio of Co to Sb in the cobalt antimony thin film was closest to 1:3 when the sputtering power was 55 W. The thermoelectric properties of the thin films deposited at room temperature were inconspicuous due to their amorphous microstructure which was characterized by x-ray diffraction. To enhance the thermoelectric properties of the thin films, cobalt antimony thin film deposited by sputtering power of 55 W was annealed at various temperatures ranging from 443 K to 593 K. It was found that all the thin films had n-type conductivity and the CoSb3 thin films annealed at 493–593 K were polycrystalline with (310) preferential orientation. The Seebeck coefficient of CoSb3 thin films annealed at 543 K increased with the raising of the measuring temperature (323–473 K), and the maximum Seebeck coefficient was −88 μV/K, which is the highest value for CoSb3 thin films deposited on flexible substrate.

Optimization of thermoelectric properties of n-type Ti, Pb co-doped SnSe

n-Type polycrystalline SnSe with Ti, Pb co-doping was synthesized by combining mechanical alloying (MA) with spark plasma sintering (SPS). It is revealed that Ti is an effective cationic dopant to convert SnSe from a p-type to an n-type semiconductor, and the thermoelectric performance of the Ti-doped SnSe is also improved in comparison with the pristine sample due to an enhanced power factor. Furthermore, after further Pb doping, an obviously improved electrical conductivity together with a moderate Seebeck coefficient can be achieved, which results in an improvement of the power factor with a maximum value of 300 μW m−1 K−2 at 773 K. Meanwhile, the lattice thermal conductivity is significantly reduced because of the enhanced phonon scattering owing to the mass and strain fluctuations. Therefore, a final ZT value of 0.4 was obtained for composition of Sn0.74Pb0.20Ti0.06Se at 773 K, which is a conservative value for n-type SnSe with cationic dopant prepared by the simple preparation process of MA and SPS.

Love-mode surface acoustic wave devices based on multilayers of TeO2/ZnO(112¯0)/Si(1 0 0) with high sensitivity and temperature stability

HighlightsLove wave mode of TeO2/ZnOSymbol/Si structure is proposed for biosensing applications.TeO2 film compensates the temperature effect and enhances the sensitivity of the Love mode device.K2, temperature coefficient and sensitivity are analyzed.Optimal design parameters are defined to achieve high sensitivity and temperature‐stable. ABSTRACT A multilayer structure of TeO2/interdigital transducers (IDTs)/ZnOSymbol/Si(1 0 0) was proposed and investigated to achieve both high sensitivity and temperature‐stability for bio‐sensing applications. Dispersions of phase velocities, electromechanical coupling coefficients K2, temperature coefficient of delay (TCD) and sensitivity in the multilayer structures were simulated as functions of normalized thicknesses of ZnO (hZnO/&lgr;) and TeO2 (hTeO2/&lgr;) films. The fundamental mode of Love mode (LM) ‐ surface acoustic wave (SAW) shows a larger value of K2 and higher sensitivity compared with those of the first mode. TeO2 film with a positive TCD not only compensates the temperature effect induced due to the negative TCD of ZnOSymbol/Si(1 0 0), but also enhances the sensitivity of the love mode device. The optimal normalized thickness ratios were identified to be hTeO2/&lgr; = 0.021 and hZnO/&lgr; = 0.304, and the devices with such structures can which generate a normalized sensitivity of −1.04 × 10−3 m3/kg, a TCD of 0.009 ppm/°C, and a K2 value of 2.76%.