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During the fabrication of crystalline silicon solar cells, kerf-loss caused by the wire-sawing of silicon ingots to produce thin wafers inevitably limits the reduction of electricity production cost. To avoid the kerf-loss, direct growth of crystalline silicon wafers of 50-150 μm with a porous separation layer that can be mechanically broken during the exfoliation process, has been widely investigated. However, several issues including flattening of the surface after the exfoliation remain unsolved. In this work an alternative method that utilizes a water-soluble Sr3Al2O6 (SAO) sacrificial layer inserted between the mother substrate and the grown crystalline silicon layers is introduced. Polycrystalline silicon layers were grown on SAO/Si by plasma-enhanced CVD process and silicon membranes could be successfully obtained after the dissolution of SAO in the water. Same process could be applied to obtain flexible amorphous silicon membranes. Further research is being conducted to increase the size of the exfoliated wafer, which expects to reduce the production cost of crystalline silicon solar cells effectively.

Intrinsic hydrogenated amorphous silicon (i-a-Si:H) films lead to excellent surface passivation of crystalline silicon wafers. However, a-Si:H deposition on a crystalline silicon wafer often results in undesired epitaxy growth, which deteriorates the passivation property, In this paper, we studied the influence of varying plasma enhanced chemical vapor deposition (PECVD) parameters, such as the product of the gas pressure (P) and the electrode distance (Di) and the hydrogen dilution ratio (P = SiH4/(H2 + SiH4) × 100), on the passivation quality and the properties of silicon heterojunction (SHJ) solar cells. Measurements showed that proper combinations of high P × Di and large P values can yield high minority carrier lifetimes (MCLTs) of passivated silicon wafers. Also, the tendency of MCLTs measured from passivated wafers is the same as that for open circuit voltages (Voc) of fabricated SHJ solar cells. A high Voc is obtained from SHJ solar cells when unwanted epitaxial growth is minimized at the wafer surface.

Microstructural, optical and electrical properties of Cl-doped CdTe crystals grown by the low pressure Bridgman (LPB) method were investigated for four different doping concentrations (unintentionally doped, 4.97 × 1019 cm−3, 9.94 × 1019 cm−3 and 1.99 × 1020 cm−3) and three different locations within the ingots (namely, samples from top, middle and bottom positions in the order of the distance from the tip of the ingot). It was shown that Cl dopant suppressed the unwanted secondary (5 1 1) crystalline orientation. Also, the average size and surface coverage of Te inclusions decreased with an increase in Cl doping concentration. Spectroscopic ellipsometry measurements showed that the optical quality of the Cl-doped CdTe single crystals was enhanced. The resistivity of the CdTe sample doped with Cl at the 1.99 × 1020 cm−3 was above 1010 Ω.cm.

Background: TlBr is of considerable technological importance for radiation detection applications where detecting high-energy photons such as X-rays and γ-rays are of prime importance. However, there were few reports on investigating optical properties of TlBr itself for deeper understandings of this material and for making better radiation detection devices. Thus, in this paper, we report on the optical characterizations of TlBr single crystals. Spectroscopic ellipsometry (SE) and photoluminescence (PL) measurements at RT were performed for this work. Materials and Methods: A 2-inch TlBr single crystalline ingot was grown by using the vertical Bridgman furnace. SE measurements were performed at RT within the photon energy range from 1.1 to 6.5 eV. PL measurements were performed at RT by using a home-made PL system equipped with a 266 nm-laser and a spectrometer. Results and Discussion: Dielectric responses from SE analysis were shown to be slightly different among the different samples possibly due to the different structural/optical properties. Also from the PL measurements, it was observed that the peak intensities of the middle samples were significantly higher than those of the other two samples. With the given values for permittivity of free space (e0 = 8.854x10-12 F·m-1), thickness (d = 1 mm), and area (A = 10x10 mm2) of the TlBr sample, capacitances of TlBr were 6.9 pF (at hν = 3 eV) and 4.4 pF (at hν = 6 eV), respectively. Conclusion: SE and PL measurement and analysis were performed to characterize TlBr samples from the optical perspective. It was observed that dielectric responses of different TlBr samples were slightly different due to the different material properties. PL measurements showed that the middle sample exhibited much stronger PL emission peaks due to the better material quality. From the SE analysis, optical, dielectric constants were extracted, and calculated capacitances were in the few pF range.

TlBr single crystals grown using the vertical Bridgman-Stockbarger method were characterized for semiconductor based radiation detector applications. It has been shown that the vertical Bridgman-Stockbarger method is effective to grow high-quality single crystalline ingots of TlBr. The TlBr single crystalline sample, which was located 6 cm from the tip of the ingot, exhibited lower impurity concentration, higher crystalline quality, high enough bandgap (>2.7 eV), and higher resistivity (2.5 × 1011Ω·cm) which enables using the fabricated samples from the middle part of the TlBr ingot for fabricating high performance semiconductor radiation detectors.

Photocatalytic and hydrophilic TiO2 thin-film applications include water purification, cancer therapy, solar energy conversion, self-cleaning devices, and antifogging windows. We demonstrate superhydrophilicity of aerosol-deposition (AD) TiO2 films on a glass substrate without use of a carrier solvent, thereby removing the possibility of impurity contamination. AD films exhibit high visible light transmittance (greater than 80%) and superhydrophilicity (0° contact angle) with even minimal UV-light irradiation exposure. This AD method represents a significant step toward the realization of economically viable, functional thin films for the aforementioned applications.

A tunable surface that promotes either hydrophobic or hydrophilic behavior of TiO2 films is produced with aerosol deposition. This process is capable of mass production by high-speed coating at room temperature without any wet chemicals, and therefore the process has the potential to be economically viable, energy efficient, and environmentally friendly. Functional TiO2 films between 1 and 18 μm thick are produced by directly depositing dry, 1-μm TiO2 powders accelerated through a supersonic nozzle. Tunable film morphology due to a rough honeycomb surface structure yields variable water contact angles. When plasma treated with CF4, the films exhibit superhydrophilicity despite the rough honeycomb surface structure. Superhydrophilicity is due to the incorporation of fluorine in the film as shown using XPS.

Resistiveswitchingbehaviorhasbeenobservedinbinaryoxides 1‐4 and perovskite oxides. 5‐9 In particular, Pr0.7Ca0.3MnO3 (PCMO)films have been studied extensively because they exhibit a reversible pulseinduced change in resistance, which is very useful for nonvolatile memory devices. 8 PCMO thin films are known to be p-type materials, andtheyshowbipolarresistiveswitchingbehavior. 5‐9 Recently,theinterestinReRAMdevicesfabricatedatlowtemperatures(≤200 ◦ C)has increased because these devices can be used in flexible electronics. 3,4 Moreover, films grown at low temperatures are preferred for integration of the oxide materials with existing technologies. The amorphous PCMO(APCMO)wasalsogrownontheITO/glasssubstrateandtheir switching properties have been investigated. 10 In this work, APCMO films were grown on TiN/SiO2/Si substrate under various oxygen pressures (OPs) using a pulsed laser deposition (PLD) method, and their microstructure and resistive switching behavior were investigated. Moreover, the resistive switching behaviors of the APCMO films were explained by the trap-charged space-charge-limited current (SCLC) mechanism. Experimental

We propose a dual-layer transparent Indium Tin Oxide (ITO) top electrode scheme and demonstrate the enhancement of the optical output power of GaN-based light emitting diodes (LEDs). The proposed dual-layer structure is composed of a layer with randomly distributed sphere-like nano-patterns obtained solely by a maskless wet etching process and a pre-annealed bottom layer to maintain current spreading of the electrode. It was observed that the surface morphologies and optoelectronic properties are dependent on etching duration. This electrode significantly improves the optical output power of GaN-based LEDs with an enhancement factor of 2.18 at 100 mA without degradation in electrical property when compared to a reference LED. (C) 2013 Optical Society of America

Surface cleaning based on the laser-induced breakdown of gas and subsequent plasma and shock wave generation can remove small particles from solid surfaces. Accordingly, several studies were performed to expand the cleaning capability of the process. In this work, the cleaning process using laser-induced plasma (LIP) under geometrical confinement is analyzed both theoretically and experimentally. Two-dimensional numerical analysis is conducted to examine the behavior of the LIP shock wave under geometrical confinement for several geometries. As a result of the analysis, we propose a simple and practical method to amplify the intensity of laser-induced shock. In the proposed method, a flat quartz plate placed close to the focal point of the laser pulse confines the expansion of the LIP, allowing the plasma to expand only in one direction. As a consequence of the plasma confinement, the intensity of the shock wave produced is increased significantly. Experiments demonstrate that the enhanced shock wave can remove smaller particles from the surface better than the existing process.