标题: | 向列型液晶之热刺激去极化电流 Thermally Stimulated Depolarization Current in Nematic Liquid Crystals |
作者: | 陈柏伟 Chen, Po-Wei 李伟 Lee, Wei 光电系统研究所 |
关键字: | 热刺激去极化电流;液态晶体;向列型;相转变;Themally stimulated depolarization current;liquid crystals;nematic;phase transition |
公开日期: | 2013 |
摘要: | 热刺激电流技术是电介质材料在研究微观介电性质中所使用的基本方法。此技术是先将样品在高温以直流电场极化,再将样品降至低温,透过线性升温的方式,使内部结构被系统不同陷阱能阶内的空间电荷脱离,或者使取向的偶极分子发生介电松弛,此松弛能在外部形成位移电流,透过自制的外部电路设计,搭配理论的公式拟和曲线可以获得材料内部空间电荷与取向偶极分子的活化能和储存的电荷密度等参数。本论文研究水平排列向列型液晶的热刺激去极化电流。在接近液晶之澄清点时,会有明显的峰值电流产生。研究发现热刺激去极化电流出现的峰值电流将随着极化电压的增加而增强。此外,若改变极化的时间,热刺激去极化电流也将改变。更进一步发现,在升温速率改变之下,热刺激去极化电流峰值将会往高温移动。 Thermally stimulated depolarization current technique is a fundamental method for the investigation of microscopic dielectric characteristics of dielectric materials. In this technique, when a system is applied with a DC voltage source, the energy can be stored in the forms of molecular dipoles, free charges, bonds and reorientation of polar fragments. Normally, as the field being released, the stored energy dissipates, and the system relaxes to its original state. With proper treatment, one can release the energy in the form of electrical current and extract useful information. Based on the measurement of the TSDC, in this study, the mechanism of obtaining phase transition temperatures of liquid crystals is presented. The behavior of the TSDC signal from a typical nematic cell is investigated with pre-applied voltages, polarization time and heating rate as variables. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT070158011 http://hdl.handle.net/11536/75106 |
显示于类别: | Thesis |