Simple Crystallization Method Research Articles

Manipulation of Crystal Morphology of Zoxamide Based on Phase Diagram and Crystal Structure Analysis

For many compounds, small needle crystals could be easily formed, and crystals with other morphologies are quite difficult to be obtained by a simple crystallization method, which will result in difficulties for downstream processing. To improve the properties of the solid state product, such as flowability, compressibility, and so on, new crystallization technology needs to be developed and designed. In this work, the manipulation of morphology and size distribution of the crystalline product was investigated by using zoxamide as a model compound. Reasons for the stubborn appearance of small needle zoxamide crystals in various solvents were explained from the intermolecular interaction by analyzing the crystal structure data. The solubility data of zoxamide in pure solvents and in ternary solvent systems were determined to aid the choice of a good solvent and poor solvent and to help to determine the agglomeration zone. The effect of process parameters on the morphology and size distribution of zoxamide ...

High performance low temperature polycrystalline Si thin-film transistors fabricated by silicide seed-induced lateral crystallization

A novel and simple crystallization method for high performance polycrystalline silicon (poly-Si) thin-film transistors (TFTs) using Ni silicide seed-induced lateral crystallization (SILC) was proposed in this study, and it includes no additional deposition and/or etching processes that are not found in the fabrication of conventional metal-induced lateral crystallization (MILC) TFTs. The poly-Si thin films crystallized by SILC were characterized by x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Micro-Raman spectroscopy. The electrical properties were obtained from ID-VG transfer curves and the interface trap density was determined by Levinson plot analysis. The results show that SILC poly-Si films have lower Ni contamination, better crystallinity, and higher crystalline fraction than MILC poly-Si films. The p-channel SILC poly-Si TFTs exhibited a mobility of 66 cm2/V·s, a minimum leakage current of 3.4 × 10−11 A at VD = −5 V, a subthreshold slope of 0.85 V/dec, and a maximum on/off ratio of 5.0 × 106, all of which resulted in a high-performance device which surpassed conventional MILC poly-Si TFTs.

High Performance Poly-Si Thin Film Transistors Fabricated by Novel and Simple Crystallization Method Using Ni-Silicide Seeds

The major problem of metal-induced crystallized (MIC) polycrystalline Si (poly-Si) thin- film transistors (TFTs) is metal contamination, from Ni and NiSi2. Many attempts have been made to address this problem, however, they all involve complicated processes. In this study, we investigate a new crystallization method, that is, seed-induced crystallization, using Ni silicide seed. There are no additional mask processes, deposition and/or etching processes. The poly-Si thin films crystallized by SIC are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Auger electron spectroscopy (AES), atomic force microscopy (AFM), micro-Raman scattering spectroscopy and the electrical properties are obtained from ID-VG transfer curve measurements. The results show that, lower Ni contamination, smoother surface and larger grain size are achieved in the SIC produced poly-Si thin films compared to those of the MIC poly-Si thin films. The p-channel SIC poly-Si TFTs, show a mobility of 62.08 cm2/V·s, minimum leakage current of 1.17 × 10−10 A at VD = 10 V, subthreshold slope of 0.7 V/dec and maximum on/off ratio of 1.7 × 106, all of which lead to a high-performance device which exceeds conventional MIC poly-Si TFTs.

Mechanism of Mutual Incorporation of Branched Chain Amino Acids and Isomorphic Amino Acids in Batch Crystallization

Toshimichi Kamei On BCAA (Branched Chain Amino Acids) crystallization process, impurity amino acids (guest amino acids) are easily incorporated to the host amino acid(a purified amino acid). Because host and guest amino acids have similar molecular structures and physical-chemical properties, therefore, in many cases, it is difficult to separate a host amino acid and a guest amino acid each other in the simple crystallization method (such as cooling or concentration crystallization conducted in water solvent). In above cases, HCl or precipitant is added to the mixed solution of a host and guest amino acid in order to separate them by generating the salt of a host amino acid. (A host amino acid crystallizes as a hydrochloride or precipitant salt.) But this process is complicated because de-hydrochloric acid or deprecipitant process is needed after crystallization to make the products. Therefore, it is thought that development of the simple crystallization method is necessary in order to make a process simpler. In order to develop the simple crystallization method, it is necessary to elucidate the incorporation mechanism of these amino acids at first, and then decide the crystallization condition based on this mechanism. We explored the mutual incorporation tendency of Branched Chain Amino Acids (L-leucine, Lisoleucine, L-valine ) and isomorphic amino acids in cooling crystallization conducted in water solvent. As a result, in most cases, a guest amino acid whose side chain is longer than that of a host amino acid was incorporated easily in a host amino acid. In this case, a solid solution was formed, and the c-axis of a host crystal structure was extended. Also the crystal growth was inhibited. Using these results, a mechanism for mutual incorporation of these amino acids was proposed.