Po Tsung Hsieh

Effects of Prestrain Applied to a Polyethylene Terephthalate Substrate Before the Coating of Al-Doped ZnO Film on Film Quality, Electrical Properties, and Pop-In Behavior During Nanoindentation

Four kinds of polyethylene-terephthalate (PET)/Al-doped zinc oxide (AZO) specimen are prepared to examine the effects of prestrain applied to the PET substrate before the coating of the AZO film on the mechanical, material, and electrical properties, and the start of pop-in in the loading phase of nanoindentation. The electrical contact resistance function is used to measure the variations of electrical current during the nanoindentation process. With the aid of the stress-strain profile, the inflection point of the load-depth profile in the loading phase is identified as the start of pop-in, at or nearby which the electrical current sharply increases due to the significant increase in the indenter-film contact area. The pop-in depth decreases with increasing prestrain. The behavior demonstrated in the pop-in depth due to the change in the prestrain is exactly opposite to those of the quantity and the mean size of submicrometer voids/cracks. Increase in the quantity/size of film voids/cracks generally reduces the specimens carrier mobility. The carrier mobility is presented to be inversely proportional to the sheet resistance. The electrical current created at the end of the loading process has its value inversely proportional to the number/size of film voids/cracks.

Molybdenum-doped zinc oxide nanocomposite transparent film derived by sputtering technique

A molybdenum (Mo)-doped zinc oxide thin film is deposited on a glass substrate by a rf magnetron sputtering technique. The structural and optical characteristics of ZnO:Mo (ZMO) thin films prepared with various deposition parameters are investigated. A series of SEM images obtained reveal that the average grain size of ZMO thin films is small and uniform. Energy dispersive spectroscopy analysis also verifies that traces of Mo are present in the as-grown thin films. The thicknesses of these ZMO films ranging from 150 to 390 nm are obtained by varying pertinent sputtering parameters. The average transmittance of ZMO thin films measured is more than 80% in the visible spectrum.

Electrochromic Properties of Nano-Columnar Nickel Oxide

Electrochromic properties of transition metal oxides had much attention in recent years. The electrochromic thin films can be assembly as electrochromic devices (ECDs) and then used for applications in devices such as mirrors, panels and smart windows. A kind of complementary ECD is popular in resent years. Therefore, a specific investigation on nickel oxide (NiO) electrochromic properties is completed in this study. The crystalline structure of the NiO films was analyzed using XRD (PANalytical X’Pert PRO) with Cu-Kα radiation. The atmosphere of oxygen concentration increasing has changed the NiO films crystalline from (200) to (111). The thicknesses and surface microstructures of the NiO films were investigated using a scanning electron microscope (SEM, Philips/FEI XL40 FEG). It is observed that films are relatively smooth deposited without oxygen. The characterization of the electrochromic properties was carried out in a two-electrode cell with an electrochemical analyzer (CHI 611B). The NiOx changes the transmittance of NiO films in the wavelength range of 300-1500 nm and the color of the film changes from transparent to brown. The nano-crack exhibits in the NiO film did enhance the electrochromic properties.

Effects of Sputtering Power on Optical and Electrical Properties of Al-Doped ZnO Thin Film on Flexible Substrates

AZO thin films were deposited using a magnetron sputtering system with an AZO target (with 3wt% Al2O3) on polyethylene terephthalate (PET) substrates with pre-strain. The effect of sputtering power on the optical and electrical properties of AZO films was investigated. For samples deposited on pre-strained PET substrates, X-ray diffraction was used to determine the c-axis orientation of AZO films deposited at 60, 80, and 100 W. Results show that resistivity decreased with increasing sputtering power, which might result from the better crystalline structure and fewer grain boundaries obtained at high power. The transmittance increased when the power was increased from 60 to 100 W. The absorption edge thus decreased for AZO film deposited at 100 W.

The Photocatalytic Characteristics of TiO2 Films: an Expeditious Evaluation

An expeditious evaluation for photocatalyst is set up (or established) in this study. The optical transmittance of the methyl blue solution is measured, and a relationship between the transmittance of solution and its concentration is established. The performance of a photocatalyst can be evaluated via the distinct change of methyl blue solution. The TiO2 films performed as a photocatalyst were prepared using sol-gel method and then annealed by rapid thermal annealing (RTA). The samples were illuminated with a high-pressure mercury lamp for exciting photocatalytic reaction. The result shows that TiO2 photocatalyst degraded the methyl blue solution up to 97.8%.

Investigation on the Mechanical Properties of Molybdenum-Doped Zinc Oxide Transparent Thin Film by Sputtering Technique

Zinc oxide thin films were prepared on the glass substrate by rf-magnetron sputtering technique and their structural, optical, and mechanical characteristics were then investigated. As the SEM images have revealed, the average grain size of ZMO thin film are influenced by pressure and sputter power, and the average value of the grain size is about 30~50 nm. The EDS analysis also revealed a successful doping of Mo in ZnO thin film. The transmittance property of ZMO thin film exhibited an excellent transparency in the visible range, where the transmittance was about 90% for ZMO film with Mo. Moreover, good transmittance was also demonstrated in the range of 350nm to 400nm (UV regime). Finally, the nano-mechanical properties of ZMO thin films were investigated using a nanoindentation technique. The corresponding result would show that the Young’s modulus and hardness both increased with decreasing pressure.

Synthetic Properties of the c-Axis Tilted AlN Thin Films

Aluminum nitride (AlN) is one of the most popular piezoelectric materials for high frequency resonators, filters and sensors. The piezoelectric property, i.e. electromechanical coupling coefficient, of AlN thin film is highly related to its crystalline orientation. AlN thin films with various c-axis-tilted angles can be fabricated by the RF sputtering technique. The crystallization and grain growth orientations of AlN thin film are examined by XRD, SEM, and TEM, while the bonding condition and nano-mechanical properties are investigated by a raman system and a nano-indentation technique.