Advanced Materials Research Vol. 529

Abstract: Hafnium oxide thin films were deposited on silicon substrates by RF reactive magnetron sputtering. The effects of oxygen partial pressure, tuned by the O2/Ar flow ratio, on the microstructure and electrical properties were characterized. All HfOx thin films exhibit monoclinic phases. As the increase of O2/Ar flow ratio from 0.08 to 0.33, the crystallinity is improved accompanied with the decreases of flat band voltage and leakage current density. However, when the O2/Ar flow ratio further increases to 0.5, the crystallinity becomes worse with the increase of flat band voltage and leakage current. The HfOx based resistive random-access memory (RRAM) has been fabricated and its storage properties were also investigated.

Abstract: Series resistance in solar cell is known to be one of the key factors which need to be optimized, especially through the design of the front pattern. This paper is the utilization of the improved diode and series resistance model to represent the solar cell. The results show: three buses are suitable for high square resistance and fine grid line. Plating technology can improve the absolute conversion efficiency over 17%. In addition, 71 fingers for three buses and 76 fingers for two buses were select in production. It is imagined that the proposed model is very useful for PV professionals who require simple, fast and accurate PV model to design their cells.

Abstract: Hysteresis current control can control the current’s changing by changing the state of the inverter’s switches, in order to realize to tail the given current quickly for actual current. Theory and experimentation of changing ring width constant single-polar hysteresis current control of the cascade inverter are proposed. In the last, the simulation and the output waveforms are given.

Abstract: This work focused on the synthesis of source powder for SiC crystal growth. SiC powder was prepared using high purity silicon and carbon powder. Broad ranges of temperature and Ar pressure were studied on the property of the as-prepared powder. X-ray diffraction (XRD) results show that SiC polytypes were determined by synthesis temperature, while not related to the variation of Ar pressure. The lattice constant of SiC would expand when Ar pressure decreased. Raman results revealed that the variation of Ar pressure would influence SiC crystallization. It was found that the concentrations of free C, free Si and nitrogen all varied with the variation of temperature or Ar pressure.

Abstract: Write-once optical recording property of the amorphous WO3 (a-WO3) thin film prepared on the glass substrate by thermal evaporation deposition, has been demonstrated by focusing the laser of 514.5 nm with a variable power to a spot with a size of 1-2μm in diameter on the surface of thin film. The mechanisms responsible for the refractive index change of thin film after the laser recording, has also been studied by monitoring the Raman signal change with the increase of the incident laser power, and by characterizing the micro-structures of the pits induced by laser irradiation. As a result, two mechanisms, the laser-induced phase transition and the laser-induced micro-explosion, are proposed to be responsible for the write-once optical recording.

Abstract: A double-side digital display device has been fabricated based on the solid-state electrochromic effect of amorphous WO3 thin film in this article. The device simply consists of a transparent anode, a transparent cathode, an amorphous WO3 thin film and a solid electrolyte. The transparent electric wiring has been achieved by the electrochemical corrosion of the designed region of ITO (indium tin oxide) film. The amorphous WO3 thin film as an electrochromic layer is prepared on the ITO film by thermal evaporation deposition. The complex of polyethylene and LiClO4 as a solid electrolyte is used in the devices. This double-side digital display can work well under the normal mobile phone battery of 3.7 V, which is compatible with the traditional driven circuit technology. Our results prove the potential application of the amorphous WO3 thin film on the double-side display devices.

Abstract: We proposed a method to simultaneously implement birefringence-phase-matching (BPM) and quasi-phase-matching (QPM) second harmonic generation (SHG) and polarization coupling including six mismatches of wave vectors, in general case, in an optical superlattice (OSL). And the numerical simulations of SHG and polarization coupling in the OSL are carried out. The results indicate that unlike those of SHG processes with only one second harmonic (SH) reported, when one e-polarized fundamental pump is injected into the OSL, another o-polarized fundamental wave, an o-polarized and an e-polarized SHs can be simultaneously generated. The magnitudes of the o-polarized fundamental wave and SHs can be manipulated by an external dc electric field, which is useful when frequency conversion and signal tuning are required simultaneously.

Abstract: LiNbO3 is an important crystal which has piezoelectric, ferroelectric and electro-optical functions. It has a wide range of applications. Transmission and reflection spectrum of the LiNbO3 samples on the infrared-visible-ultraviolet light have been measured.The wavelength range is 200nm-2000nm. The transmission and reflection spectrum. The absorption coefficient was calculated by transmission and reflection spectrum. The absorption coefficient of the three samples increased slightly in the beginning of the scanning. Then there was a sudden change upward near 8.4*1014 Hz. Forbidden band Eg was obtained from absorption spectrum. The Eg of the three samples were obtained as 3.996ev,3.407ev and 3.425ev respectively. Forbidden band of LiNbO3 crystals was decreased as the iron doped.

Abstract: Low infrared emissivity materials based on cenosphere particles are prepared by chemical electroless Ni-coating process. This metal/inorganic composites were identified by FESEM and XRD, It can be concluded that nickel coatings are formed on the surface of cenospheres by electroless plating.and infrared emissivity properties were discussed.

Abstract: A venation-like groove structure (VGS) is proposed to improve light extraction efficiency (LEE) of vertical GaN-based light-emitting-diode by reshaping the undoped GaN (U-GaN) layer. The light extraction characteristics of the venation-like groove structure are simulated and compared to the same electrode structure without grooves by the Monte Carlo photon-tracing method. It is found that VGS has a 20.3% enhancement on LEE at the chip size of 300 μm × 300 μm. The simulated LEE distribution pattern shows that VGS has advantages in brightness and uniformity compared to interdigitated-multi-fingered and square groove structures. These advantages are contributed to the partition and deformation in VGS.