Lead Zirconium Titanate Films and Devices Made by a Low- Temperature Solution-Based Process

As the most important multifunctional oxide material, lead zirconium titanate (PZT) has a diverse range of applications such as piezo actuators, ferroelectric nonvolatile memories, sensors, and transducers due to its excellent structural and electrical properties. However, it generally requires a high annealing temperature (above 600°C) to attain the desired properties, which hinders the integration of PZT with silicon-based Complementary Metal Oxide Semiconductor (CMOS). Therefore, the fabrication of PZT films by a chemical solution deposition (CSD) at temperatures compatible with Si-CMOS technology or even with polymeric substrate for flexible electronics would be of high technological interest. So far, different strategies to decrease the crystallization temperature of CSD-derived PZT films have been studied. This chapter presents a critical review on the low-temperature solution-processed PZT films and devices, and addresses challenges for fundamental understanding and practical integration of multifunctional PZT in devices. In the first part, recent advances in fabrication of CSD-derived PZT films at a low temperature are thoroughly reviewed. The second part discusses various techniques for patterning PZT into micro-nano-sized patterns. Lastly, some potential applications of the low-temperature CSD-derived PZT films and devices are demonstrated

Peptide aptamer-modified single-walled carbon nanotube-based transistors for high-performance biosensors

Biosensors employing single-walled carbon nanotube field-effect transistors (SWCNT FETs) offer ultimate sensitivity. However, besides the sensitivity, a high selectivity is critically important to distinguish the true signal from interference signals in a non-controlled environment. This work presents the first demonstration of the successful integration of a novel peptide aptamer with a liquid-gated SWCNT FET to achieve highly sensitive and specific detection of Cathepsin E (CatE), a useful prognostic biomarker for cancer diagnosis. Novel peptide aptamers that specifically recognize CatE are engineered by systemic in vitro evolution. The SWCNTs were firstly grown using the thermal chemical vapor deposition (CVD) method and then were employed as a channel to fabricate a SWCNT FET device. Next, the SWCNTs were functionalized by noncovalent immobilization of the peptide aptamer using 1-pyrenebutanoic acid succinimidyl ester (PBASE) linker. The resulting FET sensors exhibited a high selectivity (no response to bovine serum albumin and cathepsin K) and label-free detection of CatE at unprecedentedly low concentrations in both phosphate-buffered saline (2.3 pM) and human serum (0.23 nM). Our results highlight the use of peptide aptamer-modified SWCNT FET sensors as a promising platform for near-patient testing and point-of-care testing applications

Trapping probability analysis of a DNA trap using electric and hydrodrag force fields in tapered microchannels

This paper describes a quantitative analysis of the trapping probability for the DNA trap, which is a method of trapping and concentrating DNA in a tapered microchannel by electric and hydrodrag force fields. In order to calculate the trapping probability, a series of connections of triangle-shaped taper stages was used. The fluorescent intensity of trapped DNA molecules at each stage was measured. The trapping probability per stage was calculated from the distribution of the fluorescent increase rate along with the stage number. The trapping probabilities were measured as a function of DNA size, electric field, and average hydraulic velocity. The electric field that gives a trap probability of 0.5 was found to be proportional to the average hydraulic velocity for all DNA sizes. For all measured conditions and accuracy, the trapping probability was found to be determined only by the ratio of the electric field to the average hydraulic velocity. These results reveal that the DNA trap is not simply caused by balance between the dielectrophoresis and hydrodrag forces

Determination of trace amounts of sodium and lithium in zirconium dioxide (ZrO_2) using liquid electrode plasma optical emission spectrometry

This paper describes a quantitative measurement of trace elements (Na, Li) in high purity zirconium dioxide powder using liquid electrode plasma optical emission spectrometry (LEP-OES). Conventionally, for such type of measurements, inductively coupled plasma optical emission spectrometry (ICP-OES) is frequently employed. The detection limits of elements in zirconium by ICP-OES are degraded due to the spectra interference between the trace elements and zirconium of the matrix, because zirconium is a line rich element in spectra obtained by ICP-OES. LEP-OES is an elemental analysis method developed by the authors. The measurement principle is simple, as follows. Sample solution is put into a narrow channel on a small cuvette and voltage pulse is applied from both ends of the channel. At the center of the channel which is made narrower, the voltage and current are concentrated there, and plasma is generated. From the emission of the plasma, the quantitative analysis of the elements in the solution is achieved. The LEP-OES has the property that the emission of zirconium is relatively weak, so that highly sensitive measurement of trace elements in zirconium matrix can be conducted without interference. Sample solution is prepared by dissolving high purity zirconium dioxide powder and trace amounts of Na or Li with sulfuric acid. The voltage dependence and the pulse width dependence of optical emission spectra are also investigated. With increase of the voltage or the pulse width, the ratio of emission intensities of Na to those of hydrogen increases. This suggests that the ratio of sensitivity of two elements is variable, that means the element selectivity is controllable to some extent by the measurement conditions in LEP-OES. In the case of Na and H, the ratio can be controlled from 7.4 to 21.6%. Finally, the detection limits (3 S.D.) of the trace elements, Na and Li, in 4000 μg g^ zirconium dioxide aqueous solution are found to be 0.02 and 0.133 μg g^, respectively. These values correspond to 5 μg g^ for Li in original high purity zirconium dioxide powder. The correlation coefficient of calibration curve was 0.995 for Na, 0.985 for Li. Those are comparable to the literature values of detection limits using ICP-OES

Fine-patterning of sol-gel derived PZT film by a novel lift-off process using solution-processed metal oxide as a sacrificial layer

Sub-5 µm pattern of sol-gel derived lead-zirconium-titanate (PZT) film with a thickness of 80–390 nm was successfully prepared on Pt(111)/TiOx/SiO_2/Si (100) substrate by a novel lift-off process using solution-processed metal oxides as a sacrificial layer. The process is simply divided into three steps: In-Zn-O (IZO) sacrificial layer spin-coating and patterning, PZT film formation followed by lift-off process. The results suggested that the IZO layer is effective in preventing PZT crystallization because of its thermal stability during PZT post-annealing, and its barrier-effects between the spin-coated PZT precursor and the Pt/TiO_x substrate. Consequently, the micro-pattern of lift-off PZT exhibited better properties than that formed by wet-etching. In particular, the lift-off PZT films possessed better ferroelectric properties, higher break-down voltage, and more well-defined shape than those of films patterned by conventional wet-etching. This lift-off process shows great promise for highly integrated devices due to its fine pattern-ability