J.H. Hsieh

Physical properties of amorphous InGaZnO4 films doped with Mn

Amorphous InGaZnO4 (a-IGZO) films doped with various concentrations of Mn have been fabricated by using pulsed-laser deposition technique. Optical, electrical, and magnetic properties of the prepared Mn-doped a-IGZO films were investigated. The resistivity, carrier concentration, and carrier mobility of the a-IGZO films were found to be, respectively, increased, decreased, and enhanced by Mn doping. Moreover, the optical transmission is slightly increased in the visible range and the optical band gaps are not affected in the Mn-doped films. Room-temperature ferromagnetism has been observed in the field-dependent magnetization measurements.

Metal–insulator transition characteristics of Mo- and Mn-doped VO2 films fabricated by magnetron cosputtering technique

Mo- and Mn-doped VO2 thin films have been grown on c-cut sapphire substrates by the magnetron co-sputtering technique. The effects of Mo and Mn doping on the structure and metal–insulator transition of the doped VO2 thin films were studied. An enlargement of the out-of-plane lattice constant of the film caused by Mo doping was observed. As expected, the transition temperature (TMI) is reduced by Mo doping. However, the valence of the Mo ions doped in the VO2 films is determined by X-ray photoelectron spectroscopy to be 6+ on the surface, but 4+ and 3+ in the bulk part of the films. The reduction in TMI observed in this study is attributed to the variation in the band structure resulting from the incorporation of Mo4+ into the VO2 lattice. The optical transmission is remarkably enhanced by low-concentration Mo doping and then monotonically decreases with increasing Mo content. On the other hand, the out-of-plane lattice constant and TMI are not affected by Mn doping. The transmission is enhanced and then monotonically increases with increasing Mn concentration. The thermochromism of doped films is suppressed by Mo and Mn doping.

Effects of annealing on antiwear and antibacteria behaviors of TaN–Cu nanocomposite thin films

TaN–Cu nanocomposite films were deposited by reactive cosputtering on Si and tool steel substrates. The films were then annealed using rapid thermal annealing (RTA) at 400°C for 2, 4, and 8min, respectively, to induce the nucleation and growth of Cu particles in TaN matrix and on film surface. Field emission scanning electron microscopy was applied to characterize Cu nanoparticles emerged on the surface of TaN–Cu thin films. The effects of annealing on the antiwear and antibacterial properties of these films were studied. The results reveal that annealing by RTA can cause Cu nanoparticles to form on the TaN surface. Consequently, the tribological behaviors, as well as the antibacterial behavior may vary depending on particle size, particle distribution, and total exposed Cu amount. For the samples with large Cu particles, the reduction of averaged friction and wear rate is obvious. Apparently, it is due to the smeared Cu particles adhered onto the wear tracks. This Cu layer may act as a solid lubricant. F...

Effects of deposition and annealing temperatures on the electrical and optical properties of Ag2O and Cu2O-Ag2O thin films

Ag2O and Ag2O–Cu2O films were deposited on glass substrates by magnetron sputtering of Ag and Cu targets at various substrate temperatures. After deposition, some of these films were annealed using a rapid thermal annealing system, with the variation of temperature. An UV-VIS-NIR photometer and a Hall measurement system were used to characterize the optical and electrical properties of these films. On annealing, Ag2O (hexagonal) phase would slowly change to Ag+Ag2O (cubic) phases when the annealing temperature is greater than 200 °C. When the annealing temperature was higher than 450 °C, the Ag2O phase would transform into a metallic Ag phase completely. Accordingly, the band gap of these films will change, along with the optical and electrical properties. In the study of Ag2O–Cu2O films, it is found that these two-phase composite films could exist obviously when deposited at room temperature. The photoinduced current of these composite films could be increased significantly, compared with that of a singl...

Effects of RF Power and Working Pressure on the Properties of Nc-Si:H Thin Films Deposited by an ICP-CVD System

An ICP-CVD system attached with four internal antennas was used to deposit nc-Si:H thin films. These films were prepared as functions of RF power and working pressure, while the flow ratio of SiH4/H2 was fixed at 1/5. During deposition, an OES (optical emission spectrometer) and a plasma probe were used to characterize the conditions of plasma. The crystalllinity, structure, and Si-H bonding of these Si:H films were investigated using Raman scattering spectroscopy, XRD, and FTIR. It is found that the crystallinity of nc-Si:H film was significantly affected by electron density which was increased with the increase of the power and the decrease of pressure. The deposition rate increased with the increase of RF power as well as working pressure. This could be due to high electron density (when the working pressure was fixed) or less hydrogen etching (when the RF power was fixed). It was also found that crystallinity could be proportionally related to I( SiH2+SiH3)/I(SiH+SiH2+SiH3) in FTIR spectra. This was because that di-/polyhydride bonding could serve to passivate the grain boundaries of Si nano-crystalline clusters.